Formation of the early photoproduct lumi-R of cyanobacterial phytochrome cph1 observed by ultrafast mid-infrared spectroscopy.
The photoreactions of the Pr ground state of cyanobacterial phytochrome Cph1 from Synechocystis PCC 6803 have been investigated by picosecond time-resolved mid-infrared spectroscopy at ambient temperature. With femtosecond excitation of the Pr state at 640 nm, the photoisomerized Lumi-R product state is generated with kinetics and associated difference spectra indicative of vibrational cooling with tau(1) = 3 ps time constant and excited state decay with tau(1) = 3 ps, tau(2) = 14 ps, and tau(3) = 134 ps time constants. The Lumi-R state is characterized by downshifted absorption of three C=C modes assigned to C(15)=C(16), C(4)=C(6), and a delocalized C=C mode, in addition to the downshifted C(19)=O mode. The Lumi-R minus Pr difference spectrum is indicative of global restructuring of the chromophore on the ultrafast timescale, which is discussed in light of C(15) Z/E photoisomerization in addition to changes near C(5), which could be low bond order torsional angle changes.
van Thor
Jasper J
JJ
Laboratory of Molecular Biophysics, University of Oxford, Rex Richards Building, South Parks Road, Oxford OX1 3QU, UK. jasper@biop.ox.ac.uk
Ronayne
Kate L
KL
Towrie
Michael
M
D001426:Bacterial Proteins / Q000737:chemistry*; D007536:Isomerism; D010777:Photochemistry; D020283:Photoreceptors, Microbial; D010834:Phytochrome / Q000737:chemistry*; D011494:Protein Kinases / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods*; D046939:Synechocystis / Q000378:metabolism*
D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; D010834:Phytochrome; D011494:Protein Kinases; C413623:Cph1 phytochrome protein, bacteria