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CASTIGLIONI, FABIO. « Design of Functional Porous Materials with Stimuli-Responsive Mobile Elements ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2019. http://hdl.handle.net/10281/241243.
Texte intégralRésumé :
La tesi tratta il design, la sintesi e la caratterizzazione di nuovi materiali porosi avanzati contenenti elementi capaci di mostrare una dinamica allo stato solido. Il lavoro è diviso in 4 capitoli riguardanti opere originali più un capitolo di introduzione. Nel capitolo 2 è stata affrontata la sintesi di un nuovo legante rod-like per la preparazione di Metal-Organic Frameworks (MOFs). Il legante è formato da un anello p-fenilenico perdeuterato che costituisce il rotore molecolare. In posizione 1,4 sono stati introdotti tripli legami poichè è noto che la barriera di attivazione per la rotazione attorno a un legame sp-sp2 è bassa. Infine, due gruppi pirazolati costituiscono i siti di legame al metallo. Il legante è stato utilizzato per sintetizzare un MOF di Zn(II). Il materiale è stato caratterizzato dal punto di vista cristallografico ed è risultato isostrutturale all'analogo non-deuterato. Gli atomi di deuterio sul rotore sono stati introdotti per studiarne la dinamica sfruttando l'NMR al deuterio. Gli esperimenti ci hanno permesso di determinare una bassissima barriera di attivazione per la rotazione pari a 0.5 kcal/mol, fra le più basse riportate in letteratura. La frequenza di rotazione del rotore è superiore a 10^11 Hz già a 150 K. Inoltre, la dinamica dei rotori è stata finemente regolata tramite l'adsorbimento di molecole di CO2 nella struttura porosa. Il terzo capitolo si configura come una estensione del secondo. Nell'ottica di preparare materiali funzionali, è stato sintetizzato un legante strutturalmente simile a quello presentato nel capitolo due, ma avente un atomo di fluoro sull'anello centrale. La presenza del fluoro induce un momento di dipolo elettrico sul rotore (rotori dipolari), permettendo, quindi, di controllare la posizione dei rotori con un campo elettrico esterno. Il legante fluorurato è stato usato per preparare MOFs di Zn(II) e Ni(II). Tali MOFs sono stati caratterizzati dal punto di vista cristallografico e sono state valutate le loro capacità di adsorbimento di CO2. I materiali fluorurati sono isostrutturali ai loro analoghi non-fluorurati noti in letteratura, una caratteristica poco comune. Inoltre, si sono dimostrati migliori nella cattura di CO2 rispetto alle versioni non-fluorurate. Uno studio preliminare della dinamica del rotore dipolare nel MOF di Zn suggerisce barriere energetiche per la rotazione di circa 0.4 kcal/mol. Nel quarto capitolo viene presentato un progetto condotto in collaborazione con il gruppo di ricerca del Prof. Ben Feringa dell'Università di Groningen. In questo lavoro abbiamo sintetizzato un nuovo switch molecolare bistabile sfruttando un design noto ai ricercatori di Feringa. La molecola può essere vista come due metà connesse attraverso un doppio legame C-C. La metà inferiore costituisce lo statore, mentre quella superiori è il rotore. L'assorbimento di un fotone a 365 nm provoca l'isomerizzazione attorno al doppio legame, mentre un fotone a 470 nm o l'aumento di temperature induce una seconda fotoisomerizzazione con ripristino dello stato iniziale. In questo lavoro abbiamo voluto testare la possibilità di inserire tali molecole in una struttura solida porosa e verificare che fossero in grado di operare allo stato solido. Abbiamo quindi realizzato un materiale poroso sfruttando la copolimerizzazione dello switch e di un building block tetraedrico tramite reazione di accoppiamento di Yamamoto. Abbiamo quindi dimostrato con diverse tecniche che il processo di fotoisomerizzazione avviene anche allo stato solido nella matrice porosa in maniera reversibile. Infine, nel quinto capitolo ho preparato tre nuovi materiali porosi organici fluorurati contenti rotori dipolari. Questa volta sono stati sfruttati legami covalenti C-C per costruire il network poroso. Sono state valutate le capacità di cattura e separazione di CO2 e CH4 dei materiali e in futuro si prevede di studiare la dinamica in stato solido dei rotori dipolari.This thesis concerns the design, synthesis and characterization of new advanced porous materials containing mobile elements able to show solid-state dynamics. The work is divided in 4 chapter plus an introductory one. Chapter 2 describes the synthesis of a new rod-like ligand for Metal-Organic Frameworks (MOFs) synthesis. It is constituted by a central perdeuterated p-phenylenic ring that is the molecular rotor. In 1,4 positions triple bonds have been introduced as it is known that rotation around sp-sp2 bonds occurs with a low energy barrier. Two pyrazolate groups have been used as metal binding sites. The ligand was used to prepare a Zn(II) MOF. The material was characterized by XRPD and it was found to be isostructural with the previously reported non-deuterated analogue. Deuterium atoms have been introduced to study rotors dynamic with deuterium NMR. Experiments allowed us to determine a 0.5 kcal/mol value for the energy barrier for rotation. This is the lowest value ever reported for MOFs. The rotation frequency is higher than 10^11 Hz already at 150 K. Furthermore, rotors dynamics has been finely tuned by CO2 adsorption. Chapter 3 can be viewed as an extension of chapter 2. To prepare functional materials, we synthesized a new ligand, structurally similar to the one reported in chapter 2, but with a fluorine substituent on the central p-phenylenic ring. The fluorine generates an electric dipole moment on the rotors (dipolar rotors), thus allowing the control of rotors orientation with an external electric field. We employed the fluorinated ligand to prepare Zn(II) and Ni(II) MOFs. The materials are isostructural to their non-fluorinated analogues, an uncommon characteristic for MOFs. Their CO2 uptake performances are better than those of non-fluorinated compounds thanks to the presence of fluorine moieties. Preliminary evaluation of rotors dynamics in the Zn(II) material allowed to measure an energy barrier for rotation as low as 0.4 kcal/mol. In chapter 4 is presented a project in collaboration with Prof. Ben Feringa group from Groningen University. In this work we synthesized a new bistable molecular switch exploiting a design invented by Feringa Group. The molecule is composed by two halves connected through a C-C double bond. The lower half is the stator, while the upper half is the rotor. The adsorption of a 365 nm photon provokes the photo-induced isomerization around the double bond, while a 470 nm photon or high temperatures promotes the backswitch. In this work we inserted these bistable switches in a porous organic structure and we tested the photo-induced switching in solid-state. The porous material was synthesized by copolymerization of the switch moieties with a tetrahedral building block employing Yamamoto C-C cross-coupling reaction. We demonstrated employing various techniques that the photo-induced isomerization reversibly occurs in solid state in the porous matrix. Ultimately, in chapter 5 three new fluorinated organic porous materials were designed and synthesized. This time, covalent carbon-carbon bonds were exploited to build the frameworks. Their CO2 and CH4 capture and separation performances were evaluated and, in the future, we plan to study the solid state dynamics of the dipolar rotors.
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Souto, Salom Manuel. « Multifunctional Materials based on TTFPTM dyads : towards new Molecular Switches, Conductors and Rectifiers ». Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/393986.
Texte intégralRésumé :
Esta Tesis está centrada en el diseño, síntesis y caracterización de nuevos materiales moleculares multifuncionales basados en sistemas Dador-Aceptor (D-A) formados por la unidad dadora de electrones tetratiafulvaleno (TTF) enlazada a la unidad aceptora de electrones el radical policlorotrifenilmetilo (PTM) mediante diferentes puentes -conjugados. Estos compuestos pueden exhibir propiedades físicas muy interesantes como biestabilidad o propiedades ópticas no lineales en solución, conductividad en estado sólido o rectificación cuando son anclados en superficies. Por tanto, estos sistemas podrían encontrar aplicación en el campo de la electrónica molecular como interruptores, conductores o rectificadores.
En la primera parte de esta Tesis, se estudiará el fenómeno de biestabilidad en solución de un sistema D-A basado en un radical PTM conectado a un TTF mediante un puente vinileno. Este sistema puede exhibir un cambio inducido por la temperatura entre dímeros diamagnéticos a temperatura ambiente y monómeros paramagnéticos a alta temperatura. Los dos distintos estados presentan diferentes propiedades ópticas y magnéticas utilizando la temperatura como estímulo externo. Por otra parte, también se presentará el diradical A-D-A compuesto por dos subunidades PTM radicalarias conectadas mediante un puente TTF-vinileno que puede modificar reversiblemente sus propiedades ópticas, magnéticas y electrónicas al oxidarse o reducirse en solución. La modificación de la deslocalización electrónica y del acoplamiento magnético se observa cuando generamos las especies cargadas y los cambios han sido racionalizados mediante cálculos teóricos.
En la segunda parte de la Tesis, se presentará la síntesis y caracterización de distintos derivados TTF--PTM incrementando el número de vinilenos entre las unidades D y A. También se estudiará la transferencia de carga intramolecular y las propiedades ópticas no lineales (NLO) en solución y su dependencia con la estructura electrónica abierta así como con la longitud del puente de cada uno de los compuestos.
En la tercera parte de la Tesis, se estudiará las arquitecturas auto-ensambladas en estado sólido de un nuevo sistema TTF-PTM. La estructura cristalina muestra un ordenamiento supramolecular con una segregación de las unidades dadoras y aceptoras. Además, se estudiará la aparición de conductividad en los cristales del mismo sistema al aumentar la presión. El comportamiento de semiconductor a altas presiones se relacionará con el aumento de interacciones intermoleculares así como con el incremento de la deslocalización de carga.
