We are interested in studying electrostatic fields at the active site of human aldose reductase (hALR2), a 36 kDa aldo-keto reductase, which plays an important role in diabetes control. We chose this protein because extremely high resolution x-ray structures are available.  Furthermore, this protein is a target for diabetes control as it is responsible for many of the side effects of diabetes; as a result many classes of inhibitors are available.  The utility of these inhibitors is often thwarted by their binding to human aldehyde reductase, hALR1, an essential enzyme.  Differences in electrostatic potential at the active sites of these enzymes may guide the development of selective inhibitors, so we have developed vibrational probes which are sensitive to the protein electric field.  Vibrational Stark effect (VSE) spectroscopy is used to measure the sensitivity of the vibrational frequency of a probe to electric fields, and then shifts in vibrational frequency observed when inhibitors displaying these probes are bound at the active site or when mutations are made are used to obtain the projection of protein electrostatic field.  The observed shifts are then compared with calculated electric fields obtained by extensive simulations.  This system provides a sophisticated test for the accuracy of widely-used electrostatics calculations.

Based on high resolution structural data, we perform electrostatics calculations coupled with extensive molecular mechanics (MM) simulations or molecular dynamics (MD) simulations. Calculated fields are compared with field data from VSE spectroscopy experiment to test our computation strategy.

"Electric Fields at the Active Site of an Enzyme: Direct Comparison of Experiment with Theory", Ian T. Suydam, Christopher D. Snow, Vijay S. Pande, and Steven G. Boxer, Science, 313, 200-204 (2006). [pdf]

"Electrostatic Fields Near the Active Site of Human Aldose Reductase: 1. New Inhibitors and Vibrational Stark Effect Measurements", Lauren J. Webb and Steven G. Boxer, Biochemistry, 47, 1588-1598, (2008). [pdf]