No description available.

L’élaboration de nouveaux oligomères capables de mimer les propriétés des protéines naturelles est devenue un domaine de recherche très important, non seulement du point de vue structural mais aussi médicinal. Les peptides comportant des acides β-aminés ont été extensivement étudiés tandis que les recherches dans le domaine des γ-peptides sont plus récentes. Néanmoins, ces derniers montrent déjà des propriétés structurales uniques ainsi que des activités biologiques prometteuses.Dans notre laboratoire nous nous intéressons au développement d’une synthèse générale de nouveaux acides β,γ-diaminés à partir d’acides ∝-aminés naturels, notamment à la 3-déoxyaminostatine, et à leur utilisation dans la synthèse peptidique pour obtenir des peptides non-naturels afin d’étudier leurs propriétés conformationnelles. La stratégie de synthèse élaborée dans notre laboratoire et améliorée au cours de ces travaux a permis d’élargir la gamme des acides β,γ-diaminés. Deux diastéréomères cis et trans issus de la L-leucine, de la L- et D-phénylalanine ont été obtenus et engagés dans la synthèse de nouveaux peptides hybrides α/γ. Deux séries de peptides hybrides α/γ ont été étudiées. Les analyses structurales de la série comportant des acides ∝-aminés de configuration L montrent une capacité à adopter des structures secondaires bien définies, stabilisées par des liaisons hydrogènes intramoléculaires, impliquant notamment l’azote situé en β. De plus, une voie de synthèse vers un analogue d’un antibiotique naturel, le gramicidine S, a été proposée. Dans cet analogue, le motif D-Phe-L-Pro est remplacé par l’acide β,γ-diaminé issu de la D-phénylalanine. / The design of a new oligopeptides, capable to mimic the properties of natural proteins, is an important field not only for structural studies but also in the developpement of new efficient drugs. The peptides featuring β-amino acids have been extensively explored, whereas the research in γ-peptides is more recent. The studies of γ-peptides show their ability to adopt stable secondary structures and also to have a promising biological activity. Our laboratory is interested in the synthesis of new β,γ-diaminoacids.The aim of this work is a developpement of new synthetic route starting from different natural α -amino acids and to use obtained β,γ-diaminoacids to access novel unnatural peptides having specific conformational properties.The synthetic strategy, developed and optimized in our laboratory during this work, gives access to diastereomers cis and trans from L-leucine, L- and D-phenylalanine which were used in the synthesis of a new hybrid α/γ-peptides. The structural studies were performed on two series of hybrid α/γ-peptides consisting of β,γ-aminoacid from L-leucine and L- or D-α-amino acids. In the first case, the peptides are able to adopt stable secondary structures stabilized by intramolecular hydrogen bonds involving the nitrogen on the β-position. In addition, we present the synthesis of an analogue of gramicidine S, a naturally occuring antibiotic cyclic peptide. The dipeptide pattern D-Phe-L-Pro has been replaced with the β,γ-diaminoacid synthesized from D-phenylalanine.

