Jimenez Lab

Spectroscopy in microfluidics: We are developing a novel laser microscope incorporating microfluidics technology to permit experiments on kinetically evolving systems subsequent to msec time-scale mixing (e.g. enzyme and substrate) with microliter/hour sample consumption rates. This technology will permit observation of protein motions over 15 orders of magnitude in time. To date there is no single instrument capable of recording dynamics over such a time window.
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Spectroscopy of biological cofactors: We are developing multiple pulse femtosecond laser techniques for obtaining information on protein dynamics from naturally occurring biological cofactors such as hemes, whose electronic structure and internal conversion dynamics usually complicate the interpretation of femtosecond optical experiments.
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PAS-domain dynamics: PAS domains are molecular switches found in all 3 kingdoms of life whose changes in conformation and dynamics in response to stimuli (e.g., light, oxygen, voltage) are used to regulate biochemical function. We are using ultrafast spectroscopy to measure the spectrum of motions in two prototypical PAS domains: photoactive yellow protein (a halobacterial blue-light sensor) and FixL (a rhizobial oxygen sensor). Differences in the spectrum of motions between “on” and “off” states of site-directed mutants will be related to the thermodynamics of the transition. This work aims to reveal how biology utilizes a novel mechanism for switching and to provide insight that may be useful for incorporating PAS domains into bioelectronics.
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Cytochrome P450: P450s are heme oxygenases that play a critical role in human drug metabolism. Each P450 may oxidize a broad range of substrates, and in many cases the rate-limiting step of substrate oxidation is thought to involve substrate motion inside the active site.  We are using time-resolved fluorescence spectroscopy on a human enzyme to measure the motions of substrates in the active site and the dynamics of the protein.  One goal of this work is to investigate how substrate and protein motions are related, and in turn how they affect enzyme kinetics.

Femtosecond laser development: Designing the next generation of high repetition rate femtosecond laser sources for biophysics experiments.
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