An introduction is given to the background theory and scientific literature of the major subject areas of interest in this thesis, namely the chemistry of free radical and anionic polymerisation, molecular weight control in each type of polymerisation, polymerisation reactors, computer simulation of polymerisation processes and polymer characterisation by gel permeation chromatography. A novel computer model has been devised, based on the analysis of the polymerisation process in terms of the reaction extent of each reactant and the use of generation functions to describe the concentration of living and dead polymeric species, for the free radical, solution polymerisation of methylmethacrylate in a CSTR. Both heat and mass balance expressions have been described. Conversion, Mn and Mw were monitored. To test the model a reactor was designed and constructed. A detailed description of the reactor and the experimental conditions used for the validation of the model are given. The results of these studies are presented and excellent agreement is shown between model predictions and experiments up to 30% conversion for Mn w and % conversion. A similar study is described for the anionic polymerisation of styrene in tetrahydrofuran as solvent, in a CSTR. In this work the computer model becomes 'stiff' when realistic rate constants are introduced in the kinetic expressions. Experimental difficulties were encountered in obtaining reproducible results in the anionic work. A new approach of using 'scavengers' as protecting agents for the living chains is described. A scavenger was successfully employed in the preparation of block copolymers using a tubular reactor. Block copolymerisation, in addition to providing a means of checking the number of the 'living' chains inside the reactor, is of interest in its own right. All the experimental findings are discussed in relation to the currently accepted views found in the scientific literature.

No description available.

Membrane-based separation processes have been used extensively for drinking water purification, wastewater treatment, and numerous other applications. Reactive membranes synthesized through functionalization of the membrane pores offer enhanced reactivity due to increased surface area at the polymer-solution interface and low diffusion limitations. Oxidative techniques utilizing free radicals have proven effective for both the destruction of toxic organics and non-environmental applications. Most previous work focuses on reactions in the homogeneous phase; however, the immobilization of reactants in membrane pores offers several advantages. The use of polyanions immobilized in a membrane or chelates in solution prevents ferric hydroxide precipitation at near-neutral pH, a common limitation of iron(Fe(II/III))-catalyzed hydrogen peroxide (H2O2) decomposition. The objectives of this research are to develop a membrane-based platform for the generation of free radicals, degrade toxic organic compounds using this and similar solution-based reactions, degrade toxic organic compounds in droplet form, quantify hydroxyl radical production in these reactions, and develop kinetic models for both processes. In this study, a functionalized membrane containing poly(acrylic acid) (PAA) was used to immobilize iron ions and conduct free radical reactions by permeating H2O2 through the membrane. The membrane’s responsive behavior to pH and divalent cations was investigated and modeled. The conversion of Fe(II) to Fe(III) in the membrane and its effect on the decomposition of hydrogen peroxide were monitored and used to develop kinetic models for predicting H2O2 decomposition in these systems. The rate of hydroxyl radical production, and hence contaminant degradation can be varied by changing the residence time, H2O2 concentration, and/or iron loading. Using these membrane-immobilized systems, successful removal of toxic organic compounds, such as pentachlorophenol (PCP), from water was demonstrated. Another toxic organic compound of interest for water treatment applications is trichloroethylene (TCE). Due to its limited solubility in water, a majority of the TCE is often present in the form of droplets. In this study, effective TCE droplet degradation using chelate-modified, iron-catalyzed free radical reactions at near-neutral pH was demonstrated. In order to predict the degradation of aqueous and non-aqueous phase TCE for these reactions, a mathematical model was constructed through the use of droplet mass transfer correlations and free radical reaction kinetics.

In this study, ethyl methacrylate was polymerized by free radical polymerization at 600C, 700C, 800C at open atmosphere / atom transfer radical polymerization, (ATRP), at 800C in vacuum and in gamma irradiation in vacuum. The polymer obtained was white, hard material. The kinetic curves for free radical polymerization and ATRP by gamma radiation were S-type. However, the curve for polymerization by gamma irradiation raises more smoothly. For ATRP by thermal initiation gives a lineer change of conversion with time. It was observed that the molecular weight can be controlled and low molecular weight polymer could be obtained by ATRP method. The characterization of polymers were made by FTIR, DSC, 1H and 13C NMR techniques.

