Albumin provides the vital scaffolding for growth and tissue repair and supports oncotic blood pressure and hemodynamics. In hemodialysis patients, albumin aids with fluid removal by drawing excess fluid from edematous tissues back into the blood where it can then be removed by a dialyzer. The hyperglycemia seen in dialysis patients with Type II diabetes progressively damages kidney glomeruli, which permits albumin seepage into the urine, thus lowering serum albumin. The conceptual framework underpinning this research is the van't Hoff theory of osmotic pressure. Under this framework, the solute-solvent relationship largely contributes to the osmotic movement of fluid. The purpose of this study was to determine if albumin levels differed in Hispanics on dialysis with and without diabetes and if potential differences existed over time. Differences in diabetes incidence in Hispanics suggest albumin levels may be dissimilar. Albumin physiology is abundant in the literature; how and to what magnitude albumin levels are affected in patients with diabetes is unclear. This quantitative, retrospective cohort study employed ANOVA, Repeated Measures t tests, Spearman Correlation, and regression analysis to evaluate potential associations between the research variables. Data were extracted from CMS-2728 forms to amass the final cohort (N = 827). Differences in albumin levels at the first 2 intervals were observed (Baseline 1.29 -± 0.49 mg/dL, F = 2.28, p < .032; 3 months 0.47 -±0.41 mg/dL, F = 1.62, p < .004). Covariables (hypertension, peripheral vascular disease, and infections) were controlled for but showed inconclusive results. Lower serum albumin in Hispanic dialysis patients with diabetes provides the impetus for developing ethnic-specific albumin therapies, thus promoting positive social change.

Magnetic nanoparticles (MNPs) hold great promise in the fields of biology and medicine. The synthesis of functional MNPs with precisely controlled crystallographic, physicochemical, and magnetic properties on a large scale still remains the challenge today. This thesis reports the exploration of liquid-fed flame spray pyrolysis (FSP) in the synthesis of functional MNPs, their surface modifications, and potential bio-applications. Superparamagnetic and ferromagnetic maghemite (γ-Fe2O3) nanoparticles, and silica-coated maghemite (SiO2/γ-Fe2O3) nanocomposites were synthesised using FSP. The size of γ-Fe2O3 was controllable from 6 to 53 nm, with morphology evolving from a disordered near-spherical shape to fully ordered 2-D hexagonal/octagonal platelet. The saturation magnetisation (Ms) increased from 21 to 74 emu/g with increasing particle size, up to 13 nm when Ms approached the bulk γ-Fe2O3 characteristics. In the case of SiO2/γ-Fe2O3, three distinct morphologies, namely the single segregated γ-Fe2O3 core- SiO2 shell, transitional mixed morphologies, and multi γ-Fe2O3 cores embedded in submicron SiO2 shell, were obtained. The core size, composite size, and morphology of γ- Fe2O3 were tunable by varying %SiO2 loading and the use of a quartz tube enclosure during flame synthesis. The magnetic behaviour correlated well with the crystal microstructure. Following the core particle design, protein adsorption-desorption behaviour on FSP-madeMNPs was studied. Bovine serum albumin (BSA) adsorption was found to follow the Langmuir isotherm, with high binding capacities (150−348 mg BSA/g particle) and fast association constants. Electrostatically governed BSA orientations were proposed for different particle-buffer systems. The adsorbed BSA was effectively recovered by pH-shift using K2HPO4. Subsequently, terminal amine, aldehyde, carboxylic, epoxy, mercapto and maleimide functionality were anchored onto the FSP-made γ-Fe2O3 particles. These versatile functional groups led to conjugation of active trypsin. The immobilised trypsin exhibited superior durability with >60% residual activity after one week, and excellent reusability for >5 cycles. The trypsin-conjugated MNPs are promising carriers in proteomics, demonstrating good substrate specificity with equivalent or better sequence coverage compared to free trypsin in insulin and BSA digestion. In another application, a refined silanisation procedure simultaneously reduced γ-Fe2O3 to Fe3O4, and generated thiol enriched surface for matrix metalloproteinase-2 (MMP-2) conjugation. The highly active MMP-2-conjugated MNPs could potentially enhance the interstitial transport of macromolecule/nanoparticles in drug delivery.

