Siga este link para ver outros tipos de publicações sobre o tema: Chemist activity.
Teses / dissertações sobre o tema "Chemist activity"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 50 melhores trabalhos (teses / dissertações) para estudos sobre o assunto "Chemist activity".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja as teses / dissertações das mais diversas áreas científicas e compile uma bibliografia correta.
1
Fournier, Etienne. "Intérêt de la prise en compte des variabilités de l’activité et de l’acceptabilité dans le cadre d’une conception centrée utilisateurs des situations de travail collaboratives Humain-Robot". Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALH011.
Texto completo da fonteResumo:
La Commission Européenne encourage l’utilisation de robots collaboratifs (cobots) pour assister l’humain dans son travail. Cependant, les cobots semblent avoir des difficultés à transformer favorablement les situations de travail lorsqu’ils ne prennent pas en compte les variabilités des situations. Cette thèse s’est donc donnée comme objectifs de caractériser les variabilités dans le cadre d’une l’implémentation cobotique et de guider une démarche de conception centrée sur les futurs utilisateurs en mobilisant les approches d’acceptabilité, d’acceptation et d’expérience utilisateur. Une analyse de l’activité a été conduite dans un laboratoire de chimie dans le cadre d’une future implémentation cobotique. 11 opérateurs ont été observés durant leur activité et 34 ont participé à des entretiens semi-directifs. Les résultats ont permis d’identifier que l’activité en boîte à gants était le poste de travail qui bénéficierait le plus d’une collaboration cobotique. De même, ils ont montré une invisibilisation de certaines activités due à un écart entre le travail prescrit et l’activité d’où résultent des expositions aux risques régulières qui pourraient être évitées via une implémentation cobotique. Nous avons ainsi identifié plusieurs variabilités ayant des effets sur l’activité des opérateurs. Celles-ci ont servi à élaborer des paradigmes expérimentaux afin de tester l’effet d’une collaboration cobotique. Trois Tests Utilisateurs ont été réalisés avec au total 212 participants qui devaient réaliser des tâches d’assemblage de type industriel où une ou plusieurs variabilités étaient prises en charge dès la conception cobotique. La tâche était réalisée ou bien seul, ou bien en binôme avec un autre humain ou avec un cobot (YuMi d’ABB). Différents types de mesure ont été effectués : la charge de travail (évaluée via la NASA TLX, Hart, 2006 ; Hart & Staveland, 1988), le nombre d’erreurs, le nombre de gestes, le temps de réalisation, le degré d’acceptabilité de la collaboration cobotique (évalué via le TAM, Venkatesh et al., 2012) et l’exposition aux risques simulée. La collaboration cobotique a diminué les effets négatifs de plusieurs variabilités (e.g. variabilité du niveau de difficulté, variabilité de l’expertise de l’opérateur) sur la charge mentale de l’opérateur et sur le succès à la tâche. Les participants ont eu un meilleur taux de succès à la tâche lorsqu’ils collaboraient avec un cobot, même s’ils mettaient par ailleurs plus de temps à réaliser la tâche. De plus, les participants ont déclaré avoir plaisir à collaborer avec un cobot et avoir confiance en les informations qu’il fournissait (mesurés via une échelle d’items issus de l’étude de Martin, 2018). Enfin, quand le cobot s’adaptait aux contraintes de sécurité de l’humain, ce dernier s’exposait à moins de risques. D’un point de vue théorique, ces études empiriques ont permis de proposer un cadre intégrant les modèles de variabilités au travail et d’apporter des précisions sur les effets de la collaboration cobotique sur l’humain et sa tâche. D’un point de vue pratique, ces différentes études nous ont permis de proposer une grille de repérage des variabilités et de formuler des recommandations visant à accompagner l’implémentation d’une collaboration cobotiqueThe European Commission is encouraging the use of collaborative robots (cobots) to assist humans in their work. However, cobots seem to have difficulty in favorably transforming work situations when they do not consider the variabilities of the situations. The aim of this thesis was therefore to characterize variability in the context of a cobotic implementation, and to guide a design approach focused on future users, using acceptability, acceptance and user experience approaches. An activity analysis was carried out in a chemical laboratory as part of a future cobotic implementation. 11 operators were observed during their activity and 34 took part in semi-directive interviews. The results identified glovebox activity as the workstation that would benefit most from cobotic collaboration. They also showed that certain activities were rendered invisible due to a discrepancy between prescribed work and actual activity, resulting in regular exposure to risks that could be avoided through cobotic implementation. We have thus identified several variabilities with effects on operator activity. These were used to design experimental paradigms to test the effect of cobotic collaboration. Three User Tests were carried out with a total of 212 participants, who were asked to perform industrial assembly tasks where one or more variabilities were considered in the cobotic design. The task was performed either alone, or in pairs with another human or with a cobot (ABB's YuMi). Different types of measurement were carried out: workload (assessed via NASA TLX, Hart, 2006; Hart & Staveland, 1988), number of errors, number of gestures, completion time, degree of acceptability of cobotic collaboration (assessed via TAM, Venkatesh et al., 2012) and simulated risk exposure. Cobotic collaboration reduced the negative effects of several variabilities (e.g. variability in difficulty level, variability in operator expertise) on operator mental load and task success. Participants had a higher task success rate when collaborating with a cobot, even though they otherwise took longer to complete the task. In addition, participants reported enjoying collaborating with a cobot and having confidence in the information it provided (measured via a scale of items from Martin, 2018). Finally, when the cobot adapted to the human's safety constraints, the latter exposed himself to fewer risks. From a theoretical point of view, these empirical studies made it possible to propose a framework integrating models of variability at work, and to shed light on the effects of cobotic collaboration on the human and his task. From a practical point of view, these different studies have enabled us to propose a grid for identifying variabilities and to formulate recommendations designed to support the implementation of cobotic collaboration
2
Catti, Federica. "4,5-dihydropyrazoles : novel chemistry and biological activity". Thesis, St Andrews, 2007. http://hdl.handle.net/10023/351.
Texto completo da fonte
3
Davidson, Nicola E. "Glucosinolates and isothiocyanates : chemistry and biological activity". Thesis, University of St Andrews, 1999. http://hdl.handle.net/10023/14230.
Texto completo da fonteResumo:
The ability of glucosinolates to act as host recognition cues and oviposition stimulants for root flies has been previously established. To further investigate the interactions between pest and glucosinolate a number of simple and complex glucosinolates were synthesised and tested by contact chemoreception. A crude structure-activity relationship was identified whereby the stimulatory activity of the glucosinolate increased as the alkyl side chain was increased from propyl to pentyl, heptyl and nonyl. Comparison of the novel synthetic glucosinolate, naphthylmethyl glucosinolate, with glucobrassicin, a naturally occurring indole derivative, showed the former to have little or no activity whereas the latter is the most active natural stimulant. The synthetic glucosinolates were also demonstrated to act as substrates for the enzyme myrosinase, being hydrolysed to ?-D-glucose and the corresponding isothiocyanate. In addition, (7-methoxycarbonylheptyl) glucosinolate, prepared as a precursor to (7-carboxyheptyl) glucosinolate, was found to be a substrate. High resolution NMR studies of the latter compound showed this acidic glucosinolate and indeed alkyl glucosinolates to adopt an unexpected conformation in aqueous solution. Furthermore, a number of alkyl thiohydroximates were synthesised and used as HPLC and LC-MS standards to aid glucosinolate identification. Isothiocyanates have been identified as chemopreventative agents which inhibit carcinogen activation mediated by cytochrome P450 enzymes. The postulated oxidation of isothiocyanates to isocyanates by these enzymes, was studied using a number of chemical model systems. Oxidation of isothiocyanates was efficiently achieved using dimethyl dioxirane (DMD). Although, the resulting isocyanates could not be isolated, their production was confirmed by GC/MS and FT-IR analysis of reaction solutions. A number of ureas were also prepared by trapping the isocyanates in situ. These compounds were demonstrated to arise from the isocyanate and not oxidation of the corresponding thiourea. In addition, peracids were found to produce isocyanates, although less efficiently.
4
Kulkarni, M. M. "Chemistry and biological activity of natural products". Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1986. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3276.
