Superior Binding of Proteins on a Silica Surface: Physical Insight into the Synergetic Contribution of Polyhistidine and a Silica-Binding Peptide.

Controllable protein attachment onto solid interfaces is essential for the functionality of proteins with broad applications. Silica-binding peptides (SBPs) have emerged as an important tool enabling convenient binding of proteins onto a silica surface. Surprisingly, we found that removal of polyhistidines, a common tag for protein purification, dramatically decrease the binding affinity of a SBP-tagged nanobody onto a silica surface. We hypothesized that polyhistidines and SBPs can be combined to enhance affinity. Through a series of purposely designed SBPs, we identified that the relative orientation of amino acids is a key factor affecting the surface binding strength. One re-engineered SBP, SBP4, exhibits a 4000-fold improvement compared to the original sequence. Guided by physical insights, the work provides a simple strategy that can dramatically improve affinity between a SBP and a silica surface, promising a new way for controllable immobilization of proteins, as demonstrated using nanobodies.