Photochemistry of light-responsive proteins
Light-responsive proteins have evolved to use light to drive complex processes ranging from
photosynthesis to vision. These systems not only serve as an inspiration for technology, but have
also been implemented directly in biotechnologies such as bioimaging, biosensing, optogenetics,
and photodynamic therapy. However, engineering photoreceptors for use in biotechnology requires
a fundamental understanding of how these systems operate on a molecular level. To this end, we
use quantum mechanics and molecular mechanics to understand how biological systems respond
to light. A family of proteins we are currently interested in are light-oxygen-voltage (LOV) domains.
Investigating new classes of fluorescent proteins
Flavin-binding fluorescent proteins (FbFPs) and bilin-binding fluorescent
proteins (BbFPs) are recently engineered classes of fluorescent proteins that
have attractive properties. In particular, in comparison to green fluorescent
protein (GFP) derivatives, FbFPs are smaller (less genetic content to express)
and work in anaerobic conditions, while BbFPs have shown significant promise
recently as far-red or near-IR FPs for deep tissue imaging. We employ hybrid
quantum mechanical /molecular mechanical (QM/MM) models to investigate
the spectral tuning mechanism and photophysics of these systems.
Interpretation of time-resolved photoelectron spectroscopy experiments
An understanding of any photochemical or photobiological mechanism is incomplete without an
understanding of early photoinduced events. The advent of tabletop ultrashort pulsed laser sources
has made it possible to probe such ultrafast processes using pump-probe spectroscopies. Among
pump-probe techniques, time-resolved photoelectron spectroscopies are particularly powerful
because of their ability to probe all participating states directly and, in some cases, also probe the
evolving electronic character of the system. We will develop and apply tools for simulating and
interpreting time-resolved photoelectron spectroscopy and imaging experiments.
Other problems in photochemistry
We are generally interested in how a chromophore or fluorophore is affected
by its environment, be it gas-phase, solvent, or protein. A main focus of our
research is therefore to investigate the photophysics and photochemistry of 
light-responsive systems, and to understand how the environment tunes the
photophysical/photochemical properties of these systems. We regularly
employ electrostatic tuning maps (ETMs) for this purpose.
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