Protonation of β-lactoglobulin in the presence of strong polyelectrolyte chains: A study using Monte Carlo simulation

TORRES, PAOLA; BOJANICH, LUCIANO; VARRETI, FABRICIO SANCHEZ; RAMIREZ-PASTOR, ANTONIO JOSE; QUIROGA, EVELINA; BOERIS, VALERIA; NARAMBUENA, CLAUDIO F.

COLLOIDS AND SURFACES B-BIOINTERFACES

ELSEVIER SCIENCE BV

Año: 2017

0927-7765

In this work, the molecular interaction between the protein b-lactoglobulin and strongpolyelectrolyte chains was studied using Monte Carlo simulations. Different coarse-grainedmodels were used to represent the system components. Both net charge and protonation ofthe isolated dimeric protein were analyzed as a function of 𝑝𝐻. The acid-base equilibrium ofeach titratable group was distinctively modified by the presence of polyanion or polycationchains. The complexation on the wrong side of 𝑝𝐼 was more evident with the polycation than with the polyanion. It was mainly due to a charge regulation mechanism, where the reversion in net charge of the protein was more pronounced at the left of isoelectric point of the protein.The glutamic and aspartic groups play a key role in this charge reversion. Both polyanion and polycation were spatially adsorbed in different region on the protein surface, suggesting the importance of the surface charge distribution of the protein.