In this thesis, a direct method of Atomic Force Microscopy (AFM) technique has been developed to measure the adhesion forces between BSA and two different surfaces: mica (a hydrophilic surface); and polystyrene (a hydrophobic surface); in PBS solution. We have shown possible to measure interactions between proteins and substrate surface directly without any modification to the substrate and the AFM tip; this means protein molecules can keep the natural elastic property within the force measurements. The average measured value of adhesion forces between BSA and mica is 0.036 ± 0.002 nN, and between BSA and polystyrene is 0.066 ± 0.003 nN. The polystyrene surface is more adhesive to BSA than the mica surface. This is consistent with previous research, which assessed that hydrophobic surfaces enhance protein adhesion but hydrophilic surfaces do not.

Magnetic nanoparticles (MNPs) hold great promise in the fields of biology and medicine. The synthesis of functional MNPs with precisely controlled crystallographic, physicochemical, and magnetic properties on a large scale still remains the challenge today. This thesis reports the exploration of liquid-fed flame spray pyrolysis (FSP) in the synthesis of functional MNPs, their surface modifications, and potential bio-applications. Superparamagnetic and ferromagnetic maghemite (γ-Fe2O3) nanoparticles, and silica-coated maghemite (SiO2/γ-Fe2O3) nanocomposites were synthesised using FSP. The size of γ-Fe2O3 was controllable from 6 to 53 nm, with morphology evolving from a disordered near-spherical shape to fully ordered 2-D hexagonal/octagonal platelet. The saturation magnetisation (Ms) increased from 21 to 74 emu/g with increasing particle size, up to 13 nm when Ms approached the bulk γ-Fe2O3 characteristics. In the case of SiO2/γ-Fe2O3, three distinct morphologies, namely the single segregated γ-Fe2O3 core- SiO2 shell, transitional mixed morphologies, and multi γ-Fe2O3 cores embedded in submicron SiO2 shell, were obtained. The core size, composite size, and morphology of γ- Fe2O3 were tunable by varying %SiO2 loading and the use of a quartz tube enclosure during flame synthesis. The magnetic behaviour correlated well with the crystal microstructure. Following the core particle design, protein adsorption-desorption behaviour on FSP-madeMNPs was studied. Bovine serum albumin (BSA) adsorption was found to follow the Langmuir isotherm, with high binding capacities (150−348 mg BSA/g particle) and fast association constants. Electrostatically governed BSA orientations were proposed for different particle-buffer systems. The adsorbed BSA was effectively recovered by pH-shift using K2HPO4. Subsequently, terminal amine, aldehyde, carboxylic, epoxy, mercapto and maleimide functionality were anchored onto the FSP-made γ-Fe2O3 particles. These versatile functional groups led to conjugation of active trypsin. The immobilised trypsin exhibited superior durability with >60% residual activity after one week, and excellent reusability for >5 cycles. The trypsin-conjugated MNPs are promising carriers in proteomics, demonstrating good substrate specificity with equivalent or better sequence coverage compared to free trypsin in insulin and BSA digestion. In another application, a refined silanisation procedure simultaneously reduced γ-Fe2O3 to Fe3O4, and generated thiol enriched surface for matrix metalloproteinase-2 (MMP-2) conjugation. The highly active MMP-2-conjugated MNPs could potentially enhance the interstitial transport of macromolecule/nanoparticles in drug delivery.