Texto completo da fonte
5
Li, Ju-Yun. "Quantitative structure-activity relationship studies in medicinal chemistry". Case Western Reserve University School of Graduate Studies / OhioLINK, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1062596938.
Texto completo da fonte
6
Pathirana, Navin Deepal. "Chemistry and biological activity of iron quinoneoximic complexes". Thesis, London Metropolitan University, 1990. http://repository.londonmet.ac.uk/2977/.
Texto completo da fonteResumo:
The synthesis and structure of 1,2-quinone mono-oximes have been reviewed. The reaction of 3-hydroxyphenol, 3-hydroxy-2-aethylphenol, 3-hydroxy-5-methylphenol and N-acetyl-3-aminophenol with amyl nitrite/M(OEt) (M - Na or K) has been systematically examined. It has been found that the complex formed depends on the reaction temperature and phenol/M(OEt) ratio. Infra-red spectroscopic studies have shown that in the solid state 5-hydroxy-l,2-benzoquinone 2-oxime (hqoH,), 5-hydroxy-3-methyl-l,2-benzoquinone 2-oxime (3-MehqoH2), 5-hydroxy-6-methyl-l,2-benzoquinone 2-oxime (e-MehqoH,) and H-acetyl-5-amino- 1,2-benzoquinone 2-oxime (N-AcqoH) and their sodium and potassium complexes exist in the oximic form rather than the nitroso form. Nuclear magnetic resonance studies have also shown that in d,-DHSO solution hqoH,, 3-MehqoH, and 6-MehqoH} and their sodium complexes exist in one form only which is oximic in character. However, in DjO the results for the sodium complexes of hqoH, and e-MeqoH, indicate the presence of at least two species. In the case of the sodium 5-hydroxy-6-methyl-l,2-benzoquinone 2-oximate these species are oximic in character. An X-ray crystallographic study of e-HehqoH, has shown that in the solid state this compound exists in the 1,4- rather than the 1,2-quinone 2-oxlmic form. The synthesis of iron(II) complexes of hqoH,, 3-MehqoH] and 6-HehqoH] using the direct and the nitrosation methods was examined. The direct method gave rise to the complexes Fe(hqoH), OHjO, Fe(3-HehqoH), and Fe(6-MehqoH)2 '2H20 whereas the nitrosation method gave rise to ill-defined solids. Na[Fe(N-Acqo), ]-4H20 was obtained by nitrosation of N-acetyl-3-aminopnenol in the presence of Iron(II) ammonium sulphate. Hossbauer and magnetic studies indicate that Na[Fe(N-Acqo)j]-4H20 is a low spin iron(II) complex whereas the bischelates have properties indicative of the S - 1 spin state. In-vlvo assesment of the iron chelating ability of hqoHj, 3-MehqoH2, 6-MehqoH2, N-AcqoH , N,N-dimethyl-5- amino-1,2-benzoquinone 2-oxime and violuric acid was carried out using a normal rat model. The chelators hqoH, and 6-HehqoH2were found to be effective in removing iron when administered intra-muscularly but they also caused the excretion of magnesium. Their activity was lower than that of desferrioxamine and neither was effective when administered orally.
7
Cox, Kaleb Woodrow. "Synthesis and Biological Activity of Indolinones". Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1421165680.
Texto completo da fonte
8
Nunes, R. J. "The chemistry and biological activity of cyclic imidobenzenesulphonyl derivatives". Thesis, University of Hertfordshire, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370823.
Texto completo da fonte
9
Paige, Mikell Atkin. "Modular synthesis of Annonaceous acetogenins and their activity against H-116 human solid colon tumor cells". Full text, Acrobat Reader required, 2003. http://viva.lib.virginia.edu/etd/diss/ArtsSci/Chemistry/2003/Paige/Dissertation.pdf.
Texto completo da fonte
10
Murphy, Veronica L. "Optical Activity of Achiral Molecules". Thesis, New York University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10192177.
Texto completo da fonteResumo:
Optical activity is typically first introduced to a prospective chemist in her sophomore year organic chemistry course. Here, she is taught that optical activity is a consequence of chirality, for example, L-tartaric acid has a specific rotation of +12° at the sodium D-line. However, this leaves said chemist with a wildly skewed and rather vague understanding of the concept of optical activity. There are two major problems with the current understanding of optical activity. The first is that both theory and experiment have shown that optical activity is, in fact, not a consequence of chirality. Molecules belonging to one of four achiral point groups (Cs, C2 v, S4, and D 2d) can display optical activity in particular directions. However, measurement requires an anisotropic medium which presents major challenges. The second problem is that we lack structure-property relationships; specific rotations generally speaking are impossible to connect to molecular structure. Herein, we emphasize optical activity in achiral molecules whose high symmetry and simplified electronic structure are used to establish structure–property relationships. First, achiral optical activity is emphasized by showing that achiral polyaromatic hydrocarbons (PAH) are actually significantly more optically active than their helicene isomers. Next, small, planar, conjugated hydrocarbons are used to interpret optical activity by analysis of their π wave functions that can be intuited from structure. Finally, it is shown that aromaticity is generally deleterious for optical activity. A simple explanation is offered based on Kekule structures.
11
Fitzpatrick, Matthew F. "The interfacial chemistry and environmental degradation of adhesively bonded galvanised steel". Thesis, University of Surrey, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322539.
Texto completo da fonte
12
Miller, Matthew Dean Holder Andrew J. "Applications of quantum chemistry to polymerization reactions and biological activity". Diss., UMK access, 2004.
Encontre o texto completo da fonteResumo:
Thesis (Ph. D.)--Dept. of Chemistry and School of Pharmacy. University of Missouri--Kansas City, 2004."A dissertation in chemistry and pharmaceutical science." Advisor: Andrew J. Holder. Typescript. Vita. Description based on contents viewed Feb. 27, 2006; title from "catalog record" of the print edition. Includes bibliographical references (leaves 206-221). Online version of the print edition.
13
Roberts, Glyn. "The influence of catalyst precursor chemistry on methanol synthesis activity". Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317194.
Texto completo da fonte
14
Srivastava, Sanjay. "Structure-activity relationship studies in medicinal chemistry and drug design". Case Western Reserve University School of Graduate Studies / OhioLINK, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1056054628.
Texto completo da fonte
15
Ptchelintsev, Dmitri Stanislav. "Structure-activity relationship studies in chemoreception, toxicology and medicinal chemistry". Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1060866168.
Texto completo da fonte
16
Cavagnero, Silvia 1962. "Structure-activity studies of delta-selective opioid analogues". Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/278183.
Texto completo da fonteResumo:
The two structurally different peptides DPDPE and Dermenkephalin show a similar remarkably high affinity and selectivity for the delta opioid receptor subtype. An effort has been made to gain some insight into the factors responsible for the recognition ability of these two molecules by synthesizing some DPDPE-Dermenkephalin peptide hybrids and some conformationally restricted Dermenkephalin analogues. The results of the binding and the in-vitro bioassays have been compared with those of the parent peptides. A general decrease in receptor affinity has been observed in the peptide hybrids while the dermenkephalin analogues have shown a wider range of affinities and selectivities. The above findings contribute to the understanding of the structural requirements of the delta receptor, provide information about the sensitivity of Dermenkephalin to enzymatic degradation, and indicate directions for future research.
17
Ramsamy, Tanya A. "The regulation of hepatic lipase activity". Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/29156.
Texto completo da fonteResumo:
Human hepatic lipase (HL) is a 66-kDa glycoprotein that plays an important role in the metabolism of apoB-containing lipoproteins and high density lipoproteins (HDL). Both the lipid and apolipoprotein composition of lipoproteins have been shown to modulate HL activity. In this study, very low density lipoproteins (VLDL) were found to be the best lipoprotein substrates for HL followed by low density lipoproteins (LDL) and HDL. Only 1% of the fatty acids released from HDL3 by HL are derived from triglycerides (TG) whereas the remainder of fatty acids produced are from the lipolysis of diglycerides (DG (49%)) and phospholipids (PL (50%)). In order to further study the role of lipoprotein composition on HL activity, HDL and LDL fractions were isolated from subjects with familial combined hyperlipidemia (FCHL) and matched controls and used as substrates for the enzyme. HL-mediated hydrolysis of patient and control LDL and HDL fractions is similar despite elevated serum TG levels in subjects with FCHL. In both patient and control samples, the most buoyant LDL and HDL fractions are better substrates for HL than the corresponding denser fractions when normalized for total protein content. Although differences are observed in the acylglycerol and PL hydrolysis of the two patient groups, these differences are not related to the DG content of the lipoproteins.
