Conformational Fluctuations and Induced Orientation of a Protein, Its Solvation Shell, and Bulk Water in Weak Non-Unfolding External Electric Fields

Extreme external electric fields have been reported todisruptthe tertiary structure of stably folded proteins; however, the effectsof weaker electric fields on many biomolecules, especially net-unchargedproteins, and on the surrounding aqueous environment have been rarelydiscussed. To explore these effects at the atomic level, here, wehave used molecular dynamics simulations to estimate rotational motionand induced structural fluctuations in the model protein ubiquitinand its hydration layer due to applied non-unfolding electrostaticfields. When exposed to weak electric fields of up to 0.2 V nm(-1), ubiquitin displayed competition between internalstructure-maintaining molecular interactions and the external orientingforce, which disrupted the local structure in certain regions of theprotein. Moreover, relative to hydration water, bulk water showeda greater tendency to align with the electric field, indicating thatthe presence of protein caused hydration water to acquire rotationalmobility different from that in a pure-water system. The differentialinfluence of the applied electric field on the hydration and bulkwater surrounding ubiquitin will be common to almost all (nonmembrane)biomacromolecules. Our findings highlight the importance of localdipoles and their electric polarizability even in net-uncharged biomolecules.

Automated summary

Weak electric fields disrupt the local structure of proteins and induce rotational mobility of hydration water. The alignment tendency of bulk water with electric fields is stronger than that of hydration water. The findings emphasize the importance of local dipoles and their electric polarizability in net-uncharged biomolecules.