Wong Ka Shing = 兩個二級蛋白質結構組中的氨基酸序列的統計特性 / 黃嘉誠. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 88-91). / Text in English; abstracts in English and Chinese. / Wong Ka Shing = Liang ge er ji dan bai zhi jie gou zu zhong de an ji suan xu lie de tong ji te xing / Huang Jiacheng. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Predicting tertiary structures of proteins --- p.2 / Chapter 1.2 --- Introduction to secondary structures of protein --- p.5 / Chapter 1.3 --- Prediction of secondary structural classes --- p.9 / Chapter 1.3.1 --- Multi-dimensional space representation --- p.10 / Chapter 2 --- Method of analysis --- p.12 / Chapter 2.1 --- Data sets --- p.12 / Chapter 2.2 --- Basic statistics of the data sets --- p.13 / Chapter 2.3 --- Method of analysis --- p.17 / Chapter 2.4 --- An interesting sum rule --- p.20 / Chapter 3 --- Results of analysis of C-words --- p.22 / Chapter 3.1 --- A first insight --- p.22 / Chapter 3.2 --- Distributions of 〈C(j)〉 --- p.24 / Chapter 3.2.1 --- "Comparing distributions for different m, s and secondary structural classes" --- p.29 / Chapter 3.3 --- Features of each secondary structural class --- p.33 / Chapter 3.3.1 --- C-words with the largest or the smallest values of 〈C(j)〉 in the all-a class --- p.33 / Chapter 3.3.2 --- C-words with the largest or the smallest values of 〈C(j)〉 in the all-β class --- p.35 / Chapter 4 --- Results of analysis of H-words --- p.37 / Chapter 4.1 --- 〈C(j)〉 for each H-word --- p.38 / Chapter 4.1.1 --- "When m increases, 〈C(j)〉 deviates more from 1" --- p.39 / Chapter 4.1.2 --- "When spacing parameter s is small, 〈C(j)〉 deviates more from 1" --- p.40 / Chapter 4.2 --- The mean over all possible H-words --- p.41 / Chapter 4.3 --- Comparing 〈C(j)〉 of different H-words --- p.43 / Chapter 4.3.1 --- A few plots --- p.43 / Chapter 4.3.2 --- Results --- p.44 / Chapter 4.4 --- Features of each secondary structural class --- p.47 / Chapter 4.4.1 --- A first insight --- p.47 / Chapter 4.4.2 --- The H-words with the largest values of 〈C(j)〉 in the all-α class with particular number of letter m --- p.54 / Chapter 4.4.3 --- The H-words with the smallest values of 〈C(j) in the all-α class with particular number of letter m --- p.57 / Chapter 4.4.4 --- The H-words with the largest values of 〈C(j) in the all-β class with particular number of letter m --- p.60 / Chapter 4.4.5 --- The H-words with the smallest values of 〈C(j) in the all-β class with particular number of letter m --- p.63 / Chapter 4.4.6 --- A summary --- p.66 / Chapter 4.5 --- Possible indicators to predict secondary structural class --- p.67 / Chapter 4.5.1 --- H-words with the largest values of --- p.68 / Chapter 4.5.2 --- H-words with the largest magnitude of --- p.71 / Chapter 4.5.3 --- Discussion --- p.71 / Chapter 5 --- Prediction using patterns found in H-words --- p.72 / Chapter 6 --- Conclusion --- p.86 / Bibliography --- p.88

Uma das alternativas para reduzir os efeitos negativos das altas temperaturas nas plantas e, consequentemente a perda na produção e qualidade é a utilização de indutores de tolerância. Dentro deste contexto, a L-arginina, se apresenta como uma alternativa, por ser um dos aminoácidos mais funcionais e precursora de importantes compostos na regulação metabólica das plantas, com efeito na atenuação do estresse abiótico. O objetivo deste trabalho foi avaliar o efeito da aplicação foliar de diferentes doses de L-arginina (0; 0,15; 0,25; 0,5; 1,0 e 2,0 g L-1) na fisiologia, produção e qualidade do tomate cultivar Pizzadoro cultivado em ambiente protegido no período de verão. Para avaliação do efeito da L-arginina na fisiologia, foram feitas análises de indicadores de estresse dos compostos malonaldeído (MDA) e peróxido de hidrogênio (H2O2), das enzimas antioxidantes superóxido dismutase (SOD), catalase (CAT) e ascorbato peroxidase (APX), teores de aminoácidos livres e teores de nutrientes nas folhas de tomateiro. Na produção foram determinadas a produção total (PT), a produção com presença de defeitos (PRDEF), a produção não comercial (PRNC) e a produção comercial (PC) com a classificação de calibre pequeno (PROP), médio (PROM) e grande (PROG). Além