The sense of taste is one of the most important factors in regulating ingestive decisions. This is central to a number of disease conditions including but not limited to obesity, diabetes, anorexia, hypertension, coronary artery diseases and malnutrition. The detection of the molecules eliciting taste qualities in food is mediated by the coordinated actions of distinct types of taste sensory cells (TSCs) housed in taste buds within specialized papillae throughout the oral cavity. Taste receptors in the taste sensory cells that detect food molecules are the key players in selecting dietary nutrients. One such example is L-amino acids, a critical part of one's diet. L-glutamate is the prototypical umami compound and is known to increase palatability of food. A unique characteristic of umami taste is the response potentiation of glutamate by 5' ribonucleotide monophosphates, such as inosine 5' monophosphate (IMP), which is also capable of eliciting an umami taste. Candidate receptors for umami taste include a heterodimer T1r1+T1r3, brain variants of mGluR1 and mGluR4, and the truncated variants of mGluR1 and mGluR4. Studies using heterogeneous expression of T1r1+T1r3 suggest it is an umami and a broadly tuned L-amino acid receptor. While much attention is devoted to understanding glutamate transduction, the detection mechanisms for other L-amino acids by TSCs are less well understood. Here calcium imaging of isolated TSCs and taste cell clusters from the circumvallate and foliate papillae of C57BL/6J and T1r3 knockout mice was performed to determine if other receptors are involved in the detection of L-amino acids and IMP. Ratiometric imaging with Fura-2 was used to study calcium responses to IMP and four L-amino acids (monopotassium L-glutamate, L-serine, L-arginine, and L-glutamine) with and without IMP. The results of these experiments showed that the response patterns elicited by L-amino acids varied significantly across TSCs. Only a small subset of cells responded to all stimuli. Interestingly, L-amino acids other than glutamate elicited synergistic responses in a subset of TSCs. Additionally IMP alone elicited a response in a large number of TSCs. Our data indicate that synergistic and non-synergistic responses to L-amino acids and IMP are mediated by multiple receptors or possibly a receptor complex. Next the roles of mGluR1 and mGluR4 in the detection of the IMP and L-amino acids were investigated. Selective agonists for mGluR1, (RS)-3, 5-dihydroxyphenylglycine (DHPG; a group I mGluR agonist), and mGluR4, L-(+)-2-amino-4-phosphonobutyric acid (L-AP4; a group III mGluR4 agonist) elicited responses in TSCs. In addition, TSCs responsive to these agonists were also responsive to L-amino acids and IMP. More importantly, selective antagonists against different mGluRs such as (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA; a group I mGluR antagonist), and (RS)-α-methylserine-O-phosphate (MSOP; a group III mGluR antagonist) significantly suppressed L-amino acid- and IMP-mediated responses in TSCs of T1r3 knockout mice. Collectively, these data provide evidence for the involvement of taste and the brain variants of mGluR1 and mGluR4 in L-amino acid and IMP taste responses in mice, and support the hypothesis that multiple receptors contribute to the IMP and L-amino acid tastes.

No description available.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-10-10T11:51:05Z No. of bitstreams: 1 rafaeladesouzamartins.pdf: 11994443 bytes, checksum: c42e2d285fd87e325b038e9bfe95bdf5 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-10-10T12:22:21Z (GMT) No. of bitstreams: 1 rafaeladesouzamartins.pdf: 11994443 bytes, checksum: c42e2d285fd87e325b038e9bfe95bdf5 (MD5) / Made available in DSpace on 2017-10-10T12:22:21Z (GMT). No. of bitstreams: 1 rafaeladesouzamartins.pdf: 11994443 bytes, checksum: c42e2d285fd87e325b038e9bfe95bdf5 (MD5) Previous issue date: 2017-08-03 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho descrevemos a preparação de oito amino catalisadores, obtidos na forma de sal do trifluoroacetato. Quatro destes catalisadores foram preparados na forma da mistura de dois estereoisômeros, a partir do glicerol e os aminoácidos L-leucina, L-valina, L-fenilalanina e a L-prolina. Os outros quatro amino catalisadores foram preparados, em sua forma estereoisomericamente pura, a partir do D-manitol e os aminoácidos L-leucina, L-valina, Lfenilalanina e a L-prolina. Os oito amino catalisadores foram capazes de catalisar a reação de adição aldólica entre a cicloexanona e o 4-nitrobenzaldeído. Os produtos de adição foram obtidos em rendimentos que variaram de 58-95 %, sendo a maior r.d. de 1 : 9,12 (sin:anti), determinada por RMN de 1H, e maior e.e. de 94 %, determinado por cromatografia líquida de alta eficiência. O melhor resultado, considerando o rendimento, a diastereo e a enantiosseletividade dos produtos formados, foi obtido quando o catalisador enantiomericamente puro derivado da L-prolina foi utilizado. / In this work we describe a preparation of eight amino-catalysts, obtained as a trifluoroacetate salt. Four of these catalysts were prepared, in the form of the mixture of two stereoisomers, from glycerol and the amino acids L-leucine, L-valine, L-phenylalanine and L-proline. The other four amino-catalysts were prepared in stereoisomerically pure form from D-mannitol and the amino acids L-leucine, L-valine, L-phenylalanine and L-proline. The eight aminocatalysts were able to catalyze the aldol addition reaction between cyclohexanone and 4nitrobenzaldehyde. The addition products were obtained in yields ranging from 58-95 %, the highest d.r. from 1:9.1 (sin: anti), determined by 1H NMR, and higher e.e. of 94 %, determined by high performance liquid chromatography. The best result, considering the yield, diastereomer and enantioselectivity of the formed products, was obtained when the enantiomerically pure L-proline derived catalyst was used.

