Molecular mechanisms of pH-tunable stability and surface coverage of polypeptide films

Thumbnail Image
Access rights
Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Degree programme
Applied Surface Science, Volume 615
Streaming potential and quartz crystal microbalance measurements, combined with all-atom molecular dynamics simulations, were used to study the pH dependency of the adsorption of two basic homopolypeptides, poly-L-lysine (PLL) and poly-L-arginine (PARG), on α-quartz surface. We report that the observed adsorption behavior rises from an interplay of i) the change in the number of possible peptide-surface ion pairs between the charged moieties and ii) repulsive electrostatic interactions between the polypeptide molecules. For low pH values, polypeptide adsorption was strongest and stable monolayers were formed. However, electrostatic repulsion between the polypeptides led to a relatively low maximum surface coverage. On the other hand, higher pH led to more weakly bound, but significantly denser, peptide films with limited stability. Simulations indicate that electrostatic interactions are the main driving force for adsorption, while hydrogen bonding and non-specific interactions also contribute. Additionally, the important role of the counterions of the negatively charged quartz surface that form a positively charged ion adlayer is highlighted. Ion release of the condensed sodium ions at the charged surface occurs via displacement by polypeptide adsorption. The mechanisms revealed by this work provide systematic guidelines to engineering active surfaces of charged peptides with controlled surface coverage and reversible binding.
Funding Information: This work was supported by the Academy of Finland through its Centres of Excellence Programme (2022–2029, LIBER) under project no. 346111 (M.S.) , Business Finland Co-Innovation grant No. 3767/31/ 2019 (M.S.) , the National Science Centre, Poland (grant no. 2018/31/D/ ST5/01866 ) (P.B. and M.M.), and the U.S. National Science Foundation , grant No. 1905732 (J.L.). We are grateful for the support by FinnCERES Materials Bioeconomy Ecosystem. Computational resources by CSC IT Centre for Finland, PLGrid Infrastructure (Poland), and RAMI – RawMatters Finland Infrastructure are also gratefully acknowledged. Publisher Copyright: © 2023 The Authors
Adsorption mechanism, Electrostatic interactions, Hydrogen bonding, Poly-L-arginine, Poly-L-lysine, α-quartz
Other note
Harmat , A L , Morga , M , Lutkenhaus , J L , Batys , P & Sammalkorpi , M 2023 , ' Molecular mechanisms of pH-tunable stability and surface coverage of polypeptide films ' , Applied Surface Science , vol. 615 , 156331 .