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

Abstract

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.

The effect of carrageenan on the acid-induced aggregation and gelation conditions of quinoa proteins

“…As was previously discussed, this pH range is in agreement with that determined for the charge regulation mechanism (Montellano Duran et al, 2017). If the pH is extremely acid or the rate of acidification is high, the proteins precipitate, being unable to form soluble aggregates or gel structures.…”

“…QP solubility increase in the presence of Carr when the system get close to the IEP (between 2.9 and 5.5) during the acidification. This pH range is also where QP and Carr interacts electrostatically by the charge regulation mechanism (Montellano Duran et al, 2017).…”

“…A C C E P T E D M A N U S C R I P T 13 alkaline pH the presence of Carr diminishes the QP solubility due to the excluded volume effect (Montellano Duran et al, 2017;Steffolani et al, 2015).…”

Characterization of Goat Milk Hydrolyzed by Cell Envelope Proteinases from Lactobacillus plantarum LP69: Proteolytic System Optimization, Bioactivity, and Storage Stability Evaluation

“…The flocculation could be inhibited by the addition of more polysaccharides. The mechanism of carrageenan stabilization to milk beverages is due to the adsorption of carrageenan to casein particles, and then the negatively-charged carrageenan–casein complex being dispersed by electrostatic repulsive interaction [ 23 ]. The use of gellan gum was also beneficial for electrostatic interactions between proteins and ploysaccharides.…”

Insights into the ZIKV NS1 Virology from Different Strains through a Fine Analysis of Physicochemical Properties

“…51,62,63 A related point to consider here is that although more elaborated theoretical approaches might be important for protein–protein complexation in some cases, there is still an interest in general mechanisms such as the used free-energy equations using these simpler colloidal-like frameworks usually in good agreement with numerical simulations and that can contribute to rationalize more complex systems. 45,57,64,82 The variable d was seen as an adjustable parameter here 65 and assumed to be equal to r ij . 45 For the NS1–antibody association, only the charge–charge contribution was taken into account due to the severe screening from the other terms.…”