L'oxyde d'aluminium anodique poreux (AAO) est formé par anodisationde l'aluminium dans une solution électrolytique acide, sous une tensionconstante et de la température de l'électrolyte. Des techniques spectroscopiquespareilles que la spectroscopie infrarouge FT (ATR-FTIR), diffraction des rayonsX (XRD), spectroscopie Raman, la microscopie à force atomique (AFM) etmicroscopie électronique à balayage (MEB) utilisés pour caractériser la matrice.L'oxydation anodique d'acides L-aminés et des mélanges de monomèrescomprenant 0,1 M aniline et des acides L-aminés dans le milieu aqueux acide deplatine et électrode lisses électrodes Pt modifié (Pt / AAO) est étudié.L'oxydation des acides L-aminés et les électropolymérisation de l'aniline 0,1 Mavec des acides L-aminés tels que la L-alanine, la L-sérine, la L-méthionine,acide L-aspartique, la L-lysine, et phénylalanine en acide le milieu a étéeffectuée par voltammetric cyclique électrochimique couplée à microbalance àcristal de quartz (EQCM). La concentration des acides aminés, le pH del'électrolyte et les effets de balayage de numéros de voltamétrie cyclique ont étéexaminées. L'analyse spectroscopique comme réflectance totale atténuée FTspectroscopie infrarouge (ATR-FTIR), UV-visible, la spectroscopiephotoélectronique à rayons X (XPS), la spectroscopie Raman, et la diffractiondes rayons X (XRD) sont utilisés pour caractériser les couches minces obtenues.Microscopie électronique à balayage (MEB) utilisé pour étudier la morphologiede surface mince de films. La solubilité pour les polymères sont étudiées. Laprésence de liaisons peptidiques est clairement mise en évidence. DFTmodélisation de poly-L-acides aminés volet sur Pt (001) couplée à des mesuresspectroscopiques sont en faveur de L-amino-acides électropolymérisation enacides poly-L-aminés d'une manière irréversible.Les électrosynthèses de poly-L-amino acides, la polyaniline et depolymères ont été utilisées en tant que récepteur de protons à l'état solide pHcapteur solide. / Anodic aluminum oxide porous (AAO) is formed by the anodization ofaluminum in acidic electrolytic solution under at constant voltage and electrolytetemperature. Spectroscopic techniques such as FT infrared spectroscopy (ATRFTIR),X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy(AFM) and scanning electron microscopy (SEM) used to characterize thetemplate.The anodic oxidation of L-amino acids and monomer mixtures comprising0.1 M aniline and some L-amino acids in acidic aqueous medium on platinumsmooth electrodes and modified Pt electrode (Pt/AAO) is studied. The oxidationof L-amino acids and in presence of aniline 0.1 M with L-amino acids such as Lalanine,L-serine, L-methionine, L-aspartic acid, L-lysine, and L- phenylalaninein acidic media was carried out by cyclic voltammetry coupled withelectrochemical quartz crystal microbalance (EQCM). The Amino acidconcentration, pH of the electrolyte and the scan number effects on cyclicvoltammetry were examined. Spectroscopic analysis such as attenuated totalreflectance FT infrared spectroscopy (ATR-FTIR), UV-Visible, X-rayphotoelectron spectroscopy (XPS), Raman spectroscopy, and X-ray diffraction(XRD) are used to characterize the resulting thin film coatings. Scanningelectron microscopy (SEM) used to study the morphology of thin films surfaceas well as the solubility are studied. The presence of peptide bonds is clearlyhighlighted. DFT modelization of poly-L-amino acids strand on Pt(001) coupledto spectroscopic measurements are in favor of L-amino acidselectropolymerization into poly-L-amino acids in an irreversible way.The electrosynthesis of poly-L-amino acids, polyaniline and polymerswere used as proton receptor for solid state pH solid sensor.

