Littérature scientifique sur le sujet « Molecular Switche »
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Articles de revues sur le sujet "Molecular Switche"
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Burlando, Martina, Gabriella Fabbrocini, Claudio Marasca, Paolo Dapavo, Andrea Chiricozzi, Dalma Malvaso, Valentina Dini et al. « Adalimumab Originator vs. Biosimilar in Hidradenitis Suppurativa : A Multicentric Retrospective Study ». Biomedicines 10, no 10 (9 octobre 2022) : 2522. http://dx.doi.org/10.3390/biomedicines10102522.
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This study aimed to compare adalimumab originator vs. biosimilar in HS patients, and to evaluate the effect of a switch to a biosimilar, or a switch back to the originator, in terms of treatment ineffectiveness. Patients with a diagnosis of HS were enrolled from 14 Italian sites. Treatment ineffectiveness was measured using Hurley score. The major analyses were 1) comparison between the two treatment groups (non-switcher analysis), and 2) the cross-over trend of Hurley score between treatment switchers (switcher analysis). Cox and Poisson regression models were used to compare the treatment ineffectiveness between groups. A total of 326 patients were divided into four groups: 171 (52.5%) taking originator; 61 (18.7%) patients taking biosimilar; 66 (20.2%) switchers; 28 (8.6%) switchers from originator to biosimilar and switched. A greater loss of efficacy was observed in the group allocated to the biosimilar than the originator group. The switcher analysis showed an effectiveness loss in the biosimilar compared to the originator. These results seem to indicate that a switch from one drug to the other may lead to a greater risk of inefficacy. A return to the previous treatment also does not ensure efficaciousness.
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Ho, P. Joy, Ross D. Brown, Gregory J. Pelka, Antony Basten, John Gibson et Douglas E. Joshua. « Illegitimate switch recombinations are present in approximately half of primary myeloma tumors, but do not relate to known prognostic indicators or survival ». Blood 97, no 2 (15 janvier 2001) : 490–95. http://dx.doi.org/10.1182/blood.v97.2.490.
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Abstract The myeloma plasma cell is a postgerminal center, isotype-switched B cell. Chromosomal translocations into immunoglobulin heavy chain (IgH) switch regions, recombination sites in isotype switching, were initially demonstrated in myeloma cell lines but only a limited number of primary tumors. Molecular cytogenetics have since been applied to a series of primary tumors, in which IgH translocations accounted for many recurrent aberrations, among numerous nonrecurrent changes of unknown significance. This study, therefore, examined primary myeloma for IgH switch translocations using an established Southern blot assay that detected illegitimate switch recombinations. Sensitivity of the method was established by confining the analysis to 21 samples (4 stable, 17 progressive disease) with demonstrable legitimate isotype switches, of a total of 60 samples. Illegitimate recombinations were found in 12 or 57% (1 stable, 11 progressive) of 21 samples, comparable with estimates by molecular cytogenetics. The presence of switch translocations was supported by demonstrating up-regulated expression in myeloma marrow of cyclin D1 and fibroblast growth factor receptor 3 (FGFR3), candidate oncogenes on chromosomes 11q13 and 4p16, respectively. Illegitimate switches were detected most frequently in Sμ, with more than one region involved in 6 cases. Although these results confirmed the presence of switch translocations in primary myeloma, their absence in 43% of cases may imply heterogeneity of pathogenesis. In progressive disease, there was no significant difference between patients with and without illegitimate switches in survival, nor the prognostic indicators of β2microglobulin (β2m) and serum thymidine kinase (STK). Hence IgH switch translocations as a single entity are unlikely to be a feature of disease progression or have prognostic significance.
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Scognamiglio, Viviana, et Amina Antonacci. « Structural Changes as a Tool for Affinity Recognition : Conformational Switch Biosensing ». Crystals 12, no 9 (27 août 2022) : 1209. http://dx.doi.org/10.3390/cryst12091209.
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Biosensors draw inspiration from natural chemosensing based on molecular switches between different bond-induced conformational states. Proteins and nucleic acids can be adapted into switch-based biosensors with a wide plethora of different configurations, taking advantage of the variety of transduction systems, from optical to electrochemical or electrochemiluminescence, as well as from nanomaterials for signal augmentation. This review reports the latest trends in conformational switch biosensors reported in the literature in the last 10 years, focusing on the main representative and recent examples of protein-based switching biosensors, DNA nanomachines, and structure-switched aptamers being applied for the detection of a wide range of target analytes with interest in biomedical and agro-environmental sectors.
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Glintborg, Bente, Anne Gitte Loft, Emina Omerovic, Oliver Hendricks, Asta Linauskas, Jakob Espesen, Kamilla Danebod et al. « To switch or not to switch : results of a nationwide guideline of mandatory switching from originator to biosimilar etanercept. One-year treatment outcomes in 2061 patients with inflammatory arthritis from the DANBIO registry ». Annals of the Rheumatic Diseases 78, no 2 (5 novembre 2018) : 192–200. http://dx.doi.org/10.1136/annrheumdis-2018-213474.
