Session: PMSE/POLY Poster Session:

Histidine-Ni coordination bonds affect macroscopic mechanical properties in macromolecular systems containing polyhistidine sequences and Ni2+ metal ions, a configuration which is relevant to many protein separation and purification processes. These same metal-coordination bonds impart remarkable macroscopic strength in biological materials such as mussel byssal threads. Understanding how the molecular structural arrangement of these bonds enables such mechanical strength is critical in the design of bio-inspired metal-coordinated synthetic materials.

In this study, we simulate various de novo polyhistidine proteins to understand how assemblies of two to five metal coordination complexes affect the mechanical properties of the protein. Specifically, we are interested in simulating how these polyhistidine configurations will respond in different conditions when they are subjected to mechanical stress, or pulled, with particular interest in the maximum force limits before rupture. This fundamental study will allow us to explore how these bonds affect macroscopic mechanical properties in various spatial organizations.

We utilize steered molecular dynamics (SMD) to present an analysis of the response of metal coordination bonds in various protein structures to mechanical stress in both in-plane and out-of-plane shear modes of deformation. Histidine-rich protein structures are designed to be in a required sheet configuration so that the bonds can more clearly be subject to stress in normal and shear conditions. We demonstrate how these de novo structures have specific force-displacement properties. We use this insight to contribute observations on the interactions between Ni2+ and polyhistidine-tags, a system which is widely utilized but not well understood mechanistically. This theoretical approach has been taken with respect to hydrogen bonds in other proteins before, but has not yet been extended to metal coordination bonds, which are mobile and have more coordination partners, thereby presenting a unique opportunity for providing further insight into this less-studied category of bonds.

Niels Holten-Andersen

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