Thesis (Ph.D. in Pharmaceutical Sciences) -- University of Colorado Denver, 2008. / Typescript. Includes bibliographical references (leaves 219-242). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;

Submitted by ANA CAROLINA DE TOLEDO SANTANA null (actoledo@iq.unesp.br) on 2016-03-17T17:25:32Z No. of bitstreams: 1 Dissertação Carol Final.pdf: 7825510 bytes, checksum: 921c29706ed56e5ef489712bae28fc30 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-03-21T20:10:04Z (GMT) No. of bitstreams: 1 santana_act_me_iq_par.pdf: 4512361 bytes, checksum: 07a7dc911b2bdd27db8608948a16848b (MD5) / Made available in DSpace on 2016-03-21T20:10:04Z (GMT). No. of bitstreams: 1 santana_act_me_iq_par.pdf: 4512361 bytes, checksum: 07a7dc911b2bdd27db8608948a16848b (MD5) Previous issue date: 2016-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho teve como principal objetivo estudar a atividade catalítica de soroalbumina bovina (BSA) em reações formadoras de uma nova ligação C-C: Reações aldólica, de Henry e Morita-Baylis-Hillman (MBH). Em todos os casos a BSA atuou como catalisador, visto que quando as reações foram realizadas sem sua presença, não houve formação dos produtos desejados. Os rendimentos obtidos para as reações aldólica (37%), Henry (80%) e MBH (73%), variaram de bons a moderados e não foi observada enantiosseletividade para nenhuma das reações estudadas. As soroalbuminas são proteínas que formam muita emulsão dificultando os processos downstream na separação dos produtos e materiais de partida. Visando minimizar este inconveniente, a BSA foi submetida à imobilização em MCLEA (magnetic cross-linking enzyme aggregates) utilizando nanopartículas magnéticas de óxido de ferro. Nestes casos, o biocatalisador pôde ser facilmente retirado do meio reacional com aplicação de um campo magnético externo. Esta metodologia afetou diretamente no rendimento da reação de Henry, passando de 80% para 89%. Porém, para as outras reações a melhoria no rendimento não foi tão expressiva. A imobilização também não foi eficaz para o aumento dos excessos enantioméricos. Até o momento para a reação de MBH com os substratos utilizados, não há relatos na literatura para a síntese do aduto desejado catalisado pela BSA. Sendo assim, optamos por realizar um planejamento fatorial completo dessa reação visando otimizar as condições reacionais bem como os rendimentos. As variáveis estudadas foram: temperatura, concentração do biocatalisador e condição do biocatalisador (livre ou imobilizado). Os resultados obtidos mostraram que a variável com maior influência na reação, é a concentração do biocatalisador. A conversão obtida passou de 30% para 40% utilizando 2,2 μmol de BSA. Em seguida, realizamos um estudo de ascendência da concentração do catalisador visando otimizar este parâmetro. A conversão obtida passou para 73% quando foram utilizadas 3,7 μmol de biocatalisador imobilizado. Realizamos um estudo de reciclagem do biocatalisador imobilizado. Foi possível reutiliza-lo porém com diminuição da conversão a partir do segundo ciclo. Os resultados obtidos nesta dissertação evidenciam o potencial biocatalítico da BSA em reações para a formação de ligação C-C. / This work aimed to study the catalytic activity of bovine serum albumin (BSA) in reactions that form a new C-C bond: aldol reactions, Henry and Morita-Baylis-Hillman (MBH). In all cases BSA served as the catalyst, whereas when the reactions were carried out without their presence there was no formation of the desired products. The yields obtained for aldol reactions (37%), Henry (80%) and MBH (73%), ranged from good to moderate enantioselectivity and was not observed for any of the studied reactions. The serum albumins are proteins that form the much emulsion difficulting downstream processes in separation of the products and starting materials. To minimize this inconvenience, the BSA was subjected to immobilization in M-CLEA (magnetic cross-linking enzyme aggregates) using magnetic nanoparticles of iron oxide. In these cases the biocatalyst could be easily removed from the reaction medium by applying an external magnetic field. This methodology directly affect the yield of the Henry reaction, from 80% to 89%. However, for other reactions the improvement of yields was less pronounced. The immobilization was also not effective for improving the enantiomeric excess. So far for the MBH reaction with the worked substrates, there are no reports in the literature for the synthesis of the desired adduct catalyzed by BSA. So we decided to study a full factorial design of this reaction to optimize the reaction conditions and yields. The variables studied were: temperature, the biocatalyst concentration and biocatalyst conditions (free and immobilized). The concentration of biocatalyst was the major factor with interference in all reactions. The conversion increased from 30% to 40% using 2.2 μmol of BSA. Then we perform a study of catalyst concentration to optimize this parameter. The conversion increased to 73% when they were used 3.7 μmol immobilized biocatalyst. To evaluate the retention of catalytic activity of BSA immobilized, it was performed a study of the immobilized biocatalyst recycling. It was possible the reuse but with reduced conversion from the second cycle. The results obtained in this work demonstrated the potential of BSA in C-C bond formation reactions.