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ObjectivesReal-world evidence on effectiveness of switching to biosimila r etanercept is scarce. In Denmark, a nationwide guideline of mandatory switch from 50 mg originator (ETA) to biosimilar (SB4) etanercept was issued for patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA) and axial spondyloarthritis (AxSpA) in 2016. Clinical characteristics and treatment outcomes were studied in ETA-treated patients, who switched to SB4 (switchers) or maintained ETA (non-switchers). Retention rates were compared with that of a historic cohort of ETA-treated patients. Switchers who resumed ETA treatment (back-switchers) were characterised.MethodsObservational cohort study based on the DANBIO registry. Treatment retention was explored by Kaplan-Meier plots and Cox regression (crude, adjusted).Results1621 (79%) of 2061 ETA-treated patients switched to SB4. Disease activity was unchanged 3 months’ preswitch/postswitch. Non-switchers often received 25 mg ETA (ETA 25 mg pens/syringes and powder solution were still available). One-year adjusted retention rates were: non-switchers: 77% (95% CI: 72% to 82%)/switchers: 83% (79% to 87%)/historic cohort: 90% (88% to 92%). Patients not in remission had lower retention rates than patients in remission, both in switchers (crude HR 1.7 (1.3 to 2.2)) and non-switchers (2.4 (1.7 to 3.6)). During follow-up, 120 patients (7% of switchers) back-switched to ETA. Back-switchers’ clinical characteristics were similar to switchers, and reasons for SB4 withdrawal were mainly subjective.ConclusionSeventy-nine per cent of patients switched from ETA to SB4. After 1 year, adjusted treatment retention rates were lower in switchers versus the historic ETA cohort, but higher than in non-switchers. Withdrawal was more common in patients not in remission. The results suggest that switch outcomes in routine care are affected by patient-related factors and non-specific drug effects.
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Gohil, S. « POS0626 MONEY MATTERS : ASSESSING THE VALUE OF THE ADALIMUMAB BIOSIMILAR SWITCH FOR RHEUMATOLOGY PATIENTS ». Annals of the Rheumatic Diseases 80, Suppl 1 (19 mai 2021) : 551.2–551. http://dx.doi.org/10.1136/annrheumdis-2021-eular.2566.
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Background:The adalimumab biosimilar switch plan, actioned 2018-19 was one of the most complex of all biologic switches across several specialties. Non-medical switches are considered to ensure the best value medicines are prescribed for patients in line with NICE Technology Appraisals.Objectives:This 2 year follow up review explores the value of the switch for Rheumatology (R) patients in comparison to two other major specialisms; Dermatology (R) and Gastroenterology (G).Methods:403 homecare (HC) patients had been identified as eligible for switch to a citrate containing biosimilar (R;189, G;176, D;38) between April-December 2019. 35 hospital FP10 patients receiving the citrate-free originator biologic were also identified for switch to the citrate containing biosimilar and prescription processing via HC (R; 24, G; 9, D;2). Biosimilar switch information was communicated via patient letters/clinic reviews. FP10 patients also received remote pharmacist telephone support, as part of a PDSA (Plan, Do, Study, Act) quality improvement pilot. Data in regard to switch refusal, treatment cessation, withheld treatment and patient satisfaction ratings for pharmacist phonecalls (1 = unsatisfactory, 5=very satisfied) was documented.Results:235/403 HC patients successfully switched (R;99, G;107, D;29). 64/403 HC patients switched back to the originator (R;47, G;12; D;5). Of the 64 switch back HC patients; 52% = reported lack of efficacy; 27% = injection site pain and 21% = various other factors such as blepharitis, insomnia and hair loss. 38/403 HC patients refused the switch and remained on the originator biologic (R;11, G;27, D;0). 31/403 HC patients switched to an alternative biologic (R;19, G;9, D;3). 32/403 HC patients stopped treatment (R;13, G;19, D;0). Treatment was withheld for 3/403 HC patients (R;0, G;2, D;1). 100% of FP10 patients switched to HC. 31/35 FP10 patients switched to the biosimilar (R; 22, G; 7, D; 2). 3/31 patients switched back to the originator due to lack of efficacy or side effects. 4 patients refused the switch to biosimilar (R;3, G;1, D;0). 89% of patients were very satisfied with the pharmacist telephone support.Conclusion:In summary, 58% of all eligible HC patients switched in comparison to 89% of FP10 patients who received pharmacist telephone support; total cost saving following HC and FP10 switch = £270,000. Rheumatology demonstrated the least success in HC switching (52%) and the highest HC switch back figure (25%). Injection site pain and subjective lack of efficacy appear to be the main reasons for ongoing switch backs. The PDSA project demonstrates that a thorough pharmacist assessment of patient concerns in rationalising the use of a biologic agent versus biosimilar can be valuable for patients. Further cost effective adalimumab biosimilars have recently been launched. This seminal review emphasises the ongoing need for robust critical appraisals of biosimilars, with consideration for both clinical and cost effective parameters, before establishing their placement in treatment pathways.Acknowledgements:Mark Easter, UHCW and Interim Integrated Care System Chief Pharmacist, Hardeep Bagga, Deputy Chief Pharmacist, UHCW Pharmacy Homecare Team and UHCW Specialist Rheumatology, Gastroenterology and Dermatology Clinical Teams.Disclosure of Interests:None declared
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Mott, Helen R., et Darerca Owen. « Allostery and dynamics in small G proteins ». Biochemical Society Transactions 46, no 5 (9 octobre 2018) : 1333–43. http://dx.doi.org/10.1042/bst20170569.