Finalmente, en la última parte de la Tesis se presentará un nuevo compuesto TTF-PTM que ha sido funcionalizado con un grupo disulfuro para preparar monocapas auto-ensambladas (SAMs) en superficies de oro. Estas SAMs han sido caracterizadas mediante diversas técnicas espectroscópicas para estudiar la estructura electrónica del sistema. Además, se estudiará el transporte de carga a través de las SAMs para evaluar un posible comportamiento de rectificación.This Thesis is focused on the design, synthesis and characterization of new multifunctional molecular materials based on donor-acceptor (D-A) dyads formed by the electron-donor tetrathiafulvalene (TTF) unit linked to the electron-acceptor polychlorotriphenylmethyl (PTM) radical moiety through different -conjugated bridges. These compounds can exhibit interesting physical properties such bistability and nonlinear optical properties in solution, conductivity in the solid state or electrical rectification when anchored on surfaces. Thus, these systems could find potential applications in the field of molecular electronics as switches, conductors or rectifiers. In the first part of the Thesis, we have studied the bistability phenomenon in solution of a D-A dyad based on a PTM radical linked to a TTF moiety through a vinyelene bridge. This system exhibited a temperature-induced switching between diamagnetic dimers at room temperature and paramagnetic monomers at high temperature. The two different states showed different optical and magnetic properties when using the temperature as external input. On the other hand, we have also reported the A-D-A diradical triad based on two PTM radical subunits connected through a TTF-vinylene bridge that can reversibly modify the optical, electronic and magnetic properties by one-electron reduction and oxidation in CH2Cl2 solution. The modification of electron delocalization and magnetic coupling was observed when the charged species were generated and the changes were rationalized by theoretical calculations. In the second part of the Thesis, we have reported the synthesis and characterization of different TTF--PTM dyad derivatives increasing the number of vinylene units between the D and A moieties. We have studied the intramolecular charge transfer and non-linear optical (NLO) properties in solution and their dependence on the open-shell structure as well as on the bridge length for this family of compounds. In the third part of the Thesis, we have studied self-assembled architectures in the solid state of a new D-A dyad based on a PTM radical linked to a TTF moiety through a -phenyl-pyrrole bridge. The crystal structure showed an interesting supramolecular arrangement with segregated donor and acceptor units. Moreover, we reported the appearance of conductivity in single crystals of the same system when increasing the pressure. The semiconducting behavior at high pressures has been attributed to the enhanced intermolecular interactions and charge delocalization due to incorporation of TTF units which force the formation of close packed stacks of molecules. Finally in the last part of the Thesis, we have reported a new TTF-PTM dyad that was functionalized with a disulfide group in order to prepare self-assembled monolayers (SAMs) on gold. These SAMs were fully characterized by different spectroscopic techniques in order to study the electronic structure of the system. Moreover, charge transport measurements through the SAMs were performed in order to evaluate the possible rectification behavior.
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Villabona, Pedemonte Marc. « Photofunctional processes and materials based on molecular switches ». Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/673837.
Texte intégralRésumé :
Els interruptors moleculars han estat un camp de recerca important en els últims anys degut a la seva capacitat per interconvertir-se entre múltiples estats al estar exposats a un estímul (escriptura) i al fet de modificar les seves propietats després del canvi (lectura). Els interruptors moleculars que interaccionen amb llum per canviar d’estat o bé que modifiquen les seves propietats òptiques són d’especial interès ja que la llum permet un alt control espai temporal de forma no invasiva i la seva detecció té una alta sensibilitat. Per aquest motiu, durant aquesta tesis s’han desenvolupat múltiples materials i processos fotofuncionals els quals poden resumir-se en dues parts:
Per una banda, el caràcter multiestat d’una família de interruptors molecular (fluoro)cròmics basats en compostos espirocíclics zwitteriònics de Meisenheimer (SZMC), es va ampliar mitjançant la identificació d’un nou estat catiònic amb propietats òptiques distintives, el qual és pot generar tant electroquímicament com a través de l’adició d’un àcid. A més, es va investigar el comportament termo(fluoro)cròmic dels SZMC i es va demostrar que podien respondre tant a canvis en el dissolvent com a la presència d’anions. Aquest comportament multiestat i de resposta a múltiples estímuls va ser emprat en la preparació de una sèrie de materials fotofuncionals basats en SZMC com: un detector de pH d’ampli espectre, dispositius electro(fluoro)cròmics i sensors iònics, termals i de dissolvents.
Per altra banda, es van controlar tres processos químics amb ditieniletens (DTE) mitjançant llum. Primer, la introducció d’un grup electroacceptor EWG va permetre la modulació del pKa de fenols funcionalitzats amb DTEs. Després, el control amb dues longituds d’ona d’una reacció d’amidació es va aconseguir amb un estratègia similar a l’anterior utilitzant un éster activat basat en DTE. Aquest va reaccionar fins a 24 vegades més ràpid en el estat tancat generat amb llum UV (ie. activació amb UV) que amb l’estat obert obtingut sota irradiació amb llum visible (ie. desactivació amb visible). Finalment, la estratègia de controlar reaccions amb dos colors també va ser aplicada en la fotoligació mitjançant una reacció de oxo-Diels Alder d’un dienòfil basat en DTE actiu en la forma tancada (ie. Activacióamb llum UV, desactivació amb llum visible) i un diè generat en llum UV basat en orto-metilbenzaldèhid.Los interruptores moleculares han sido un campo de investigación importante en los últimos años debido a la capacidad de interconvertir-se entre múltiples estados al exponerse a un estímulo (escritura) y modificar sus propiedades (lectura). De especial interés han sido los interruptores moleculares que interaccionan con la luz ya sea para cambiar de estado o bien modificar sus propiedades ópticas en la transformación. Esto és debido a que la luz permite un alto control espaciotemporal al mismo tiempo que és no invasiva y altamente sensible a la detección. Por estos motivos, durante esta tesis se han desarrollados múltiples materiales y procesos fotofuncionales los cuales pueden resumirse en dos partes: Por un lado, el carácter multiestado de una familia de interruptores moleculares (fluoro)crómicos basados en compuestos espirocíclicos zwitteriònicos de Meisenheimer (SZMC) se amplió mediante la identificación de un nuevo estado catiónico, con propiedades ópticas distintivas, que se puede generar tanto electroquímicamente, como a través de la adición de ácido. Además, se investigó el comportamiento termo(fluoro)crómico de los SZMC y se demostró que podían responder tanto a cambios en el disolvente como a la presencia de iones. Este comportamiento multiestado i de respuesta a múltiples estímulos fue utilizado en la preparación de varios materiales fotofuncionales basados en SZMC como: un detector de pH de amplio espectro, dispositivos electro(fluoro)crómicos i sensores iónicos, termales i de disolventes. Por otro lado, se controlaron tres procesos químicos diferentes con interruptores moleculares fotoinducidos de tipo ditienileteno (DTE) mediante luz. Primero, la introducción de un grupo electroacceptor permitió la modulación del pKa de un fenol funcionalizado con un DTE. Segundo el control de una reacción de amidación con dos longitudes de onda fue conseguido con una estrategia similar a la anterior utilizando un ester activado basado en DTE. Este reacciona hasta 24 veces más rápido en el estado cerrado generado con luz ultravioleta (ie. activación con UV) que en el estado abierto que se obtiene al irradiar con luz visible (ie. desactivación con visible). Finalmente, el control de reacciones con dos colores de luz fue utilizado para controlar la reacción de oxo-Diels Alder entre un dienófilo basado en DTE activo en el estado cerrado (ie. activación con UV, desactivación con luz visible) i un dieno generado con luz UV basado en orto-metilbenzaldehido.
Molecular switches have been an important research field in the recent years due to its capacity to interconvert between multiple states through a stimulus (writing) and change their properties (reading). Of special interest are molecular switches that interact with light by either changing their optical properties or reacting as stimulus, due to its noninvasive high spatiotemporal control and sensitivity. As a result, several photofunctional materials and processes based on molecular switches were developed during this thesis which can be summarized in two topics. On the one hand, the multistate character of a family of (fluoro)chromic molecular switches based on spirocyclic zwitterionic Meisenheimer compounds (SZMC) was broadened by identifying a novel cationic state with distinctive optical properties, which could be achieved electrochemically or via acid addition. Moreover, the thermo(fluoro)chromic behavior of SZMCs was investigated and successfully demonstrated that they can respond to certain ions and solvents. This multistimuli-responsive and multistate character was then exploited for the preparation of a variety of photofunctional materials based on SZMCs: wide-range pH detectors, electro(fluoro)chromic displays, and thermal, ionic and solvent sensors. On the other hand, light controlled reactivity with dithienylethenes (DTE) was achieved for three chemical processes. First, the introduction of electrowithdrawing groups (EWG) allowed the modulation of the pKa in acetonitrile of a series of DTEs tethering phenol moieties. Second, a similar strategy allowed for the dual-color control of an amidation reaction employing DTE-based active esters which react up to 24 times faster in the UV-generated closed state (ie. activation with UV irradiation) than in the open state formed under visible illumination (ie depletion with visible light). Finally, two-wavelength control was also achieved for an oxo-Diels Alder reaction between a DTE-dienophile active in the closed state and a UV-generated diene based on orto-methylbenzaldehyde.
Universitat Autònoma de Barcelona. Programa de Doctorat en Química
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Schoevaars, Anne Marie. « Chiroptical molecular switches ». [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 1991. http://irs.ub.rug.nl/ppn/291295282.
Texte intégral
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Huck, Hubertina Petronella Maria. « Chiroptical molecular switches ». [S.l. : [Groningen : s.n.] ; University of Groningen] [Host], 2008. http://irs.ub.rug.nl/ppn/.
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Rohatgi, Priyanka. « Engineering Protein Molecular Switches To Regulate Gene Expression with Small Molecules ». Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/19852.
Texte intégralRésumé :
Small molecule dependent molecular switches that control gene expression are important tool in understanding biological cellular processes and for regulating gene therapy. Nuclear receptors are ligand activated transcription factors that have been engineered to selectively respond to synthetic ligands and used as regulators of gene expression. In this work the retinoid X receptor (RXR), has been used to develop an inducible molecular switch with a near drug like compound LG335. Three RXR variants (Q275C; I310M; F313I), (I268A; I310A; F313A; L436F), (I268V; A272V; I310M; F313S; L436M) were created via site-directed mutagenesis and a structure based approach, such that they preferentially bind to the synthetic ligand LG335 and not its natural ligand, 9-cis retinoic acid. These variants show reverse ligand specificity as designed and have an EC50 for LG335 of 80 nM, 30 nM, 180 nM, respectively. The ligand binding domains of the RXR variants were fused to a yeast transcription factor Gal4 DNA binding domain. This modified chimeric fusion protein showed reverse response element specificity as designed and recognized the Gal4 response element instead of the RXR response element. The modified RXR protein did not heterodimerize with wild type RXR or with other nuclear receptor such as retinoic acid receptor. These RXR-based molecular switches were tested in retroviral vectors using firefly luciferase and green fluorescence protein and they maintain their inducible behavior with LG335. These experiments demonstrate the orthogonality of RXR variants and their possible use in regulating gene therapy.
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Wiik, Jhonny. « Naphthyridine Based Molecular Switches ». Thesis, Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-15477.
