RESUMO
Fluorescence spectroscopy is an important method to study protein conformational dynamics and solvation structures. Tryptophan (Trp) residues are the most important and practical intrinsic probes for protein fluorescence due to the variability of their fluorescence wavelengths: Trp residues emit in wavelengths ranging from 308 to 360 nm depending on the local molecular environment. Fluorescence involves electronic transitions, thus its computational modeling is a challenging task. We show that it is possible to predict the wavelength of emission of a Trp residue from classical molecular dynamics simulations by computing the solvent-accessible surface area or the electrostatic interaction between the indole group and the rest of the system. Linear parametric models are obtained to predict the maximum emission wavelengths with standard errors of the order 5 nm. In a set of 19 proteins with emission wavelengths ranging from 308 to 352 nm, the best model predicts the maximum wavelength of emission with a standard error of 4.89 nm and a quadratic Pearson correlation coefficient of 0.81. These models can be used for the interpretation of fluorescence spectra of proteins with multiple Trp residues, or for which local Trp environmental variability exists and can be probed by classical molecular dynamics simulations. © 2018 Wiley Periodicals, Inc.
Assuntos
Fluorescência , Simulação de Dinâmica Molecular , Proteínas/química , Triptofano/química , Espectrometria de FluorescênciaRESUMO
En este trabajo se presentan los resultados obtenidos de la calorimetría de inmersión en benceno sobre monolitos de carbón activado tipo disco y panal, que se obtuvieron mediante activación química de cascara de coco con cloruro de zinc a diferentes concentraciones. Adicionalmente, las estructuras fueron caracterizadas por adsorción de N2 a 77 K. Las entalpías de inmersión determinadas se encuentran entre 73,5 y 164,2 Jg-1; con los datos de inmersión se calculó el área accesible y se comparó con el área obtenida mediante adsorción de N2 a 77K, encontrando una buena correlación. En todas las muestras se observó un aumento de la entalpía de inmersión en benceno con el área superficial, igualmente una disminución de la energía característica con el aumento del volumen de poro.
This work presents the results obtained from immersion calorimetry in benzene on activated carbon monoliths disc and honeycomb type that were obtained from coconut shell using chemical activation with zinc chloride at different concentrations. The structures were characterized by adsorption N2 at 77 K. The immersion enthalpies are between 73.5 and 164.2 Jg-1. Using immersion enthalpy data the accessible area was calculated and compared with the area obtained by N2 adsorption at 77K. A good correlation was found. In all the samples was observed an increase in the immersion enthalpy into benzene with the surface area. In addition there was a decrease in the energy characteristic with increasing pore volume.
Neste trabalho se apresentam os resultados obtidos da calorimetría de imersão em benzeno sobre monolitos de carvão ativado tipo disco e panal que se obtiveram mediante activação química de casca de coco com cloreto de zinco a diferentes concentrações. Adicionalmente as estruturas foram caracterizadas por adsorção de N2 a 77 K. As entalpías de imersão determinadas se encontram entre 73,5 e 164,2 Jg-1, com os dados de imersão se calculo o área acessível e se comparo com o área obtida mediante adsorção de N2 a 77K, encontrando uma boa correlação. Em todas as mostras se observo um aumento da entalpía de imersão em benzeno com o área superficial. Ademais se observou uma diminuição da energia característica com o aumento do volume de poro.