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The Ras family of small guanine nucleotide-binding proteins behave as molecular switches: they are switched off and inactive when bound to GDP but can be activated by GTP binding in response to signal transduction pathways. Early structural analysis showed that two regions of the protein, which change conformation depending on the nucleotide present, mediate this switch. A large number of X-ray, NMR and simulation studies have shown that this is an over-simplification. The switch regions themselves are highly dynamic and can exist in distinct sub-states in the GTP-bound form that have different affinities for other proteins. Furthermore, regions outside the switches have been found to be sensitive to the nucleotide state of the protein, indicating that allosteric change is more widespread than previously thought. Taken together, the accrued knowledge about small G protein structures, allostery and dynamics will be essential for the design and testing of the next generation of inhibitors, both orthosteric and allosteric, as well as for understanding their mode of action.
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Harris, Jared D., Mark J. Moran et Ivan Aprahamian. « New molecular switch architectures ». Proceedings of the National Academy of Sciences 115, no 38 (16 juillet 2018) : 9414–22. http://dx.doi.org/10.1073/pnas.1714499115.
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In this paper we elaborate on recently developed molecular switch architectures and how these new systems can help with the realization of new functions and advancement of artificial molecular machines. Progress in chemically and photoinduced switches and motors is summarized and contextualized such that the reader may gain an appreciation for the novel tools that have come about in the past decade. Many of these systems offer distinct advantages over commonly employed switches, including improved fidelity, addressability, and robustness. Thus, this paper serves as a jumping-off point for researchers seeking new switching motifs for specific applications, or ones that address the limitations of presently available systems.
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Rowe, Helen. « Satellite DNA arrays barcode chromosomes to regulate genes ». Open Access Government 36, no 1 (5 octobre 2022) : 138–39. http://dx.doi.org/10.56367/oag-036-10174.
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Satellite DNA arrays barcode chromosomes to regulate genes In this piece, Dr Helen Rowe summarizes how arrays or strings of multi-copy satellite DNAs can barcode chromosomes to regulate cell fate, by acting as molecular switches. Rowe explores Dark matter in relation to DNA and its unknown function and that makes up a huge 98% of our genome. Intense research in this area has revealed that dark matter contributes to gene-regulatory networks that serve to control where and when sets of genes are switched ON or OFF. Specialised cell types work by each expressing a unique set of genes: for example, a cell that functions in the adaptive immune system, such as an activated T cell, will switch on a different subset of genes than a neuron in the brain. Likewise, development is a highly regulated process, whereby different sets of genes are progressively switched on in different tissues. Thus, the dark matter within our genome contributes to the control of gene regulatory networks and biological systems.
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Li, Ming. « Delay Analysis of Networked Control Systems Based on 100 M Switched Ethernet ». Scientific World Journal 2014 (2014) : 1–7. http://dx.doi.org/10.1155/2014/751491.
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For the delay may degrade the performance of networked control systems, networked control systems based on 100 M switched Ethernet are proposed in this paper. According to the working principle of Ethernet switch, the formulas of the upper bound delay of the single-level switched Ethernet and the multiple-level switched Ethernet are deduced by the timing diagram method, and the values of the upper bound delay are also given. The key factors that influence the upper bound delay of switched Ethernet are analyzed; then, the characteristics of the upper bound delay are presented, which show that the delay induced by the single-level 100 M switched Ethernet has little effect on the performance of control systems, while the delay induced by the multiple-level 100 M switched Ethernet may meet the time requirements of all classes of control systems if the numbers of levels and the numbers of nodes connecting to switches are set properly. Finally, the performance of networked control systems is simulated by TrueTime, and the results further show the feasibility and superiority of 100 M switched Ethernet based networked control systems without modification of the network protocols.
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Pokhilko, Alexandra, Oliver Ebenhöh, W. Marshall Stark et Sean D. Colloms. « Mathematical model of a serine integrase-controlled toggle switch with a single input ». Journal of The Royal Society Interface 15, no 143 (juin 2018) : 20180160. http://dx.doi.org/10.1098/rsif.2018.0160.