Made available in DSpace on 2015-07-22T20:50:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-03-25. Added 1 bitstream(s) on 2015-08-11T03:25:26Z : No. of bitstreams: 1 Publico-00235.pdf: 311178 bytes, checksum: 4bdcda98426ffee2492755dd8ae27d33 (MD5) / Verificar a relacao entre as concentracoes de substancias reativas ao acido tiobarbiturico, a atividade das enzimas glutationa peroxidase e catalase com a ocorrencia de gravidez, com o estimulo hormonal administrado e com a presenca ou nao de um fator de infertilidade feminino. Metodo: Foi realizado um estudo prospectivo caso controle com o liquido folicular de 146 pacientes que foram submetidas ao programa de Reproducao Assistida da UNIFESP. Como criterios de inclusao foram considerados apenas as pacientes que realizaram o protocolo de fertilizacao in vitro (FIV) atraves de injecao intracitoplasmatica de espermatozoide (ICSI). Os grupos experimentais foram subdivididos de acordo com a presenca ou nao de gestacao, com hormonio administrado durante o estimulo (FSH ou FSH e hMG) e com a presenca ou nao de pelo menos um fator de infertilidade feminina. As aliquotas dos liquidos foliculares foram coletadas apos a retirada dos oocitos e analisadas por espectrofotometro para mensurar as concentracoes de substancias reativas ao acido tiobarbiturico (TBARS) . um marcador de peroxidacao lipidica, e das enzimas catalase e glutationa peroxidase presentes em cada amostra. Um modelo de regressao logistica foi construido utilizando numero de embrioes de alta qualidade no terceiro dia de cultivo transferidos, presenca de pelo menos um fator de infertilidade feminino e a atividade da glutationa peroxidase, maximizando a preditibilidade da ocorrencia de gravidez. Resultados: No grupo de mulheres nao gravidas foi observada uma maior atividade da enzima glutationa peroxidase (p=0,04). Nos outros grupos nao foi observada diferenca estatistica entre nenhum dos parametros avaliados. Na regressao logistica, o melhor modelo preditivo para gravidez incluiu os valores de fator de infertilidade, classificacao embrionaria no terceiro dia de cultivo e a atividade de glutationa peroxidase (73,68%, p=0.00001). O valor de odds-ratio para a atividade de glutationa peroxidase foi 0,98, indicando que valores crescentes de atividade glutationa levaram a diminuicao da chance de ocorrencia de gravidez. Conclusao: Nas condicoes deste estudo, (i) mulheres com ƒÀ-hCG negativo possuem uma maior atividade da glutationa peroxidase, (ii) diferentes estimulos ovarianos nao provocam alteracao nas concentracoes de TBARS e na atividade das enzimas antioxidantes e (iii) a presenca de pelo menos um fator de infertilidade feminino nao altera a concentracao de TBARS e a atividade da enzimas antioxidantes. / Objective: to verify the relation between thiobarbituric acid reactive substances concentrations, glutathione peroxidase and catalase activities, and occurrence of pregnancy, hormonal stimulation protocol utilized, and presence or not of a female infertility factor. Method: a prospective case-control study was carried with follicular fluid from 146 patients submitted to the Assisted Reproduction program at the Sao Paulo Federal University. Only patients submitted to in vitro fertilization (FIV) through intracytoplasmic sperm injection (ICSI) were included. The experimental groups were subdivided according to presence or absence of pregnancy, hormonal stimulation protocol used (FSH or FSH and hMG) and presence or absence of at least one female infertility factor. An aliquot of follicular fluid was collected after retrieval of the oocyte for analysis of thiobarbituric acid reactive substances concentrations, and glutathione peroxidase and catalase activities. All these analyses were carried out using a spectrophotometer. Groups were compared using Student’s T-test. A logistic regression model were calculated using embryo quality on day 3, presence or not of a female infertility factor, thiobarbituric acid reactive substances levels, and glutathione peroxidase (GPX) and catalase activities as independent variables, occurrence of pregnancy as a binary dependent variable. Results: Patients who did not achieve pregnancy presented higher glutathione peroxidase activity levels, when compared with patients who achieved pregnancy (p=0,04). In the other groups, no