Two specific aspects of PYP dynamics will be discussed in addressing how ultrafast dynamics can shed light on the 3-D structure of PYP: (1) We show that UV light below 300 nm generate the first photocycle intermediate of PYP UV-B light is efficient at generating the first two photocycle intermediate in the blue light photoreceptor PYP through two independent excitation pathways: (a) direct UV absorption by the chromophore cofactor p-coumaric acid initiates the same photochemistry as blue light and (b) Excitation of tryptophan and tyrosine residues leads to FRET to p-coumaric acid. (2) The photoactivity in the forward (pG ? pG) and reverse (pB ? pG) excitation initiated pathways are resolved and interleaved dual-wavelength pump-probe signals are used to identify residue-induced inhomogeneity in the ground state and how it couples measurable changes in the dynamics. We will demonstrate that the observed excited-state proton transfer reaction in the reverse photoactivity provides a powerful tool to generate constraints on the pB signaling-state structure. This is especially important, since the extent of conformational changes involved in the formation of the pB signaling state is still an unresolved controversy.

Sub-picosecond excited-state proton transfer precedes isomerization during the photorecovery of the photoactive yellow protein

244th National Meeting (2012)

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