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Dual-state genetic switches that can change their state in response to input signals can be used in synthetic biology to encode memory and control gene expression. A transcriptional toggle switch (TTS), with two mutually repressing transcription regulators, was previously used for switching between two expression states. In other studies, serine integrases have been used to control DNA inversion switches that can alternate between two different states. Both of these switches use two different inputs to switch ON or OFF. Here, we use mathematical modelling to design a robust one-input binary switch, which combines a TTS with a DNA inversion switch. This combined circuit switches between the two states every time it receives a pulse of a single-input signal. The robustness of the switch is based on the bistability of its TTS, while integrase recombination allows single-input control. Unidirectional integrase-RDF-mediated recombination is provided by a recently developed integrase-RDF fusion protein. We show that the switch is stable against parameter variations and molecular noise, making it a promising candidate for further use as a basic element of binary counting devices.
Thèses sur le sujet "Molecular Switche"
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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.
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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.
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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.
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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.
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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.
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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.
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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.
Texte intégralLivres sur le sujet "Molecular Switche"
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L, Feringa Ben, dir. Molecular switches. Weinheim : Wiley-VCH, 2001.
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Feringa, Ben L., et Wesley R. Browne, dir. Molecular Switches. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527634408.
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Nishikawa, Michihiro. Photofunctionalization of Molecular Switch Based on Pyrimidine Ring Rotation in Copper Complexes. Tokyo : Springer Japan, 2014. http://dx.doi.org/10.1007/978-4-431-54625-2.
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Pines, Maya. From egg to adult : What worms, flies, and other creatures can teach us about the switches that control human development. Sous la direction de Howard Hughes Medical Institute. Bethesda, Md : Howard Hughes Medical Institute, 1992.
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Petros, Kefalas, Păun Gheorghe 1950-, Rozenberg Grzegorz, Salomaa Arto et SpringerLink (Online service), dir. Membrane Computing : 8th International Workshop, WMC 2007 Thessaloniki, Greece, June 25-28, 2007 Revised Selected and Invited Papers. Berlin, Heidelberg : Springer-Verlag Berlin Heidelberg, 2007.
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Sardi, Bill. The anti-aging pill : Is the 125-year life span about to become common ? Scientists find the genetic switch for longevity and a natural molecule that turns it on. San Dimas, CA : Here and Now Books, 2004.
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Feringa, Ben L., dir. Molecular Switches. Wiley, 2001. http://dx.doi.org/10.1002/3527600329.
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Feringa, Ben L., et Wesley R. Browne. Molecular Switches. Wiley & Sons, Incorporated, John, 2011.
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Feringa, Ben L., et Wesley R. Browne. Molecular Switches. Wiley & Sons, Incorporated, John, 2011.
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Paradise, Christopher J., et A. Malcolm Campbell. Molecular Switches. Momentum Press, 2016.
Trouver le texte intégralChapitres de livres sur le sujet "Molecular Switche"
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de Jong, Jaap, Ben L. Feringa et Jan van Esch. « Responsive Molecular Gels ». Dans Molecular Switches, 517–61. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527634408.ch14.
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de Silva, A. Prasanna, Thomas P. Vance, Boontana Wannalerse et Matthew E. S. West. « Molecular Logic Systems ». Dans Molecular Switches, 669–96. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527634408.ch18.
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Browne, Wesley R., et Ben L. Feringa. « Chiroptical Molecular Switches ». Dans Molecular Switches, 121–79. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527634408.ch5.
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Warford, C. Chad, Vincent Lemieux et Neil R. Branda. « Multifunctional Diarylethenes ». Dans Molecular Switches, 1–35. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527634408.ch1.
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Ciardelli, Francesco, Simona Bronco, Osvaldo Pieroni et Andrea Pucci. « Photoswitchable Polypeptides ». Dans Molecular Switches, 321–60. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527634408.ch10.
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Amendola, Valeria, Marco Bonizzoni et Luigi Fabbrizzi. « Ion Translocation within Multisite Receptors ». Dans Molecular Switches, 361–98. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527634408.ch11.
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Mendonça, Cleber R., Débora T. Balogh, Leonardo De Boni, David S. dos Santos, Valtencir Zucolotto et Osvaldo N. Oliveira. « Optically Induced Processes in Azopolymers ». Dans Molecular Switches, 399–422. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527634408.ch12.
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Sekkat, Zouheir, et Wolfgang Knoll. « Photoresponsive Polymers ». Dans Molecular Switches, 423–515. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527634408.ch13.
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Volgraf, Matthew, Matthew Banghart et Dirk Trauner. « Switchable Proteins and Channels ». Dans Molecular Switches, 563–93. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527634408.ch15.
