Ascorbic Acid and BSA Protein in Solution and Films: Interaction and Surface Morphological Structure

Rafael R G Maciel,Adriele A De Almeida,Filipe D S Gorza,Odin G C Godinho,Nara C De Souza,Tarquin F Trescher,Josmary R Silva,Graciela C Pedro

doi:10.1155/2013/461365

Rafael R G Maciel, Adriele A De Almeida + Show 6 more

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https://doi.org/10.1155/2013/461365

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Abstract

This paper reports on the study of the interactions between ascorbic acid (AA) and bovine serum albumin (BSA) in aqueous solution as well as in films (BSA/AA films) prepared by the layer-by-layer technique. Regarding to solution studies, a hyperchromism (in the range of ultraviolet) was found as a function of AA concentration, which suggested the formation of aggregates from AA and BSA. Binding constant, K, determined for aggregates from BSA and AA was found to be about 102 M−1, which indicated low affinity of AA with BSA. For the BSA/AA films, it was also noted that the AA adsorption process and surface morphological structures depended on AA concentration. By changing the contact time between the AA and BSA, a hypochromism was revealed, which was associated to decrease of accessibility of solvent to tryptophan due to formation of aggregates. Furthermore, different morphological structures of aggregates were observed, which were attributed to the diffusion-limited aggregation. Since most of studies of interactions of drugs and proteins are performed in solution, the analysis of these processes by using films can be very valuable because this kind of system is able to employ several techniques of investigation in solid state.

Highlights

Interactions between drugs and proteins have important implications for processes related to health [1]
We have investigated the behavior of the interaction of the ascorbic acid (AA) with bovine serum albumin (BSA) protein in the form of aqueous solution and BSA/AA films prepared by the layer by layer (LbL) technique
This experiment was repeated for solution without BSA at pH adjusted to 7 (Supplementary Materials) in order to rule out the effect of AA

Summary

Introduction

Interactions between drugs and proteins have important implications for processes related to health [1]. Studies on the mechanisms of interactions between drugs and proteins have been performed with techniques such as spectroscopy, chromatography, and electrochemical and atomic force microscopy. Self-assembly layer-by-layer deposition technique (LbL technique) is a convenient method for the formation of films from electrolytes. Several experimental investigations have been performed using LbL technique, in which proteins, enzymes, nucleic acids, or carbohydrates are used [2,3,4]. LbL technique is based on adsorption process which can be understood by analyzing the adsorption kinetics (study of layer growth over time) and adsorption isotherms (study of adsorbed amount versus concentration). Morphological analysis may reveal information about the interaction between molecules [5]

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