Texte intégralRésumé :
This thesis is focused on the synthesis and halogenation of 1,5-naphthyridine and 2,6-naphthyridine with the aim of finding a suitable method to synthesize mono- and bis-naphthyridine centered tridentate ligands for ruthenium complexes. Firstly the halogenated naphthyridines were synthesized, then 2-(2-thienyl)-6-ributylstannylpyridine was synthesized, and the two building blocks were coupled through a Stille cross coupling reaction. The thesis describes the synthesis of 2,6-dichloro-1,5-naphthyridine, 2-chloro-1,5-naphthyridine, 1,5-dichloro-2,6-naphthyridine and 1-chloro-2,6-naphthyridine. The synthesis of many of the halogenated naphthyridines have previously been reported, with the exception of 1,5-dichloro-2,6-naphthyridine and some of its intermediates which, at present, to the best of the authors knowledge , has not been reported. Three strategies have been successfully tested for the synthesis of 1,5-dichloro-2,6- naphthyridine. Secondly the thesis describes the synthesis of 2-(2-thienyl)-6-tributylstannylpyridine. The method of choice for synthesizing this Stille reagent was a Negishi coupling between 2-bromo-6- tributylstannylpyridine and 2-thiophenyl zinc chloride. Thirdly the thesis describes a method for the synthesis of bis-2,6-(2-(2-thienyl)6-pyridinyl)-1,5-naphthyridine through a Stille cross-coupling
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Foster, Brian K. « Carbon Isotope controlled molecular switches / ». May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Iancu, Violeta. « Single Molecule Switches and Molecular Self-Assembly : Low Temperature STM Investigations and Manipulations ». Ohio : Ohio University, 2006. http://www.ohiolink.edu/etd/view.cgi?ohiou1159980375.
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Kudernáč, Tibor. « Light-controlled conductance using molecular switches photochromic switches get wired / ». [S.l. : Groningen : s.n. ; University Library Groningen] [Host], 2007. http://irs.ub.rug.nl/ppn/304519308.
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Лопаткін, Юрій Михайлович, Юрий Михайлович Лопаткин, Yurii Mykhailovych Lopatkin, A. G. Malashenko, Yu A. Shevchenko et T. N. Sakun. « Prototype of Stable Molecular Switch ». Thesis, Sumy State University, 2016. http://essuir.sumdu.edu.ua/handle/123456789/45768.
Texte intégralRésumé :
One of the goals of molecular electronics is search of structures that can serve as the memory elements, switches, transistors and etc.
As molecular switch may be a molecule which has two conformations, the transition between them is made by an external exposure, for example, the electric field of different polarity. In order to work of element was stable, the molecule must has sufficiently high potential barrier between the two stable states.
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Bogdan, Elena. « Theoretical and experimental characterizations of the first hyperpolarizabilities of organic molecules and molecular switches ». Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14255/document.
Texte intégralRésumé :
Cette thèse a pour objectif l’étude des propriétés optiques non linéaires (ONL) de second ordre de molécules de référence et de composés organiques photochromes, via des calculs de chimie quantique et des expériences de diffusion Hyper-Rayleigh (HRS). L’étude des réponses optiques de second harmonique d’une série de solvants organiques met tout d’abord en évidence la nécessité d’utiliser des méthodes théoriques intégrant les effets de la corrélation électronique, les effets d’environnement, ainsi que des bases très étendues pour évaluer quantitativement les premières hyperpolarisabilités moléculaires. La décomposition du tenseur de première hyperpolarisabilité en contributions dipolaires et octupolaires via le formalisme des harmoniques sphériques permet également d’illustrer l’effet de la symétrie des composés sur leurs réponses ONL. La seconde étude porte sur la caractérisation des effets de solvant sur les propriétés ONL d’un dérivé anil présentant un équilibre entre une forme énol et une forme cétone. Il est démontré que l’équilibre énol/cétone peut être déplacé vers la forme cétone en augmentant la proportion d’éthanol dans le mélange binaire de solvants éthanol/cyclohexane, conduisant à une augmentation de l’intensité HRS du mélange. La dernière partie de la thèse propose une étude théorique systématique des effets de substitution sur les propriétés ONL de sels de flavylium, dans le but d’optimiser le contraste des réponses ONL entre les différentes formes des composés. Il est démontré qu’une combinaison optimale de substituants permet d’obtenir de forts contrastes, démontrant le potentiel de ces composés comme systèmes multi-états pour des applications ONLThis PhD addresses the nonlinear optical (NLO) properties of the reference organic molecules and molecular switches, by means of quantum chemical calculations and Hyper-Rayleigh Scattering (HRS) measurements. The thorough investigation of the NLO responses of a series of organic solvents first evidences the need of using theoretical methods including environment and electron correlation effects, as well as highly extended basis sets to quantitatively evaluate the molecular first hyperpolarizabilities. Decomposing the first hyperpolarizability tensor into dipolar and octupolar contributions via the spherical harmonics formalism also highlights the impact of the molecular symmetry on the NLO responses. The second part addresses the solvent effects on the NLO properties of an anil derivative, which exhibits an equilibrium between a enol and a keto form. It is shown that the enol/keto equilibrium is shifted towards the keto form when increasing the ethanol ratio in ethanol/cyclohexane solvent mixtures, leading to an increase of the HRS intensity. The last part addresses the effects of the chemical substituents on the NLO properties of flavylium salts, with the aim of optimizing the NLO contrasts between the various forms of the compounds. It is found that optimal combinations of chemical substituents lead to high NLO contrats, which demonstrates the potential of these compounds as multi-states systems for NLO applications
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Huxley, Allen John McAllister. « Switches based on molecular recognition processes ». Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322948.
Texte intégral
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Kushnir, Oleg. « Molecular switches based on dihydroazulene-vinylheptafulvene photochromism ». [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976115832.
Texte intégral
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Schiavo, Ebe. « Molecular mechanisms controlling immunoglobulin class switch recombination ». Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAJ084/document.
Texte intégralRésumé :
Lors des réponses immunitaires, le répertoire des lymphocytes B est diversifié par l’hypermutation somatique (HMS) et la commutation isotypique (CI), dépendant d’«activation-induced cytidine deaminase» (AID), qui introduit des lésions dans les gènes Ig. Une déficience d’AID cause un défaut d’HMS et de CI; par contre, une délétion du domaine C-terminal d’AID cause un défaut spécifique de la CI, suggérant que ce domaine interagit avec des facteurs spécifiques de la CI. Pour identifier ces facteurs, nous avons étudié une immunodéficience présentant un défaut de la CI non lié à la carence d’AID ni à un défaut d’HMS. De plus, les cassures de l’ADN ne sont pas détectées au niveau des gènes Ig suggérant qu’AID n’est pas correctement ciblée dans ces loci. Nous avons identifié et analysé des candidats : Spt6, les cohésines et le complexe Smc5/6. Dans les cellules B activées, AID interagit avec Spt6, Spt5, l’ARN polymérase II et le complexe PAF. Par contre, les cohésines pourraient réguler la structure du locus IgH lors de la CI et la voie de réparation des cassures de l’ADN générées pendant la CI. Ces résultats contribuent à une meilleure compréhension des étapes de la CIDuring immune responses, B cell repertoire is diversified through somatic hypermutation (SHM) and class switch recombination (CSR). SHM and CSR require activation-induced cytidine deaminase (AID), which induces DNA damage. While AID deficiency abrogates SHM and CSR, C-terminal truncations impair CSR without affecting SHM and it has been proposed that AID C-terminal domain associates with CSR-specific factor(s). In order to identify these factors, we studied a human CSR-specific immunodeficiency, characterized by normal SHM and AID expression. B cells from these patients do not display DSBs at switch (S) regions, suggesting that they might lack an AID-binding factor(s) required to target AID to S regions during CSR. Through a multi- approach strategy, we identified and analyzed candidate factors, including Spt6, the cohesin complex and the Smc5/6 complex. We show that, in B cells poised to undergo CSR, AID is in a complex with Spt6, Spt5, the RNA polymerase II and the PAF complex while cohesins might regulate the 3D structure of the IgH locus and the pathway of DSBs repair at the Ig S regions. Our work thus contributes to a better understanding of the CSR reaction
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Selvanathan, Pramila. « Photochromic switches for luminescence, plasmonic resonance, single molecule magnetic properties, and molecular wires for nano junctions ». Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S145.
Texte intégralRésumé :
Ce travail est consacré à la synthèse et la caractérisation des commutateurs et des fils moléculaires incorporant l'unité et le ruthénium organométalliques fractions photochromiques. La première partie traite de lanthanides complexe Yb combiné avec l'unité et le ruthénium acétylure fractions photochromiques afin de moduler la luminescence avec l'aide de redox et de stimuli lumineux. Dans la deuxième partie explique la combinaison d'unités DTE photochromiques avec des fragments acétylures de ruthénium pour fixer sur la surface de nanoparticules métalliques afin d'affiner leur résonance plasmonique grâce à la modification de l'environnement de surface en utilisant la lumière et redox stimuli. La troisième partie décrit la préparation de complexes de lanthanides combinés avec une unité photochromique spiropyranne pour commuter les propriétés SMM des complexes via photoisomérisation de l'unité spiropyranne. Dans la dernière partie, nous présentons la synthèse de Oligo (phénylène éthylène) Les fils moléculaires avec différents noyaux centraux afin d'obtenir une variété de fil avec différents niveaux d'énergie HOMO-LUMO pour vérifier l'effet de l'épinglageThis work is devoted to the synthesis and characterization of novel molecular switches and wires incorporating photochromic unit and ruthenium organometallic moieties. The first part deals with lanthanide Yb complex combined with photochromic unit and ruthenium acetylide moieties in order to modulate the luminescence with the help of redox and light stimuli. In the second part explained the combination of photochromic DTE units with ruthenium acetylide moieties to attach on the surface of metal nanoparticles in order to tune their plasmonic resonance through the surface environment modification by using light and redox stimuli. The third part describes the preparation of lanthanide complexes combined with a spiropyran photochromic unit in order to switch the SMM properties of the complexes via photoisomerization of the spiropyran unit. In the last part, we report the synthesis of Oligo(phenylene ethylene) molecular wires with different central cores in order to obtain various wire with different HOMO-LUMO energy levels to check the effect of pinning
17
Nenov, Artur. « Relation between molecular structure and ultrafast photoreactivity with application to molecular switches ». Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-150470.
Texte intégral
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Jager, Wolter Frens. « Chiroptical molecular switches application of inherently dissymmetric alkenes / ». [S.l. : [Groningen : s.n.] ; University of Groningen] [Host], 1994. http://irs.ub.rug.nl/ppn/.