The association of HL with pure heparan sulfate proteoglycans (HSPG) has little effect on hydrolysis of HDL particles, but significantly inhibits (>80%)the hydrolysis of LDL and VLDL. Lipolytic inhibition is associated with a differential ability of the lipoproteins to remove HL from the HSPG. LDL and VLDL are unable to displace HL, while HDL readily displaces the enzyme from the HSPG. This is consistent with the view that HSPG-bound HL is inactive. HDL also displaces HL from the surface of the hepatoma cell line, HepG2, and Chinese Hamster Ovary (CHO) cells stably overexpressing human HL. Purified apolipoprotein (apo) A-I is more efficient than HDL at liberating HL from both pure and cell surface HSPG. Furthermore, different HDL fractions vary in their abilities to displace the enzyme from the cell surface. The buoyant HDL2 has a greater capacity to remove HL from the cell surface and intracellular compartments when compared to the smaller denser HDL particles.
Displacement of HL by apoA-I does not enhance the hydrolysis of VLDL. This somewhat paradoxical finding appears to result from the direct inhibition of HL by apoA-I, as both apoA-I and HDL are able to inhibit VLDL-lipid hydrolysis. The different HDL subspecies also uniquely affect the activity of the enzyme. A detailed evaluation of different HDL fractions shows that HDL2 stimulates HL-mediated hydrolysis of VLDL-TG, while the smaller HDL3 is inhibitory. Inhibition of VLDL hydrolysis appears to result from a decreased interlipoprotein shuttling of HL between VLDL and the smaller more dense HDL particles. These findings suggest that high HDL2 levels are positively related to efficient TG hydrolysis by their ability to enhance the liberation of HL into the plasma compartment and by a direct stimulation of VLDL-TG hydrolysis.
Taken together, these results demonstrate that the lipid and apolipoprotein composition of lipoproteins, hence lipoprotein structure, in addition to interlipoprotein interactions are central to the regulation of HL activity.
18
Rabindran, Ray 1964. "Inhibition of tau kinase activity by ATP". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/47691.
Texto completo da fonte
19
Moi, Giulia. "Chemistry and biological activity of Kigelia pinnata relevant to skin conditions". Thesis, King's College London (University of London), 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601502.
Texto completo da fonte
20
Mathabathe, Kgadi Clarrie. "Manifestations of metacognitive activity in an upper undergraduate organic chemistry laboratory". Thesis, University of Pretoria, 2016. http://hdl.handle.net/2263/60839.
Texto completo da fonteResumo:
This study was carried out to investigate how metacognitive activity, particularly cognitive regulation, manifests in the collaborative planning of chemistry practical investigations by senior undergraduate students in a simulated industrial project. The participating students worked in home groups to evaluate three synthetic routes for a given compound, and decided on a preferred route while considering the criteria of cost, technical challenge, and environmental impact. This is consistent with the jigsaw learning technique. During the planning session, the students who were evaluating the same synthetic routes convened in specialist groups to draw up detailed experimental procedures for their routes.
Audio recordings of the two specialist and the four home group discussions were purposively selected, transcribed, and analysed for manifestations of metacognitive regulation. This study started with a partial theory of what constitutes cognitive regulation in collaborative group discussions, and as the research progressed, verbal indicators of each component of cognitive regulation were inductively determined from analysing the pilot study data. These were then compiled into a coding scheme. The coding scheme was further refined following recommendations of an analytic audience. The students' self-reports were collected through retrospective stimulated recall interviews and were used to triangulate the findings inferred from the group discussions. This study has made important theoretical and methodological contributions.
The coding scheme proved to be both conceptually and methodologically useful in that it allowed for fine-grained coding. The system of coding interrogated not only the manifestations of metacognitive regulation at play (planning, monitoring, control and evaluation), but facilitated an in-depth look at the types of regulation, i.e. self or other, the areas where students applied their efforts towards regulation (cognition, behaviour and task performance) as well as the depth of cognitive regulation (low or high). The coding scheme went beyond serving as a tool for characterising manifestations of metacognitive activity, it developed into a framework which provides a finer theoretical elucidation of the social nature of metacognition.
I show in this thesis how in group work metacognitive activity was found to be predominantly other-regulatory, manifesting mostly as control and monitoring, with much fewer instances of planning and evaluation. These observations were made across all groups despite the differences in social context. The low occurrence of planning, evaluation and high-level regulation seemed to suggest a hierarchy in terms of the level of difficulty of metacognitive regulation. An even deeper look revealed that individual patterns of regulation differed in terms of individual dispositions and personal goals. Investigating the transferability of the individual patterns of regulation increased the originality of this study. Both the personal characteristics (extrovert vs introvert) and the personal style of regulation (assertive vs tentative) were found to be transferable and not group dependent.
The findings of this study show that peer interaction in collaborative tasks can facilitate achievement of collective conceptual understanding and learning gain through inter-individual regulation in social contexts. However, students find planning, evaluation and high-level regulation challenging, especially in social contexts. I suggest that concerted efforts should be made to teach students to make the most of group work by identifying and introducing instructional strategies that develop the desirable skills of egalitarian collaboration and the more difficult aspects of cognitive regulation and high-level engagement. Strategies such as metacognitive prompts, teaching students about team development techniques and exposing students to collaborative ill-structured tasks could be helpful in this regard. Some suggestions have also been made in terms of directions for future research.Thesis (PhD)--University of Pretoria, 2016.
Chemistry
PhD
Unrestricted
21
Price, Craig Justin. "Structure-activity relationships in olefin polymerization catalysts". [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1678.
Texto completo da fonte
22
Escribano, Rivero Juan Ricardo. "Studies on natural Raman optical activity". Thesis, University of Glasgow, 1985. http://theses.gla.ac.uk/8690/.
Texto completo da fonteResumo:
Optical activity associated with vibrations of chiral molecules can provide much stereochemical information. There are two techniques which observe vibrational optical activity (VOA), namely: infrared circular dichroism (IRCD) and vibrational Raman optical activity (VROA). The first, IRCD, is an extension of circular dichroism into the infrared and measures a difference in absorbance of incident left and right circularly polarized infrared radiation. VROA is concerned with a difference in the intensity of Raman scattering when the chiral system is illuminated with left and right circularly polarized radiation. Recent reviews that cover both techniques are in the references of the Summary. This thesis is divided into two main parts. The first (Chapters 1 to 4) is concerned with theoretical studies of ROA. The second (Chapters 5 to 8) with calculations of the observable parameters in VROA and their comparison with experimental results. Chapter 1 comprises a theoretical study in molecular scattering tensors: one significant new result was the discovery of a Stokes-antiStokes asymmetry in the ROA observables. In Chapter 2 is reviewed the experimental conditions in which VROA experiments have been carried out and how the artifacts will affect their spectra. For this, firstly, it has been necessary to provide a general extension of the established equations which give the ROA observables at any point in space. Subsequently a new and more realistic parameter in ROA is defined in terms of power. The difference with the original one is not important in the experimental conditions in which the spectra are recorded, but it is relevant from the scientific aesthetic point of view. Particular cases are derived from these general equations in total agreement with the original and well established ones. In all cases the influence of artifacts coming from imperfectly modulated right and left circularly polarized incident light has been considered. Chapter 3 is a generalization of the "two group model" in VROA using the bond polarizability theory. The model has been extended to include deformations of non-axially symmetric groups. A general critical revision of these formulae is provided. Chapter 4 is a survey of miscellanea in VROA. An interesting prediction is given in the case of Fermi resonance. At the end of this chapter a new selection rule is proposed in VROA which relates polarized and depolarized VROA spectra. This rule is analogous to that which relates polarized and depolarized conventional Raman spectra. The second part of the thesis is devoted to calculations of the observable parameters in VROA and their comparison with the experimental results. The molecule CBrC1FH has not yet been studied experimentally but it is a good (Chapter 5) example for calculations because the results can be compared with those from other theories such as the "atom dipole interaction model". Chapter 6 treats another easy chiral molecule, epoxypropane. The advantage of this molecule is that it can be tested with its experimental spectrum and considering the approximate force field we can say that the comparison is good. Chapters 7 and 8 deal with small chiral molecules derived from cyclohexanone, deuterated and methylated.