differences were observed. Logistic regression produced a model which best predicted pregnancy including presence of female infertility factor, embryo quality on day 3 and GPX activity (73.7% total predictive value, p=0.00001). Odds-ratio for GPX activity was 0.98, indicating that increasing values of GPX activity decreased the odds of occurrence of pregnancy. Conclusion: Based on our results, we may conclude that (i) higher GPX activity is associated to negative outcomes in ICSI cycles, (ii) different ovarian stimulation protocols does not alter concentrations of TBARS and activity of antioxidant enzymes, and (iii) the presence of at least one female infertility factor does not alter TBARS levels or antioxidant activity. / TEDE / BV UNIFESP: Teses e dissertações

Made available in DSpace on 2014-06-11T19:25:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-01-15Bitstream added on 2014-06-13T18:26:25Z : No. of bitstreams: 1 almeida_mgj_me_arafcf_parcial.pdf: 82683 bytes, checksum: 49424d5182616aaa8e926f756efd65e1 (MD5) Bitstreams deleted on 2015-02-09T14:35:42Z: almeida_mgj_me_arafcf_parcial.pdf,Bitstream added on 2015-02-09T14:36:22Z : No. of bitstreams: 1 000710077.pdf: 903439 bytes, checksum: 7ad6ad625787ddd4aff6f1d6cad4169e (MD5) Bitstreams deleted on 2015-02-09T17:15:05Z: 000710077.pdf,Bitstream added on 2015-02-09T17:15:41Z : No. of bitstreams: 1 000710077.pdf: 903439 bytes, checksum: 7ad6ad625787ddd4aff6f1d6cad4169e (MD5) / A tendência atual na indústria cosmética é o desenvolvimento de produtos multifuncionais, ou seja, aqueles com capacidade de apresentar diferentes funções, possibilitando diferentes resultados para o consumidor. Seguindo esta tendência, ativos naturais são alternativas interessantes como substitutos a um único composto ativo, uma vez que são matrizes complexas e apresentam diversos componentes que podem possuir diferentes mecanismos de ação e, assim, conferir ao produto mais de uma função. Por este motivo, nos últimos anos o uso de extratos naturais tem crescido muito nesta área. Com o aumento da aplicação de extratos naturais em produtos cosméticos, há também a necessidade de estudos que comprovem sua eficácia e segurança. Uma das principais funções buscadas em produtos cosméticos é a ação antienvelhecimento, ou seja, a capacidade dos produtos em atuar neutralizando radicais livres. Neste contexto, o objetivo deste trabalho foi avaliar a eficácia e segurança do extrato de Ascophyllum nodosum, além de desenvolver um sistema emulsionado para sua incorporação e verificar a eficácia deste sistema. Os resultados de citotoxicidade mostraram que este extrato pode ser utilizado com segurança na concentração proposta (1,2% m/m). Além disso, foi avaliado, por metodologias in vitro, o potencial antioxidante e o potencial de inibir a atividade da tirosinase, sendo verificado que o extrato de A. nodosum apresenta a capacidade de atuar neutralizando radicais livres e inibindo a atividade enzimática da tirosinase no processo de melanogênese. Apesar de serem necessários estudos complementares para garantir a eficácia, o fitocosmético desenvolvido com o extrato aquoso de A. nodosum apresenta enorme potencial de aplicação podendo resultar em preparações cosméticas multifuncionais / The current trend in the cosmetic industry is the development of multifunctional products, or, those with the ability to have different functions, facilitating the results to the consumer. Following this trend, natural actives are interesting alternatives as substitutes for a single active compound, since they are complex matrices and present various components that may have different mechanisms of action and thereby give the product more than one function. For this reason, in recent years the use of natural extracts has grown a lot in this area. With the increased use of natural extracts in cosmetic products, there is also a need for studies to prove its effectiveness and safety. A major function is sought in cosmetic anti-aging action, for instance, the ability of the products act by neutralizing free radicals. In this context, the aim of this study was to evaluate the effectiveness and safety of the extract of Ascophyllum nodosum, and develop a system for incorporation emulsified and verify the effectiveness of this system. The results of cytotoxicity have shown that this extract can be safely used in the proposed concentration (1.2% w/w). Furthermore, it was evaluated by in vitro methods, the antioxidant potential and the potential to inhibit the activity of tyrosinase, and found that the extract of A. nodosum has the ability to act by neutralizing free radicals and inhibiting the enzymatic activity of tyrosinase in the process of melanogenesis. Although additional studies are needed to ensure effectiveness, phytocosmetic developed with aqueous extract of A. nodosum has enormous potential application may result in multifunctional cosmetic preparations

