Thesis--Catholic Univ. of America. / Includes bibliographical references (p. 70-73).

Thesis (Ph.D.)--Uniformed Services University of the Health Sciences, 2006 / Typescript (photocopy)

The concerns of the present study were to determine 1) the conditions necessary to measure displaceable [³H] L-aspartate binding to membrane fractions of the rat brain, 2) whether the binding demonstrated the charcteristics of the site which is active in vivo, and 3) whether the acidic amino acid neurotransmitters aspartate and glutamate bind to identical or different sites by comparing the pharmacological specificities of the [³H] L-aspartate binding with that of [³H] L-glutamate. The conditions of the [³H] L-aspartate binding assay were determined in synaptosomal and total particulate fractions of whole rat brain. The reaction mixture which included the membrane fraction suspended in Tris-HCl buffer (pH 7.4) in the presence or absence of the compound under test, was incubated at 37°C for 30 minutes. The reaction was stopped by centrifugation and the radioactivity in the pellet counted by liquid scintillation spectrometry. The [³H] L-aspartate binding was characterized in total particulate fractions of rat cerebellum. The apparent dissociation constant (K[sub=D]) and maximum binding (Bmax), as determined by Scatchard analysis, are 1.64 ± 0.34 μM and 7711 ± fmol/mg protein respectively. The displaceable binding is reversible, saturable, independent of the presence of NA⁺, has an affinity in the range where the neurotransmitter is active in vivo, and demonstrates a pharmacological specificity which includes stereospecificity. The compounds tested to demonstrate the pharmacological specificity were L-aspartate (IC[sub=50] = 1.81 μM), D-aspartate (IC[sub=50] = 46.6 μM), L-glutamate (IC[sub=50] = 1.24 μM), N-methyl-DL-aspartate (inactive), kainate (inactive), D-alpha-aminoadipate (inactive), and L-alpha-aminoadipate (IC[sub=50] =7.12 μM). The pharmacological specificity of [³H] L-aspartate binding was different from that of [³H] L-glutamate. When the binding data only are considered, therefore, separate receptors for aspartate and glutamate are indicated. The pharmacological specificity of the [³H] L-aspartate binding, that is the affinity of the binding site for N-methyl-DL-aspartate, D- and L-alpha-aminoadipate, however, does not correlate with the potency of these compounds derived from iontophoretic studies. L-alpha-aminoadipate is very effective while N-methyl-DL-aspartate and D-alpha-aminoadipate do not displace the [³H] L-aspartate binding. In iontophoretic studies, N-methyl-D-aspartate and D-alpha-aminoadipate are very potent as compared to aspartate while L-alpha-aminoadipate Is inactive. The [³H] L-aspartate binding then may not represent the site which is active in vivo. The characteristics of the aspartate site in vivo, however, may not be truely represented in iontophoretic studies because of, for example, uptake of the compounds. The aspartate binding site, therefore, must be identified as that which is activated in vivo. The question of separate receptors for aspartate and glutamate then must still be resolved. / Science, Faculty of / Zoology, Department of / Graduate

Novel terpolymers of leucine (L), aspartic acid (D), and valine (V) were developed as targeting drug delivery carriers that specifically interact with the α 4 β 1 integrin, which is over-expressed in human malignant melanoma cells. As such, copolymerization and terpolymerization of leucine-N-carboxyanhydride (NCA), β-benzyl-aspartate-NCA, and valine-NCA, in dioxane, initiated with triethylamine, were investigated to determine the random nature of the terpolymer composition, for potential application as a targeting drug delivery carrier. The reactivity ratio of each monomer was determined by using Fineman-Ross, Kelen-Tüdös, and nonlinear least-squares curve fitting methods. The product of the estimated reactivity ratios from the monomers in the binary copolymerizations indicated that random polymers were predominantly formed. Based on the