23
Wilson, Mark James. "Activity relationships for aromatic crown ethers". Thesis, University of Strathclyde, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249872.
Texto completo da fonte
24
Poisot, Vazquez Martha Emilia [Verfasser]. "Studies to develop high activity MoS2 : crystallography, thermal analysis and catalytic activity / Martha Emilia Poisot Vazquez". Kiel : Universitätsbibliothek Kiel, 2008. http://d-nb.info/1019613386/34.
Texto completo da fonte
25
Saran, Dayal. "Novel phosphotransferase ribozyme with ATPgammaS hydrolase activity". [Bloomington, Ind.] : Indiana University, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3215205.
Texto completo da fonteResumo:
Thesis (Ph. D.)--Indiana University, Dept. of Chemistry, 2006.Source: Dissertation Abstracts International, Volume: 67-04, Section: B, page: 1995. Adviser: Donald H. Burke. "Title from dissertation home page (viewed June 20, 2007)."
26
Mukherjee, Herschel. "On the Biological Activity of the Natural Product (+)-Avrainvillamide". Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467289.
Texto completo da fonteResumo:
Nucleophosmin (NPM1) is a multifunctional phosphoprotein localized predominantly within the nucleoli of eukaryotic cells. Mutations within its C-terminal domain are frequently observed in patients with acute myeloid leukemia (AML), are thought to play a key role in the initiation and progression of the disease, and result in aberrant, cytoplasmic localization of the mutant protein. It has previously been demonstrated that the electrophilic antiproliferative natural product (+)-avrainvillamide binds to proteins, including nucleophosmin, by ¬S-alkylation of cysteine residues. In this thesis we report that the biological activity of avrainvillamide is mediated by NPM1 and the nuclear export receptor exprtin-1 (Crm1). Using mass spectrometry, we demonstrate that the antiproliferative activity of a series of avrainvillamide analogs correlates with their ability to bind C-terminal NPM1 truncation constructs; it is also observed that the interaction between avrainvillamide and the C-terminal domain of NPM1 is fully reversible under our experimental conditions. We report that avrainvillamide restores nucleolar localization of certain AML-associated mutant forms of NPM1 and provide evidence that this relocalization is mediated by interactions of avrainvillamide with mutant NPM1 and Crm1. Immunofluorescence and mass spectrometric experiments employing a series of different NPM1 constructs suggest that a specific interaction between avrainvillamide and cysteine-275 of certain NPM1 mutants mediates the relocalization of these proteins to the nucleolus. Avrainvillamide is further shown to inhibit nuclear export of Crm1 cargo proteins, including AML-associated NPM1 mutants; this marks the first evidence that avrainvillamide directly influences the biology of a cellular target other than NPM1. We also observe that avrainvillamide treatment displaces thr199-phosphorylated NPM1 from duplicated centrosomes, leads to an accumulation of supernumerary centrosomes, and causes mitotic defects in vitro. Finally, we show that avrainvillamide treatment increases levels of thr199-phosphorylated NPM1 by inhibiting the action of protein phosphatase 1 beta on phosphorylated NPM1, thereby indirectly displacing NPM1 from nucleoli and destabilizing nucleolar and nuclear structure.Chemistry and Chemical Biology
27
He, Qing 1973. "Understanding and improving the anticancer activity of cisplatin". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/44508.
Texto completo da fonteResumo:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2001.Vita.
Includes bibliographical references.
The purpose of this thesis is to further our understanding of the mechanism of action of cis-diamminedichloroplatinum(II) (cisplatin), one of the most effective anticancer drugs. Since its serendipitous discovery in 1970, cisplatin has served to help cure testicular cancer and treat a variety of human malignancies. It is widely accepted that DNA is the cellular target for cisplatin. Prior to this work, several structures of duplex DNA modified by cisplatin revealed the distinctive distortions caused by cisplatin-DNA adducts. High mobility group (HMG) domain proteins are DNA binding proteins that bind to cisplatin-modified DNA in vitro with high specificity and affinity. HMG-domain proteins block nucleotide excision repair of cisplatin-DNA adducts in vitro, suggesting that such proteins may mediate cisplatin cytotoxicity in cells. The structure of HMG1 domain A bound to site-specifically cisplatin modified DNA reveals an unprecedented protein-DNA binding mode and a key phenylalanine side-chain intercalation. Factors contributing to the affinity of HMG-domain proteins for cisplatin-modified DNA are not well understood. In Chapter 2 is described a biochemical approach to evaluate the contribution of intercalating residues to the affinity of HMG-domain proteins for platinated DNA. Site-directed mutagenesis, bandshifts and footprinting methods show that the position of the side-chain intercalator determines the protein binding mode. This study provides a new paradigm to understand why and how HMG domains interact with platinated DNA. In addition to understanding the molecular basis of protein platinated-DNA interaction, the role of HMG-domain proteins in the cisplatin mechanism was investigated on the cellular level. Overexpression of HMG1 had been predicted to enhance the sensitivity of mammalian cells to cisplatin. Previous attempts from our laboratory and others failed to overexpress HMG1 stably in cells. When it was reported that HMG1 mRNA is upregulated in mammalian breast cancer MCF-7 cells after estrogen treatment, the effects of steroid hormone treatment on HMG1 protein expression and cisplatin sensitivity in mammalian cell lines from breast and ovarian tumors were studied. The ability to modulate cisplatin sensitivity in cells has useful clinical implications such as enhancing the efficacy of cisplatin chemotherapy. The results of this study led to a phase I clinical trial to investigate the efficacy of hormonecarboplatin combination therapy for treatment of ovarian cancer patients. It can concluded from Chapters 2 and 3 respectively, that the affinity of HMG domains for cisplatin-modified DNA can be improved by protein modifications and that the cytotoxicity of cisplatin can be enhanced by HMG1 overexpression. Because cisplatin lesions are not natural targets for HMG domain proteins, the protein-DNA binding affinity may not be optimal. It is of interest to design novel proteins to be used in gene therapy for further improvement of the therapeutic effects of cisplatin in patients. In order to achieve this goal, the phage display method was employed to search for novel HMG domain proteins with higher affinity for cisplatin-modified DNA than those naturally occurring. It was successfully demonstrated that HMG-domains can be expressed on the phage surface, and protocols were established to enable selection for cisplatin-damaged DNA targets based on DNA structure rather than sequence. Chapter 4 sets the foundation for future phage display protocols to design proteins of high affinity for cisplatin-modified DNA.
by Qing He.
Ph.D.
28
Moore, Madeleine Henrietta. "Structure-activity relationships in Werner clathrates". Doctoral thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/17038.
Texto completo da fonteResumo:
Includes bibliographical references.The synthesis and characterization of a series of inorganic coordination compounds which, upon crystallization, have the ability to include solvent or guest molecules spatially within the lattice are reported. The compounds have the following general formula: [NiX2B4] - where X is isothiocyanate or bromine and B is 4-ethylpyridine, 4-vinylpiridine or 3,5-dimethylpyridine; [NiX2B2]n - where X is isothiocyanate, B is 2-aminopyridine and n indicates it is a polymer; [NiX2AB2]2 - where X is isothiocyanate, B is 3-aminopyridine (two of these four ligands in the dimer are bridging) and A is water. The various guest molecules have been carefully chosen, according to their point symmetry, which is a key factor in yielding structures of a particular type. The structures of seventeen compounds have been elucidated by single crystal x-ray analysis. The difficulty has been found to lie in refining disordered guest molecules. Other techniques employed in the initial characterization of these compounds are Microanalysis, Mass Spectrometry and UV/Visible Spectrophotometry. An intramolecular potential energy study on the [Ni(NCS)2(3,5-diMepy)4] complex reveals that the orthohydrogens on the 3,5-dimethylpyridine ligands control the conformation of the molecule. Packing densities and volume comparisons of the [Ni(NCS)2(4-Etpy)4] and [Ni(NCS)2(4-Vipy)4] complexes and their clathrates have been carried out. The exact sizes and shapes of the cavities in which the guest molecules are located in the x-ray crystal structures have been evaluated by both intermolecular potential energy and molecular volume calculations. Thermodynamic and spectroscopic properties of the [Ni(NCS)2(4-Etpy)4] and [Ni(NCS)2(4-Vipy)4] clathrates have been studied in both solution and the solid state. The techniques used are x-ray powder diffractometry, IR spectroscopy and Thermogravimetry (including Differential Thermal Analysis).