disso, foram determinados o número de frutos totais (NFT), número de frutos com presença de defeitos (NDEF), número de frutos não comerciais (NFNC) e número de frutos comerciais (NFC) com classificação de calibre pequeno (NFP), médio (NFM) e grande (NFG). Amostras de frutos maduros foram colhidas para a determinação de sólidos solúveis (SST), pH da polpa, ácido ascórbico (AA) e acidez total titulável (ATT) para determinação da qualidade do tomate. A aplicação de 1,0 g L-1 de L-arginina diminuiu o teor de MDA, e aumentou a atividade das enzimas CAT e APX. Além disso, essa dose do aminoácido aumentou a PC, PT, NFC, NFT e diminuiu a produção de NFNC. / Tolerance inductor products are one of the alternatives to reduce the negative effects of abiotic factors in plants, for instance the decrease of crop yield and quality. In this context, L-arginine is one option of this products to mitigate abiotic plant stress, due to its importance as a functional amino acid and precursor of metabolic plant compounds. Hence, the project objective was to evaluate the exogenous foliar application of different rates of L-arginine (0; 0.15; 0.25; 0.5; 1.0 e 2.0 g L-1) on physiology, yield and quality of tomato cultivar Pizzadoro growth in protected enviroment during Summer. Physiological effect were analized by markers of oxidative stress, as malondialdehyde (MDA) and hydrogen peroxide; activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) enzymes; free amino acids and nutrient contents in tomato leaves. Yield was estimated by total production (TP), production of defective fruit (PDF), non-commercial fruit production (NCFP) and commercial fruit production (CP). CP was classified as small (SPRO), medium (MPRO) and large (LPRO) sizes. Number of total fruit (NTF), number of defective fruit (NDF), number of non-commercial fruit (NNCF) and number of commercial fruit (NCF) were classified as small (NSF), medium (NMF) and large (NLF) sizes. Sample of mature tomatoes were harvested to assess quality, by content of soluble solids (SST), pH of tomato pulp, ascorbic acid (AA) and titratable acidity (TA). Application of L-arginine at rate of 1.0 g L-1 reduced MDA and increased CAT and APX. Besides physiological aspects, this level of amino acid increased CP, TP, NCF, NTF and decreased NNCF.

Neste trabalho estudamos as propriedades ópticas não lineares de aminoácidos utilizando pulsos de laser com duração de femtossegundos. O índice de refração não linear (n2) da L-alanina, L-prolina, L-serina, L-treonina e L-arginina em solução aquosa foram determinados. Foi também estudada a influência do pH na magnitude de n2 dos aminoácidos em solução. Paralelamente, determinamos a dispersão de n2 em cristais de L-treonina nos três eixos principais, x, y e z. Os aminoácidos têm despertado grande interesse devido as suas boas propriedades ópticas de segunda ordem. Todavia, suas propriedades ópticas de terceira ordem ainda não haviam sido estabelecidas. Além disso, implementamos a técnica de espalhamento hiper-Rayleigh para determinar a primeira hiperpolarizabilidade (P) de moléculas orgânicas, onde uma mudança foi introduzida para permitir medidas mais rápidas e com melhor precisão. Foram encontrados os valores de P de algumas porfirinas e corantes orgânicos. / In this work we have studied nonlinear optical properties of amino acids using femtosecond laser pulses. The nonlinear index of refraction (nz) of L-alanine, L-proline, L-serine, L-threonine and L-arginine in aqueous solution have been determined. Also, the influence of pH in the magnitude of nz of amino acids in solution has been studied. Besides, we have determined the n;, dispersion in the three main axis, x, y and z, in L-threonine crystals. The amino acids have attracted a great deal of attention due to their good second-order optical properties. However, their third-order optical properties had not been established yet. Furthermore, we have implemented the hyper-Rayleigh scattering technique to determine the first hyperpolarizability (P) of organic molecules, leading to fast and more precise measurements. It was found the P value of some porphyrins and organic dyes.

Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-06-22T19:13:45Z No. of bitstreams: 1 SandraGasparini.pdf: 349340 bytes, checksum: 0464691b140faa8019f9a16a1192d667 (MD5) / Made available in DSpace on 2017-06-22T19:13:45Z (GMT). No. of bitstreams: 1 SandraGasparini.pdf: 349340 bytes, checksum: 0464691b140faa8019f9a16a1192d667 (MD5) Previous issue date: 2014-03-27 / Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA) / Two experiments to determine the metabolizable energy in different ages and true digestibility of amino acids of rice bran (RB), broiler slow growth were performed. In the first experiment, 352 birds were distributed in a completely randomized design with three treatments and six replicates of eight or six birds per experimental unit as experimental age. The RB replaced 40% references diets formulated for three age groups (1-30, 31-60 and 61-90 days). The method used was the total collection and 1.0% iron oxide was used as a fecal marker. In the second experiment, 168 birds at 41 days of age fed a diet free of protein (DFP) and formulated with 55% of RB as the sole source of dietary crude protein and amino acids were used. All birds were killed by cervical dislocation and open the abdominal cavity to collect the contents at the terminal ileum portion. The samples were sent for amino acid analysis using HPLC. Was used 0.5% of chromic oxide as a marker for determining the digestibility of amino acids of the RB and the endogenous excretion of amino acids. The mineral content of the RB, with a value of 3.94%, below those content presented in the literature. The apparent metabolizable energy, true and true corrected for nitrogen balance, found for the RB in birds 70-79 days of age (2,801, 3,002 and 2,394 kcal / kg, respectively), statistically different (P <0.05) from values obtained with birds 40-49 days (2,415, 2,566 and 2,427 kcal / kg, respectively) and birds 10-19 days of age (2,131, 2,266 and 2,214 kcal / kg, respectively). The coefficients of apparent metabolism of dry matter (CMADM), with values of 65.80% (70 to 79 days), 59.20% (40 to 49 days) and 53.10% (10 to 19 days of age), statistically different (P <0.05). The coefficient of real gross energy metabolization corrected for nitrogen balance (CMVGEn), found in birds 70-79 days (56.40%), statistically different (P <0.05) of the value found in poultry 10 to 19 days of age (49.10%). Thus, in the formulation of rations, should be considered the differences in energy values of RB for young and adult birds, because the digestibility of dry matter and gross energy, increases with age. The average true digestibility of amino acids of the RB was 79.5%, as fed, where the methionine had the lowest coefficient of true digestibility, with a value of 78.12% and the highest arginine, with a value of 82.10 %. The true digestible values were 0.51% for lysine, 0.18% for methionine, 0.41% for methionine + cystine, 0.39% for threonine and 0.52% for valine. / Foram realizados dois experimentos com o objetivo de determinar a energia metabolizável em diferentes idades e a digestibilidade verdadeira dos aminoácidos do farelo de arroz integral (FAI), para frangos de corte de crescimento lento. No primeiro experimento, 352 aves foram distribuídas em delineamento inteiramente casualizado com três tratamentos e seis repetições de oito ou seis aves por unidade experimental, conforme idade experimental. O FAI substituiu em 40% as dietas referências, formuladas para três idades (1 a 30, 31 a 60 e 61 a 90 dias). O método utilizado foi o de coleta total de excretas e 1,0% de óxido de ferro foi utilizado como marcador fecal. No segundo experimento, foram utilizadas 168 aves com 41 dias de idade, alimentadas com uma dieta isenta de proteína (DIP) e uma dieta formulada com 55% de FAI como única fonte de proteína bruta e aminoácidos. Todas as aves foram abatidas por deslocamento cervical e abertas na cavidade abdominal para coleta do conteúdo na porção íleo terminal. As amostras foram enviadas para análise