reactivity ratios determined from the binary copolymers, Alfrey-Goldfinger equations were used to estimate the composition of the terpolymers. There was no statistical difference between the actual monomer compositions and the calculated compositions of the terpolymers, which validate the randomness of the terpolymers. Therefore, the poly (Leucine-Aspartate-Valine) synthesized in this study is primarily a random terpolymer. The probability of the appearance of LDV sequences occurring within the random polymers were assessed by analyzing the influence of tacticity on the 13 C NMR signals of LDV terpolymers, a statistical method based on the terminal terpolymerization model, and the Poisson distribution, with the highest probability (∼13%) of LDV occurring in a random terpolymer of LDV to be approximately 8 to 9 triad units. Poly (LDV) polymers were shown to exhibit strong binding affinity for A-375 human malignant melanoma cells. The effectiveness of poly (LDV) to target malignant melanoma was evaluated and it showed that 21.3 ± 2.10% of melanoma cells adhered to poly (LDV) films compared to 39.0 ± 3.90% with the positive control fibronectin, whereas binding to HTB-129 human breast carcinoma cells and NHEK normal human keratinocytes were not significant. Poly (LDV)-doxorubicin conjugates displayed excellent selectivity and cytotoxicity in the delivery of doxorubicin. It was shown that the poly (LDV)doxorubicin conjugates exhibited cytotoxicity toward human malignant melanoma cells, but were less toxic than free doxorubicin. In addition, poly (LDV)-doxorubicin conjugates displayed a substantial reduction in toxicity per mole of doxorubicin against normal human keratinocyte cells when compared to free doxorubicin. Fluorescence microscopy showed poly (LDV)-FITC conjugates bound to the A-375 cells and were internalized within 30 minutes. Scatchard plots of poly (LDV)-doxorubicin conjugates were generated, which determined the association constants and established that there is one class of binding sites. It was shown that poly (LDV) could be internalized in a target specific manner by human malignant melanoma cells, which is dependent on the number of LDV targeting moieties in the polymer. These results established that poly (LDV) could be used as a drug delivery carrier that specifically targets the α 4 β 1 integrin.

No description available.

Hidróxidos Duplos Lamelares (HDLs), são materiais lamelares constituídos de camadas positivamente carregadas de um hidróxido misto de dois metais (um di e um trivalente), com ânions hidratados no domínio interlamelar. Apesar de serem potenciais adsorventes, o estudo da adsorção de aminoácidos sobre estes sólidos ainda não foi realizado. Este é importante, pois abre caminho para a aplicação de HDLs na remoção e recuperação de aminoácidos de soluções aquosas, provenientes de processos industriais. Este trabalho teve por objetivo estudar a adsorção e a sorção dos aminoácidos: Ácido Aspártico (Asp), Ácido Glutâmico (Glu) e Fenilalanina (Phe), a partir de soluções aquosas, em HDLs do sistema [Mg-Al-CO3], verificando o efeito de variáveis como temperatura, pH e força iônica (FI) do meio. O adsorvente foi preparado pelo método de coprecipitação a pH variável e caracterizado quanto à composição, organização estrutural, textura e morfologia. A adsorção de Asp, Glu e Phe no HDL não calcinado indicaram que não ocorre a substituição do ânion interlamelar (CO32-), mas sim a adsorção por interação do aminoácido com as cargas residuais na superfície do HDL. O processo mostrou uma grande dependência das variáveis estudadas. A adsorção de Asp e Glu tem comportamento semelhante, embora o aumento da força iônica, seja mais pronunciado em pH 7 para o Asp, e em pH 10 para o Glu. Sem aumento da força iônica, as isotermas atingem ou se aproximam do patamar de adsorção destes aminoácidos, e o aumento na temperatura diminui a quantidade máxima adsorvida. A adsorção de Phe apresentou comportamento similar aos anteriores, exceto pelo fato do aumento da força iônica causar uma diminuição na adsorção. Os