29
Caporali, Roberto. "Understanding the activity and the chemistry of Pd-based diesel oxidation catalysts". Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.669674.
Texto completo da fonteResumo:
Several technologies offer a promising strategy for the exhaust after-treatment of diesel engines in which continuing to further thrift Pt/Pd alloy diesel oxidation catalysts (DOC) by increasing Pd content, the prospect of an essentially Pt-free DOC catalyst is very attractive because Pd is cheaper than Pt. However, to determine the viability of this approach a much better understanding of PdO/AI20 3 chemistry and reactivity is needed. Therefore, the aim of this work is (1) to improve the catalytic performance of the Pd based ?iesel oxidation catalyst by using different preparation method and to investigate the effect of the thermal aging' on the catalyst activity towards CO and C3H6 oxidation. (2) clarify the effect of H20 and NO in the CO and C3H6 catalytic oxidation reactions in terms of reaction mechanism. (3) to investigate the catalyst deactivation induced by sulphur poisoning. It has been found that the structure, morphology and textures properties of the catalysts were significantly affected by both the preparation method and the thermal aging. In particular, the formation of highly catalytically active palladium nanoparticles showing a high density of defects and/or corners, have been observed when the sample was prepared by solution combustion synthesis and when thermal aging was carried out between 500 - 750 ·C. Regardless of the preparation method and the thermal aging, the presence of water in the reaction mixture resulted to promote the catalyst performances with the respect to CO oxidation which occurred via reaction with water derived species rather than dioxygen. Beside, water has also been found beneficial in modulating the NO, C3H6 and S02 inhibition. The formation of strongly bonded sulphate species on the catalyst surface along with the permanent loos of the structure and morphology properties of the catalyst, have been identified as the main cause of the catalyst deactivation induced by sulphur poisoning.
30
Salem, M. A. A. "Electron transfer activity of some oxide catalysts". Thesis, Queen's University Belfast, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374993.
Texto completo da fonte
31
Harries, C. M. "Antidepressant activity of N-desmethylclomipramine". Thesis, Cardiff University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370790.
Texto completo da fonte
32
Gabrielli, William Fullard. "Structure activity relationship studies of ochratoxin A analogues". Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/53070.
Texto completo da fonteResumo:
Thesis (MSc)--Stellenbosch University, 2002.ENGLISH ABSTRACT: Mycotoxins have assumed worldwide importance due to the ubiquitous occurrence of toxigenic fungi, their infestation of plant-based foods and feeds and the subsequent economical and health impact it because of their contamination of commercial products. Ochratoxin A (OA) is a nephrotoxic mycotoxin produced by isolates of Aspergillus ochraceus and Penicillium verrucosum and occurs frequently in nature. The major target for toxicity of OA in mammalian species is the kidneys and it has been the major cause of Danish Porcine Nephropathy. OA has also been extensively implicated in the aetiology of Balkan Endemic Nephropathy and Chronic Interstitial Nephropathy in Northern-Africa. Furthermore, OA has been identified as a carcinogen, an immunosuppressant and a teratogen with respect to the foetal central nervous system. Although a large amount of research has been conducted into the chemical nature of the toxicity of OA, the exact molecular mechanism of action of OA is not yet conclusive. Numerous structure activity relationship studies have suggested that the toxicity of OA may be assigned to three major processes: (i) inhibition of ATP production; (ii) inhibition of protein synthesis; and (iii) the disruption of hepatic microsomal calcium homeostasis through the promotion of membrane lipid peroxidation. It is the aim of this thesis to gain a better understanding, through the synthesis ofOA analogues, of the chemical structure responsible for the toxic function of the ochratoxins. The halogen-group has extensively been implicated in the toxicity of the ochratoxins. This is evident in ochratoxin B (OB), the dechloro analogue of OA, which is approximately ten times less toxic than OA. Preliminary tests have indicated that bromo-ochratoxin B(BrOB), the bromo analogue of OA, is more toxic than ochratoxin A to renal cells. Fluoro-ochratoxin B and other analogues of OA, where other amino acids are incorporated, should provide invaluable information on the structure-activity relationships and the mode of action of the ochratoxins. Our research effort addresses both these aspects (i) fluorination of the dihydroisocoumarin moiety and (ii) the coupling of different amino acids and dipeptides to the non-toxic hydrolysed product of OA, ochratoxin a. Chapter one includes a review of the important biological aspects of OA that has served as a guideline to the synthesis of effective OA analogues. An overview of the relevant chemistry involved in the modification of OA will conclude the chapter. Chapter two entails a discussion of fluorine in bio-organic chemistry. This includes an overview of the impact that fluorine substitution has on the biological reactivity of molecules. A review on the synthesis of organofluorine compounds, which forms the emphasis of this study, concludes the chapter. Chapter three elaborates on the different methodologies used in our attempts to synthesise fluoro-ochratoxin B and other analogues. These included the direct electrophilic fluorination of OB and different analogous aromatic model compounds by xenon difluoride, N-fluorobenzenesulfonimides and Selectfluor™ as fluorinating agents. Also involved is an investigation into an alternative route for the synthesis of fluoro aromatic compounds from bromo and chloro analogues by means of palladium catalysed trimethyl- and tributylstannyl and trimethylsilylation which in tum may be substituted with fluorine by means of xenon difluoride. Efforts towards the direct catalytic fluorosubstitution of aryl halides are also investigated. The synthesis of a key intermediate, fluoroacetoacetaldehyde, in a de nova synthetic route to fluoroochratoxin B is also discussed. Furthermore, the synthesis of novel OA analogues with respect to the replacement of the L-phenylalanine moiety is addressed. This includes the conversion of OA to Oa, by acid hydrolysis, followed by the coupling of ortho-, meta- and para- substituted DL-fluorophenylalanine to the lactone acid. This is followed by the synthesis of histidylhistidine methyl ester and attempted coupling to Oa. The coupling of halosalicylic acids and salicylic acid to L-phenylalanine, for use as model aromatic substrates for fluorination, IS discussed. Peptide coupling by dicyclohexylcarbodiimide carboxyl activation, with reference to the protection of the phenolic hydroxyl group in 5-chlorosalicylic acid for application to Oa, concludes this work.