Orientador: Chung Man Chin / Coorientador: Vera Lucia Borges Isaac / Banca: Marcos Antônio Correa / Banca: Helena Margarida Ribeiro / Resumo: A tendência atual na indústria cosmética é o desenvolvimento de produtos multifuncionais, ou seja, aqueles com capacidade de apresentar diferentes funções, possibilitando diferentes resultados para o consumidor. Seguindo esta tendência, ativos naturais são alternativas interessantes como substitutos a um único composto ativo, uma vez que são matrizes complexas e apresentam diversos componentes que podem possuir diferentes mecanismos de ação e, assim, conferir ao produto mais de uma função. Por este motivo, nos últimos anos o uso de extratos naturais tem crescido muito nesta área. Com o aumento da aplicação de extratos naturais em produtos cosméticos, há também a necessidade de estudos que comprovem sua eficácia e segurança. Uma das principais funções buscadas em produtos cosméticos é a ação antienvelhecimento, ou seja, a capacidade dos produtos em atuar neutralizando radicais livres. Neste contexto, o objetivo deste trabalho foi avaliar a eficácia e segurança do extrato de Ascophyllum nodosum, além de desenvolver um sistema emulsionado para sua incorporação e verificar a eficácia deste sistema. Os resultados de citotoxicidade mostraram que este extrato pode ser utilizado com segurança na concentração proposta (1,2% m/m). Além disso, foi avaliado, por metodologias in vitro, o potencial antioxidante e o potencial de inibir a atividade da tirosinase, sendo verificado que o extrato de A. nodosum apresenta a capacidade de atuar neutralizando radicais livres e inibindo a atividade enzimática da tirosinase no processo de melanogênese. Apesar de serem necessários estudos complementares para garantir a eficácia, o fitocosmético desenvolvido com o extrato aquoso de A. nodosum apresenta enorme potencial de aplicação podendo resultar em preparações cosméticas multifuncionais / Abstract: The current trend in the cosmetic industry is the development of multifunctional products, or, those with the ability to have different functions, facilitating the results to the consumer. Following this trend, natural actives are interesting alternatives as substitutes for a single active compound, since they are complex matrices and present various components that may have different mechanisms of action and thereby give the product more than one function. For this reason, in recent years the use of natural extracts has grown a lot in this area. With the increased use of natural extracts in cosmetic products, there is also a need for studies to prove its effectiveness and safety. A major function is sought in cosmetic anti-aging action, for instance, the ability of the products act by neutralizing free radicals. In this context, the aim of this study was to evaluate the effectiveness and safety of the extract of Ascophyllum nodosum, and develop a system for incorporation emulsified and verify the effectiveness of this system. The results of cytotoxicity have shown that this extract can be safely used in the proposed concentration (1.2% w/w). Furthermore, it was evaluated by in vitro methods, the antioxidant potential and the potential to inhibit the activity of tyrosinase, and found that the extract of A. nodosum has the ability to act by neutralizing free radicals and inhibiting the enzymatic activity of tyrosinase in the process of melanogenesis. Although additional studies are needed to ensure effectiveness, phytocosmetic developed with aqueous extract of A. nodosum has enormous potential application may result in multifunctional cosmetic preparations / Mestre

