Sequence control over emergent nano-patterns in dipeptide adlayers at the graphene interface

Abstract

Modification of peptide sequence offers versatile control over their self-organization capability within adlayers adsorbed on surfaces. However, to gain full control over the self-organization, clear links between peptide sequence and the lateral ordering in these adlayers must be established. Using molecular dynamics simulations of WA or AW dipeptides, spontaneous emergence of ordered nano-patterns in adlayers containing neutral, zwitterion, or neutral-zwitterion states at the in-vacuo graphene interface is investigated. All cases support spontaneous patterning, but the WA dipeptide appears to have a greater propensity to self-pattern on graphene compared with the AW dipeptide. In addition, for the WA case, the neutral adlayer features the co-existence of a unique herringbone nano-structure and a monomer row structure. Nano-patterns in the neutral adlayers were driven by complex and concerted intra-row interactions, whereas motifs in zwitterion-containing adlayers were mediated by mostly inter-peptide terminus-terminus contacts. The findings identify fundamental rules of sequence modification that can induce unique residue-residue pair contacts, steering lateral ordering within the adsorbed adlayers, which ultimately affects the self-patterning capability of the dipeptide. Overall, this work provides key guidance on sequence control over peptide self-patterning on graphene, for the design of non-covalently modified graphene derivatives with desired interfacial properties.