Texte intégral
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Panchakshari, Rohit. « Investigating Mechanisms of DNA Double Strand Break Joining of Switch Regions During IgH Class Switch Recombination ». Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493369.
Texte intégralRésumé :
During B cell development, RAG endonuclease cleaves immunoglobulin heavy chain (IgH) V, D, and J gene segments and orchestrates their fusion as deletional events that assemble a V(D)J exon in the same transcriptional orientation as adjacent Cμ constant region exons. In mice, six additional sets of constant region exons (CHs) lie 100–200 kilobases downstream in the same transcriptional orientation as V(D)J and Cμ exons. Long repetitive switch (S) regions precede Cμ and downstream CHs. In mature B cells, class switch recombination (CSR) generates different antibody classes by replacing Cμ with a downstream CH. Activation-induced cytidine deaminase (AID) initiates CSR by promoting deoxycytidine deamination lesions within Sμ and a downstream acceptor S-region; these lesions are converted into DNA double-strand breaks (DSBs) by general DNA repair factors which are then joined by end-joining pathways. Productive CSR must occur in a deletional orientation by joining the upstream end of an Sμ DSB to the downstream end of an acceptor S-region DSB. However, the relative frequency of deletional to inversional CSR junctions has not been measured. Thus, whether orientation-specific joining is a programmed mechanistic feature of CSR as it is for V(D)J recombination and, if so, how this is achieved is unknown. To address this question, we adapt high-throughput genome-wide translocation sequencing (HTGTS) into a highly sensitive DSB end-joining assay and apply it to endogenous AID-initiated S-region in mouse B cells. We show that CSR is programmed to occur in a productive deletional orientation and does so via an unprecedented mechanism that involves in cis IgH organizational features in combination with frequent S-region DSBs initiated by AID. We further implicate ATM-kinase-dependent DSB-response (DSBR) factors including histone variant H2AX, 53BP1 and its associated effector protein Rif1 in enforcing this mechanism.
We go on to use HTGTS to study influence of different DSBR factor deficiencies on the structure of CSR junctions between AID-initiated DSBs in the 5' portion of the donor Sμ region to those across the length of downstream acceptor S regions. Based on analyses of thousands of switch junctions, we find that absence of DSBR factors leads to varying increases in micro-homology (MH)-mediated junctions, with 53BP1-deficiency having the greatest increase. However, while translocation junctions between Cas-9/gRNA-induced DSB in c-myc to AID-initiated S region DSBs in ATM- or 53BP1-deficient B cells show similar biases in MH-usage to those observed in the context CSR junctions, translocation junctions to other general DSBs genome-wide had no MH-usage increase in ATM-deficient cells and only a modest increase in 53BP1-deficient cells. We discuss these findings with respect to potential roles of AID-initiated DSBs in S regions to be especially prone to MH-usage potentially due to their increased resection along with their highly repetitive nature that provides abundant micro-homologous sequence.Medical Sciences
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Harzmann, Gero [Verfasser]. « Novel Tailor-Made Externally Triggerable Single- Molecular Switches for Molecular Electronics / Gero Harzmann ». München : Verlag Dr. Hut, 2016. http://d-nb.info/1097817806/34.
Texte intégral
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Blümmel, Pascal [Verfasser]. « Functionalization of Carbon Nanotubes with Molecular Switches / Pascal Blümmel ». Berlin : Freie Universität Berlin, 2013. http://d-nb.info/1043197958/34.
Texte intégral
22
VALENTE, Filippo. « Synthesis of Biomimetic Light-Driven E/Z Molecular Switches ». Doctoral thesis, Università degli studi di Ferrara, 2009. http://hdl.handle.net/11392/2389202.
Texte intégralRésumé :
Our work is devoted to the synthesis of new biomimetic molecular switches, capable to
convert light-energy into a E/Z isomerization process. Computational studies performed on
Rhodopsin have defined the penta-2,4-dieniminium cation as the minimal chromophore
whose excited-state mimics the one of the natural pigment responsible of the vision
mechanism. By embedding this π system into conformational rigid molecules we developed
a new class of molecular switches featuring a selective and ultra-fast light-driven E/Z
photoisomerization.
An intriguing process, we named “cyclopropyl ring-opening/nitrilium ion ring-closing
tandem reaction”, has been conveniently used to approach “one-pot” the pivotal
chromophore. The successful functionalization of these molecules potentially allows their
grafting to a peptide domain.
23
Tai, Feng-i. « Photochromic molecules in polymer switch diodes ». Thesis, Linköping University, Department of Science and Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-6810.
Texte intégralRésumé :
Photochromism has been investigated extensively during recent years. The large interest for information storage in memory applications is associated with the bi-stable character of the photochromism phenomena. In molecular photochromics, two isomers with different absorption spectrum can be obtained according to the specific wavelength of the light exposure. This reversible transformation process can be considered as optical writing/erasing step of a memory.
Here we first report the absorption spectra of solid-state films based on the blends consisting of PC molecules, the spirooxazine 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3’-[3H]phenanthr[9,10-b](1,4)oxazine] (PIII, Sigma-Aldrich, 32,256-3) and a polymer matrix host, poly(2-methoxy-5(2’-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV). The bi-stability in conjugated polymer matrix is studied by following the time evolution of the optical properties of the blends.
Thereafter, the electrical performance of PC-polymer diodes is characterized and reported. While the PIII molecules in the blend bulks are switched to their low energy gap state, forming external energy levels above the valence band of MEH-PPV, the injected charges (hole-dominated) will be trapped by the low energy gap isomer of PIII and that leads to current modulation. PIII molecules can be switched between two energy gap states upon the photo-stimulation, and the I-V characteristics of the device can also be controlled reversibly via the photoisomerization. The retention time of the diode’s electrical switching fits quite well with the absorption characteristics of the blend films; this correspondence builds a good link between the film property and the device behavior.
Furthermore, we observed a two-trap system in the blend diodes from the I-V curves, and a model is proposed which can explain the schematic concept of the trap-limited current modulation. To combine the knowledge and information from the investigations above, we tested a novel device design based on a bi-layer of the PC and polymer materials, and the promising result for future work is presented in the end.
24
Tai, Feng-I. « Photochromic molecules in polymer switch diodes ». Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-6810.
Texte intégralRésumé :
Photochromism has been investigated extensively during recent years. The large interest for information storage in memory applications is associated with the bi-stable character of the photochromism phenomena. In molecular photochromics, two isomers with different absorption spectrum can be obtained according to the specific wavelength of the light exposure. This reversible transformation process can be considered as optical writing/erasing step of a memory. Here we first report the absorption spectra of solid-state films based on the blends consisting of PC molecules, the spirooxazine 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3’-[3H]phenanthr[9,10-b](1,4)oxazine] (PIII, Sigma-Aldrich, 32,256-3) and a polymer matrix host, poly(2-methoxy-5(2’-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV). The bi-stability in conjugated polymer matrix is studied by following the time evolution of the optical properties of the blends. Thereafter, the electrical performance of PC-polymer diodes is characterized and reported. While the PIII molecules in the blend bulks are switched to their low energy gap state, forming external energy levels above the valence band of MEH-PPV, the injected charges (hole-dominated) will be trapped by the low energy gap isomer of PIII and that leads to current modulation. PIII molecules can be switched between two energy gap states upon the photo-stimulation, and the I-V characteristics of the device can also be controlled reversibly via the photoisomerization. The retention time of the diode’s electrical switching fits quite well with the absorption characteristics of the blend films; this correspondence builds a good link between the film property and the device behavior. Furthermore, we observed a two-trap system in the blend diodes from the I-V curves, and a model is proposed which can explain the schematic concept of the trap-limited current modulation. To combine the knowledge and information from the investigations above, we tested a novel device design based on a bi-layer of the PC and polymer materials, and the promising result for future work is presented in the end.
25
Ellis, Sara. « Characterisation of the cellular functions of Rho family GTPases ». Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271921.
Texte intégral
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Octavio, Leah M. (Leah Mae Manalo). « Molecular systems analysis of a cis-encoded epigenetic switch ». Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68433.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Computational and Systems Biology Program, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references.
An ability to control the degree of heterogeneity in cellular phenotypes may be important for cell populations to survive uncertain and ever-changing environments or make cell-fate decisions in response to external stimuli. Cells may control the degree of gene expression heterogeneity and ultimately levels of phenotypic heterogeneity by modulating promoter switching dynamics. In this thesis, I investigated various mechanisms by which heterogeneity in the expression of FLO 11 in S. cerevisiae could be generated and controlled. First, we show that two copies of the FLOJ1 locus in S. cerevisiae switch between a silenced and competent promoter state in a random and independent fashion, implying that the molecular event leading to the transition occurs in cis. Through further quantification of the effect of trans regulators on both the slow epigenetic transitions between a silenced and competent promoter state and the fast promoter transitions associated with conventional regulation of FLO11, we found different classes of regulators affect epigenetic, conventional, or both forms of regulation. Distributing kinetic control of epigenetic silencing and conventional gene activation offers cells flexibility in shaping the distribution of gene expression and phenotype within a population. Next, we demonstrate how multiple molecular events occurring at a gene's promoter could lead to an overall slow step in cis. At the FLO] 1 promoter, we show that at least two pathways that recruit histone deacetylases to the promoter and in vivo association between the region -1.2 kb from the ATG start site of the FLO11 ORF and the core promoter region are all required for a stable silenced state. To generate bimodal gene expression, the activator Msnlp forms an alternate looped conformation, where the core promoter associates with the non-coding RNA PWR1's promoter and terminator regions, located at -2.1 kb and -3.0 kb from the ATG start site of the FLO]1 ORF respectively. Formation of the active looped conformation is required for Msnlp's ability to stabilize the competent state without destabilizing the silenced state and generate a bimodal response. Our results support a model where multiple stochastic steps at the promoter are required to transition between the silenced and active states, leading to an overall slow step in cis. Finally, preliminary investigations of heterozygous diploids revealed possible transvection occurring at FLO] 1, where a silenced allele of FLO 11 appeared to transfer silencing factors to a desilenced FLO11 allele on the homologous chromosome. These observations suggest a new mechanism through which heterogeneity in FL011 expression could be further controlled, in addition to the molecular events at the FL011 promoter we elucidated previously.
by Leah M. Octavio.
Ph.D.
27
Weber, Christopher. « Real-time studies of coupled molecular switches in photoresponsive materials ». Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17401.