Orientador: Adriana Zerlotti Mercadante / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-11T02:48:48Z (GMT). No. of bitstreams: 1 Barreto_GiselaPizarrodeMattos_D.pdf: 1819752 bytes, checksum: 73ae705ff5b48a9b194ef27159fe6ab1 (MD5) Previous issue date: 2008 / Resumo: O aumento da demanda dos consumidores por maior qualidade de vida tem impulsionado o interesse da indústria de alimentos pelo segmento de alimentos funcionais, definidos como qualquer alimento com potencial para conferir benefícios à saúde do consumidor. Os compostos bioativos, como os carotenóides, compostos fenólicos e ácido ascórbico, presentes em alimentos estão envolvidos nestas ações benéficas. Inicialmente, foi realizado um estudo com alguns padrões de carotenóides, que não somente apresentam atividade anti-radical livre como também são responsáveis pela cor de vários alimentos. Foi avaliado o comportamento destes carotenóides, em diferentes concentrações, em relação à sua atividade anti-radical livre (ABTS) e parâmetros de cor CIELAB. Os resultados revelaram que, o número de ligações duplas conjugadas e a presença do grupo carbonila influenciaram tanto na atividade anti-radical livre como nos parâmetros de cor dos carotenóides, assim como a concentração. Posteriormente, para a determinação da atividade anti-radical livre de extratos complexos, pelo método ABTS, foram preparadas no laboratório extratos de polpas de 18 frutas tropicais, aplicando análises estatísticas multivariadas, especificamente Análise de Componentes Principais (ACP) e Análise Hierárquica de Agrupamentos (AHA), para caracterizar e agrupar as 18 polpas de frutas e verificar a correlação entre atividade anti-radical livre e alguns constituintes químicos que apresentam funcionalidade como ácido ascórbico, compostos fenólicos, flavonóides e carotenóides totais. As frutas foram agrupadas em 5 grupos, segundo análise hierárquica de agrupamentos (AHA). Na Análise de Componentes Principais, observou-se que a atividade antioxidante apresentou alta correlação com os fenóis (r = 0,99) e flavonóides (r = 0,86) totais, porém apresentou baixa correlação com ácido ascórbico (r = 0,02) e carotenóides totais (r= 0,08). Em especial, foi estudado o caju, pois, o processamento de suco a partir do pseudofruto (pedúnculo) de caju gera como subproduto um bagaço, que constitui uma rica fonte de compostos fenólicos, ácido ascórbico (AA) e carotenóides. Considerando que este bagaço pode ser transformado para produzir ingredientes funcionais, o caju clone CCP-076, proveniente da Estação Experimental de Paraipaba (CE) da Embrapa Agroindústria Tropical, foi prensado e o bagaço obtido foi umidificado e novamente prensado até exaustão (retentado), sendo a fase líquida filtrada (extrato bruto) e concentrada (extrato concentrado). O retentado apresentou maior teor de fenóis totais, de carotenóides totais e de atividade anti-radical livre, além de apresentar cor amarela mais intensa. Por outro lado, o extrato concentrado apresentou o maior teor de AA. Os principais carotenóides encontrados, tanto no retentado como nos extratos, foram all-trans-b- criptoxantina e all-trans-b-caroteno. Uma outra fruta também analisada em separado foi o mamão papaia (Carica papaya cv. Golden) que tem uma grande demanda de exportação para os mercados da América do Norte e Europa; entretanto, é uma fruta climatérica sendo susceptível a perdas após a colheita. O mamão-papaia foi dividido em três grupos: controle (sem tratamento), etileno (tratamento com etileno) e 1- metilciclopropeno (1-MCP) (tratamento com 1-MCP). A composição de carotenóides e os parâmetros de cor de todos os grupos foram determinados durante o amadurecimento da fruta. A presença do gás etileno e 1-MCP reduziram o teor de carotenóides e favoreceram a biossíntese de carotenóides acíclicos. Entretanto, mesmo com menor teor de carotenóides que o grupo controle, os valores de cor (a*, b*) foram similares nos três grupos durante o amadurecimento / Abstract: The increased demand for high life quality has been associated to healthy food, increasing the industry interest for functional foods, which are defined as any food or bioactive compounds with potential to be benefic for the consumer health. The bioactive compounds found in foods, such as carotenoids, phenolic compounds and ascorbic acid (AA) are involved with these benefic actions. Firstly, some carotenoid standards in different concentrations