de aminoácidos utilizando o HPLC. Foi utilizado 0,5% de óxido de cromo como indicador para determinação dos coeficientes de digestibilidade dos aminoácidos do FAI e da excreção endógena de aminoácidos. O conteúdo mineral do FAI, com valor de 3,94%, apresentou teor abaixo daqueles descritos na literatura. Os valores de energia metabolizável aparente, verdadeira e verdadeira corrigida para o balanço de nitrogênio, encontrados para o FAI em aves de 70 a 79 dias de idade (2.801, 3.002 e 2,394 kcal/kg, respectivamente), diferiram estatisticamente (P<0,05) dos valores obtidos com aves de 40 a 49 dias (2.415, 2.566 e 2.427 kcal/kg, respectivamente) e aves de 10 a 19 dias de idade (2.131, 2.266 e 2.214 kcal/kg, respectivamente). Os coeficientes de metabolização aparente da matéria seca (CMAMS), com valores de 65,80% (70 a 79 dias), 59,20% (40 a 49 dias) e 53,10% (10 a 19 dias de idade), diferiram estatisticamente (P<0,05). O valor do coeficiente de metabolização verdadeiro da energia bruta corrigido para o balanço de nitrogênio (CMVEBn), encontrado em aves de 70 a 79 dias (56,40%), diferiu estatisticamente (P<0,05) do valor encontrado em aves de 10 a 19 dias de idade (49,10%). Assim, nas formulações de rações, devem ser consideradas as diferenças nos valores energéticos do FAI para aves jovens e adultas, pois a digestibilidade da matéria seca e da energia bruta, aumenta com a idade. O valor médio de digestibilidade verdadeira dos aminoácidos do FAI foi de 79,5%, na matéria natural, onde a metionina apresentou o menor coeficiente de digestibilidade verdadeira, com valor de 78,12% e a arginina o maior, com valor de 82,10%. Os valores digestíveis verdadeiros foram de 0,51% para lisina, 0,18% para metionina, 0,41% para metionina+cistina, 0,39% para treonina e 0,52% para valina.

Wong, Kin Sing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 86-98). / Abstract also in Chinese. / THESIS COMMITTEE --- p.i / ABSTRACT (ENGLISH) --- p.ii / ABSTRACT (CHINESE) --- p.iv / ACKNOWLEDGEMENTS --- p.v / DECLARATION --- p.vi / ABBREVIATIONS --- p.vii / TABLE OF CONTENTS --- p.x / LIST OF TABLES --- p.xiv / LIST OF FIGURES --- p.xv / Chapter CHAPTER 1 --- INTRODUCTION / Chapter 1.1. --- Antibiotics market and β-lactam antibiotics --- p.1 / Chapter 1.2. --- Semi-synthetic cephems --- p.1 / Chapter 1.3. --- Conversion of CPC to 7-ACA --- p.3 / Chapter 1.4. --- Chemical production versus enzymatic bioconversion --- p.5 / Chapter 1.5. --- Industrial two-step bioconversion of CPC --- p.11 / Chapter 1.6. --- Phylogenetics and physiological roles of DAAO --- p.15 / Chapter 1.7. --- Yeast DAAOs are suitable candidates for enzymatic bioconversion --- p.17 / Chapter 1.8. --- Structural and mechanistic studies of DAAOs --- p.18 / Chapter 1.9. --- "Modifications of pkDAAO, RgDAAO and TvDAAO" --- p.25 / Chapter 1.10. --- Objectives of the study --- p.26 / Chapter CHAPTER 2 --- HOMOLOGY MODELLING / Chapter 2.1. --- Introduction --- p.27 / Chapter 2.2. --- Methods / Chapter 2.2.1. --- Sequence alignment and selection of homologs --- p.28 / Chapter 2.2.2. --- Generation of three-dimensional TvDAAO model --- p.28 / Chapter 2.3. --- Results --- p.29 / Chapter 2.4. --- Discussion --- p.33 / Chapter CHAPTER 3 --- "MUTAGENESIS, EXPRESSION, PURIFICATION AND SCREENING OF MUTANTS" / Chapter 3.1. --- Introduction --- p.38 / Chapter 3.2. --- Materials and methods / Chapter 3.2.1. --- Cloning of TvDAAO mutants / Chapter 3.2.1.1. --- Preparation of competent E. coli --- p.39 / Chapter 3.2.1.2. --- Transformation of E. coli --- p.40 / Chapter 3.2.1.3. --- Agarose gel electrophoresis and gel-purification --- p.41 / Chapter 3.2.1.4. --- Plasmid extraction --- p.42 / Chapter 3.2.1.5. --- Site-directed mutagenesis of TvDAAO --- p.42 / Chapter 3.2.2. --- Heterologous expression and purification of mutants / Chapter 3.2.2.1 --- Shake flask fermentation --- p.45 / Chapter 3.2.2.2. --- Cell harvest and disruption --- p.45 / Chapter 3.2.2.3. --- Purification of WT and mutants --- p.47 / Chapter 