Texte intégralRésumé :
Künstliche molekulare Schalter, wie beispielsweise Azobenzole, Diarylethene, Fulgide, Stilbene oder Spiropyrane wurden in den letzten Jahren intensiv erforscht, da sie zur Datenspeicherung, in selbstheilenden Materialien, molekularer Elektronik, Energiespeichern und mikromechanischen Anwendungen eingesetzt werden können. Eine der größten Herausforderungen im Forschungsfeld der molekularen Schalter ist die Frage, wie die Photoreaktion isolierter Moleküle in eine kontrollierte Photoreaktion wohldefinierter supramolekularer Systeme, wie z.B. organischer Dünnfilme oder 3D Nanostrukturen, übersetzt werden kann. Die Integration molekularer Schalter, beispielsweise von Azobenzolen, in supramolekulare Anordnungen kann zu emergenten Phänomenen wie kooperativem Schaltverhalten führen. Kooperatives Schalten bedeutet, dass die energetische Landschaft und daher auch die Isomerisationskinetik eines einzelnen molekularen Schalters von den isomerischen Zuständen benachbarter Schalter beeinflusst werden. Kooperatives Schaltverhalten, oder überhaupt Schaltbarkeit in geordneten Ensembles molekularer Schalter auf Oberflächen bewusst zu erzeugen hat sich allerdings aufgrund von sterischer Behinderung oder Delokalisierung angeregter Zustände als schwierig herausgestellt. Deshalb wäre ein besseres Verständnis der Voraussetzungen für Schaltbarkeit und kooperatives Verhalten molekularer Schalter in supramolekularen Systemen ein großer Schritt in Hinblick auf die Entwicklung von Bauelementen, die auf der gemeinsamen Bewegung molekularer Schalter basieren. Die in dieser Arbeit erzielten Resultate gewähren neue Einblicke in das Verhältnis zwischen der Photoisomerisierung einzelner Azobenzole und der Photoreaktion supramolekularer Systeme, was dabei helfen wird, neuartige und optimierte stimulireaktive Materialien zu entwickeln.Synthetic molecular switches, such as azobenzenes, diarylethenes, fulgides, stilbenes or spiropyranes, have been intensively investigated in recent times because of their possible use in data storage, self-healing materials, molecular electronics, energy and information storage and optomechanics. One of the biggest challenges in the research field of molecular switches is the translation of the photoresponse of isolated molecules into a controlled photoresponse of well-defined supramolecular systems, such as organic thin films or functional nanostructures. The main focus of this thesis lies on the photoisomerization of multi-azobenzene compounds in different structural environments. Incorporation of molecular switches, for example azobenzene, into supramolecular assemblies can lead to emergent phenomena like cooperative switching behavior. Cooperative switching means that the energetic landscape and thus also the isomerization kinetics of a single molecular switch is influenced by the isomeric state of adjacent switches. However, it has proven difficult to establish cooperative switching behavior or even switching functionality at all in ordered ensembles of molecular switches on surfaces due to steric hindrance or delocalisation of excited states. Therefore, understanding the prerequisites for switching functionality and cooperative behavior of molecular switches in supramolecular assemblies is a crucial step towards the development of devices that make use of concerted motion of molecular switches. This thesis yields unprecedented insight into the relation between the photoisomerization of isolated azobenzenes and the photoresponse of supramolecular systems, which will ultimately help to build novel and optimized stimuli-responsive materials.
28
Desjardins, Pierre. « Novel mononuclear ruthenium bisphenylcyanamide complexes, precursors to a molecular switch ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ32430.pdf.
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McNellis, Erik R. [Verfasser]. « First-principles modeling of molecular switches at surfaces / Erik R. McNellis ». Berlin : Freie Universität Berlin, 2010. http://d-nb.info/1024784681/34.
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Scheil, Katharina [Verfasser]. « Scanning tunneling and atomic force microscopy of molecular switches / Katharina Scheil ». Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1151120391/34.
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Karan, Sujoy [Verfasser]. « Exploiting Spin Manipulation and Stereo-Isomerization in Molecular Switches / Sujoy Karan ». Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1169652719/34.
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Huber, Ludwig Alexander [Verfasser], et Henry [Akademischer Betreuer] Dube. « Indigoid molecular motors and switches / Ludwig Alexander Huber ; Betreuer : Henry Dube ». München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/123320050X/34.
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Upadhyay, Abhishek. « Molecular switches facilitate rhythms in the circadian clock of Neurospora crassa ». Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22752.
Texte intégralRésumé :
Zirkadiane Rhythmen haben sich in allen Lebensbereichen aufgrund täglicher Wechselwirkungen zwischen internen Zeitgebern und Umweltreizen entwickelt. Molekulare Oszillatoren bestehen aus einer Transkriptions-Translations-Rückkopplungsschleife (TTFL), die selbsterregte Rhythmen ermöglicht. Eine verzögerte negative Rückkopplungsschleife ist zentral für dieses genregulatorische Netzwerk. Die Theorie sagt voraus, dass selbsterregte Oszillationen robuste Verzögerungen und Nichtlinearitäten (Ultrasensitivität) erfordern. Wir untersuchen die zirkadianen Rhythmen in dem filamentösen Pilz Neurospora crassa, um die zugrundeliegenden Uhrmechanismen zu studieren. Seine TTFL umfasst den aktivierenden White Collar Complex (WCC) und den hemmenden FFCKomplex, der aus FRQ (Frequency), FRH (FRQ-interacting RNA Helicase) und CK1a (Caseinkinase 1a) besteht. Darüber hinaus gibt es mehrere Phosphorylierungsstellen auf FRQ (~100) und WCC (~ 95). FRQ wird durch CK1a phosphoryliert. Während wir die zeitliche Dynamik dieser Proteine erforschen, untersuchen wir: 1) wie multiple, langsame und zufällige Phosphorylierungen die Verzögerung und Nichtlinearität in der negativen Rückkopplungsschleife bestimmen. 2) wie Grenzzyklus-Oszillationen entstehen und wie molekulare Schalter selbsterregte
Rhythmen unterstützen. In der ersten Veröffentlichung simulieren wir FRQ-Multisite-Phosphorylierungen mit Hilfe gewöhnlicher Differentialgleichungen. Das Modell zeigt zeitliche und stationäre Schalter für die freie Kinase und das phosphorylierte Protein. In der zweiten Veröffentlichung haben wir ein mathematisches Modell von 10 Variablen mit 26 Parametern entwickelt. Unser Modell offenbarte einen Wechsel zwischen WC1-induzierter Transkription und FFC-unterstützter Inaktivierung von WC1. Zusammenfassend wurde die Kernuhr von Neurospora untersucht und dabei die Mechanismen, die den molekularen Schaltern zugrunde liegen, aufgedeckt.Circadian rhythms have evolved across the kingdoms of life due to daily interactions between internal timing and environmental cues. Molecular oscillators consist of a transcription-translation feedback loop (TTFL) allowing self-sustained rhythms. A delayed negative feedback loop is central to this gene regulatory network. Theory predicts that self-sustained oscillations require robust delays and nonlinearities (ultrasensitivity). We study the circadian rhythms in the filamentous fungi Neurospora crassa to investigate the underlying clock mechanisms. Its TTFL includes the activator White Collar Complex (WCC) (heterodimer of WC1 and WC2) and the inhibitory FFC complex, which is made of FRQ (Frequency protein), FRH (Frequency interacting RNA Helicase) and CK1a (Casein kinase 1a). Moreover, there are multiple phosphorylation sites on FRQ (~ 100) and WCC (~ 95). FRQ is phosphorylated by CK1a. While exploring the temporal dynamics of these proteins, we investigate: 1) how multiple, slow and random phosphorylations govern delay and nonlinearity in the negative feedback loop. 2) how limit cycle oscillations arise and how molecular switches support selfsustained rhythms. In the first publication, we simulate FRQ multisite phosphorylations using ordinary differential equations. The model shows temporal and steady state switches for the free kinase and the phosphorylated protein. In the second publication, we developed a mathematical model of 10 variables with 26 parameters consisting of WC1 and FFC elements in nuclear and cytoplasmic compartments. Control and bifurcation analysis showed that the model produces robust oscillations. Our model revealed a switch between WC1-induced transcription and FFC-assisted inactivation of WC1. Using this model, we also studied possible mechanisms of glucose compensation. In summary, the core clock of Neurospora was examined and mechanisms underlying molecular switches were revealed.
34
Ouyang, Jiangkun. « Helicenes for chiral molecular switches, magnetic materials, and chiral fullerene derivatives ». Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S160.
Texte intégralRésumé :
Dans ce travail de thèse, nous avons d'abord développé deux études basées sur des unités dites ''stilbène rigide'' qui sont connues pour s'interconvertir de manière réversible entre deux formes trans et cis grâce à la lumière. La première étude correspond à des photocommutateurs chiraux à base d'hélicènes, l'autre à des complexes photocommutables alcynyles d'or(I). Ensuite, nous avons examiné la synthèse et la caractérisation de complexes de Dy(III) à base d'hélicène-bipyridine comme nouveaux types d'aimants moléculaires (SMM) chiraux et comparé la différence des propriétés magnétiques entre les SMM racémique et énantiopurs. Enfin, nous avons développé la première utilisation de la cycloaddition réversible d'hélicènes racémiques sur le [60]fullerène et de sa rétrocycloaddition ultérieure comme une stratégie alternative efficace pour le dédoublement énantiomérique d'un hélicène-carboxaldéhydeIn this PhD work, we firstly developed two studies based on the so-called ''stiff stilbene'' units that are known to reversibly interconvert between two trans and cis forms through light. The first study corresponds to photoresponsive chiral switches based on helicenes, the other one to photoresponsive gold(I) complexes. Then, we dealt with the synthesis and characterization of helicene-bipyridine based Dy(III) complexes as novel kinds of chiral single molecule magnets (SMMs) and compared the difference of the magnetic properties between racemic and enantiopure SMMs. Finally, we developed the first use of the reversible sterodivergent cycloaddition of racemic helicenes onto [60]fullerene with its subsequent retro-cycloaddition as an efficient alternative strategy for the enantiomeric resolution of a helicene-carboxaldehyde
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FARINA, Grazia. « Biomimetic Light-Driven E/Z Switcher : Design and Syntesis ». Doctoral thesis, Università degli studi di Ferrara, 2011. http://hdl.handle.net/11392/2388755.