This thesis applies the ab initio techniques of computational chemistry to studies of molecular clusters containing covalent (strong) or van der Waals (weak) bonds formed in chemistry and biochemistry in the temperature range 10-300 K. Van derWaals complexes with an enthalpy of formation from reactants of less than 25 kJ mol-1 and covalent clusters are described in this thesis. The first group of van der Waals complexes involved the molecule carbon monoxide that possesses a small permanent dipole that could lead to dipole - induced dipole interaction and dipole - dipole interaction with another reactant in addition to dispersion. The substrates investigated were methanimine and cyanogen where endergonic unstable molecules were formed, and the clustering of carbon monoxideon a porphin surface leading to the formation of carbon - carbon fragments. TheFaraday effect was invoked to suggest that this was the original method by which thechirality of the D-sugars was selected. Coordination of imino-compounds on thesame surface involving induction and electrostatic interactions could lead to the preferential formation of L-aziridones, hydrolysable to L-amino-acids.The preferred formation of D-ribose, and the more stable D-2-deoxyribose, andnucleotides polymerisable to deoxyribonucleic acids was described. The second group of van der Waals complexes involved the polymerisation of acetylene molecules, to di- and tri-acetylene complexes where the exchange interaction involved the quadrupole moment of the acetylene radical reacting with acetylene or diacetylene. The reaction of carbon monoxide was extended to include its interaction with diacetylene. The entire potential energy surface for the interaction with diacetylene was investigated. The reaction was shown to be endergonic to produce a reactive species, here postulated to rearrange with a reasonable activation energy toform an aldehyde. The energetics of the formation of diacetylene, triacetylene andhigher polymers was briefly investigated. The reactivity of the acetylene polymeraldehydes with other substrates was briefly investigated. This work has apparently laid a firm basis both, qualitative and quantitative, tounderstand some of the weakest interactions in nature involving the simplest ofreactions that have been important in atmospheric chemistry.

The purpose of this study was the investigation of several transport systems expressed at the BBB. The identification and functional characterization of such transport systems is essential to provide a basis for strategies to regulate drug disposition into the brain. Immortalized rat brain endothelial cells (RBE4 cells) have been used in this study as an in vitro model of the BBB. The present study has shown that the RBE4 cells are a suitable model of the BBB for transporter studies. These cells do express the amino acid transport systems L and y+, which are known to be present at the BBB. The uptake of L-tryptophan, a neutral amino acid transported by system L, exhibited a half saturation constant (Kt) of 31 µM and a maximal velocity rate (Vmax) of about 1 nmol/mg/min in RBE4 cells. The kinetic constants of the L-arginine uptake, representing system y+ transport activity, into RBE4 cells were determined with a Kt value of about 55 µM and a Vmax of 0.56 nmol/mg/min. Furthermore the expression of two sodium dependent transporters, the 5-HT transporter (SERT) and the organic cation/carnitine transporter OCTN2, was shown at the RBE4 cells. Uptake studies with radiolabeled 5-HT exhibited a saturable, sodium dependent transport at RBE4 cells with a Kt value of about 0.40 µM and a Vmax of about 52 fmol/mg/min. L-carnitine and TEA (tetraethylammonium) are known to be transported by the OCTN2 transporter. The uptake of L-carnitine into RBE4 cells was shown to be sodium dependent and saturable with a Kt value of 54 µM and a maximal velocity of about 3.6 pmol/mg/min. In contrast, the organic cation TEA follows a sodium independent uptake mechanism at RBE4 cells. Also a sodium independent choline uptake into the cells was discovered but the molecular identity remained unknown. This saturable choline transport exhibited a Kt value of about 22 µM and a maximal velocity of about 52 pmol/mg/min.