Record Details
Excited State Structural Events of a Dual-Emission Fluorescent Protein Biosensor for Ca²⁺ Imaging Studied by Femtosecond Stimulated Raman Spectroscopy
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Excited State Structural Events of a Dual-Emission Fluorescent Protein Biosensor for Ca²⁺ Imaging Studied by Femtosecond Stimulated Raman Spectroscopy |
| Names |
Wang, Yanli
(creator) Tang, Longteng (creator) Liu, Weimin (creator) Zhao, Yongxin (creator) Oscar, Breland G. (creator) Campbell, Robert E. (creator) Fang, Chong (creator) |
| Date Issued | 2015-02-12 (iso8601) |
| Note | This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the American Chemical Society and can be found at: http://pubs.acs.org/journal/jpcbfk |
| Abstract | Fluorescent proteins (FPs) are luminescent biomolecules that emit characteristic hues upon irradiation. A group of calmodulin (CaM)-green FP (GFP) chimeras have been previously engineered to enable the optical detection of calcium ions (Ca²⁺). We investigate one of these genetically encoded Ca²⁺ biosensors for optical imaging (GECOs), GEM-GECO1, which fluoresces green without Ca²⁺ but blue with Ca²⁺, using femtosecond stimulated Raman spectroscopy (FSRS). The time-resolved FSRS data (<800 cm⁻¹) reveal that initial structural evolution following 400-nm photoexcitation involves small-scale coherent proton motions on both ends of the chromophore two-ring system with a <250 fs time constant. Upon Ca²⁺ binding, the chromophore adopts a more twisted conformation in the protein pocket with increased hydrophobicity, which inhibits excited-state proton transfer (ESPT) by effectively trapping the protonated chromophore in S₁. Both the chromophore photoacidity and local environment form the ultrafast structural dynamics basis for the dual-emission properties of GEM-GECO1. Its photochemical transformations along multidimensional reaction coordinates are evinced by distinct stages of FSRS spectral evolution, particularly related to the ~460 and 504 cm⁻¹ modes. The direct observation of lower frequency modes provides crucial information about the nuclear motions preceding ESPT, which enriches our understanding of photochemistry and enables the rational design of new biosensors. |
| Genre | Article |
| Topic | Femtosecond stimulated Raman spectroscopy |
| Identifier | Wang, Y., Tang, L., Liu, W., Zhao, Y., Oscar, B. G., Campbell, R. E., & Fang, C. (2015). Excited state structural events of a dual-emission fluorescent protein biosensor for Ca²⁺ imaging studied by femtosecond stimulated Raman spectroscopy. The Journal of Physical Chemistry B, 119(6), 2204-2218. doi:10.1021/jp505698z |