Texte intégralRésumé :
This thesis examines the design and synthesis of a new class of biomimetic switches that replicate
different aspect of the Z/E photoisomerization of rhodopsin. Theoretical studies on rhodopsin
showed that a penta-2,4-dieniminium moiety is the minimal structure responsible of the
photochemical properties of the visual pigment. By trapping this π system into conformational rigid
molecules we synthesized NAIP (N-alkylated indanylidene-pyrroline Schiff base) switches
featuring a selective and ultra-fast light-driven E/Z photoisomerization. Computational and
spectroscopic studies performed on the particular NAIPzw, have shown it constitutes the prototype
of a novel generation of electrostatic switches potentially capable to influence the conformational
state of macromolecular structures (as a protein). Our efforts are now directed towards the
functionalization of this kind of system to create the specific molecular linkages on NAIP structure
so as to allow its insertion in a peptide domain.
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Alexander, Nathan Austin. « Molecular Switches : The Design, Synthesis and Biological Applications of Photoactive Enzyme Inhibitors ». Thesis, University of Canterbury. Chemistry, 2006. http://hdl.handle.net/10092/1314.
Texte intégralRésumé :
This thesis examines the design, synthesis and biological applications of a series of inhibitors which incorporate an azobenzene photoswitch, a peptidyl backbone and a trifluoromethyl ketone warhead. The photoswitch can be isomerised by irradiation with UV or visible light and has been employed to modulate the reactivity of the enzyme. Chapter one gives a brief outline of some of the important areas related to this work. Examples of previously utilised photoswitches as well as some background on serine protease and the uses of fluorine in medicine has been covered. Chapter two outlines the synthesis of the key trifluoromethyl carbinol 2.6 by two different methods. The condensation of a fluorinated aldehyde with a nitroalkane affords an α-nitro trifluoromethyl carbinol which can be reduced to give the desired amine 2.6. Treatment of oxazolones with trifluoroacetic anhydride via a modified Dakin-West reaction gives trifluoromethyl ketones which can be reduced to give trifluoromethyl carbinols. Chapter three investigate the synthesis of substituted stilbenes and phenanthrenes as alternative molecular switches to azobenzenes. Molecular modelling of phenanthrenes suggests they may be suitable mimics of E-azobenzenes. Chapter four outlines the synthesis of a series of mono and disubstituted azobenzenes by direct sulfonation of azobenzene or by condensation of nitroso arenes with aryl amines. The switches incorporate one or two peptidyl residues designed to improve specificity towards the enzyme. Chapter five examines the photoisomerisation of eight potential inhibitors by irradiating with UV or visible light. Irradiation with UV light enriches the sample to give 78-93 % of the Z-isomer. Irradiation with visible light gave photostationary states with 14-21 % Z-isomer. Ambient photostationary states are ca. 22 % Z-isomer. Chapter six looks at the testing of five trifluoromethyl ketones as potential inhibitors ofα-chymotrypsin. The inhibitors vary in substituents, substitution patterns and chain length. The inhibitors were tested at both ambient and Z-enriched photostationary states and were found to exhibit slow binding kinetics. In all cases the Z-enriched inhibitor solution was at least 3-fold more potent than the ambient solution. Chapter seven is an experimental chapter and outlines the synthesis of the compounds prepared in this thesis.
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Taylor, Jennifer. « Engineering and improving a molecular switch system for gene therapy applications ». Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39501.
Texte intégralRésumé :
Molecular switch systems that activate gene expression by a small molecule are effective technologies that are widely used in applied biological research. Previously, two orthogonal ligand receptor pairs (OLRP) were developed as potential molecular switch systems by modifying nuclear receptors, ligand-activated transcription factors, to bind and activate gene expression with the synthetic ligand LG335 and not with the natural ligand 9-cis retinoic acid (9cRA). The two OLRP previously discovered were RXR variant 130 (I268A, I310A, F313A, and L436F) (also known as GR130) and the RXR variant QCIMFI (Q275C, I310M, and F313I) and (also known as GRQCIMFI).
The OLRP were further developed into molecular switches to provide controlled gene expression and potentially benefit gene therapy applications by replacing the DNA binding domain (DBD) with a Gal4 DBD, a yeast transcription factor. Both molecular switches are able to bind Gal4 RE in response to LG335 and activate expression of a luciferase or GFP reporter gene in either a two- or one-component system. When characterizing the GR130 variant in the two-component system, no activation was observed with the natural ligand 9cRA, and the variant displayed a 19±5-fold activation and a 50 nM EC50 value in the presence of LG335. When the GRQCIMFI variant was evaluated in the two-component system, activation was observed in the presence of LG335 with a 10 nM EC50 value and a 6±2-fold induction, and 9cRA induced activation only at the highest concentration. The GRQCIMFI variant was also characterized with the one-component system containing the reporter gene GFP in a transient transfection as well as through retroviral transduction, displaying green fluorescence in 30% of the cells in the presence of 10 µM LG335.
Several attempts were made to improve the molecular switch system. The VP16 activation domain was fused to GRQCIMFI in an effort to increase the fold induction; however, the addition of the VP16 created a constitutively active protein. Another approach to improve the molecular switch incorporated error-prone PCR to discover a new variant, Q275C, I310M, F313I, L455M (QCIMFILM), which displayed a 10-fold increase in sensitivity towards LG335 with a 5 nM EC50 value. Examination of the L455 position in the crystal structure of RXR revealed this residue is located outside of the ligand binding pocket on helix 12 (H12), but is able to significantly enhance receptor function. In fact, the single variant, L455M, was able to enhance receptor activation, compensate for a nonfunctional variant, as well as influence coactivator association.
The long-term goal of this research is to develop a gene regulation system that would be used in human gene therapy trials. In the process of creating this system a deeper assessment of the nuclear receptor structure and function is made, which can be used for the enhancement and development of transcriptional regulation mechanisms.
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Egriboz, Onur. « THE MOLECULAR MECHANISMS GOVERNING THE GAL GENE SWITCH OF SACCHAROMYCES CEREVISIAE ». The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338319985.
Texte intégral
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Harvey, Stacy L. « Regulation of entry into mitosis by a multi-state molecular switch / ». Diss., Digital Dissertations Database. Restricted to UC campuses, 2008. http://uclibs.org/PID/11984.
Texte intégral
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Han, Jinchi. « Tunneling nanoelectromechanical switches based on compressible self-assembled molecules ». Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120403.
Texte intégralRésumé :
Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 115-122).
Nanoelectromechanical (NEM) switches are investigated as a promising candidate for energy-efficient logic devices. They promise quasi-zero static leakage, large on-off current ratio, small subthreshold slope and high robustness in harsh environments. However, strong van der Waals interaction at the nanoscale usually results in high hysteresis and the risk of stiction failure, thereby bringing about an inevitably high actuation voltage and unfavorable dynamic power consumption in practical device designs. The low switching speed, poor reliability and absence of scalable manufacturing technique also set barriers to the maturation of NEM switches to complement or substitute semiconductor transistors for applications with energy constraints. To accelerate the development of NEM switches for digital logic, this thesis presents a novel squeezable NEM switch, termed a "squitch", based on direct tunneling through a metal-molecule-metal junction, whose tunneling gap can be electromechanically modulated by compressing the molecular layer. A sub-5 nm change in the tunneling gap in the absence of direct contact between electrodes leads to at least several orders of magnitude current modulation, enabling a squitch to exhibit a low actuation voltage near 2 V, a low hysteresis and a high switching speed, which support the prospects of squitches as ultra-low power beyond-CMOS devices. A scalable and versatile dielectrophoretic trapping technique for fabrication of devices involving nanoparticles in design has also been developed in this thesis as a critical fabrication step.
by Jinchi Han.
S.M.
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Presa, i. Rodríguez Andreu. « Diarylethene-based Pt(II) molecular switches : a novel approch to photoactivated chemotherapy ». Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400875.
Texte intégralRésumé :
The photoactivation of metal complexes with potential anticancer activity is a hot topic of current research, as it may lead to the development of more selective and efficient drugs. Photoactivated chemotherapy (PACT) with coordination compounds is usually based on photochemical processes taking place at the metal center. In contrast, an innovative ligand-mediated photoactivation approach that exploits the outstanding photochemical properties of diarylethenes has been developed in the present PhD thesis.
Platinum(II) complexes from dithienylcyclopentene-based photoswitchable ligands have been designed and prepared. These systems exhibit two thermally stable, interconvertible photoisomeric forms, which present clearly distinct properties. The photochemical behavior of all ligands and metal complexes has been examined by means of 1H NMR and UV-Vis spectroscopies, and a number of crystal structures have been determined.
Additionally, DFT calculations have been performed to analyze the effect produced by the attachment of different metal-binding units on the photochemical performance of the diarylethene synthon.
Subsequently, the interaction of each photoisomer of the platinum(II) complexes with DNA has been thoroughly investigated using different techniques. These studies revealed that the light-triggered transformation of these systems effectively translates into different DNA binding modes and affinities, as desired for a photoactivatable drug. The antiproliferative activity of the complexes prepared has then been evaluated through various cell viability in vitro assays, which validated the potential applications of such diarylethene-based photoswitches for the development of a new class of photochemotherapeutic metallodrugs.La fotoactivació de complexos metàl·lics amb potencial activitat antitumoral és un camp de recerca amb un interès creixent, que persegueix el desenvolupament de tractaments més selectius i eficients. Tradicionalment, la quimioteràpia fotoactivada (PACT) basada en compostos de coordinació inorgànics s'ha centrat en els processos fotoquímics que tenen lloc en el centre metàl·lic. En canvi, en aquesta tesi doctoral s'ha desenvolupat una estratègia alternativa enfocada en la fotoactivació dels lligands, aprofitant les excel·lents propietats fotoquímiques dels diariletens. Amb aquest objectiu, s'han dissenyat i preparat diferents complexos dinuclears de Pt(II) amb lligands basats en l'estructura del ditienilciclopentè. Aquestes molècules presenten dues formes fotoisomèriques interconvertibles i tèrmicament estables, que a més difereixen notablement en les seves propietats. El comportament fotoquímic dels lligands i complexos sintetitzats s'ha estudiat per mitjà d'espectroscòpia 1H RMN i UV-Vis, i d’altra banda també s'han resolt diverses estructures cristal·lines. Addicionalment, s'han emprat càlculs computacionals DFT per tal d'analitzar l'efecte sobre l'activitat fotoquímica del fragment diariletè produït per l'acoblament de diferents grups funcionals. Seguidament, s'ha investigat la interacció amb ADN de cadascun dels fotoisòmers dels complexos de Pt(II) preparats, mitjançant diferents tècniques. Els estudis realitzats han posat de manifest que la fotointerconversió d'aquest tipus de sistemes dóna lloc a diferents modes d’unió i graus d'afinitat envers l'ADN, tal i com és desitjable per un fàrmac fotoactivable. En darrer lloc, l'activitat antiproliferativa dels compostos ha estat avaluada a través de diferents assaigs cel·lulars in vitro, que han permès corroborar el gran potencial dels sistemes basats en diariletens per ser aplicats en el disseny de fàrmacs.