AFRIKAANSE OPSOMMING: Mikotoksiene is van wêreld-wye belang as gevolg van die alomteenwoordige voorkoms van toksigeniese fungi, hul besmetting van plantaardige kossoorte en voerstowwe en die gevolglike ekonomiese en gesondheidsimpak deur die besoedeling van kommersiële produkte. Ochratoksien A (OA) is 'n nefrotoksiese mikotoksien wat geproduseer word deur isolate van Aspergillus ochraceus en Penicillium verrucosum en kom algemeen in die natuur voor. Die niere is die hoof teiken vir vergifiting deur OA in soogdierspesies en is as die vername oorsaak van "Danish Porcine Nephropathy" aangewys. OA word verder aangedui as die oorsaak vir "Balkan Endemic Nephropathy" en "Chronic Interstitial Nephropathy" in Noord- Afrika. OA is verder geïdentifiseer as 'n karsinogeen, immuno-onderdrukker en is teratogenies ten opsigte van die sentrale senuweestelsel van fetusse. Alhoewel aansienlike navorsing alreeds gewei is aan die chemiese natuur van die toksisiteit van OA, is die presiese molekulêre meganisme van OA reaktiwiteit onbeslis. Verskeie struktuur-aktiwitweit verwantskaps studies dui daarop dat die toksisiteit van OA hoofsaaklik toegeskryf kan word aan drie hoof prosesse: (i) inhibisie van ATP produksie; (ii) inhibisie van proteïen sintese; en (iii) die ontwrigting van hepatiese mikrosomale kalsiumhomeostase deur die bevordering van membraanlipiedperoksidasie. Hierdie tesis het ten doel, deur die sintese van OA analoë, om 'n beter insig oor die chemiese struktuur wat verantwoordelik is vir die toksiese funksionaliteit van ochratoksiene te verkry. Die halogeen substituent is grootliks geïmpliseer in die toksisiteit van OA. 'n Bewys hiervan is ochratoksien B (OB), die dechlooranaloog van OA, wat ongeveer tien maal minder toksies is as OA. Voorlopige ondersoeke het aangetoon dat bromoochratoksien B (BrOB), die broomanaloog van OA, meer toksies is vir nierselle as OA. Fluoorochratoksien B en ander analoë van OA, waar ander aminosure geïnkorporeer word, behoort waardevolle inligting te voorsien met betrekking tot die struktuur-aktiwiteitsverwantskappe en die wyse waarop ochratoksiene funksioneer. Hierdie navorsingspoging spreek beide aspekte aan; (i) die fluorering van die dihidroïsokumarien gedeelte en, (ii) die koppeling van verskillende armnosure en dipeptiede aan die nie-toksiese hidrolieseproduk van OA, nl. ochratoksien a. Hoofstuk een vervat 'n oorsig van die belangrike biologiese aspekte van OA wat dien as riglyn vir die sintese van doeltreffende OA analoë. Die hoofstuk word afgesluit met 'n oorsig van die relevante chemie betrokke by die modifisering van die struktuur van OA. Hoofstuk twee bevat 'n bespreking van die aanwending van fluoor in bio-organiese chemie. Dit bevat 'n oorsig van die impak wat fluoorsubstitusie het op die biologiese reaktiwiteit van molekules. 'n Opsomming oor die sintese van organofluoorverbindings, wat die essensie van hierdie studie is, beëindig die hoofstuk. Hoofstuk drie handeloor die veskillende metodes wat toegepas is in pogings om fluoorochratoksien B en ander analoë te sintetiseer. Dit sluit in die direkte elektrofiliese fluorering van OB en ander verwante aromatiese modelverbindings deur gebruik te maak van xenondifluoried, N-fluoorbenseensulfonimied en Selectfluor™ as fluoreringsreagense. Dit behels verder ook 'n ondersoek na 'n alternatiewe roete tot die sintese van fluooraromatiese verbindings vanaf broom- en chlooranaloë. Vir die doel word palladiumgekataliseerde trimetiel- en tributielstannilering, en trimetielsililering wat vervolgens deur middel van xenondifluoried met fluoor gesubstitueer kan word, aangewend. Pogings tot die direkte katalitiese fluoorsubstitusie van arielhaliede word ook bespreek. Die sintese van 'n sleutelintermediêr, fluoroasetoasetaldehied, in 'n de nova sintese roete tot fluoorochratoksien B word bespreek. Die sintese van nuwe OA analoë, met betrekking to die vervangmg van die Lfenielalanien (L-Phe) groep word ondersoek. Dit bevat die omsetting van OA na Oa, deur suurhidrolise, gevolg deur die koppeling van orto-, meta- en paragesubstitueerde DL-fluoorfenielalanien aan die laktoonsuur, Oa. Daarna word die sintese van histidielhistidienmetielester en die verdere pogings aangaande koppeling met Oa bespreek. Die koppeling van halosalisielsure en salisielsuur aan L-Phe wat dien as model aromatiese verbindings vir fluorering, word behandel. Peptiedkoppeling met behulp van disikloheksielkarbodiimied-karboksielaktivering, met inbegrip van die beskerming van die fenoliese hidroksiel groep m 5-chloorsalisielsuur Vir die toepassing op Oa, beëindig hierdie werk.
33
Mah, Wayne. "Single molecule study of RecA recombinase enzyme activity". Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18743.
Texto completo da fonteResumo:
Homologous recombination is an essential pathway in the repair of DNA damage during the DNA replication process. RecA protein promotes the central steps in homologous recombination, after coating single-stranded DNA (ssDNA), RecA carries out a pairing and strand exchange reaction involving homologous DNA. This research project aims to characterize RecA function in homologous recombination using single molecule tethered particle motion (TPM). Using TPM to observe RecA extension along DNA, the RecA extension rate on ssDNA was determined for the first time. The rate obtained for dsDNA was similar, implying that RecA polymerizes along only one strand of a DNA substrate. The nucleation behaviour of RecA on DNA was also obtained from the extension trace, confirming the hypothesis that rapid nucleation on ssDNA is pH independent, while nucleation on dsDNA is pH dependent. Several pilot single molecule experiments aimed at monitoring the pairing and strand exchange reaction in real time were attempted. Although these experiments were unsuccessful, successful ensemble biochemical analogues of these experiments proved the feasibility of the single molecule experiments. These attempts gave insights into possible factors hindering success and led to experimental suggestions essential to the success of future experiments.La recombinaison Homologue est un chemin essentiel dans la réparation de dommages d'ADN pendant le procédé de réplication d'ADN. La protéine de RecA promeut les étapes centrales dans la recombinaison homologue, après avoir revêtu ADN seul-abandonné (ssDNA), RecA exécute un mettre et la réaction d'échange de brin impliquant ADN homologue. Ce projet de recherche vise à caractériser la fonction de RecA dans la recombinaison homologue utilisant la molécule seule mouvement de particule attaché (TPM). TPM d'utilisation pour observer l'extension de RecA le long d'ADN, le taux d'extension de RecA sur ssDNA a été déterminé pour la première fois. Le taux obtenu pour dsDNA était similaire, impliquant ce RecA polymerizes le long de seulement un brin d'un substrat d'ADN. Le comportement de nucleation de RecA sur ADN a été aussi obtenu de la trace d'extension, confirmant l'hypothèse ce nucleation rapide sur ssDNA est indépendant du pH, pendant que nucleation sur dsDNA est dépendant du pH. Plusieurs pilote plusieurs expériences de molécule seules ont visé à contrôlant le mettre et la réaction d'échange de brin a été tentée en temps réel. Bien que ces expériences étaient les ensembles infructueuses et réussies analogues biochimiques de ces expériences ont prouvé la possibilité des expériences de molécule seules. Ces tentatives ont donné de l'aux perspicacités dans les facteurs possibles freinant le succès et a mené à l'élément essentiel de suggestions expérimental au succès d'expériences futures
34
Hsu, Bryan Boen. "Investigation of microbicidal activity of surface-immobilized hydrophobic polycations". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/62728.
Texto completo da fonteResumo:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references.
Hydrophobic polycations have been shown to completely kill bacterial, fungal, and viral pathogens, on-contact. Herein we describe advances with this technology on two fronts: (1) innovation of a polycationic-derivative that simplifies the labor-intensive covalent-immobilization procedure, and (2) elucidation of the current mechanistic understanding of this phenomenon. First, we developed and characterized a novel polycationic polymer capable of crosslinking to cotton via activation with ultraviolet light. The resultant, covalently-immobilized, Nalkyl polyethylenimine (PEI) demonstrates complete bactericidal activity against S. aureus and E. coli (i.e., representative Gram-positive and Gram-negative bacteria, respectively). In addition, by utilizing light to activate the covalent cross-linking, this immobilization procedure is simpler and more versatile than similar chemically-attached bactericidal polycations. Second, we shed light onto how the coating inactivates microbial pathogens. Gramnegative and Gram-positive bacteria exposed to the polycationic coating revealed substantial structural deformation, which allowed for the leakage of their intracellular contents. Characterization of the enzymes leaked into solution from Gram-negative bacteria indicated a disproportionately greater damage done to the outer-membrane than the inner-membrane. In addition, the quantity of proteins leaked into solution showed striking similarity to results obtained from bacteria subjected to lysozyme/EDTA treatment (i.e., a traditional cell lysis technique that degrades the cellular wall). In total, these results suggest that it is this interaction between the polycation and cellular structure (i.e., outer membrane and cell wall) that ultimately compromises bacterial integrity. Expanding our investigation, we studied the effect of the polycationic coating on another membrane-enclosed microbe: the influenza virus. We found that the viral particles adhere to the polycationic coating, which results in a structural deformation, similar to that borne-out by bacteria. As a consequence, viral genomic material is leaked into solution, revealing the viruses' state of inactivation upon adherence to the coating.
by Bryan Boen Hsu.