resultados obtidos para a sorção no HDL calcinado mostraram que inicialmente o HDL é reconstituído contendo ânions OH- intercalados que são deslocados pelo aminoácido conforme a concentração deste aumenta. Neste caso, Asp e Glu também apresentaram comportamentos semelhantes: as isotermas atingem um patamar onde a sorção torna-se constante e o aumento da temperatura diminui a quantidade sorvida. Para a Phe, a quantidade sorvida é muito maior que para os demais e não se observa o patamar de sorção constante. A temperatura não causa alteração significativa na quantidade sorvida. Os resultados de remoção dos aminoácidos, obtidos para o HDL calcinado se mostraram mais eficientes do que àqueles observados no HDL não calcinado. / Layered Double Hydroxides (LDHs), are lamellar materials constituted of positively charged layers of two cations mixed hydroxide (a bi and a trivalent one), with hydrated anions in the interlayer domain. In spite of they being potential adsorbents, the study of the adsorption of amino acids on these solids has not been done yet. This is important, because it opens the perspective for the application of LDHs to remove and to recover amino acids from aqueous solutions, resultant from industrial processes. The aim of this work was to study the adsorption and the sorption of the amino acids: Aspartic Acid (Asp), Glutamic Acid (Glu) and Phenylalanine (Phe), from aqueous solutions, in [Mg-Al-CO3] LDHs, verifying the effect of the variables: temperature, pH and ionic strength of the medium. The adsorbent was prepared by the coprecipitation method and characterized with respect to their composition, structural organization, texture and morphology. The adsorption of Asp, Glu and Phe in LDH indicated that the substitution of the interlayer anion (CO32-) doesn\'t occur, but the adsorption process occurs by the interaction of the amino acid with the residual charges on the LDH surface. The process showed a dependence on the parameters studied. The adsorption of Asp and Glu presented similar behavior, although the ionic strength effect is more pronounced in pH 7 for Asp, and in pH 10 for Glu. Without the increase in ionic strength, the isotherms reach or approach a plateau, and the increasing in the temperature reduces the maximum amount adsorbed. The adsorption of Phe has similar behavior to the previous ones, except at higher ionic strength, in which a decrease in the adsorption was observed. The results for the sorption in calcined LDH showed that the LDH are reconstituted with the OH- anions intercalated at low amino acid concentrations. The intercalation of amino acid becomes important as their concentration increase. In this case, Asp and Glu also presented similar behaviors: the isotherms reach a plateau where the sorption becomes constant and the increase of the temperature reduces the amount of sorbed amino acid. For Phe, the amount sorbed is higher than those for the others amino acids and the plateau of constant sorption was not observed. The temperature doesn\'t cause any significant alteration in the sorbed amount. The results of removing the amino acids on calcined LDH showed to be more efficient than those observed for the adsorption in LDH.

Hidróxidos Duplos Lamelares (HDLs), são materiais lamelares constituídos de camadas positivamente carregadas de um hidróxido misto de dois metais (um di e um trivalente), com ânions hidratados no domínio interlamelar. Apesar de serem potenciais adsorventes, o estudo da adsorção de aminoácidos sobre estes sólidos ainda não foi realizado. Este é importante, pois abre caminho para a aplicação de HDLs na remoção e recuperação de aminoácidos de soluções aquosas, provenientes de processos industriais. Este trabalho teve por objetivo estudar a adsorção e a sorção dos aminoácidos: Ácido Aspártico (Asp), Ácido Glutâmico (Glu) e Fenilalanina (Phe), a partir de soluções aquosas, em HDLs do sistema [Mg-Al-CO3], verificando o efeito de variáveis como temperatura, pH e força iônica (FI) do meio. O adsorvente foi preparado pelo método de coprecipitação