Molecular Mechanism of Flavonoids Using Fluorescence Spectroscopy and Computational Tools

With more than 4000 compounds identified up to now, flavonoids are present in human diet since they can be found in fruits, vegetables, seeds, grains, and beverages, such as wine and tea. Over the years, medicinal properties of these polyphenolic compounds have been noticed. Consequently, the search for the biological targets and for the description of flavonoids action mechanism has been growing. Fluorescence spectroscopy and molecular docking are techniques based on physical theories which have been helping researchers to describe the interaction between flavonoids and biological targets. In this way, this chapter comes not only as an attempt to gather some works dedicated to explain flavonoid molecular mechanisms of action but also to introduce a brief theory of steady-state fluorescence spectroscopy and molecular docking

Morfološke i strukturne značajke biofilmova na bazi zeina s dodatkom ksantanske gume

Morphological and structural characteristics of zein-based biofilms have been studied in this work. The sorbitan component in the control formulation of the film was substituted with xanthan gum at concentrations between 0.01 and 0.04 % to analyze its effect on lipid dispersion. Scanning electron microscopy (SEM) showed a surface for the control (0 % xanthan) with good lipid distribution. However, when the samples were investigated by optical microscopy (OM), lipid globules in the control biofilm appeared larger and more dispersed in the matrix than in the other samples. Fourier transform infrared (FTIR) spectroscopy indicated that xanthan concentrations deeply affected C=O linkages from amide I group, as well as the functional N-H group of amide II of the zein structure. Other weak interactions of amide I and II with carboxylic acids and aliphatic compounds were also observed. UV/VIS analysis as well as transparency measurements indicated that the addition of xanthan to the film matrix lowered significantly its transparency properties. Overall, the addition of xanthan gum favoured lipid dispersion in the matrix, making biofilms more homogeneous, although less transparent.U ovom su radu ispitane morfološke i strukturne značajke biofilmova na bazi zeina. U formulaciju je umjesto sorbitana dodana ksantanska guma koncentracije od 0,01 do 0,04 %, kako bi se ispitao utjecaj ksantana na disperziju lipida u biofilmu. Pretražnom elektronskom mikroskopijom prikazan je dobar raspored lipida na površini kontrolnog uzorka biofilma (s 0 % ksantana), a optičkim je mikroskopom utvrđeno da su lipidni globuli veći i raspršeniji u matriksu kontrolnog uzorka nego u ostalim uzorcima. Fourierova transformirana infracrvena spektroskopija pokazala je da koncentracija ksantana bitno utječe na C=O vezu amidne skupine I i na funkcionalnu N-H skupinu amida II u zeinu. Također su utvrđene slabe interakcije amida I i II s karboksilnim kiselinama i alifatskim skupinama. UV/VIS analizom i mjerenjem transparentnosti filmova ustanovljeno je da dodatak ksantana matriksu znatno smanjuje transparentnost filma. Zaključeno je da dodatak ksantanske gume poboljšava disperziju lipida u matriksu i homogenost, a smanjuje transparentnost filmova

Validação das unidades arbitrárias do teor de clorofilas obtido em folhas intactas de seringueira.

A determinação do conteúdo de clorofilas foliares é uma característica de interesse dos ecofisiologistas e dos produtores rurais. Com vistas à utilização prática e nas publicações científicas, objetivou-se com o presente trabalho estabelecer, para folhas de seringueira, equações capazes de converter para o sistema internacional as unidades arbitrárias que expressam os teores de clorofila a (Chla), clorofila b (Chlb) e clorofila total (Chltot) obtidos em folhas intactas com uso de clorofilômetro portátil. Folhas em diferentes posições da planta e diferentes estádios de maturação, representativas de um grande intervalo de concentração de pigmentos, foram coletadas e analisadas em campo com uso do ClorofiLOG Falker ®, através de quatro avaliações em 45 folíolos medianos. Estes foram posteriormente processados em laboratório para a obtenção do extrato de pigmentos com uso de dimetilsulfóxido (DMSO) por incubação em banho-maria, dosagem em espectrofotômetro de absorção molecular e conversão em teor de pigmentos por unidade de massa fresca, com uso de equações convencionais. Os dados foram avaliados quanto ao coeficiente de correlação de Pearson e testados diferentes modelos de regressão. Para todas as variáveis, o ajuste linear é o mais adequado, com coeficientes de correlação das equações de ajuste (r) de 0,74 para Chlb e 0,88 para Chla e Chltot

