Molecular dynamics study on membrane fouling by oppositely charged proteins

Membrane fouling continues to hamper the performance of membrane-filtration processes. A challenge with macromolecular foulants like proteins is that macroscopic characterizations, like net electrical charge, may be poorly correlated with membrane fouling. This necessitates a molecular-scale analysis of the local interactions. In this study, molecular dynamics simulations have been performed to understand the interactions between two similar-sized proteins with opposite overall charges (namely, lysozyme and alpha-lactalbumin) and a negative-charged membrane. Surprisingly, the protein-membrane distances and adsorption probabilities of both proteins are similar. Compared with the positive-charged lysozyme, the negative-charged alpha-lactalbumin exhibits (a) greater protein-membrane attractive interaction energy due to synergy among adsorption sites; (b) lower root-mean-squared deviations (RMSD); and (c) greater number of residues that show low root-mean-squared fluctuations (RMSF). These results indicate that local interactions are critical and thus highlight the pitfall of using the overall protein characteristics as predictors of membrane fouling.

Automated summary

Membrane fouling in membrane-filtration processes is still a challenge due to poor correlation between macroscopic characteristics like net electrical charge and fouling. Molecular dynamics simulations were used to study interactions between similarly-sized proteins with opposite charges and a negatively-charged membrane. Results suggest that local interactions play a critical role, highlighting limitations of using overall protein characteristics to predict membrane fouling.