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Dokić, Jadranka. « Quantum mechanical study of molecular switches : electronic structure, kinetics and dynamical aspects ». Phd thesis, Universität Potsdam, 2009. http://opus.kobv.de/ubp/volltexte/2010/4179/.
Texte intégralRésumé :
Molecular photoswitches are attracting much attention lately mostly because of their possible applications in nano technology, and their role in biology.
One of the widely studied representatives of photochromic molecules is azobenzene (AB). With light, by a static electric field, or with tunneling electrons this specie can be "switched" from the flat and energetically more stable trans form, into the compact cis form. The back reaction can be induced optically or thermally. Quantum chemical calculations, mostly based on density functional theory, on the AB molecule, AB derivatives and related systems are presented. All the calculations were done for isolated species, however, with implications for latest experimental results aiming at the switching of surface mounted ABs. In some of these experiments, it is assumed that the switching process is substrate mediated, by attaching an electron or a hole to the adsorbate forming short-lived anion or cation resonances. Therefore, we calculated also cationic and anionic ABs in this work. An influence of external electric fields on the potential energy surfaces, was also studied.
Further, by the type, number and positioning of various substituent groups, systematic changes on activation energies and rates for the thermal cis-to-trans isomerization can be enforced. The nature of the transition state for ground state isomerization was investigated. Applying Eyring's transition state theory, trends in activation energies and rates were predicted and are, where a comparison was possible, in good agreement with experimental data. Further, thermal isomerization was studied in solution, for which a polarizable continuum model was employed. The influence of substitution and an environment leaves its traces on structural properties of molecules and quantitative appearance of calculated UV/Vis spectra, as well.
Finally, an explicit treatment of a solid substrate was demonstrated for the conformational switching, by scanning tunneling microscope, of a 1,5-cyclooctadiene (COD) molecule at a Si(001) surface, treated by a cluster model. At first, we studied energetics and potential energy surfaces along relevant switching coordinates by quantum chemical calculations, followed by the switching dynamics using wave packet methods. We show that, in spite the simplicity of the model, our calculations support the switching of adsorbed COD, by inelastic electron tunneling at low temperatures.Um den technologischen Fortschritt zu gewährleisten, ist man in vielen technischen Gebieten auf der Suche nach neuen und leistungsfähigeren Materialien. In der Computer- und Informationstechnologie folgte daraus die stetige Miniaturisierung von Bauelementen. Molekulare Photoschalter sind häufig an biologischen Prozessen beteiligt und äußerst vielversprechend, auf diesem Gebiet Anwendung zu finden. Ein sehr umfangreich studiertes photochromes Molekül ist Azobenzol (AB). Diese Spezien können durch Licht, statische elektrische Felder oder elektronisches Tunneln von der energetisch stabilen trans Form zur geometrisch kompakten cis Form "geschaltet" werden. Die Rückreaktion kann optisch oder thermisch erfolgen. In dieser Arbeit werden vorwiegend auf der Dichtefunktionaltheorie beruhende quantenchemische Rechnungen von AB, AB-Derivaten und verwandten Systemen vorgestellt. Alle Rechnungen betrachten isolierte Moleküle, werden jedoch in Zusammenhang mit neuesten experimentellen Ergebnissen zu oberflächengebundenen AB-Schaltern gestellt. In einigen dieser Experimente wird angenommen, dass der Schaltprozess substratvermittelt erfolgt, indem dem Adsorbat ein Elektron zugeführt oder entzogen und so eine kurzlebige anionische oder kationische Resonanz erzeugt wird. Daher werden sowohl ionische AB berechnet als auch der Einfluss eines externen elektrischen Feldes auf die Potentialhyperfläche studiert. Weiterhin können Aktivierungsenergie und Reaktionsrate der thermischen cis-trans-Isomerisierung durch Art, Anzahl und Position verschiedener Substituenten variieren. Die Natur des Übergangszustandes wird daher intensiv erforscht. Mit Hilfe der Theorie des Übergangszustandes nach Eyring werden Reaktionsraten prognostiziert, welche gut mit experimentellen Daten übereinstimmen. Daneben wird die thermische Isomerisierung in einem Lösungsmittel unter Verwendung des polarizable continuum model untersucht, da der Einfluss des Substituenten und die Anwesenheit einer Umgebung zu Veränderungen der strukturellen Eigenschaften der Moleküle und dem quantitativen Verlauf der berechneten UV/Vis-Spektren führen. Abschließend wird unter expliziter Einbeziehung eines festen Substrates das elektronisch getriebene konformale Schalten von 1,5-Cyclooctadien (COD) an einer Si(001)-Oberfläche demonstriert. Zunächst wird die Energetik und die Potentialhyperfläche entlang der relevanten Schaltkoordinaten durch quantenchemische Rechnungen ermittelt und das Schaltverhalten durch Wellenpaketmethoden beschrieben. Trotz der Einfachheit wird gezeigt, dass ein derartiges Modell das elektronische Schalten von adsorbiertem COD bei niedrigen Temperaturen gut beschreibt.
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Brazdova, Barbora. « Synthesis and studies of carbohydrate mimetics as glycosidase inhibitors and molecular switches ». Scholarly Commons, 2006. https://scholarlycommons.pacific.edu/uop_etds/2651.
Texte intégralRésumé :
Part I . We explored the synthesis of a C -glycoside synthesis from L-fucose and malononitrile in the presence of a base catalyst. The reaction was much faster than the previously studied Henry condensation, and went further---to a double cyclization of 2:1 adduct with a novel dioxabicyclic structure. It provides a new route for the synthesis of chiral polysubstituted dihydropyrans and dihydropurans. A series of carbasugars was synthesized and tested for inhibitory activity towards fungal glycosidases from Aspergillus oryzae and Penicillium canescens . In order to reveal the dependence of inhibition on the alkyl group R, several derivatives with variable alkyl chain lengths were prepared and screened. Part II . Cyclohexane-based conformationally controlled ionophores, an emerging new class of molecular switches, provide a new and promising approach to allosteric systems with negative cooperativity. Protonation of trans -2-aminocyclohexanols was observed to cause dramatic conformational changes: due to an intramolecular hydrogen bond, a conformer with equatorial position of ammonio- and hydroxy-groups becomes predominant. This signal is mechanically transmitted by the structure of the molecule, inducing a conformational change in the second site and decreasing its affinity for an appropriate guest. Thus, these structures can serve as powerful conformational pH-triggers. The trans -2-aminocyclohexanol moiety has been used for pH-triggered conformational switching of crown ethers and podands, and their complexes with metal ions. The variation of the NR 2 group allows broad tuning of the conformational equilibrium, and thus tuning of the complexing ability of these allosteric ionophores. Heterotropic allosteric systems with high negative cooperativity may find many applications, such as membrane transport and drug delivery.
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Maldonado, Illescas María del Pilar. « Spin Crossover Phenomena : Towards Molecule-based Memories and Switches ». Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/444445.
Texte intégralRésumé :
Avui en dia, la idea d'utilitzar molècules com a base de dispositius electrònics desperta molt d'interés en la comunitat científica arreu del món. La capacitat d'emmagatzemament d'informació des d'un punt de vista tecnològic creix a nivell exponencial i depén del desenvolupament en Nanociència. L'objectiu és l'emmagatzemament de dades ràpidament i amb miniaturització dels dispositius. Amb aquesta idea en ment, una de les estratègies més interessants està basada en el concepte de biestabilitat entre dos estats electrònics en una molècula, és a dir, anar d'un estat inicial (OFF) a un estat final (ON) sota la influència d'un estímul extern.
En la present tesi, per una banda, hem sintetitzat nous materials de transició d'espín aniònics amb lligams derivats de 1,2,4-triazol amb la intenció de ser una matèria primera en l'obtenció de materials funcionals, aconseguint així trímers amb transició d'espín per sobre temperatura ambient. A més a més, amb una TTIESST rècord en aquest tipus de compostos. També, per mitjà d'intercanvi catiònic hem aconseguit un nou compost amb propietats magnètiques diferents a l'original.
D'altra banda, hem estudiat diferents composites a partir d'un polímer conductor y compostos de transició d'espín, concretament trímers i polímers amb lligams derivats del 1,2,4-triazol, amb la finalitat de modificar les propietats elèctriques i termoelèctriques y generar una sinergia entre els comportaments magnètic i elèctric.Hoy en día, la idea de que una molécula pueda ser usada como base en un dispositivo electrónico despierta mucho interés en toda la comunidad científica en todo el mundo. La capacidad de almacenamiento de información desde un punto de vista tecnológico crece a nivel exponencial y depende del desarrollo en Nanociencia. El objetivo es el almacenamiento de datos rápidamente y con la miniaturización de los dispositivos y por ello, una de las más alentadoras estrategias está basada en el concepto de biestabilidad entre dos estados electrónicos en una molécula yendo de un estado inicial (OFF) a otro estado final (ON) bajo la influencia de un estímulo externo. En la presente tesis, por una parte, hemos sintetizado nuevos materiales de transición de espín aniónicos con ligandos derivados del 1,2,4-triazol con la intención de ser una materia prima en el empleo de materiales funcionales, obteniendo así trímeros con transición de espín por encima de temperatura ambiente y, además, con una TTIESST récord en este tipo de compuestos. Además, mediante el intercambio catiónico hemos logrado modificar sus propiedades magnéticas en base al compuesto original. Por otra parte, hemos estudiado diferentes composites a partir de un polímero conductor y compuestos de transición de espín, concretamente trímeros y polímeros con ligandos derivados del 1,2,4-triazol, con el fin de modificar las propiedades eléctricas y termoeléctricas y crear una sinergia entre comportamientos magnético y eléctrico.
