Thermodynamic Modeling and Experimental Data Reveal That Sugars Stabilize Proteins According to an Excluded Volume Mechanism
Andrea Arsiccio, Tim Sarter, Ilaria Polidori, Gerhard Winter, Roberto Pisano, Joan–Emma Shea
Abstract
We present a new thermodynamic model to investigate the relative effects of excluded volume and soft interaction contributions in determining whether a cosolute will either destabilize or stabilize a protein in solution. This model is unique in considering an atomistically detailed model of the protein and accounting for the preferential accumulation/exclusion of the osmolyte molecules from the protein surface. Importantly, we use molecular dynamics simulations and experiments to validate the model. The experimental approach presents a unique means of decoupling excluded volume and soft interaction contributions using a linear polymeric series of cosolutes with different numbers of glucose subunits, from 1 (glucose) to 8 (maltooctaose), as well as an 8-mer of glucose units in the closed form (γ-CD). By studying the stabilizing effect of cosolutes along this polymeric series using lysozyme as a model protein, we validate the thermodynamic model and show that sugars stabilize proteins according to an excluded volume mechanism.