A carcinogênese epitelial ovariana tem sido foco de estudos científicos em todo o mundo desenvolvido. A angiogênese tumoral ovariana é um processo multifatorial que resulta em vários produtos pró-angiogênicos. Entre eles, o fator de crescimento vascular endotelial (VEGF) é predominante. Os objetivos deste estudo foram relacionar as dosagens do VEGF dos fluidos peritoneais, do plasma periférico e do infundíbulo pélvico aos níveis de citorredução em pacientes operadas de adenocarcinoma epitelial de ovário (CEO); formular um modelo probabilístico de citorredução e utilizar estas dosagens para estimar a probabilidade do desfecho de citorredução. Além disto, foi criada uma nova variável chamada carga de VEGF. Pelo procedimento step-wise a citorredução foi melhor descrita pela carga de VEGF, mas faltou Normalidade aos resíduos, não sendo possível a adequação de um modelo matemático. Porém, a curva ROC, forneceu uma área sob a curva de 0,84, com sensibilidade de 71,4 % e especificidade variando de 69,5 a 73,9%. O ponto de corte ótimo foi 15,52 log de picograma de carga de VEGF. A odds-ratio (OR) calculada para citorredução ótima descrita pela carga de VEGF foi de 11 (IC= 2,59 ; 46,78). No grupo com estágio avançado (III e IV), a OR foi de 6 (IC= 1,15; 31,22). Apesar do pequeno número de casos, esta nova variável pode vir a ser um auxiliar na determinação de situações onde cirurgia citorredutora deixa de ser a pedra fundamental do tratamento primário do CEO e a indução quimioterápica passe a ter o principal papel na citorredução química antes da cirugia nestes casos. / Epithelial ovarian carcinogenesis has been the focus of scientific studies in developed world. The ovarian tumor angiogenesis is a multifactorial process that results in pro-angiogenic products. Among them, vascular endothelial growth factor (VEGF) is predominant. This study aimed to relate VEGF levels in peritoneal fluids, peripheric plasma and pelvic infundibular plasma to debulking levels in patients operated on for epithelial ovarian carcinoma (EOC), formulate a probabilistic model for debulking and use these measurements to estimate the probability of the outcome of debulking. Moreover, it was created a new variable called burden of VEGF. For step-wise procedure, cytoreduction was better described by of burden VEGF, but missed Normality of residuals, so the adequacy of a mathematical model was not possible. Nevertheless, the ROC curve provided an area under the curve of 0.84, with sensitivity of 71.4 % and especificity varying from 69.5 to 73,9%. The optimal cutoff point was 15.52 log of picograms of VEGF burden. An odds-ratio for optimal cytoreduction described by the VEGF burden was 11 (CI= 2.59; 46.78). In the group with advanced stages (III & IV), the OR was 6 (CI= 1.15; 31.22). Apart from the small number of cases, this new variable might help to determine situations where cytoreductive surgery leaves behind the cornerstone of primary treatment of CEO and the chemotherapic induction comes to have main role in chemical cytoreduction prior to surgery in these cases.