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Balzani, Vincenzo, Monica Semeraro, Margherita Venturi et Alberto Credi. « Reading and Powering Molecular Machines by Light ». Dans Molecular Switches, 595–627. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527634408.ch16.
Texte intégralActes de conférences sur le sujet "Molecular Switche"
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Avanessian, Tadeh, et Gisuk Hwang. « Adsorption-Controlled Thermal Switch Using Nonequilibrium Molecular Dynamics Simulation ». Dans ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66707.
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A thermal switch is a system to control the heat transfer “on/off” for the desired functionalities, and this serves as a basic building block to design advanced thermal management systems in various applications including electronic packaging, waste heat recovery, cryogenic cooling, and new applications such as thermal computers. The existing thermal switches employ the macroscale mechanical-based, relatively slow transient “on/off” switch mechanisms, which may be challenging to provide solutions for micro/nanoscale applications. In this study, a fast and efficient thermal switch mechanism without having extra mechanical controlling system is demonstrated using gas-filled, heterogeneous nanogaps with asymmetric surface interactions in Knudsen regime. Argon gas atoms confined in metal-based solid surfaces are employed to predict the degree of thermal switch, S. Non-equilibrium molecular dynamics simulation is used to create the temperature gradient over the two nanogaps, and the maximum degree of thermal switch is Smax ∼ 13, which results from the difference in adsorption-controlled thermal accommodation coefficient (TAC) and pressure between the two sides of the gaps.
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Avanessian, Tadeh, et Gisuk Hwang. « Nanostructure-Driven Thermal Switch Using Molecular Simulations ». Dans ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-72663.
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A thermal switch is a basic building block to design various advanced thermal management systems including electronic packaging, waste heat recovery, cryogenic cooling, and new applications, e.g., thermal logic gates. Majority of existing thermal switches have been demonstrated in large scales (mm to cm), but these may not be ideal to provide viable thermal management solutions in micro/nanoscale applications which require a small size with a fast transient response. To address this challenge, a new nanostructure-driven thermal switch mechanism is demonstrated in argon-filled nanogaps with/without nanoposts (one surface only) through a controlled adsorption-capillary transition at given pressure. Grand Canonical Monte Carlo (GCMC) simulation combined with Non-equilibrium Molecular Dynamics (NEMD) simulations is employed to examine the heat flux across the nanogap at given pressure and to calculate the degree of thermal switch, S. Smax ∼ 65 is found with a fast transient response, ∼ 10 ns. We also found that S increases as the height of the nanoposts increases and the empty space between the nanoposts decreases. This work also shows that a stronger interatomic potential between the solid and fluid particles results in having the thermal switch effect in a wider temperature operating window.
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Smith, F. W., H. Q. Le, M. Frankel, V. Diadiuk, M. A. Hollis, D. R. Dykaar, G. A. Mourou et A. R. Calawa. « Picosecond GaAs-Based Photoconductive Optoelectronic Detectors ». Dans Picosecond Electronics and Optoelectronics. Washington, D.C. : Optica Publishing Group, 1989. http://dx.doi.org/10.1364/peo.1989.osda176.
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Picosecond photoconductive-switch performance was demonstrated with a novel material deposited by molecular beam epitaxy at low substrate temperatures using Ga and As4 beam fluxes. For a photoconductive-gap switch fabricated on a coplanar transmission line, the speed is 1.6 ps (full width at half maximum) and the voltage response is 10 to 100 times greater than that of conventional photoconductive switches. Since LT GaAs is compatible with GaAs device and IC technologies, this photoconductive switch may find extensive use in high-speed device and circuit testing.
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Alper, Joshua, et Kimberly Hamad-Schifferli. « Biomolecular Activity Switch : An Application of Metallic Nanoparticle Plasmon Resonance and Femtosecond Pulsed Lasers ». Dans ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68104.
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With an increased effort within the engineering community to design molecular machines, it has become clear that a specific, external control method is required. Here we propose a simple mechanism for a molecular switch involving conjugating a molecule within the machinery to a gold nanorod. Then actuate that machinery’s active state by affecting a change in the conjugated molecule. We demonstrate the feasibility of the method using a fluorescent probe, and we report on progress we have made toward demonstrating it with a protein.
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Yulin Huang, Jingfu Bao, Xinyi Li, Yiling Wang et Yijia Du. « A 4-bit switched-line phase shifter based on MEMS switches ». Dans 2015 IEEE 10th International Conference on Nano/Micro Engineered and Molecular Systems (NEMS). IEEE, 2015. http://dx.doi.org/10.1109/nems.2015.7147454.
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Faheng Zang, Guifu Ding, Zhijuan Su, Jun Tang et Min Deng. « A quadruple-anchored RF-MEMS switch for switched-line phase shifters ». Dans 2010 5th IEEE International Conference on Nano/Micro Engineered and Molecular Systems (NEMS 2010). IEEE, 2010. http://dx.doi.org/10.1109/nems.2010.5592174.