were evaluated regarding not only their radical scavenger activity, but also their color parameters (CIELAB), since these pigments are responsible for the color of many foods. The results showed that the number of conjugated double bonds, presence of carbonyl group and concentration influenced both the radical scavenger activity and the color parameters. After that, the radical scavenger activity of complex extracts were determined, by ABTS assay, obtained from pulps extracts prepared in the laboratory from 18 tropical fruit applying Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) to characterize and grouped the 18 extracts, as well as to correlate radical scavenger and the bioactive compounds, such as AA, phenolic compounds, flavonoids and total carotenoids. The fruits were divided into five groups, following Hierarchical Cluster Analysis (HCA). Principal Component Analysis (PCA) indicated that antioxidant activity showed high correlation to total phenolic compounds (r= 0.99) and flavonoids (r= 0.86); however, correlation was found to be very poor with AA (r= 0.02) and total carotenoid levels (r= 0.08). The cashew-apple was specially evaluated since the processing of juice from the cashew-apple fruit generates a pomace that constitutes a rich source of phenolic compounds, AA and carotenoids. Considering that this pomace can be processed into functional ingredients, the cashew-apple clone CCP-076, from Estação Experimental de Paraipaba (CE) at Embrapa Agroindústria Tropical, was pressed and than the pomace formed was humidified and pressed again until exhaustion (retentado), followed by filtration (raw extract) and concentration (concentrated extract). The retentado presented significantly higher total phenol and total carotenoid contents, higher free radical scavenger activity, as well as higher yellow color intensity, indicated by higher b* and chroma (C*) values. On the other hand, the concentrated extract showed the highest AA content. The major carotenoids identified in both retentado and extracts were all-trans-b-cryptoxanthin and all-trans-b-carotene. These results showed that the retentado has a good potential to be applied as a functional ingredient. Another fruit also specially analyzed was the papaya fruit (Carica papaya cv. Golden) that has a great export demand to North American and Europe markets; however, since it is a climacteric fruit, it is susceptible to postharvest losses. The papaya fruits were divided into three groups: control (without treatment), ethylene (treated with ethylene) and 1-methylcyclopropene (1-MCP) (treated with 1-MCP). In all groups, carotenoid composition, carried out by HPLC, and color parameters were evaluated during ripening. The treatment with ethylene and 1-MCP decreased carotenoid accumulation and enhanced acyclic carotenoid biosynthesis. Although the gas treated fruits presented lower carotenoid content as compared to the control, the color values (a*, b*) were similar in treated and non-treated fruits during ripening / Doutorado / Doutor em Ciência de Alimentos

N,N,N\',N \'-tetrametil-p-fenilenodiamina (TMPD) catalisa a autoxidação de coenzimas piridínicos (NADH, NADPH) e modelos (ClBCH ,ClPCH ) ao cátion piridínico com rendimentos de 80-100%. A velocidade destas reações mostrou dependência de primeira ordem com respeito à concentração da 1,4-dihidronicotinamida e de meia ordem em relação às concentrações de O2 e TMPD. Estes dados cinéticos e testes com captadores de ion superóxido e superóxido dismutase indicam que os radicais HO•2 oriundos da autoxidação lenta do TMPD promovem a oxidação da dihidronicotinamida numa reação em cadeia; no término os radicais HO•2 se aniquilam por dismutação. O mecanismo proposto também é confirmado (1º) pela razão kC-H/kC-D=2,3 quando se substitui um dos hidrogênios do C4 de ClBCH por deutério, (2º) pelas idênticas velocidades iniciais em H2O e D2O, (3º) pelo valor da Ea = 10 kcal/mol na autoxidação do NADH e (4º) pelo aumento da velocidade de pH = 7,8 a pH 6,5. TMPD também promove a autoxidação do derivado 5, 6-hidratado (PHTN) da dihidronicotinamida ao cátion piridínico (ClPC+) apenas de fosfato ou arsenato estão presentes. O ClPC+ nã o se forma a partir do ClPCH em equilíbrio com o PHTN. Muito provavelmente se forma a partir do intermediário fosforilado no C6 por