The interaction between two proteins into salt aqueous solutions is investigated throughout this thesis. Experiments, modeling and molecular simulations were carried out to get a better understanding of the phenomenon. Bovine serum albumin was used as a model protein. An analytical expression for the structure factor for globular proteins in aqueous solution is presented in this work. This expression was obtained considering an intermolecular potential given by the sum of a hard core, a van der Waals attractive and a screened Coulomb contribution. Experimental data of Small Angle X-Ray Scattering for bovine serum albumin in aqueous solutions containing sodium salts at different protein concentrations and pH values are also presented. The expression developed for the structure factor describes accurately these experimental data provided a dependence of the attractive parameter on protein concentration is established. An expression for the osmotic pressure was derived from the structure factor. With attractive parameters adjusted from X-ray scattering data, the osmotic pressure of bovine serum albumin aqueous solutions could be predicted with very good agreement with experimental data. A derivation of the thermodynamic potentials, such as the chemical potential, using the new osmotic equation of state is presented. Applying the phase equilibrium criterion, the fluid-fluid phase equilibrium for bovine serum albumin in salt aqueous solution was calculated. Although such separation was not experimentally observed at the isoelectric point, it was indeed experimentally observed for a pH value below the isoelectric point. The predictions seem to be valuable to discuss how ion specificity affects the phase diagram of proteins. To apply molecular dynamic techniques to simulate how proteins interact to each other in salt aqueous solutions, two new coarse-grained force fields are proposed. The first one, meant for sodium sulfate aqueous solution, avoids the unphysical association observed for non-polarizable atomistic force fields; and allows the prediction of thermodynamic and dynamic properties. The second one, meant for bovine serum albumin in aqueous solution, is used as a new strategy to evaluate the scattering form factor of proteins as a low resolution technique for protein structure prediction. / Nesta tese apresenta-se uma investigação sobre a interação entre duas proteínas em soluções aquosas salinas. Experimentos, modelagem e simulações moleculares foram realizadas para conseguir um melhor entendimento do fenômeno. Albumina de soro bovina foi usada como proteína modelo. Uma expressão para o fator de estrutura de proteínas globulares em solução aquosa é apresentada neste trabalho. Esta expressão foi obtida considerando-se um potencial intermolecular dado pela soma de um núcleo duro, uma contribuição atrativa tipo vander Waals e uma contribuição de potencial coulômbico blindado. Dados experimentais de espalhamento de raios-X a baixos ângulos para a albumina de soro bovino em soluções aquosas contendo sais de sódio com diferentes concentrações de proteína e valores de pH também são apresentados. A expressão desenvolvida para o fator de estrutura descreve com precisão estes dados experimentais, desde que uma dependência entre o parâmetro atrativo com a concentração de proteína seja estabelecida. Uma expressão para a pressão osmótica foi derivada do fator de estrutura. Com parâmetros atrativos ajustados aos dados de espalhamento de raios-X, a pressão osmótica da albumina de soro bovino em solução aquosa pôde ser predita com grande correlação com os dados experimentais. Uma derivação dos potenciais termodinâmicos usando a nova equação osmótica de estado é apresentada. Aplicando o critério de equilíbrio de fases, foi possível calcular o equilíbrio fluido-fluido para a albumina de soro bovino em solução aquosa. Embora tal separação não tenha sido observada experimentalmente em um pH igual ao ponto isoelétrico, ela foi de fato observada experimentalmente para um valor de pH menor do que o ponto isoelétrico. As predições parecem ser valiosas para discutir como a especificidade iônica afeta o diagrama de fases de proteínas. De modo a avaliar como proteínas interagem umas com as outras usando técnicas de dinâmica molecular, dois novos campos de força coarse-grained são propostos. O primeiro, para o sulfato de sódio em solução aquosa, evita a associação não-física que é observada para campos de força atomísticos não-polarizáveis. Este modelo é capaz de prever propriedades dinâmicas e termodinâmicas. O segundo, para a albumina de soro bovino em solução aquosa, é usado como uma nova estratégia para avaliar o fator de forma de espalhamento de proteínas como uma ferramenta de baixa resolução na predição de estruturas proteicas.