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Feringa, Ben L. « Molecular switches and motors ». Dans NOBEL SYMPOSIUM 153 : NANOSCALE ENERGY CONVERTERS. AIP, 2013. http://dx.doi.org/10.1063/1.4794713.
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Du, Y., J. Bao, Z. He et J. Jiang. « A X-band switched-line 5-bit phase shifter with RF MEMS multithrow switches ». Dans 2013 8th IEEE International Conference on Nano/Micro Engineered and Molecular Systems (NEMS). IEEE, 2013. http://dx.doi.org/10.1109/nems.2013.6559735.
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Koydeen, T. Rafsa, S. Devisree, Anand Kumar et Rusal Raj. « Simulation and Analysis of BDT Molecule with Au Electrodes as a Molecular Switch ». Dans 2016 UKSim-AMSS 18th International Conference on Computer Modelling and Simulation (UKSim). IEEE, 2016. http://dx.doi.org/10.1109/uksim.2016.10.
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Parakka, James P., Robert R. Schumaker, Brenda S. Kesler et John D. Thoburn. « Molecular-based chiroptical dipole switches ». Dans Optical Engineering for Sensing and Nanotechnology (ICOSN '01), sous la direction de Koichi Iwata. SPIE, 2001. http://dx.doi.org/10.1117/12.427073.
Texte intégralRapports d'organisations sur le sujet "Molecular Switche"
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Iancu, Violeta. Single Molecule Switches and Molecular Self-Assembly : Low Temperature STM Investigations and Manipulations. Office of Scientific and Technical Information (OSTI), août 2006. http://dx.doi.org/10.2172/955626.
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Tour, James M., et Ruilian Wu. Extension of Branches for Orthogonally Fused Molecular Switches. Fort Belvoir, VA : Defense Technical Information Center, mai 1991. http://dx.doi.org/10.21236/ada236252.
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David C. Ward et Patricia Bray-Ward. Monitoring Gene Expression In Vivo with Nucleic Acid Molecular Switches. Office of Scientific and Technical Information (OSTI), janvier 2005. http://dx.doi.org/10.2172/836260.
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Gomer, Charles J. Photodynamic Therapy Oxidative Stress as a Molecular Switch Controlling Therapeutic Gene Expression for the Treatment of Locally Recurrent Breast Carcinoma. Fort Belvoir, VA : Defense Technical Information Center, juin 2001. http://dx.doi.org/10.21236/ada396793.
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LaBonte, Don, Etan Pressman, Nurit Firon et Arthur Villordon. Molecular and Anatomical Characterization of Sweetpotato Storage Root Formation. United States Department of Agriculture, décembre 2011. http://dx.doi.org/10.32747/2011.7592648.bard.
Texte intégralRésumé :
Original objectives: Anatomical study of storage root initiation and formation. Induction of storage root formation. Isolation and characterization of genes involved in storage root formation. During the normal course of storage root development. Following stress-induced storage root formation. Background:Sweetpotato is a high value vegetable crop in Israel and the U.S. and acreage is expanding in both countries and the research herein represents an important backstop to improving quality, consistency, and yield. This research has two broad objectives, both relating to sweetpotato storage root formation. The first objective is to understand storage root inductive conditions and describe the anatomical and physiological stages of storage root development. Sweetpotato is propagated through vine cuttings. These vine cuttings form adventitious roots, from pre-formed primordiae, at each node underground and it is these small adventitious roots which serve as initials for storage and fibrous (non-storage) “feeder” roots. What perplexes producers is the tremendous variability in storage roots produced from plant to plant. The marketable root number may vary from none to five per plant. What has intrigued us is the dearth of research on sweetpotato during the early growth period which we hypothesize has a tremendous impact on ultimate consistency and yield. The second objective is to identify genes that change the root physiology towards either a fleshy storage root or a fibrous “feeder” root. Understanding which genes affect the ultimate outcome is central to our research. Major conclusions: For objective one, we have determined that the majority of adventitious roots that are initiated within 5-7 days after transplanting possess the anatomical features associated with storage root initiation and account for 86 % of storage root count at 65 days after transplanting. These data underscore the importance of optimizing the growing environment during the critical storage root initiation period. Water deprivation during this phenological stage led to substantial reduction in storage root number and yield as determined through growth chamber, greenhouse, and field experiments. Morphological characterization of adventitious roots showed adjustments in root system architecture, expressed as lateral root count and density, in response to water deprivation. For objective two, we generated a transcriptome of storage and lignified (non-storage) adventitious roots. This transcriptome database consists of 55,296 contigs and contains data as regards to differential expression between initiating and lignified adventitious roots. The molecular data provide evidence that a key regulatory mechanism in storage root initiation involves the switch between lignin biosynthesis and cell division and starch accumulation. We extended this research to identify genes upregulated in adventitious roots under drought stress. A subset of these genes was expressed in salt stressed plants.