Electron migration in DNA matrix: an electron transfer reaction

Este artigo apresenta uma área de pesquisa atual, ativa e interessante. Descreve a investigação da química de transferência de elétrons (TE) de um modo geral e resultados de TE em DNA em particular. Dois intercalantes de DNA foram utilizados: Ethidium Bromide como doador (D) e Methyl-viologen como receptor (A), o primeiro intercala-se entre as bases do DNA e o último na sua superfície. Utilizando o modelo de Perrin e medidas de Supressão de Fluorescência obteve-se a distância de migração do elétron; aqui a distância foi considerada o espaçamento linear entre as moléculas de doador e receptor ao longo da molécula de DNA. O valor determinado foi de 22,6 ± 1,1 angstrons e o número de pares de bases entre doador e receptor de 6,6. Na literatura os valores encontrados foram de 26 angstrons e de quase 8 pares de bases. Considera-se que a transferência de elétrons em DNA seja mediada através das interações através do espaço entre os elétrons do tipo p contido nos pares de bases.This paper brings an active and provocative area of current research. It describes the investigation of electron transfer (ET) chemistry in general and ET reactions results in DNA in particular. Two DNA intercalating molecules were used: Ethidium Bromide as the donor (D) and Methyl-Viologen as the acceptor (A), the former intercalated between DNA bases and the latter in its surface. Using the Perrin model and fluorescence quenching measurements the distance of electron migration, herein considered to be the linear spacing between donor and acceptor molecule along the DNA molecule, was obtained. A value of 22.6 (± 1.1) angstroms for the distance and a number of 6.6 base pairs between donor and acceptor were found. In current literature the values found were 26 angstroms and almost 8 base pairs. DNA electron transfer is considered to be mediated by through-space interactions between the p-electron-containing base pairs

Morphological and Structural Characteristics of Zein Biofilms with Added Xanthan Gum

Morphological and structural characteristics of zein-based biofilms have been studied in this work. The sorbitan component in the control formulation of the film was substituted with xanthan gum at concentrations between 0.01 and 0.04 % to analyze its effect on lipid dispersion. Scanning electron microscopy (SEM) showed a surface for the control (0 % xanthan) with good lipid distribution. However, when the samples were investigated by optical microscopy (OM), lipid globules in the control biofilm appeared larger and more dispersed in the matrix than in the other samples. Fourier transform infrared (FTIR) spectroscopy indicated that xanthan concentrations deeply affected C=O linkages from amide I group, as well as the functional N-H group of amide II of the zein structure. Other weak interactions of amide I and II with carboxylic acids and aliphatic compounds were also observed. UV/VIS analysis as well as transparency measurements indicated that the addition of xanthan to the film matrix lowered significantly its transparency properties. Overall, the addition of xanthan gum favoured lipid dispersion in the matrix, making biofilms more homogeneous, although less transparent

A computational–experimental investigation of the molecular mechanism of interleukin-6-piperine interaction

