Protochlorophyllide a: A Comprehensive Photophysical Picture.
The photochemistry of protochlorophyllide a, a precursor in the biosynthesis of chlorophyll and substrate of the light regulated enzyme protochlorophyllide oxidoreductase, is investigated by pump-probe spectroscopy. Upon excitation into the lowest lying Q-band the light induced changes are recorded over a wide range of probe wavelengths in the visible and near-IR region between 500 and 1000 nm. Following excitation, an initial ultrafast 450 fs process is observed related to the motion out of the Franck-Condon region on the excited state surface; thus directly unraveling previous suggestions based on time-resolved fluorescence measurements (ChemPhysChem 2006, 7, 1727-1733). Furthermore, the data reveals a previously concealed photointermediate, whose formation on a nanosecond timescale matches the overall fluorescence decay and is assigned to a triplet state. The implications of this finding with respect to the photochemistry of NADPH:protochlorophyllide oxidoreductase (POR) are discussed.
Institute for Physical Chemistry, University Jena, Lessingstrasse 10, 07743 Jena, Germany.
Benjamin
B
Dietzek
Stefanie
S
Tschierlei
Gudrun
G
Hermann
Arkady
A
Yartsev
Torbjörn
T
Pascher
Villy
V
Sundström
Michael
M
Schmitt
Jürgen
J
Popp
D055162:Biocatalysis; D007700:Kinetics; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000737:chemistry / Q000378:metabolism; D010777:Photochemistry; D011521:Protochlorophyllide / Q000737:chemistry*; D019265:Spectroscopy, Near-Infrared; D013997:Time Factors
D011521:Protochlorophyllide; D044925:Oxidoreductases Acting on CH-CH Group Donors; C023886:protochlorophyllide reductase