Estudio de la afinidad del Rotavirus con proteínas probióticas PEGiladas: Teorías de aproximación de medio efectivo para la caracterización de la afinidad molecular

Abstract

The Infectious Diseases Group of the Pontifical Javierian University (GEI-PUJ) has been working on the development of probiotic antiviral treatments against rotavirus. The treatment consists of protecting the intestinal walls with proteins produced by the metabolism of the bacterium bifidobacterium adolescentis. In spite of the demonstrated efficacy of the treatment, there are still problems to be solved, for example: the protection of the proteins on their way through the intestine to prevent them from being altered by the stomach pH or other acids. For this, the use of PEGylation has been tried, which consists of coating the protein with polyethylene glycol (PEG), which is a high-density polymer. However, although GEI-PUJ has different PEGylation protocols, the characteristics of the coatings achieved on proteins with this technique, in terms of thickness and coated area, are unknown. There is also no quantitative information related to the changes produced by PEGylation in the affinity of rotavirus to proteins. Spectroscopic ellipsometry (SE) is an optical characterization technique with which it is possible to measure, among others, the complex refractive index of materials. Thin films and multilayers are the systems that benefit the most from the advantages offered by this technique, since its extraordinary sensitivity makes it possible to measure films of only a few angstroms in thickness. The technique is very versatile even for organic samples, as it is non-destructive, non-invasive and does not require sample preparation treatments for characterization. With the implementation of effective medium approximation theories (EMA) for the analysis of ellipsometric data, it is also possible to calculate structural parameters of the samples such as porosity and roughness, in the case of solid samples. The main objective of this work is to characterize the polyethylene glycol coating of proteins produced by the metabolism of the bacterium bifidobacterium adolescentis after random PEGylation protocol. The experimental data is analyzed in the light of EMA to obtain, on the one hand, the pseudo-optical constants of PBS in which the PEGylated proteins are suspended, as well as of the PEG and the probiotic proteins. This analysis also allows us to determine the characteristics of PEGylation in terms of the volume ratio of the coating on the protein.