(577g) Modeling Protein Conformational Stability On Chromatography Media With a G?-Like Model

In protein-based drug development, hydrophobic interaction chromatography (HIC) is a vital commercial method used to separate desired proteins from complex mixtures. However, interactions between the protein and the chromatographic surface used for separation may lead to unfolding or misfolding of the protein. We test how well a Gō-like model simulated with Hybrid Monte Carlo (HMC) can describe folding and unfolding of proteins on chromatographic surfaces as well as explore the trends connecting surface unfolding to temperature and the level of surface attraction.

       The Gō-like model implemented in this study uses a residue-level coarse grain representation of the protein as a linear chain of beads and requires the classification of all possible contacts as either native or nonnative. The surface is modeled as a flat plane of point interaction sites, which are treated as native contacts to protein hydrophobic residues. With this level of approximation, we can guarantee convergence of the folding curves while still preserving residue-level details of the protein stability.

       In this study, we compare the efficiency of HMC to traditional MD and pure MC simulation protocols for simulating coarse-grained models of biopolymers. We also quantitatively characterize the thermal stability of the B1 domain of protein G, on surfaces of varying attractive strength in terms of the PMF with respect to surface distance, PMF with respect to fraction native contacts, and entropic and enthalpic contributions to folding and unfolding by the surface.  Finally, we compare the residue-level stability from simulations to experimental (HXMS) hydrogen exchange mass spectroscopy both in solution and in the adhered phase in actual HIC operation.