Herein, we elucidate the biophysical aspects of the interaction of an important protein, Interleukin-6 (IL6), which is involved in cytokine storm syndrome, with a natural product with anti-inflammatory activity, piperine. Despite the role of piperine in the inhibition of the transcriptional protein NF-κB pathway responsible for activation of IL6 gene expression, there are no studies to the best of our knowledge regarding the characterisation of the molecular interaction of the IL6-piperine complex. In this context, the characterisation was performed with spectroscopic experiments aided by molecular modelling. Fluorescence spectroscopy alongside van’t Hoff analyses showed that the complexation event is a spontaneous process driven by non-specific interactions. Circular dichroism aided by molecular dynamics revealed that piperine caused local α-helix reduction. Molecular docking and molecular dynamics disclosed the microenvironment of interaction as non-polar amino acid residues. Although piperine has three available hydrogen bond acceptors, only one hydrogen-bond was formed during our simulation experiments, reinforcing the major role of non-specific interactions that we observed experimentally. Root mean square deviation (RMSD) and hydrodynamic radii revealed that the IL6-piperine complex was stable during 800 ns of simulation. Taken together, these results can support ongoing IL6 drug discovery efforts

The Cytokine IL-1β and Piperine Complex Surveyed by Experimental and Computational Molecular Biophysics

The bioactive piperine, a compound found in some pepper species, has been widely studied because of its therapeutic properties that include the inhibition of an important inflammation pathway triggered by interleukin-1 beta (IL-1β). However, investigation into the molecular interactions between IL-1β and piperine is not reported in the literature. Here, we present for the first time the characterisation of the complex formed by IL-1β and piperine through experimental and computational molecular biophysical analyses. Fluorescence spectroscopy unveiled the presence of one binding site for piperine with an affinity constant of 14.3 × 104 M−1 at 298 K. The thermodynamic analysis indicated that the interaction with IL-1β was spontaneous (∆G = −25 kJ/mol) and, when split into enthalpic and entropic contributions, the latter was more significant. Circular dichroism spectroscopy showed that piperine did not affect IL-1β secondary structure (~2%) and therefore its stability. The set of experimental data parameterized the computational biophysical approach. Through molecular docking, the binding site micro-environment was revealed to be composed mostly by non-polar amino acids. Furthermore, molecular dynamics, along with umbrella sampling, are in agreement with the thermodynamic parameters obtained by fluorescence assays and showed that large protein movements are not present in IL-1β, corroborating the circular dichroism data

Effect of modified clays on the structure and functional properties of biofilms produced with zein Efeito das argilas modificadas na estrutura e propriedades funcionais de biofilmes produzidos com zeína

The purpose of this study was to evaluate changes in the structure and some functional properties of biofilms added with modified clays (Cloisite® 15A and Cloisite® 30B) prepared by the casting method. The analysis of the microstructure of the films, scanning electron microscopy (SEM), Optical microscopy (MO), and Infrared Spectroscopy (FTIR) indicated that the addition of clay in the films resulted in the formation of a heterogeneous microstructure, microcomposite or tactoid. Due to the formation of a microcomposite structure, functional properties of the films added with both clays such as opacity, solubility, and permeability to water vapor (PVA), were not better than those of the control film. Thus, it was concluded that although it is possible to produce a film added with modified clays using the casting method, it was not possible to obtain intercalation or exfoliation in a nanocomposite, which would result in improved functional properties.<br>O propósito deste estudo foi avaliar mudanças na estrutura e em algumas propriedades funcionais de biofilmes de zeína adicionados de argilas modificadas (Cloisite® 15A e Cloisite® 30B) elaborados pela técnica casting. Por meio do uso de técnicas de análise de microestrutura dos filmes, Microscopia Eletrônica de Varredura (MEV), Microscopia Ótica (MO) e Espectroscopia no Infravermelho (FTIR), observou-se que os acréscimos de argilas resultaram na formação de uma microestrutura heterogênea, formando um microcompósito ou tactoide. Devido à formação da estrutura tipo tactoide, as propriedades funcionais de opacidade, solubilidade e permeabilidade ao vapor d'água (PVA), para os filmes adicionados de argilas, não foram melhores do que as obtidas para o filme controle. Assim, concluiu-se que é possível elaborar um filme adicionado de argilas modificadas usando a técnica casting, porém não foi possível obter intercalação ou esfoliação em nanocompósito, os quais resultariam em melhores propriedades funcionais