oxidação no C4 seguida de eliminação de fosfato. Quando PHTN e ClPCH foram oxidados pelo sistema O2/TMPD na presença de fosfato de piridínio ou de tetra-n-butilamônio em meio piridínico houve formação de pirofosfato, isolado por cromatografia de papel e por resina de troca aniônica. Adicionando-se ADP de tetra-n-butilamôneo ao sistema, constatou-se a formação de pirofosfato e de ATP com rendimentos mínimos de 5% e 3% , respectivamente. Por outro lado se a mistura de reação contém AMP de tetra-n-butilamôneo pôde-se verificar a formação de pirofosfato, ADP e ATP com rendimento total de 28% de \"ligações ricas\". A reação estudada foi proposta como modelo para síntese de ATP no sítio I da cadeia respiratória. / N,N,N\',N\'-tetramethyl-p-phenylenediamine (TMPD) catalyses the autoxidation of the pyridine coenzymes and of their models to the pyridinium form (80-100% yields). The first arder dependence of the rate upon the dihidronicotinamide concentration and half order upon both the O2 and TMPD concentrations, indicates that the relatively slow autoxidation of TMPD is the source of free radicals: dihydronicotinamide autoxidizes by the HO•2 chain mechanism and in the termination step the HO•2 radicals decay by dismutation. Such a mechanis is also supported by the inhibitory effects of cathecol, a scavenger of the HO•2 radical, and of superoxide dismutase, an enzyme which accelerates the dismutation of the O-2/ HO•2 species. The mecanism is further supported by (1) kC-H/kC-D=2,3 for substitution in 1-benzyl-1,4-dihydronicotinamide (ClBCH), (2) identical rates in H2O and D2O buffers, (3) Ea = 10 kcal/mole in the autoxidation of NADH and (4) the increase in rate from pH 7,8 to 6,5. TMPD promotes also the autoxidation of 1-n-propyl-6-hydroxy-1,4,5,6 - tetrahydronicotinamide (PHTN) to the 1-propyl-3-carboxamidopyridinium cation (ClPC+) provided phosphate ar arsenate are present. ClPC+ originates not from 1-n-propyl-1,4-dihydronicotinamide (ClPCH) in equilibrium with PHTN but most certainly from a C6 phosphorylated intermediate by oxidation at C4 and loss of phosphate. When PHTN an ClPCH were oxidated by the system O2/TMPD in the presence of pyridinium phosphate or tetra-n-butylammonium phosphate in pyridineas solvent, formation of pyrophosphate occurred. Pyrophosphate was isolated and identified by paper and ionic exchange resin chromatography. If tetra-n-butylammonium ADP is also present in the system, one can observe the formation of both pyrophosphate and ATP (5% and 3% minimum yields, respectively). In the presence of tetra-n-butylammonium AMP there, formation of pyrofosphate, ADP and ATP occurs. The total yield of energy rich bond is 28%. We suggest that the reaction is a model for the generation of the first ATP in the respiratory chain.

Polyorganosilany spadají do skupiny hybridních materiálů třídy II, které nabízejí nové možnosti materiálových funkcí a jejich vlastností. Ačkoliv byly v této kategorii již některé materiály zkoumány a stejně tak i jejich aplikace, nebyly doposud vlákna na základě polyorganosilanu v mikro a nano rozměru popsány což bylo motivací pro tuto práci. Předkládaná diplomová práce se zabývá podrobným zkoumáním poly(vinylmethyldimethoxysilanu) jako možného prekurzoru pro elektrostatické zvlákňování. Za účelem přípravy polymeru na bázi vinylmethylsilanu byla provedena radikálová polymerace a podmínky reakce byly modifikovány se záměrem změny molekulové hmotnosti získaného polymeru. Stupeň polymerace byl upravován na základě změny koncentrace iniciátoru a byl stanovován dynamickým rozptylem světla v roztoku polymeru a spektroskopickou metodou nukleární magnetické rezonance. Elektrostatické zvlákňování je velkou měrou spojeno s vlastnostmi roztoku a důraz byl proto kladen právě na zjištění těchto vlastností. Na základě experimentů bylo zjištěno, že syntetizovaný polymer je na přípravu vláken vhodný. Nicméně byly získány i fragmenty vláken a to s využitím polymeru v roztoku methanolu. Předpokladem zvlákňování je dostatek propojení mezi polymerními řetězci. Tento přístup byl studován se zapojením sol-gel postupu a bylo zjištěno, že fáze sol-gel procesu je velmi významná s ohledem na tvorbu vláken. Dalším využitým postupem pro získání vláken bylo začlenění dalšího polymeru do směsi jako nosiče a tímto postupem byla získána vlákna s různým průměrem.