Resumo O presente trabalho teve como objetivo sintetizar e caracterizar um novo complexo trinuclear de rutênio, [Ru3O(CH3OO)6(3-pic)2(NO)]+, através de rotas sintéticas previamente descritas na literatura para complexos análogos. Para a obtenção deste complexo, foram necessárias cinco etapas de síntese, cada qual gerando o precursor da etapa seguinte. Os complexos precursores [Ru3O(CH3OO)6(3-pic)3]+, [Ru3O(CH3OO)6(3-pic)2(CO)] e [Ru3O(CH3OO)6(3-pic)2(H2O)]+, foram caracterizados por técnicas espectroscópicas e voltamétricas. Para o complexo de interesse, [Ru3O(CH3OO)6(3-pic)2(NO)]+, além da caracterização por técnicas espectroscópicas e voltamétricas, foram realizados estudos de fotólise e de interação com albumina de soro humano (HSA). Pelas técnicas espectroscópicas, pudemos ratificar as estruturas propostas tanto para o nitrosilo quanto para os precursores estudados. Para a caracterização do complexo [Ru3O(CH3OO)6(3-pic)2(NO)]+, utilizando a técnica de espectroscopia de infravermelho verificamos a coordenação do ligante NO ao centro metálico [Ru3O], devido ao estiramento característico deste ligante. Os espectros de absorção UV-vis e RMN mostraram que existe uma forte interação entre o elétron desemparelhado do centro metálico e o elétron do ligante NO. Pelos estudos de voltametria cíclica, observamos que os processos redox envolvendo o ligante NO, são compartilhados com o centro metálico. A fotólise do complexo [Ru3O(CH3OO)6(3-pic)2(NO)]+, mostrou-se eficiente, uma vez que a liberação fotoinduzida do NO ocorreu na região do visível e em pH fisiológico. Pelos estudos de supressão de fluorescência, observamos que o complexo realmente interage com a HSA na proporção de 1:1, na região em que se encontra o resíduo de triptofano. / The aim of the present study was synthesize and characterize a new trinuclear ruthenium complex, [Ru3O(CH3OO)6(3-pic)2(NO)]+, via synthetic routes previously described in the literature for analogous complexes. To obtain this complex, it took five synthetic steps, each one yielding a precursor for the next step. The precursor complexes [Ru3O(CH3OO)6(3-pic)3]+, [Ru3O(CH3OO)6(3-pic)2(CO)] and [Ru3O(CH3OO)6(3-pic)2(H2O)]+, were characterized by spectroscopic and voltammetric techniques. For the complex of interest, [Ru3O(CH3OO)6(3-pic)2(NO)]+, in addition to characterization by spectroscopic and voltammetric studies, it was carried out photolysis and interaction with human serum albumin. By spectroscopic techniques, we could confirm the proposed structures for both the nitrosyl and precursors. For characterization of the complex [Ru3O(CH3OO)6(3-pic)2(NO)]+, infrared spectroscopy allowed us to verify that the ligand coordination to the metal center [Ru3O], due to the characteristic stretching band of that ligand. The absorption spectra of UV-vis and NMR showed that there is a strong interaction between the unpaired electron of the metal center and the NO ligand. By cyclic voltammetry studies, we observed that the redox processes involving the NO ligand are shared with the metal center processes. The photolysis of the complex [Ru3O (CH3OO) 6 (3-pic) 2 (NO)] +, was efficient, since the photoinduced release of NO occurred in the visible region and at physiological pH. By fluorescence quenching studies, we observed that the complex actually interacts with the HSA in a 1:1 ratio, in the region which is the residue of tryptophan.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2017-06-06T12:34:21Z No. of bitstreams: 1 2010 - Alessandra Medeiros Ribeiro .pdf: 4846590 bytes, checksum: 525d2754e1be01d1117fe6e9f3362d1f (MD5) / Made available in DSpace on 2017-06-06T12:34:21Z (GMT). No. of bitstreams: 1 2010 - Alessandra Medeiros Ribeiro .pdf: 4846590 bytes, checksum: 525d2754e1be01d1117fe6e9f3362d1f (MD5) Previous issue date: 2010-03-19 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior, CAPES, Brasil. / Spectroscopic studies for several comercial flavonoids (flavone (FVA), alphanaphthoflavone (?