Protochlorophyllide a: A Comprehensive Photophysical Picture

Chemphyschem. 2009 Jan 12;10(1):144-50. doi: 10.1002/cphc.200800536.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biocatalysis
  • Kinetics
  • Oxidoreductases Acting on CH-CH Group Donors / chemistry
  • Oxidoreductases Acting on CH-CH Group Donors / metabolism
  • Photochemistry
  • Protochlorophyllide / chemistry*
  • Spectroscopy, Near-Infrared
  • Time Factors

Substances

  • Protochlorophyllide
  • Oxidoreductases Acting on CH-CH Group Donors
  • protochlorophyllide reductase