Resolving the excited and ground state reaction coordinates in the green fluorescence protein and mutants with dispersed pump-dump probe spectroscopy

PHYS 24

Delmar S. Larsen, dlarsen@ucdavis.edu1, Jie Pan, jiepan@ucdavis.edu1, Mikas Vengris, Mikas.Vengris@ff.vu.lt2, Deborah Stoner-Ma, dstonerma@hotmail.com3, and Peter J. Tonge, peter.tonge@sunysb.edu4. (1) Department of Chemistry, University of California, Davis, One Shields Ave, Davis, CA 95616, (2) Dept. of Chemistry, University of California, Davis, One Shields Ave, Davis, 95616, (3) Department of Chemistry, Stony Brook University, Nicholls Road, Stony Brook, NY 11794-3400, (4) Department of Chemistry, SUNY Stony Brook, Stony Brook, NY 11794-3400
The excited- and ground-state photodynamics of wild-type (wt), S65T/H148D and S65T/H148E mutants of the Green Fluorescent Protein (GFP) system were characterized with femtosecond time-resolved dispersed multi-channel pump-dump-probe measurements. Discrete transient intermediates with specific spectral properties are identified to describe the evolution in the mutant variants with greater complexity than in wt-GFP. For the first time, excited- and ground state structural evolution of the chromophore is observed as non-stationary dumping kinetics. The proton transfer kinetics observed in wt-GFP is accelerated two orders of magnitude faster in S65T/H148D presumably due to a low-barrier hydrogen bond between the intrinsic chromophore and the introduced aspartate residue. Modification with glutamate residue in S65T/H148E decreases the proton transfer kinetics by 2 orders of magnitude. These results are discussed in terms of the geometry of the residues surrounding the chromophore. Dump induced signals resolve a bifurcation of the proton transfer kinetics resulting in multiple resting spots.
 

Optical Probes of Dynamics in Complex Environments
8:00 AM-12:00 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. 344, Oral

Division of Physical Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008