S.M.
35
Centani, Luyanda. "Structure activity and structure property relationships of antimalarial imidazopyridazines". Master's thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/31315.
Texto completo da fonteResumo:
Malaria is one of the most pressing human health issues. Despite being an ancient disease, it is estimated to have an annual death rate of 445 000 with out of 216 million malaria related cases in 2016. Malaria is most widespread in developing regions of the world. Forty percent of the world’s population is exposed to varying degrees of malaria. Malaria is caused by different species of the Plasmodium genus and the disease is vector-borne. The disease may be cured if diagnosed early. Most drugs that were once effective in the treatment of malaria have become ineffective due to the emergence of resistance, which has become the main driving force behind efforts to discover and develop new drugs able to circumvent the resistance. Imidazopyridazines have been shown to have potent antiplasmodium activity. The lead compound MMV652103 has been shown to display potent activity against the multidrug resistant K1 strain and the drug sensitive NF54 strain of the human malaria parasite Plasmodium falciparum. However, the majority of the antimalarial imidazopyridazine compounds evaluated to date have solubility and off-target human ether-a-go-go-related gene (hERG) potassium ion channel liabilities. Towards improving solubility and de-risking the hERG liability, a series of analogues was designed and synthesised. Structure-Activity Relationship (SAR) and Structure-Property Relationship (SPR) studies aimed at retaining the good antiplasmodium activity while improving solubility and reducing hERG channel inhibition, were conducted. Previous studies conducted on this series of imidazopyridazines have shown that incorporation of hydrogen bond donors or acceptors resulted in improving solubility and hERG channel inhibition. While the lead compound MMV652103 at pH 6.5 has a sub-optimal solubility of 5 µM, all target compounds showed an improvement in solubility. Five analogues 59, 78, 84, 85, and 86 exhibiting impressive in vitro asexual blood stage antiplasmodium potency (IC50< 100 nM) and aqueous solubility (> 200 µM) were identified from the study. The identified compounds also displayed good activity against the sexual late-stage gametocytes, the transmissible forms of the parasite.
36
Briscoe, N. A. "Ultrastructure and catalytic activity of some complex oxides". Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355717.
Texto completo da fonte
37
Lau, S. "Cobalt(III) acetate - its structures and catalytic activity". Thesis, University of Hull, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233969.
Texto completo da fonte
38
Wilson, Gary. "Vibrational Raman optical activity of peptides and proteins". Thesis, University of Glasgow, 1996. http://theses.gla.ac.uk/6144/.
Texto completo da fonteResumo:
Vibrational Raman optical activity (ROA) which is the difference in the Raman scattering of left and right circularly polarised incident light, has recently emerged as a new and incisive probe of biomolecular structure. This thesis is based on new applications of ROA to some current biochemical problems. The first chapter is a brief explanation of the origin of chirality and the development of vibrational optical activity with special emphasis on ROA. Chapter 2 is a theoretical analysis of ROA and provides a fundamental explanation of the phenomenon. This involves a description as to how the ROA effect is generated using molecular property tensors. The third chapter concentrates on the instrumentation required to measure ROA and the importance of CCD detectors and holographic notch filters in establishing the technique with respect to biopolymers. Chapter 4 is a brief introduction to protein structure and includes an analysis of the strengths and weaknesses of current biophysical techniques used for structure determination. Chapters 5 and 6 describe detailed applications of ROA to polypeptides and native proteins. The polypeptides are a suitable starting point since from other spectroscopic techniques they are known to adopt certain conformations, such as -helix, -sheet and random coil. Native proteins are examined in Chapter 6 and the ability of ROA to detect not only secondary but also tertiary structure is highlighted. Chapter 7 is concerned with the important topics of the structure and dynamics of unfolded proteins, molten globules and ligand bound proteins. Finally, in the appendix there is a summary of the assignments made to secondary structure and to loops and turns.
39
McDonald, Russell Walker. "Synthesis and anticancer activity of NDGA and analogues". Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274867.
Texto completo da fonte
40
Lear, Tim. "Structure/activity correlations in alumina supported palladium catalysts". Thesis, University of Glasgow, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275617.
Texto completo da fonte
41
Park, Seongsoon. "Enhancing hydrolase activity and selectivity by medium, substrate, and protein engineering". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83088.
Texto completo da fonteResumo:
Researchers use enzymes for enantio- and regioselective reactions because of their high selectivity and activity toward natural substrates. However, researchers sometimes need to modify the reaction system or the enzyme itself to get reliable selectivity and activity when they deal with unnatural substrates. To obtain researcher's need, one can change the solvent, modify the substrates, or alter the enzyme itself. These processes are called medium, substrate, and protein engineering, respectively.This thesis deals with hydrolases, which are classified by EC 3. We applied the proper approach to improve their activity and selectivity depending on the reactions. For the first approach, highly polar ionic liquids were applied to lipase-catalyzed acylation. Ionic liquids worked reliably in enantio- and regioselective lipase-catalyzed reactions. In particular, ionic liquids dissolved polar substrates such as glucose and L-ascorbic acid, thereby facilitating their acylations. In the second approach to improving enantioselectivity of CAL-B (Candida antarctica lipase B) in beta-lactam ring opening reactions, we changed the nucleophile from water to a range of alcohols. Longer, secondary alcohols increased the reaction rate as well as the enantioselectivity. Molecular modeling revealed that the high enantioselectivity of CAL-B and the critical role of alcohols. For the last approach, structure-guided random mutagenesis was applied to increase the enantioselectivity of PFE ( Pseudomonas fluorescens esterase) toward MBMP (methyl 3-bromo-2-methylpropionate). The homology model was used to select amino acid residues for mutagenesis near the stereocenter of the docked tetrahedral intermediate of the substrate. Randomization of these residues yielded a Val122Ser mutant with E increased to 61 (from 12 of wild type enzyme), as well as a Val122Met mutant to 36.
42
Torrie, Joan P. "Extracellular beta-D-mannanase activity from Trichoderma harzianum E58". Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7732.
Texto completo da fonteResumo:
In this work, 4 yeasts (Pichia wickerhammi, Candida wickerhammi, Pichia stipitis CBS5776, Pichia stipitis CBS5876), and 5 fungi (Theivalia spp., Thermoascus aurantiacus, Tyromyces palustris A, Aspergillus niger, Trichoderma harzianum), known to excrete enzymes capable of hydrolyzing polysaccharides found in association with $\beta$-D-mannans, were assessed for their ability to degrade $\beta$-D-mannans. The $\beta$-D-mannanase activity found in the culture filtrate of T. harzianum was selected for further study and a 'cellulase-free' $\beta$-D-mannanase isolated from culture filtrates of T. harzianum grown on medium supplemented with 1% w/v locust bean gum studied. $\beta$-D-Mannanase activity was detected in T. harzianum culture filtrates from media supplemented with 1% (w/v) Avicel, locust bean gum galactomannan, konjac root glucomannan, or spruce wood water-solubles. Medium supplemented with 1% (w/v) mannose did not induce $\beta$-D-glucomannanase or $\beta$-D-galactomannanase activity. However, when 0.5% (w/v) $\beta$-D-galactomannan was added with mannose, $\beta$-D-mannanase activity was detected in the culture filtrate. Growth of the fungus on mannan-rich locust bean gum resulted in the highest specific $\beta$-D-glucomannanase and $\beta$-D-galactomannanase values. A zymogram assay was developed to selectively detect $\beta$-D-mannanase activity in crude culture filtrates. The presence of different polysaccharides in the growth medium resulted in different $\beta$-D-mannanase zymogram profiles. Analyses of the protein profiles of the culture filtrates separated by isoelectric focusing revealed several bands having $\beta$-D-mannanase and endoglucanase activity. A protein band having $\beta$-D-mannanase activity but lacking detectable cellulase activity was identified. This enzyme was purified to homogeneity via a sequence involving ultrafiltration, ion exchange and gel filtration. This 'cellulase-free' $\beta$-D-mannanase has the highest reported pI for a fungal $\beta$-D-mannanase. The isolated enzyme had a molecular weight of 42.9 $\pm$ 4 kD, an optimum temperature of 60-65$\sp\circ$C, an optimum pH of 5.8, a pI of 6.55, and possessed at least 75% of maximum activity over a pH range from 3.21-6.8. Enzymatic activity was stable during 12 months of storage at 4$\sp\circ$C. $\beta$-D-mannanase activity was resistant to pepsin, $\alpha$-chymotrypsin, trypsin, and Staphylococcus V8 protease. The effect of metal ions, detergent and solvents on $\beta$-D-mannanase activity was also determined. Although the enzyme did not degrade Avicel or Solka floc, it did associate with both celluloses. Enzyme associated with these celluloses remained active towards locust bean gum galactomannan. The overall efficiency of the enzyme (V$\sb{\rm max}$/K$\sb{\rm m})$ for the target substrate, locust bean gum galactomannan, was reduced by the presence of 1.0% w/v Avicel. Of the four $\beta$-D-mannans tested, the enzyme had greatest overall efficiency towards konjac glucomannan. However, deacetylation of konjac glucomannan lowered the efficiency of the enzyme by 41.5%. (Abstract shortened by UMI.)