a pH variável e caracterizado quanto à composição, organização estrutural, textura e morfologia. A adsorção de Asp, Glu e Phe no HDL não calcinado indicaram que não ocorre a substituição do ânion interlamelar (CO32-), mas sim a adsorção por interação do aminoácido com as cargas residuais na superfície do HDL. O processo mostrou uma grande dependência das variáveis estudadas. A adsorção de Asp e Glu tem comportamento semelhante, embora o aumento da força iônica, seja mais pronunciado em pH 7 para o Asp, e em pH 10 para o Glu. Sem aumento da força iônica, as isotermas atingem ou se aproximam do patamar de adsorção destes aminoácidos, e o aumento na temperatura diminui a quantidade máxima adsorvida. A adsorção de Phe apresentou comportamento similar aos anteriores, exceto pelo fato do aumento da força iônica causar uma diminuição na adsorção. Os resultados obtidos para a sorção no HDL calcinado mostraram que inicialmente o HDL é reconstituído contendo ânions OH- intercalados que são deslocados pelo aminoácido conforme a concentração deste aumenta. Neste caso, Asp e Glu também apresentaram comportamentos semelhantes: as isotermas atingem um patamar onde a sorção torna-se constante e o aumento da temperatura diminui a quantidade sorvida. Para a Phe, a quantidade sorvida é muito maior que para os demais e não se observa o patamar de sorção constante. A temperatura não causa alteração significativa na quantidade sorvida. Os resultados de remoção dos aminoácidos, obtidos para o HDL calcinado se mostraram mais eficientes do que àqueles observados no HDL não calcinado. / Layered Double Hydroxides (LDHs), are lamellar materials constituted of positively charged layers of two cations mixed hydroxide (a bi and a trivalent one), with hydrated anions in the interlayer domain. In spite of they being potential adsorbents, the study of the adsorption of amino acids on these solids has not been done yet. This is important, because it opens the perspective for the application of LDHs to remove and to recover amino acids from aqueous solutions, resultant from industrial processes. The aim of this work was to study the adsorption and the sorption of the amino acids: Aspartic Acid (Asp), Glutamic Acid (Glu) and Phenylalanine (Phe), from aqueous solutions, in [Mg-Al-CO3] LDHs, verifying the effect of the variables: temperature, pH and ionic strength of the medium. The adsorbent was prepared by the coprecipitation method and characterized with respect to their composition, structural organization, texture and morphology. The adsorption of Asp, Glu and Phe in LDH indicated that the substitution of the interlayer anion (CO32-) doesn\'t occur, but the adsorption process occurs by the interaction of the amino acid with the residual charges on the LDH surface. The process showed a dependence on the parameters studied. The adsorption of Asp and Glu presented similar behavior, although the ionic strength effect is more pronounced in pH 7 for Asp, and in pH 10 for Glu. Without the increase in ionic strength, the isotherms reach or approach a plateau, and the increasing in the temperature reduces the maximum amount adsorbed. The adsorption of Phe has similar behavior to the previous ones, except at higher ionic strength, in which a decrease in the adsorption was observed. The results for the sorption in calcined LDH showed that the LDH are reconstituted with the OH- anions intercalated at low amino acid concentrations. The intercalation of amino acid becomes important as their concentration increase. In this case, Asp and Glu also presented similar behaviors: the isotherms reach a plateau where the sorption becomes constant and the increase of the temperature reduces the amount of sorbed amino acid. For Phe, the amount sorbed is higher than those for the others amino acids and the plateau of constant sorption was not observed. The temperature doesn\'t cause any significant alteration in the sorbed amount. The results of removing the amino acids on calcined LDH showed to be more efficient than those observed for the adsorption in LDH.