3.2.2.4. --- Determination of protein concentration --- p.47 / Chapter 3.2.2.5. --- SDS-PAGE --- p.48 / Chapter 3.2.3. --- Screening of mutants --- p.48 / Chapter 3.3. --- Results / Chapter 3.3.1. --- Preparation of purified TvDAAO mutants --- p.50 / Chapter 3.3.2. --- Evaluation of activity and thermostability --- p.50 / Chapter 3.4. --- Discussion --- p.53 / Chapter CHAPTER 4 --- ENZYME KINETICS / Chapter 4.1. --- Introduction --- p.57 / Chapter 4.2. --- Materials and methods / Chapter 4.2.1. --- Standard assay --- p.58 / Chapter 4.2.2. --- Determination of kinetic parameters --- p.59 / Chapter 4.2.3. --- Inhibitory studies --- p.59 / Chapter 4.2.4. --- Effects of pH --- p.60 / Chapter 4.2.5. --- Heat treatments --- p.60 / Chapter 4.2.6. --- CD measurements --- p.61 / Chapter 4.3. --- Results / Chapter 4.3.1. --- Time progress curve analysis --- p.61 / Chapter 4.3.2. --- Kinetics of WT and mutants --- p.62 / Chapter 4.3.3. --- Temperature-dependent and time-dependent thermostability --- p.67 / Chapter 4.3.4. --- Secondary structure measurements --- p.71 / Chapter 4.4. --- Discussion --- p.71 / Chapter CHAPTER 5 --- CONCLUSIONS AND PERSEPECTIVES --- p.83 / BIBLIOGRAPHY --- p.86

Neste trabalho foi realizada a síntese de amidas, bem como de ácidos e ésteres borônicos, derivados dos aminoácidos L-cistina e L-cisteína, através de rota sintética simples, curta e de baixo custo, com o intuito de busca e a identificação de novo(s) inibidor(es) do proteassomo 20S. Esta classe de compostos possui estrutura que permite a inserção de diversos grupos funcionais, o que confere versatilidade e a construção de biblioteca de compostos que contém partes hidrofílicas e hidrofóbicas importantes para posterior avaliação inibitória. Para tanto, empregou-se rota sintética química convencional e rota biocatalisada para a formação da ligação amida. Os compostos derivados de L-cisteína foram obtidos via síntese clássica de peptídeos a qual forneceu os compostos desejados em rendimentos de até 85%. Por outro lado, tentativas de obtenção das amidas via biocatálise não se mostraram efetivas. Já amidas derivadas de L-cistina foram obtidas em rendimentos de até 79%, via síntese tradicional e até 100% de conversão através de rota biocatalítica. A inserção do átomo de boro nas estruturas se deu utilizando-se metodologias sintéticas já bem estabelecidas na literatura. Os ésteres borônicos derivados de L-cisteína foram obtidos em bons rendimentos (até 78%), enquanto que não foi possível obter-se compostos de boro derivados de L-cistina. Por sua vez, os compostos contendo ácido borônico na estrutura foram sintetizados via reação de hidrólise dos respectivos ésteres borônicos, em rendimentos moderados (até 34%). Após a obtenção dos compostos contendo grupamentos organoboro realizou-se avaliação inibitória dos mesmos frente ao proteassomo 20S. Valores de IC50 iguais a 52 &#181;M foram obtidos para composto derivado de L-cisteína contendo grupamento éster borônico, que se mostraram inibidores moderados e reversíveis. Ácidos borônicos se mostraram sem capacidade de inibir o proteassomo 20S. Adicionalmente, realizaram-se estudos de modelagem molecular com a finalidade de elucidar os resultados obtidos experimentalmente. Inicialmente realizaram-se cálculos de modelagem molecular através da realização de docking de alguns compostos e após geração de modelo farmacofórico. De maneira geral observou-se que os inibidores derivados da L-cisteína não ocupam a mesma cavidade que o fármaco bortezomibe, o que pode explicar a diferença na atividade dos compostos frente à inibição do proteassomo 20S. Também se observou que, tendo-se a interação dos inibidores com a enzima, a vizinhança do átomo de boro tem grande influência na capacidade inibitória, uma vez que estes grupamentos determinam qual a região da cavidade do proteassomo 20S será ocupada pelo inibidor. / In our study, amides, boronic acids and esters derivatives from L-cysteine and L-cysteine were synthesized by simple, short and inexpensive