Quantum-chemical modeling of molecular complexes structure in "uronatic polyesacharides – Сa²⁺" system

Abstract

Quantum-chemical modeling of the process of ionotropic gelling in systems of uronate polysaccharides (high-guluronate sodium alginate and low-esterified pectin) with calcium is carried out. Calculation the interaction of active functional groups of uronate polysaccharides with calcium ion shows the possibility of this process passage with the formation of calcium-guluronate (CaGul₄), calcium-galacturonate (CaGal₄) and calcium-guluronate-galacturonate (CaGal₂Gul₂) chelate complexes. The process of interaction occurs when the carboxyl and hydroxyl groups of the uronate polysaccharides are chemically bound to the calcium ion. It was established that calcium-guluronate complex has an eight binding centres with calcium whereas calcium-galacturonate and calcium-guluronate-galacturonate complexes have four binding centres. This article describes the binding centres in systems that are considered by ionotropic gel formation. This clearly illustrated the spatial atoms arrangement in the systems of individual polysaccharides and their combination; location and value of bond lengths, values of torsion and valence angles. Presented quantum-chemical models are allowed to estimate chemical activity of fragments macromolecular structures during ionotropic gelation. This makes it possible to predict the amount of external bound water, calculate the optimum proportions of substances for the formulation of rational food recipes. The fact of the ionotropic gelation in the combined system "alginate-pectin-Ca" was installed on the basis of the obtained models and their geometric characteristics. In this case the chelate complexes CaGul₂Gal₂ was formed. It is stable during storage, more plastic and soft in contrast to CaGul₄ and stronger than CaGal₄.Проведено квантово-химическое моделирование процесса ионотропного гелеобразования в системах уронатных полисахаридов (альгината натрия высокогулуронатного и пектина низкоэтерефицированного) с кальцием. Расчет взаимодействия активных функциональных групп уронатных полисахаридов с ионом кальция показывает возможность прохождения данного процесса с образованием хелатных комплексов кальций-гулуронатного, кальций-галактуронатного и кальций-гулуронат-галактуронатного.