Molecular dynamics study on membrane fouling by oppositely charged proteins

YQ Ma and AL Zydney and R Wang and JW Chew, AICHE JOURNAL, 67, e17335 (2021).

DOI: 10.1002/aic.17335

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.

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