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Gantt, Elisabeth, Avigad Vonshak, Sammy Boussiba, Zvi Cohen et Amos Richmond. Carotenoid-Rich Algal Biomass for Aquaculture : Astaxanthin Production by Haematococcus Pluvialis. United States Department of Agriculture, août 1996. http://dx.doi.org/10.32747/1996.7613036.bard.
Texte intégralRésumé :
The synthesis of carotenoids has been studied toward enhancing the production of ketocarotenoids, since fish and crustaceans raised by aquaculture require astaxanthin and other ketocaroteinoids in their feed for desirable pigmentation. Notable progress has been made in attaining the goals of determining improved conditions for ketocarotenoid production in Haematococcus pluvialis and in elucidating the carotenoid biosynthetic pathway. For production of astaxanthin a number of strains of the green alga Haematococcus were evaluated, a strain CCAG was found to be optimal for photoautotrophic growth. Of four mutants, selected for enhanced carotenoid production, two hold considerable promise because caroteinoid accumulation occurs without encystment. The biosynthetic pathway of carotenoids was elucidated in photosynthetic organisms by characterizing novel genes encoding carotenoid enzymes and by examining the function of these enzymes in a bacterial complementation system. Two cyclases (b- and e-) were cloned that are at a critical branch point in the pathway. One branch leads to the formation of b-carotene and zeaxanthin and astaxanthin, and the other to the production of a-carotene and lutein. Cyclization of both endgroups of lycopene to yield b-carotene was shown to be catalyzed by a single gene product, b-lycopene cyclase in cyanobacteria and plants. The formation of a-carotene was found to require the e-cyclase gene product in addition to the b-cyclase. By cloning a b-hydroxylase gene we showed that a single gene product forms zeaxanthin by hydroxylatin of both b-carotene rings. It is expected that a second hydroxylase is required in the synthesis of astaxanthin, since canthaxanthin rather than zeaxanthin is the precursor. Evidence, from inhibitor studies, suggests that astaxanthin is formed from canthaxanthin and that b-carotene is a major precursor. Feasibility studies with the photobioreactors have shown that a two-stage system is the most practical, where Haematococcus cultures are first grown to high cell density and are then switched to high light for maximal astaxanthin production. The basic knowledge and molecular tools generated from this study will significantly enhance Haematococcus as a viable model for enhanced astaxanthin production.
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Abbo, Shahal, Hongbin Zhang, Clarice Coyne, Amir Sherman, Dan Shtienberg et George J. Vandemark. Winter chickpea ; towards a new winter pulse for the semiarid Pacific Northwest and wider adaptation in the Mediterranean basin. United States Department of Agriculture, janvier 2011. http://dx.doi.org/10.32747/2011.7597909.bard.
Texte intégralRésumé :
Original objectives: [a] Screen an array of chickpea and wild annual Cicer germplasm for winter survival. [b] Genetic analysis of winter hardiness in domesticated x wild chickpea crosses. [c] Genetic analysis of vernalization response in domesticated x wild chickpea crosses. [d] Digital expression analysis of a core selection of breeding and germplasm lines of chickpea that differ in winter hardiness and vernalization. [e] Identification of the genes involved in the chickpea winter hardiness and vernalization and construction of gene network controlling these traits. [f] Assessing the phenotypic and genetic correlations between winter hardiness, vernalization response and Ascochyta blight response in chickpea. The complexity of the vernalization response and the inefficiency of our selection experiments (below) required quitting the work on ascochyta response in the framework of this project. Background to the subject: Since its introduction to the Palouse region of WA and Idaho, and the northern Great Plains, chickpea has been a spring rotation legume due to lack of winter hardiness. The short growing season of spring chickpea limits its grain yield and leaves relatively little stubble residue for combating soil erosion. In Israel, chilling temperatures limit pod setting in early springs and narrow the effective reproductive time window of the crop. Winter hardiness and vernalization response of chickpea alleles were lost due to a series of evolutionary bottlenecks; however, such alleles are prevalent in its wild progenitor’s genepool. Major conclusions, solutions, achievements: It appears that both vernalization response and winter hardiness are polygenic traits in the wild-domesticated chickpea genepool. The main conclusion from the fieldwork in Israel is that selection of domesticated winter hardy and vernalization responsive types should be conducted in late flowering and late maturity backgrounds to minimize interference by daylength and temperature response alleles (see our Plant Breeding paper on the subject). The main conclusion from the US winter-hardiness studies is that excellent lines have been identified for germplasm release and continued genetic study. Several of the lines have good seed size and growth habit that will be useful for introgressing winter-hardiness into current chickpea cultivars to develop releases for autumn sowing. We sequenced the transcriptomes and profiled the expression of genes in 87 samples. Differential expression analysis identified a total of 2,452 differentially expressed genes (DEGs) between vernalized plants and control plants, of which 287 were shared between two or more Cicer species studied. We cloned 498 genes controlling vernalization, named CVRN genes. Each of the CVRN genes contributes to flowering date advance (FDA) by 3.85% - 10.71%, but 413 (83%) other genes had negative effects on FDA, while only 83 (17%) had positive effects on FDA, when the plant is exposed to cold temperature. The cloned CVRN genes provide new toolkits and knowledge to develop chickpea cultivars that are suitable for autumn-sowing. Scientific & agricultural implications: Unlike the winter cereals (barley, wheat) or pea, in which a single allelic change may induce a switch from winter to spring habit, we were unable to find any evidence for such major gene action in chickpea. In agricultural terms this means that an alternative strategy must be employed in order to isolate late flowering – ascochyta resistant (winter types) domesticated forms to enable autumn sowing of chickpea in the US Great Plains. An environment was identified in U.S. (eastern Washington) where autumn-sown chickpea production is possible using the levels of winter-hardiness discovered once backcrossed into advanced cultivated material with acceptable agronomic traits. The cloned CVRN genes and identified gene networks significantly advance our understanding of molecular mechanisms underlying plant vernalization in general, and chickpea in particular, and provide a new toolkit for switching chickpea from a spring-sowing to autumn-sowing crop.