Nowadays, the idea that molecules can be used as basis in an electronic device arouses scientific community around the World. The information storage capacity from technological demand a growing exponentially and depend on the development of Nanoscience. The aim is the storage of data quicker and the miniaturization of the devices and because of this, one of the most promising strategies is based on the concept of bistability between two electronic states of a molecule passing from an initial state (OFF) to a finale state (ON) under the influence of an external stimulus. In this thesis, on one hand, we synthetized successfully new anionic spin crossover materials with 1,2,4- triazole derivatives as coordinated ligand being used in multifunctional materials, obtaining trimers with spin transition above room temperature and in addition, with a record TTIESST in this kind of compounds. Moreover, with a cation exchange, we carried out to tune new compounds modifying theirs magnetic properties. On the other hand, we have studied several composites since a conductor polymer and spin transition compounds, specifically trimers and polymers with 1,2,4- triazole derivative ligands, with the purpose of modify the electrical and thermoelectric properties and create a synergy between the magnetic, electrical and thermoelectric behavior.
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Santos, Ana Rita Faria dos. « CD5, a molecular switch regulating signaling at the surface of T cells ». Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13747.
Texte intégralRésumé :
Mestrado em Biologia Molecular e CelularT cell receptor recognition of peptide-MHC expressed on antigen presenting cells (APC) involves the formation of a tight cell-cell contact area, named immunological synapse. Upon successful T cell activation, several signal transduction pathways are triggered culminating with the induction of gene transcription. The T cell surface glycoprotein CD5, an inhibitor of TCR signaling, is one of the molecules that targets to the immunological synapse upon T cell activation, although no ligand in the APCs has yet been discovered. We have determined that a sequence containing two tyrosine residues (Y429 and Y441) within the cytoplasmic domain of CD5 is determinant both in the inhibitory function as well as in the synaptic localization of the molecule. In the current project we dissect the role of each of the two tyrosine residues in the modulatory properties of CD5. For this purpose, tyrosine-to-phenylalanine substitutions were introduced in the CD5 molecule, which was expressed in a CD5- negative T cell line. These mutants will be relevant for unveiling the molecular mechanisms induced upon T cell receptor-mediating triggering, such as intracellular phosphorylation, calcium signals and proliferation. Our results in calcium and proliferation assays confirm the inhibitory role of the ITAM sequence, and more precisely, of the Y429 residue, although the other tyrosine may also play a somewhat lesser part. These mutants will also be analyzed by fluorescence microscopy for their ability to translocate to the immunological synapse upon T cell interaction with superantigen-loaded APCs. An additional CD5 mutant, one devoid of the extracellular domain, will also be monitored and will determine the requirement for an APCexpressed ligand to induce CD5 translocation to the synapse. We found two new putative intracellular binding partners that can be part of, and help assembling, CD5 signalosomes. In vitro studies show that CD5 can associate with the adapter protein Crk, maybe acting as a bridge to other protein-protein interactions. On the other hand, the calcium-binding protein S100A4 also associates with CD5, Fyn and Lck. We hypothesized that S100A4 controls Lck-dependent Tcell proliferation and Fyn-dependent differentiation of T helper subsets through a CD5-dependent mechanism, highlighting once again a putative role of CD5 as a molecular switch. In the future, CD5 can be used as a therapeutic target in order to modulate immune responses.
O reconhecimento por parte do receptor de células T (TCR) de péptidos processados e apresentados pelas células apresentadoras de antigénios (APC) via MHC envolve a formação de uma zona de contacto célula-célula, chamada sinapse imunológica. Após ativação das células T, diversas vias de sinalização celular são ativadas culminando na indução de transcrição génica. A glicoproteína de superfície, CD5, é considerada um inibidor da ativação via TCR, sendo uma das primeiras moléculas a ser recrutada para a sinapse imunológica após ativação da célula T. No entanto, até ao momento nenhum ligando na célula apresentadora de antigénios foi devidamente identificado e aceite como sendo o ligando do CD5. No nosso grupo, foi estabelecido que a sequência da cauda citoplasmática do CD5 que contém dois resíduos de tirosina (Y429 e Y441) é determinante para a sua função inibitória bem como para a translocação desta molécula para a sinapse imunológica. Neste projeto, propomos dissecar o papel de cada uma destas duas tirosinas nas propriedades modulatórias do CD5. Com esse propósito, foram introduzidas substituições na molécula do CD5, substituindo cada uma das referidas tirosinas por fenilalaninas. Estes mutantes foram expressos numa linha celular negativa para a expressão de CD5 endógeno e ajudarão a desvendar os mecanismos moleculares induzidos após ativação das células T e através dos quais o CD5 exerce o seu papel inibitório, avaliando por exemplo, fosforilação intracelular, fluxos de cálcio, e proliferação. Os nossos resultados nos ensaios de cálcio e de proliferação vieram confirmar o papel inibitório do pseudo-ITAM e, mais precisamente, da tirosina Y429. Estes mutantes serão também analisados por microscopia de fluorescência para avaliar a sua responsabilidade na mobilização do CD5 para a sinapse imunológica. Adicionalmente, será também monitorizada esta mobilização num mutante desprovido da porção extracelular, de forma a determinar a necessidade de estimulação por parte de um ligando expresso na célula apresentadora de antigénios. Um dos nossos resultados pioneiros mostram uma associação entre o CD5 e a proteína adaptadora Crk, que poderá funcionar como uma ponte para outras interações. A proteína dependente de cálcio S100A4 também se associa com CD5 bem como a Fyn e Lck, levando-nos a propor que S100A4 controla os mecanismos de proliferação e de diferenciação de populações de células T auxiliares, dependentes de Lck e de Fyn, respetivamente, através de um mecanismo dependente do CD5. No futuro, CD5 poderá ser usado como alvo terapêutico com o objetivo de modular a resposta imune.
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Nenov, Artur [Verfasser], et Regina de [Akademischer Betreuer] Vivie-Riedle. « Relation between molecular structure and ultrafast photoreactivity with application to molecular switches / Artur Nenov. Betreuer : Regina de Vivie-Riedle ». München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2012. http://d-nb.info/1029288372/34.
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Kukolj, George. « Protein-DNA interactions regulating the lytic-lysogenic switch in transposable Mu-like bacteriophage D108 ». Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39356.
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D108 is a temperate, transposable bacteriophage of Escherichia coli, that is closely related to phage Mu. Multiple protein-DNA regulatory complexes span the D108 left-end intergenic region during different stages of phage development. A diverging and asymmetric pattern of transcription is initiated from the opposing Pc and Pe promoters in this region. During lysogeny, the phage genome remains quiescent through the action of c repressor, expressed from the Pc promoter. DNase I footprinting revealed that oligomers of c repressor bind two operators (O1 and O2), one of which (O2) overlaps the early promoter (Pe) such that bound c repressor prevented RNA polymerase binding and transcription of the early operon. During lytic growth, transcription of the early (transposase) operon is controlled by the phage encoded ner repressor in conjunction with the host protein IHF. The purified Ner protein, an 8.6 kDa monomer, bound a large region that overlaps the transcription initiation sites for both the repressor (Pc) and early (Pe) promoters. This operator spans five turns of the DNA helix and is composed of two 11 bp inverted repeats separated by an 8 bp AT-rich spacer. Enzymatic and chemical footprinting studies, in addition to protein cross-linking experiments, indicated that the structural features of Ner-DNA binding represent a novel form of such interactions. The apex of the intrinsically bent ner-operator was localized to the AT-rich spacer. This operator was conformationally altered upon Ner binding. In the absence of IHF, bound Ner prevented RNA polymerase from binding to either Pc or Pe. However, in the presence of IHF, which binds and bends the DNA upstream of Pe, RNA polymerase associated with Pe irrespective of the Ner-DNA complex. The IHF-induced DNA structural change may partially relieve Ner repression of the early promoter, thus ensuring stable transposase gene expression during lytic phage development. Molecular analysis of these protein-DNA interactions has
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Tameling, Wladimir Igor Leander. « Disease resistance proteins of the NBS-LRR class : molecular switches of plant defense ». [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2005. http://dare.uva.nl/document/88684.
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Upadhyay, Abhishek [Verfasser]. « Molecular switches facilitate rhythms in the circadian clock of Neurospora crassa / Abhishek Upadhyay ». Berlin : Humboldt-Universität zu Berlin, 2021. http://d-nb.info/1232239488/34.
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Benchohra, Amina. « Magnetic molecular switches : from their synthesis to their integration into hybrid (nano)materials ». Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS489.
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Les commutables moléculaires sont des molécules qui peuvent moduler leurs propriétés (physiques, chimiques) sous l'influence d'un stimulus externe). Les remarquables propriétés des objets ont suscité un vif intérêt dans l'électronique moléculaire, et plus généralement, dans le domaine des matériaux multifonctionnels. Ce projet de thèse s'est inscrit dans le cadre d'une première collaboration entre les équipes ERMMES et Polymères de l'Institut Parisien de Chimie Moléculaire (IPCM). L' objectif a consisté à développer des voies de synthèses générales de (nano)matériaux hybrides à partir de commutables moléculaires magnétiques. Ce travail s'est essentiellement appuyé sur l'utilisation de complexes à transition de spin ainsi que sur une famille de composés cyanurés Fe/Co photomagnétiques. Ces systèmes ont été fonctionnalisés à leur périphérie, sur les ligands "scorpionates" de type tris(pyrazolyl)borate utilisés pour leur préparation. L'influence du groupement fonctionnel sur les propriétés des différents commutables a ensuite été étudiée, afin de déterminer les meilleurs candidats pour la conception des matériaux hybrides. Finalement, la déposition ou l'intégration des commutables magnétiques fonctionnalisés sur surfaces ou dans des polymères organiques respectivement, a été approchée par différentes méthodes en solution. Ce manuscrit reprend ainsi l'ensemble de ces étudesMolecular switchesare molecules that can asdjust their(chemical, physical) properties in response to an external stimulus. The fascinating properties of molecular switches have drawn most attention in molecular electronics and more generally in advances materials research. This PhD project was developped at the frontiers of ERMMES and Polymeres research themes, in the framework of a first collaboration. Our major interest was to establish reliable synthetic routes for the design of hybrid (nano)materials based on magnetic molecular switches. The work was particularly focused on spin crossover complexes and a family of photomagnetic cyanide-bridged Fe/Co cages. These switches were first functionalized at their periphery, on the tris(pyrazolyl)borate capping ligand used for their synthesis. The functionalization influence on the switches properties were carried out to target the best candidates for hybrid materials design. Then, we dedicated efforts on the intergration of magnetic molecular switches into two main classes of materials, (i) surfaces and (ii) organic polymers, through wet-chemistry approaches. This manuscript combines this set of studies