synthetic route, in order to search for new inhibitor(s) of the 20S proteasome. This class of compounds has a structure that allows inclusion of various functional groups, giving it versatility and allowing the construction of library compounds containing hydrophilic and hydrophobic moieties, important for further evaluation. To this end, we used conventional chemical synthetic route and biocatalysis for peptide bond formation. The compounds derived from L-cysteine were obtained by classical synthesis of peptides which provided the desired compounds up to 85% yields. On the other hand, attempts to obtain the amides via biocatalysis were not effective. However, amides derived from L-cystine were obtained with up to 79% yields via chemical synthesis and conversion up to 100% using biocatalytic route. The insertion of the boron atom in the structures was possible using synthetic methodologies well established in literature. Boronic esters derived from L-cysteine were obtained in good yields (up to 78%), whereas it was not possible to obtain boron compounds derived from L-cystine. In turn, compounds containing boronic acids in the structure were synthesized by hydrolysis reaction of the respective boronic esters in moderate yields (up to 34%). With organoboron compounds in hand, we turned our attention to inhibitory assessment against the 20S proteasome. IC50 up to 52 &#181;M were obtained when L-cysteine boronic ester derivatives were evaluated. These compounds are moderate and reversible inhibitors. L-cysteine boronic acids derivatives have shown not ability to inhibit the 20S proteasome. Additionally, molecular modeling studies were carried out in order to elucidate the results obtained experimentally. Initially molecular modeling calculations were carried out by performing docking experiments of some compounds. Generation of pharmacophoric model calculations was also executed. In general, it was observed that inhibitors derived from L-cysteine do not occupy the same cavity that drug bortezomib, which may explain the difference in the activity of compounds against the inhibition of 20S proteasome. We also observed that, with the interaction of inhibitors and enzyme, the side chains around boron atom has a great influence on inhibitory capacity, since these groups determine which region of the 20S proteasome cavity is occupied by the inhibitor.

No description available.

There has been limited investigation as to whether a predominantly forage-based diet can provide adequate amounts of limiting amino acids (AA) to horses. The first objective was to determine if AA supplementation of AA believed to be limiting to protein synthesis in forage-based diets would affect measures of whole-body protein metabolism in sedentary mature horses. The effect of forage type (timothy or alfalfa) and AA supplementation (lysine, threonine or histidine) on plasma urea nitrogen (PUN) and AA concentrations and measures of whole-body phenylalanine kinetics were evaluated. There was no effect of either forage type or AA supplement on rates of whole-body protein synthesis (P > 0.05). The second objective was to determine the effects of either timothy or alfalfa hay supplemented with either a high or low protein ration balancer on measures of whole-body protein metabolism in yearling horses. The effect of forage type and the ration balancer protein level on concentrations of PUN, plasma AA and measures of wholebody phenylalanine kinetics were evaluated. There was no effect of treatment on average daily gain (P = 0.18). When horses consumed the alfalfa-based diets, rates of phenylalanine flux, oxidation and use for protein synthesis were greater than when they consumed timothy-based diets (P < 0.05). Phenylalanine use for protein synthesis was not affected by the protein level of the ration balancer (P = 0.3). Yearling horses achieve greater rates of protein synthesis when fed alfalfa-based diets, compared to timothy-based diets, supplemented with a low protein ration balancer.