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Grumet, Rebecca, Rafael Perl-Treves et Jack Staub. Ethylene Mediated Regulation of Cucumis Reproduction - from Sex Expression to Fruit Set. United States Department of Agriculture, février 2010. http://dx.doi.org/10.32747/2010.7696533.bard.
Texte intégralRésumé :
Reproductive development is a critical determinant of agricultural yield. For species with unisexual flowers, floral secualdifferentation adds additional complexity, that can influenec productivity. The hormone ethylene has long, been known to play a primary role in sex determination in the Cucumis species cucumber (C. sativus) and melon (C. melo). Our objectives were to: (1) Determine critical sites of ethylene production and perception for sex determination; (2) Identify additional ethylene related genes associated with sex expression; and (3) Examine the role of environment ami prior fruit set on sex expression, pistillate flower maturation, and fruit set. We made progress in each of these areas. (1) Transgenic melon produced with the Arabidopsis dominant negative ethylene perception mutant gene, etrl-1, under the control of floral primordia targeted promoters [AP3 (petal and stamen) and CRC (carpel and nectary)], showed that ethylene perception by the stamen primordia, rather than carpel primordia, is critical for carpel development at the time of sex determination. Transgenic melons also were produced with the ethylene production enzyme gene. ACS, encoding l-aminocyclopropane-lcarboylate synthase, fused to the AP3 or CRC promoters. Consistent with the etr1-1 results, CRC::ACS did not increase femaleness; however, AP3::ACS reduced or eliminated male flower production. The effects of AP3:ACS were stronger than those of 35S::ACS plants, demonstratin g the importance of targeted expression, while avoiding disadvantages of constitutive ethylene production. (2) Linkage analysis coupled with SNP discovery was per formed on ethylene and floral development genes in cucumber populations segregating for the three major sex genes. A break-through towards cloning the cucumber M gene occurred when the melon andromonoecious gene (a), an ACS gene, was cloned in 2008. Both cucumber M and melon a suppress stamen development in pistillate flowers. We hypothesized that cucumber M could be orthologous to melon a, and found that mutations in CsACS2 co-segregated perfectly with the M gene. We also sought to identify miRNA molecules associated with sex determination. miRNA159, whose target in Arabidopsis is GAMYB[a transcription factor gene mediating response to10 gibberellin (GA)], was more highly expressed in young female buds than male. Since GA promotes maleness in cucumber, a micro RNA that counteracts GAMYB could promote femaleness. miRNA157, which in other plants targets transcription factors involved in flower development , was expressed in young male buds and mature flower anthers. (3) Gene expression profiling showed that ethylene-, senescence-, stress- and ubiquitin-related genes were up-regulated in senescing and inhibited fruits, while those undergoing successful fruit set up-regulated photosynthesis, respiration and metabolic genes. Melon plants can change sex expression in response to environmental conditions, leading to changes in yield potential. Unique melon lines with varying sex expression were developed and evaluated in the field in Hancock, Wisconsin . Environmental changes during the growing season influenced sex expression in highly inbred melon lines. Collectively these results are of significance for understanding regulation of sex expression. The fact that both cucumber sex loci identified so far (F and M) encode isoforms of the same ethylene synthesis enzyme, underscores the importance of ethylene as the main sex determining hormone in cucumber. The targeting studies give insight into developmental switch points and suggest a means to develop lines with earlier carpel-bearing flower production and fruit set. These results are of significance for understanding regulation of sex expression to facilitate shorter growing seasons and earlier time to market. Field results provide information for development of management strategies for commercial production of melon cultivars with different sex expression characteristics during fruit production.