Sharon Hammes-Schiffer

 Sharon Hammes-Schiffer

Contact Information

Department of Chemistry
University of Illinois
A410 CLSL, Box 56-6
600 South Mathews Avenue
Urbana, IL 61801
Swanlund Chair and Professor of Chemistry
Visit Website

Biography

Professor Hammes-Schiffer received her B.A. degree in Chemistry from Princeton University in 1988 and her Ph.D. in Chemistry from Stanford University in 1993. After working as a postdoctoral fellow at AT&T Bell Laboratories, she was a faculty member at the University of Notre Dame from 1995-2000 and at The Pennsylvania State University from 2000-2012.  In August 2012, Professor Hammes-Schiffer joined the faculty of the Department of Chemistry at the University of Illinois.  She is also the Editor-in-Chief of Chemical Reviews.

Research Interests

  • electron, proton, and proton-coupled electron transfer reactions in solution; proteins and electrochemistry; hybrid quantum-classical molecular dynamics; non-Born-Oppenheimer electronic structure methods; nonadiabatic dynamics of photoinduced processes; molecular electrocatalysts; enzyme and ribozyme mechanisms

Research Description

Our research centers on the development and application of theoretical and computational methods for describing chemical reactions in condensed phases and at interfaces.  The group is divided into three general areas: proton-coupled electron transfer reactions, enzymatic processes, and non-Born-Oppenheimer electronic structure methods.  Our overall objective is to elucidate the fundamental physical principles underlying charge transfer reactions.  Our theories also assist in the interpretation of experimental data and provide experimentally testable predictions. 

Proton-coupled electron transfer

Proton-coupled electron transfer (PCET) reactions play a critical role in a wide range of chemical and biological processes. We have developed a general theoretical formulation for PCET and have applied this theory to experimentally studied reactions in solution, proteins, and electrochemistry.  This theory treats the electrons and transferring proton(s) quantum mechanically and includes the solvent and solute reorganization as well as the proton donor-acceptor motion.  We have derived a series of analytical expressions for the rate constants of PCET reactions and for the current densities of electrochemical PCET processes.   We have also developed methodology to simulate the nonadiabatic ultrafast dynamics of photoinduced PCET reactions.  Applications of this theory have provided explanations for the experimental trends in the rates and deuterium kinetic isotope effects, and in some cases the temperature and pH dependences.  Current applications focus on the design of molecular electrocatalysts and photocatalysts for hydrogen oxidation and production in energy conversion devices such as solar cells. 

Enzymatic processes

We have developed a hybrid quantum/classical molecular dynamics approach for simulating proton and hydride transfer reactions in enzymes.  This hybrid approach includes electronic and nuclear quantum effects, as well as the motion of the entire solvated enzyme. The methodology provides detailed mechanistic information at the molecular level and allows the calculation of rate constants and kinetic isotope effects. Applications of this methodology have led to the concept of a network of coupled equilibrium motions extending throughout the enzyme and representing conformational changes that facilitate the chemical reaction. Mutations distal to the active site can significantly impact the catalytic rate constant by altering the conformational motions of the entire enzyme and thereby changing the probability of sampling conformations conducive to the catalyzed reaction.  Currently we are developing methods for calculating the vibrational Stark effect in enzymes to further probe the roles of hydrogen bonding, electrostatics, and conformational motions in enzyme catalysis.  We are also extending our studies to ribozymes (RNA enzymes) as well as protein enzymes.

Non-Born-Oppenheimer electronic structure methods

We have developed the nuclear-electronic orbital (NEO) method for the incorporation of nuclear quantum effects into electronic structure calculations. In the NEO approach, specified nuclei are treated quantum mechanically on the same level as the electrons, and mixed nuclear-electronic wavefunctions are calculated variationally with molecular orbital methods. Correlation among electrons and nuclei can be included with multiconfigurational methods, perturbation theory, or density functional theory. For hydrogen transfer and hydrogen bonding systems, typically the key hydrogen nuclei and all electrons are treated quantum mechanically.  The advantages of the NEO approach are that the Born-Oppenheimer separation between electrons and specified protons is avoided, nonadiabatic effects are inherently included, and excited electron-proton vibronic states may be calculated.  Current efforts are directed toward including electron-proton correlation with explicitly correlated wavefunction methods and multicomponent density functional theory.

Distinctions / Awards

  • Fellow, Biophysical Society, 2015
  • Member, International Academy of Quantum Molecular Science, 2014
  • Fellow, American Association for the Advancement of Science, 2013
  • Member of American Academy of Arts and Sciences, 2012
  • Fellow of the American Chemical Society, 2011
  • NIH MERIT Award, 2011
  • Fellow of the American Physical Society, 2010

In The News