Structured Water Modulates the Ion Coordination at Biointerface

Coordination of metal ions with biointerfaces plays essential roles in numerous physiological and pathological processes, such as signal transduction, enzymatic catalysis, and membrane organization. Growing insights underscore the ubiquitous and significant role of water structure in modulating interactions at biointerfaces. The intrinsic surface heterogeneity of biointerfaces significantly modulates water structure and affects interfacial interactions. Especially, the surfaces of proteins and membranes are complex and heterogeneous, both chemically and geometrically, with nanoscale mixed hydrophilic/hydrophobic groups and dislocated positions. However, little is known about the effect of dislocated heterogeneity on metal ion coordination at biointerfaces. Herein, we developed a simplified ion coordination biointerface model with dislocated chemical and geometrical heterogeneity and explored the effect of atomic-scale dislocated proximal groups on interfacial properties and the resultant influence on ion coordination. Results showed that the surface charging state, hydrogen bonding environment, and interfacial water structure were modulated by the atomic-scale dislocated hydrophobic and hydrophilic mixing, thereby affecting ion coordination. Importantly, we found that structured water (water molecules at or near the biointerface with ordered hydrogen-bonded networks) plays a dominant role in interfacial ion coordination, where enhanced hydrogen-bonded structured water significantly hindered ion coordination. These findings underscore the important role of atomic dislocation and structured water in modulating the interactions between biological heterogeneous surfaces and ions, providing valuable guidance for the design and application of ion coordination-involved surfaces in both biological and industrial fields.