-NAF), beta-naphthoflavone (?-NAF), thioflavone (TFA), S,Sdioxythioflavone (SDF), flavanone (FNA) and quercetin (QUE)), natural flavonoids (biflavonoids such as agatisflavone (ATF), 7?-O-methylagatisflavone (OMA), amentoflavone (AMF) and (DOF)) and thiochromanone (TCR) were performed in different solvents (acetonitrile (ACN), ethanol (ETOH), cyclohexane (CEX), dichloromethane (DCM) and milli-Q water (AD)). Irradiation of TFA, SDF and TCR in acetonitrile, employing the nanosecond laser flash photolysis, lead to the formation of their corresponding triplet excited state. Fluorescence emission spectroscopy studies showed that commercial and natural flavonoids and thiochromanone are not fluorescent. UV/visible spectroscopy studies for QUE, ATF, OMA, AMF and DOF, in the same previous solvents, revealed that for these flavonoids the ground-state absorption spectrum in polar solvents, such as water or PBS (pH=7.4), is completely different than the obtained in dichloromethane. This difference is more pronounced for ATF. For DOF the absorption spectrum in water shows remarkable variations when compared to that in PBS. The interaction between BSA and the flavonoids QUE, ATF, OMA, AMF and DOF in PBS solution, pH = 7.4, was studied by UV/visible spectroscopy, fluorescence emission spectroscopy, circular dicroism and molecular modelling. From these studies it was clearly demonstrated that the interaction observed was directly dependent on the flavonoid concentration and almost independent on temperature variation. The ground state absorption spectrum for BSA showed a hypsochromic effect on the absorption band around 208 nm, corresponding to the n?* transition of the BSA ?-helix structure, as a function of flavonoid concentration. Similar behavior was observed for the absorption at 280 nm, corresponding to the tryptophan absorption in BSA. The fluorescence emission spectrum for BSA in the presence of QUE, ATF, OMA, AMF and DOF, in PBS, at T = 22?C, 27?C, 32?C, 37?C and 42?C, shows a blue-shift on the protein emission as a function of flavonoid concentration. These results suggest that the BSA chromophore is in a more hydrophobic environment when compared with that sensed by the protein in the absence of the flavonoid. In this case, quenching of BSA fluorescence (tryptophan residues) was clearly observed with the high values obtained for the quenching rate constant kq (? 1013 to 1014 L/mol.s) indicating a static quenching process. The distance (r) observed for the tryptophan residues and the flavonoids was smaller than 7 nm, which indicates that there is a reasonable probability for a non-radiative energy transfer process between tryptophan and the flavonoids, based on the F?rster theory for energy transfer. Circular dicroism results at T = 25?C, 37?C and 42?C revealed a significant decrease on the ?-helix percentage for BSA at 208 nm and 222 nm, corresponding to the n?* transition for the secondary structure of BSA, as a function of flavonoid concentration. These effects can be attributed to the formation of a complex BSA/flavonoid which can induce conformational variations on the BSA structure. Molecular modelling indicates that the main regions for the interaction between flavonoids and ASB are located in hydrophobic cavities on the sub-domains IB and IIA, which contain tryptophan residues (Trp-158 and Trp-237). A large hydrophobic cavity containing the Trp-237 is present in the sub-domain IIA, which is responsible for the formation of the complex flavonoid-BSA through a strong interaction flavonoid-tryptophan. / Estudos espectrosc?picos para diversos flavon?ides comerciais (flavona (FVA), alfanaftoflavona (?