Sequence−conformation relationship of zwitterionic peptide brushes : theories and simulations

Abstract

Zwitterionic polymer brushes have broad applications in antifouling, biolubrication, and drug delivery. The charge distribution on polymers is critical to the structure and properties of surface-tethered zwitterionic polymer brushes. However, there is a lack of understanding of the relationship between the charge distribution and conformation in these systems, which is important for designing and predicting the functionality of controllable surfacetethered polymer brushes. Zwitterionic peptides with different sequences of charged amino acids are excellent model systems to elucidate such a charge−conformation relationship. By performing all-atom molecular dynamics (MD) simulations and developing a discrete-charge mean-field theory, we perform a systematic investigation on the effect of charge distribution on the conformations of zwitterionic peptide brushes. All-atom MD simulations reveal that the height of the peptide brush strongly depends on the distribution of the charges along the peptide chain. Contact map analysis reveals that the charge sequence also determines the preferred intrachain (loops and extended) and interchain (head-to-tail and parallel) structures. Through the theory developed by us, we show that the interchain electrostatic interactions are responsible for the contraction of peptide brushes with long charged blocks, while elasticity drives the contraction of peptide brushes with alternating-charged segments. This study provides a clear illustration of the factors influencing the sequence−conformation relationship of zwitterionic peptide brushes.