Complex Effects of Salt on Small-Angle X-ray Scattering of BSA Originate From the Interplay of Ions and Hydration Water

TL;DR

This study combines experimental SAXS data with molecular dynamics simulations to reveal how salts influence protein structure through interactions with ions and hydration water.

Contribution

It introduces a novel approach integrating FMAPIq with explicit-solvent simulations to elucidate salt effects on protein SAXS data.

Findings

Salt effects on BSA SAXS arise from ion and hydration water interplay.

The combined method provides a detailed picture of protein-ion-water interactions.

Complex salt effects can be explained by this integrated modeling approach.

Abstract

Salts are an integral part of the environment for living systems and, therefore, understanding their effects on proteins and other biomolecules is of fundamental interest. Small-angle X-ray scattering (SAXS) of protein solutions can provide valuable information on salt effects, but extracting this information has been a significant challenge. For example, SAXS data of bovine serum albumin (BSA) at various salt concentrations were fit to three different spherical models. Here we combined the newly developed FMAPIq approach with explicit-solvent all-atom molecular dynamics simulations to show that the complex effects of salt on the SAXS of BSA originate from the interplay of ions and hydration water, leading to a general picture of protein-ion-water interactions.