Wed, Jan. 7, 2015, 3:15pm - 5:30pm
Frick Chemistry Laboratory, Taylor Auditorium
Host: Roberto Car
3:15 p.m. – Public research seminar, Taylor Auditorium
4:30 p.m. – Research proposal, A81
Quantum Fluctuations in Hydrogen Bond Networks
Hydrogen bond networks are inherently quantum mechanical in nature due to the low mass of the proton. In this talk I will show how quantum fluctuations can lead to large qualitative and quantitative changes in hydrogen bond networks, based on ab initio path integral simulations that incorporate the quantum nature of both the nuclei and electrons. In particular, I will show how nuclear quantum effects significantly increase proton sharing and hydrogen bond distortion in liquid water. These quantum effects give rise to isotope effects that are widely used in geochemistry to track the evolution of the global water cycle. I will also discuss our recent work on the enzyme ketosteroid isomerase where we have shown that quantum fluctuations facilitate proton delocalization in the enzyme’s active site hydrogen bond network. This greatly stabilizes the deprotonation of a key active-site tyrosine residue, leading to a 10,000 fold increase in its acid dissociation constant. These investigations are made possible by combing a series of recent advances that greatly enhance the efficiency of including quantum mechanical fluctuations in simulating condensed phase systems and extracting isotope effects. The ability to efficiently perform such simulations thus allows us to examine hydrogen bond networks in chemical and biological systems for which the inclusion of quantum mechanical effects is essential to provide the correct description.