-NAF), beta-naftoflavona (?-NAF), tioflavona (TFA), S,S-di?xidotioflavona (SDF), flavanona (FNA) e quercetina (QUE)), flavon?ides naturais (biflavon?ides como agatisflavona (ATF), 7?-O-metilagatisflavona (OMA), amentoflavona (AMF) e diidroochnaflavona (DOF)) e tiocromanona (TCR), foram realizados em diferentes solventes (acetonitrila (ACN), etanol (ETOH), cicloexano (CEX), diclorometano (DCM) e ?gua millliQ (AD)). A irradia??o de TFA, SDF e TCR, em acetonitrila, por fot?lise por pulso de laser de nanossegundo, levou ? forma??o de seus respectivos estados excitados triplete. Por espectroscopia de fluoresc?ncia, verificou-se que os flavon?ides comerciais e naturais, e a tiocromanona n?o apresentam emiss?o de fluoresc?ncia. Por espectroscopia de absor??o no ultravioleta/vis?vel (UV-Vis) para QUE, ATF, OMA, AMF e DOF, nestes solventes, percebeu-se que os espectros em presen?a de solventes polares, como AD, foram bem diferentes dos espectros em DCM, principalmente, para ATF, e os espectros em solu??o de tamp?o PBS (pH = 7,4) foram semelhantes aos em AD, exceto para DOF, apresentando mudan?as substanciais. A intera??o entre ASB e os flavon?ides (QUE, ATF, OMA, AMF e DOF) em solu??o tamponada (PBS, pH = 7,4) foi estudada por espectroscopia no ultravioleta/vis?vel, espectroscopia de emiss?o de fluoresc?ncia, dicro?smo circular e modelagem molecular sendo diretamente dependente da concentra??o adicionada de flavon?ides e muito pouco dependente com a varia??o da temperatura. No UV-Vis ocorreu deslocamento para o azul das bandas de absor??o pr?ximas a 208 nm (correspondente a ASB, referente ?s transi??es n?* da estrutura ?-h?lice da albumina) e 280 nm (correspondente ao triptofano da ASB), em fun??o do aumento de concentra??o dos flavon?ides. Na espectroscopia de fluoresc?ncia (T = 22?C, 27?C, 32?C, 37?C e 42?C) houve deslocamento para o azul na emiss?o da prote?na com o aumento da concentra??o dos flavon?ides, sugerindo que o crom?foro da ASB est? em um ambiente mais hidrof?bico em rela??o ?quele quando para ASB livre. Neste caso, observou-se supress?o da fluoresc?ncia de ASB (res?duos de triptofano), como consequ?ncia de um processo de supress?o est?tica como demonstrado pelos altos valores observados para kq (? 1013 a 1014 L/mol.s). A dist?ncia entre os res?duos de triptofano e os flavon?ides (r) foi menor que 7 nm, um indicativo da grande probabilidade de ocorrer transfer?ncia de energia entre ASB e flavon?ides, de acordo com a teoria de transfer?ncia de energia n?o-radiativa de F?rster (Teoria de F?rster). No dicro?smo circular (T = 25?C, 37?C e 42?C) foi verificada uma diminui??o do % de ?-h?lice da ASB em 208 nm e 222 nm (regi?es de transi??o n?* da estrutura secund?ria ?-h?lice da ASB no espectro de absor??o UV), devido ao aumento de concentra??o dos flavon?ides. Esses efeitos podem ser atribu?dos ? forma??o de um complexo flavon?ide-ASB que pode estar induzindo varia??es conformacionais na ASB. Por modelagem molecular, atrav?s do programa docking, percebeuse que as regi?es principais para a liga??o dos flavon?ides com os s?tios de liga??o da ASB est?o localizadas em cavidades hidrof?bicas nos subdom?nios IB e IIA (consistentes com os s?tios I e II) e os res?duos de triptofano (Trp-158 e Trp-237) de ASB est?o nesses subdom?nios, respectivamente. Existe uma grande cavidade hidrof?bica presente no subdom?nio IIA, onde os flavon?ides podem se ligar com o res?duo de triptofano Trp-237 (melhor s?tio de liga??o), formando o complexo flavon?ide-ASB.