43
Auer, Erich Nicholaus. "Methods of blocking efflux pump activity in Escherichia coli". University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1524660216368043.
Texto completo da fonte
44
Howes, Melanie-Jayne Rosemarie. "Chemistry and biological activity of plants with traditional uses relevant to Alzheimer's disease". Thesis, King's College London (University of London), 2001. https://kclpure.kcl.ac.uk/portal/en/theses/chemistry-and-biological-activity-of-plants-with-traditional-uses-relevant-to-alzheimers-disease(57cd4b39-dee2-445e-b6f8-74bb88d30437).html.
Texto completo da fonte
45
Techatanawat, Isariya. "Chemistry and cytotoxic activity of some Thai medicinal plants used to treat cancer". Thesis, King's College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427990.
Texto completo da fonte
46
Stoerzinger, Kelsey A. (Kelsey Ann). "Understanding the catalytic activity of oxides through their electronic structure and surface chemistry". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104113.
Texto completo da fonteResumo:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
The intermittent nature of renewable energy sources requires a clean, scalable means of converting and storing energy. Water electrolysis can sustainably achieve this goal by storing energy in the bonds of oxygen and hydrogen molecules. The efficiency of this storage-conversion process is largely determined by the kinetic overpotential required for the oxygen evolution and reduction reactions (OER and ORR), respectively. This thesis focuses on transition metal oxides as alternative oxygen catalysts to costly and scarce noble metals. In order to develop descriptors to improve catalytic activity, thus reducing material cost for commercial technologies, this work studies fundamental processes that occur on model catalyst systems. Electrochemical studies of epitaxial oxide thin films establish the intrinsic activity of oxide catalysts in a way that cannot be realized with polydisperse nanoparticle systems. This thesis has isolated the activity of the catalyst on a true surface-area basis, enabling an accurate comparison of catalyst chemistries, and also revealed how different terminations and structures affect the kinetics. These studies of epitaxial thin films are among the first to probe phenomena that are not straightforward to isolate in nanoparticles, such as the role of oxide band structure, interfacial charge transfer (the "ligand" effect), strain, and crystallographic orientation. In addition, these well-defined surfaces allow spectroscopic examinations of their chemical speciation in an aqueous environment by using ambient pressure X-ray photoelectron spectroscopy. By quantifying the formation of hydroxyl groups, we compare the relative affinity of different surfaces for this key reaction intermediate in oxygen electrocatalysis. The strength of interaction with hydroxyls correlates inversely with activity, illustrating detrimental effects of strong water interactions at the catalyst surface. This fundamental insight brings molecular understanding to the wetting of oxide surfaces, as well as the role of hydrogen bonding in catalysis. Furthermore, understanding of the mechanisms of oxygen electrocatalysis guides the rational design of high-surface-area oxide catalysts for technical application.
by Kelsey A. Stoerzinger.
Ph. D.
47
Al-Salihi, Suhad Adnam Ahmed. "Unlocking the genetics and the chemistry behind the antimicrobial activity of Hypholoma species". Thesis, University of Bristol, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.752777.
Texto completo da fonte
48
Vignes, Maéva. "Development and activity of in vitro neuronal networks : learning organic chemistry through games". Thesis, Paris 5, 2013. http://www.theses.fr/2013PA05T080/document.
Texto completo da fonteResumo:
Ma thèse comporte deux grandes parties, la première en biophysique et la seconde en science de l’éducation. La première partie présente des travaux à la frontière entre neurobiologie et microfluidique. Le but de ces travaux est de pouvoir reconstruire et étudier des réseaux complexes de neurones in vitro avec une topologie de connections synaptiques bien contrôlées. Une série de micro-structures mécanique et/ou chimique ont été étudiées pour leur capacité à (i) positionner les corps cellulaires des neurones, (ii) orienter la pousse des neurites, et (iii) différencier les axones des dendrites. Un premier réseau comportant trois populations de neurones connectées en série a été reconstruit à l’intérieur d’un circuit microfluidique. Ce réseau qui mime la voie perforante de l’hippocampe pourra être exploité pour des études en physiologie ou en neuro-dégénerescence. Une méthode entièrement optique de stimulation et d’observation de l’activité neuronal a été mise au point. Elle ouvre de nouvelles portes pour étudier des processus cognitifs complexes dans des systèmes simplifiés in vitro. La seconde partie de mon travail a permis le développement et l’étude de jeux pédagogiques pour l’apprentissage de la chimie en licence. Ces jeux, qui peuvent selon les cas remplacer un cours ou une séance d’exercices, donnent des résultats prometteurs pour l’aide à la compréhension et à la mémorisation de concepts tels que la géométrie des molécules ou la réactivité entre molécules organiquesMy PhD is divided in two parts one on biophysic of neuronal networks and one on science of education. The first part present results at the frontier between neurobiology and microfluidic. The overarching goal of this work was to develop tools and methods to build and study complex neuronal networks controlling the topology of synaptic connexions. Micro-patterning techniques with mechanical and/or chemical constraints were explored regarding their capacity to (i) position cell bodies, (ii) orient neurite outgrowth and (iii) polarize neurons. For the first time, a network comprising three different neuronal populations connected in specified directions was reconstructed in a microfluidic device. This network that mimics the perforant pathway of the hippocampus can be used to study physiological rythms or neurodegenerative processes including Alzheimer’s disease. A novel and fully optical method is presented to stimulate and record neuronal activity in vitro. It opens new routes to study complex cognitive processes in simplified in vitro systems. The second part of my work present the development and assessment of educational games in chemistry at the undergraduate level. These games that can either be used to replace courses or exercises, seem promising to improve the understanding and memorization of chemistry concepts og geometries of molecules and organic reactivity
49
De, Nisi Assunta <1987>. "Novel insights into gold(I) chemistry: from anticancer activity to new synthetic methodologies". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amsdottorato.unibo.it/8597/1/DNA%20PhDFull14mar18.pdf.
Texto completo da fonteResumo:
The work herein presented, embraces various aspects of gold chemistry: the documentation of novel [alkynyl(triphenylphosphine)gold(I)] complexes carrying differently substituted propargylic amines and their pharmacological investigation on a series of cancer cell lines and the investigation of the dearomative cycloaddition reaction of indoles with electron-rich allenes catalysed by commercially available gold(I) complexes that show competence in performing the chemo-, regio- and diastereoselective formal [2+2]-cycloaddition between a wide range of substrates under mild conditions. It has also been developed the combined efficiency of Bu4N+ and F− ions in performing a cascade sequence involving intramolecular hydroamination of the C–C triple bond, cleavage of silyl-protecting groups and site-selective sigmatropic aza-Cope-type [3,3]-rearrangement.
50
McFadyen, Iain James. "Structure-activity relationships of opioid ligands". Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/33189.
Texto completo da fonteResumo:
There are three different types of opioid receptor, namely mu, delta and kappa. Morphine and related clinically useful analgesics exert their actions through the mu opioid receptor. Such compounds represent a huge structural diversity, including both peptides and alkaloids. Nevertheless, there exists a common pharmacophore comprising two critical features, namely an amine nitrogen and an aromatic ring, usually with a hydroxyl substituent; the spatial relationship between them is also vital.