Targeted drug delivery is desired in cancer therapy since most of the side effects common to chemotherapy are related to the toxicity of the drug. Integrin over-expression has been shown in various cancer cells and can be exploited for targeted drug delivery. The goal of this study is to design amphiphilic conjugates with targeting motifs as a targeted drug delivery carrier. Toward this effort, novel amphiphilic conjugates of the Arg-Gly-Asp (RGD) peptide or GRGDS was linked to aliphatic acids of varying chain length. The hypothesis is that these novel amphiphilic conjugates, at concentrations above the critical micelle concentration (CMC), can form micelles in aqueous environment, encapsulate poorly-water soluble drugs, and target the α v β 3 integrin. The amphiphilic conjugate is also hypothesized to serve as targeting moiety in mixed micelle drug delivery system using Pluronic block copolymer. Synthesis of RGD amphiphilic conjugates was achieved by converting carboxylic acids into more reactive N-hydroxysuccinimidyl derivative and converting the carboxylic functional group of peptide into methyl ester. Then the activated NHS aliphatic ester was conjugated with methyl-protected peptide in the presence of organic base and methyl ester was removed in NaOH and subsequently neutralized. Intermediates and final products were characterized by MS, FTIR, and NMR. Micelle formation occurred in concentration of 0.015 to 0.12 mM for C 14 -RGD, C 16 -RGD, C 18 -RGD, and C 18 -GRGDS. Amphiphilic conjugate mixed with Pluronic L121 and Pluronic P104 (5% C 18 -RGD/L121 and 10% C 18 -GRGDS/P104) formed micelles at lower CMC of 0.0006 and 0.01 mM, respectively. Solubility of Taxol in water was improved by 87% when encapsulated in C 18 -RGD micelle above CMC. The solubility was increased 7 fold and 18 fold in mixed micelles of 5% C 18 -RGD/P104 and 5% C 18 -RGD/L121 above CMC. Three different drugs (DOX, Taxol, and etoposide) were used to evaluate the efficacy of the targeting C 18 -GRGDS micelle carrier alone or C 18 -RGD mixed with Pluronic block copolymers micelle. All 3 drugs significantly enhanced cytotoxicity toward cancer cells when loaded in micelle carrier above CMC. With same DOX concentration, C 18 -GRGDS micelle carrier significantly decreased percent of viable cells (12.9 ± 1.2%) above CMC when compared to concentrations below CMC (24.1 ± 1.0%). Mixed micelle of targeting amphiphile and Pluronic loaded with Taxol above CMC significantly decreased the percent of viable cells (38.3 ± 7.9%) when compared to non-targeting Pluronic block copolymer micelle (56.0 ± 2.8%). (Abstract shortened by UMI.)

Esta pesquisa bibliográfica teve o propósito de elucidar a via do acido aspártico, apontando como fonte deste estudo os cereais. O objetivo principal desta pesquisa consistiu em estudar a via do acido aspártico, visando descrever uma variedade de técnicas de engenharia genética e bioquímicas que podem ser empregadas para aumentar a qualidade nutricional de cereais, podendo, assim, compreender o que acarreta o aumento do acumulo de lisina, metionina e treonina nos grãos para suprir essa necessidade na formação de uma proteína balanceada nutricionalmente. Foi realizada uma busca exaustiva em bases de dados Google Scholar, Portal Capes, ISI web of Science, no período de publicação de 1970 a 2012. Foram adotados textos de referencia internacional e nacional. Esta pesquisa foi dividida em três etapas: via do acido aspártico e seus aminoácidos derivados em plantas superiores de 1970 a 1997, via metabólica do acido aspártico no período de 1997 a 2006 e estratégias interessantes para aumentar o nível dos aminoácidos essenciais da via do acido aspártico em plantas no período de 2006 ate o momento. A primeira etapa foi desenvolvida relatando o acido aspártico como precursor dos aminoácidos essenciais: metionina, lisina, treonina e isoleucina. Entre os essenciais, a lisina e um dos mais estudados devido a escassez em muitos cereais, o que contribuiu para o estudo extensivo da via do acido aspártico, revelando, assim, a importância da aspartato quinase (AK), homoserina desidrogenase (HSDH) e dihidrodipicolinato sintase (DHDPS) como enzimas chaves para a regulação da síntese de lisina. A aspartato quinase (AK) exerce um controle sobre via do acido aspártico. A enzima dihidrodipicolinato sintase (DHDPS) regula a síntese de lisina. Na segunda etapa foi apresentada a importância dos aminoácidos sintetizados nas plantas através de complexas vias metabólicas que são controladas por enzimas, intermediários, substratos e aminoácidos. Este estudo também relata os aspectos importantes para uma melhor compreensão da síntese e o acumulo de aminoácidos solúveis e incorporados em proteínas. A terceira etapa foi apresentar estratégias interessantes para utilização em estudos, visando aumentar o nível de aminoácidos essenciais através da manipulação de genes já existentes, como também a introdução de genes estranhos nas plantas. Devido a importância nutricional, essa via tem sido extensivamente estudada, utilizando técnicas de engenharia genética e bioquímica. Pesquisadores tem apresentado esforços considerados no estudo desta via a fim de contribuir para futuras manipulações genéticas, cujo objetivo e produzir plantas com alto conteúdo de lisina, metionina e treonina. / The aim of this research was to elucidate the aspartate metabolic pathway using grains of cereal as a source of study. Therefore, it was necessary to understand the aspartate metabolic pathway in order to depict various biochemical and genetic techniques which can be used to enhance the nutritional value in cereals. After studying theses issues, it was possible to understand the results of having cereals with a high lysine, methionine, and threonine content, so that grains can have balanced protein content. For that reason, an exhaustive research was done by using international and national scientific data published in 1970 to 2012. These data were found in Google Scholar, Portal Capes, and ISI Web of Science. This research was divided in three parts: studies of aspartate metabolic pathway and their essential amino acids derived from plants published in 1970 to 1997, studies of aspartate metabolic pathway published in the period of 1997 to 2006, and interesting strategies to enhance the level of essential amino acids of the aspartate metabolic pathway in plants from 2006 to this moment. Firstly, this investigation reported about the aspartic acid as a precursor of essential amino acids such as methionine, lysine, threonine, and isoleucyne. Among the essential amino acids, lysine has been the most researched due to its lack in many kinds of grains. Needless to say, it has contributed to the intensive study showing the relevancy of aspartate kinase (AK), homoserine dehydrogenase (HSDH), dihydrodipicolinate synthase (DHDPS), as key enzymes for lysine regulation. The aspartate kinase (AK) has an important role on the aspartate metabolic pathway, meanwhile the dihydrodipicolinate synthase (DHDPS) is intrinsically involved on lysine synthesis regulation. Secondly, this investigation presented the importance of the amino acids which are synthesized by plants through metabolic pathways that are controlled by enzymes, intermediates, substrates, and amino acids. In addition, this research reported relevant aspects whereby scientists can improve their understanding about the synthesis and accumulation of soluble amino acids which are incorporated in proteins. Finally, the third part showed interesting strategies which can be used in future researches in order to increase not only the level of essential amino acids by manipulating genes, but also the introduction of odd genes in plants. Given the nutritional relevancy, this pathway has been extensively investigated by using techniques used by biochemical and genetic engineering. Hence, researchers have demonstrated a considerable effort on this matter contributing for future genetic manipulations, so that plants with high lysine, methionine, and threonine content can be produced.