A combined experimental and molecular simulation study of factors influencing interaction of quinoa proteins–carrageenan

• Published in: International journal of biological macromolecules Vol. 107; no. Pt A; pp. 949 - 956
• Main Authors: Montellano Duran, Natalia, Spelzini, Darío, Wayllace, Natael, Boeris, Valeria, Barroso da Silva, Fernando L.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.02.2018
• Subjects: Adsorption; Carrageenan; Carrageenan - chemistry; Chenopodium quinoa - chemistry; Complex formation; Hydrogen-Ion Concentration; Molecular Dynamics Simulation; Monte Carlo Method; Plant Proteins - chemistry; Polyelectrolytes - chemistry; Quinoa proteins; Static Electricity; Quinoa proteins; Complex formation; Carrageenan
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2017.09.076

•Quinoa proteins (QP) – carrageenan (Carr) interact positively at acid pH (1–6).•QP forms soluble aggregates at alkaline pH.•Around pH 4.1 there are hydrophobic interactions between QP and Carr.•Simulations allow to characterize qualitatively QPI and Carr interaction.•The charge regulation mechanism was found in the QP-Carr interaction. The interaction between quinoa proteins isolate (QP isolate) and the negatively charged polysaccharide ι-Carragennan (Carr) as a function of pH was studied. Experimental measurements as turbidity, hydrophobic surface, ζ-potential, and hydrodynamic size were carried out. Associative interaction between QP and Carr was found in the pH range between 1 and 2.9. When both molecules are negatively charged (pH>5,5), a pure Coulombic repulsion regime is observed and the self-association of QP due to the Carr exclusion is proposed. In the intermediate pH range, the experimental data suggests that the charge regulation mechanism can overcome the electrostatic repulsion that may take place (and an attraction between QP and Carr can still be observed). Computational simulations by means of free energy derivatives using the Monte Carlo method were carried out to better understand the interaction mechanism between QP and Carr. QP was modeled as a single protein using one of the major proteins, Chenopodin (Ch), and Carr was modeled as a negatively charged polyelectrolyte (NCP) chain, both in the cell model framework. Simulation results showed attractive interactions in agreement with the experimental data.