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Computer simulations within the Density Functional Theory (DFT) formalism were accomplished to find the structural, electronic and vibrational properties of aspartic acid (Asp) crystals in the L-anhydrous, L-monohydrated, and DL-anhydrous phases. Aspartic acid is a non-essential amino acid with a role in the fadigue resistance mechanism. It also works as an excitatory neurotransmitter in the brain, contributes to eliminate any excess of toxins from the cells and is capable to affect RNA synthesis. The computer codes CASTEP (for crystals) and GAUSSIAN (for molecules) were employed in the present study. For the aspartic acid crystals, LDA and GGA-PBE exchange-correlation functional were used in the simulations, the last one taking into account empirical corrections for dispersive forces (PBE+TS) following the scheme proposed by Tkatchenko and Scheffler. Molecular calculations were carried out using the Gaussian09 program with the hybrid exchange-correlation functional B3LYP and the 6-311+G(d,p) basis set. The molecules were simulated in the gaseous phase and solvated in water within the Polarizable Continuum Model (PCM). Crystalline (optimized unit cells) and molecular (smallest energy conformations) structures obtained from the calculations were compared with experimental results and other theoretical computations. For the L-Asp anhydrous crystal, the optical and vibrational infrared (IR) and Raman spectra were contrasted with experimental measurements, and its band structure suggests it is a semiconductor. For the monohydrated L-Asp crystal, an indirect gap 0,1 eV larger than the gap of the anhydrous crystal is caused due to the role of water in its electronic structure. The DL-Asp anhydrous crystal, on the other hand, exhibits a wide direct band gap, which suggests possible optoelectronic uses. Effective masses obtained for all crystals exhibit an anisotropy which must affect their electronic transport properties, with electric conduction more likely along a direction parallel to the molecular planes for the L-Asp anhydrous system. The analysis of the density of electronic states revealed the contributions per atom and per functional group to the valence and conduction band states. A nice agreement was found between the theoretical IR and Raman spectra and the experimental data for the L-Asp anhydrous crystal, allowing for an adequate interpretation of the normal modes involved in each spectral feature. / SimulaÃÃes computacionais no formalismo DFT (Density Functional Theory) foram realizadas para a determinaÃÃo das propriedades estruturais, eletrÃnicas e vibracionais de cristais de Ãcido aspÃrtico (Asp) nas formas cristalinas L-Asp anidro, L-Asp monohidratado e DL-Asp anidro. O Ãcido aspÃrtico à um aminoÃcido nÃo essencial com papel na fisiologia da resistÃncia fÃsica, atuando como neurotransmissor excitatÃrio no cÃrebro, contribuindo para a eliminaÃÃo do excesso de toxinas nas cÃlulas, alÃm de ser capaz de afetar a sÃntese de RNA. Os cÃdigos CASTEP (para cristais) e GAUSSIAN (para molÃculas) foram utilizados no presente estudo. Para os cristais de Ãcido aspÃrtico, os funcionais de troca e correlaÃÃo LDA e GGA-PBE foram empregados nas simulaÃÃes, este Ãltimo incluindo correÃÃes empÃricas para interaÃÃes dispersivas (PBE+TS) de acordo com o esquema de Tkatchenko e Scheffler. Os cÃlculos moleculares foram realizados utilizando o programa Gaussian09 com o funcional hibrido de troca e correlaÃÃo B3LYP e o conjunto de base 6-311+G(d,p). As molÃculas foram simuladas em fase gasosa e em meio aquoso (modelo de solvataÃÃo contÃnuo PCM). As estruturas cristalinas (cÃlulas unitÃrias otimizadas) e moleculares (conformaÃÃes de menor energia) obtidas nos cÃlculos foram comparadas com resultados experimentais e outros cÃlculos teÃricos. No caso do cristal L-Asp anidro, a absorÃÃo Ãptica e os espectros vibracionais IR e Raman tambÃm foram confrontados com medidas experimentais, e sua estrutura de bandas sugere um possÃvel carÃter semicondutor. No caso do cristal L-Asp monohidratado, um gap indireto 0,1 eV maior do que o do cristal anidro reflete o impacto da Ãgua sobre a estrutura eletrÃnica desse cristal. O cristal DL-Asp anidro, por outro lado, exibe um gap direto largo, o que sugere possÃveis usos em optoeletrÃnica. As massas efetivas obtidas para todos os cristais revelam uma anisotropia das propriedades de transporte eletrÃnico, sendo a conduÃÃo elÃtrica mais favorÃvel na direÃÃo paralela aos planos moleculares para o caso L-Asp anidro. A anÃlise da densidade de estados eletrÃnicos permitiu estabelecer a contribuiÃÃo por Ãtomo e por grupo funcional para os estados das bandas de valÃncia e conduÃÃo e um Ãtimo acordo foi obtido entre os espectros vibracionais IR e Raman teÃricos e experimentais do cristal L-Asp anidro, permitindo uma adequada interpretaÃÃo dos modos normais envolvidos em cada pico espectral.