Ultrafast evolution of the excited states in the chlorophyll a/b complex CP29 from green plants studied by energy-selective pump-probe spectroscopy

Biochemistry. 1998 Jan 27;37(4):1143-9. doi: 10.1021/bi9722655.

Abstract

The energy transfer process in the minor light-harvesting antenna complex CP29 of green plants was probed in multicolor transient absorption experiments at 77 K using selective subpicosecond excitation pulses at 640 and 650 nm. Energy flow from each of the chlorophyll (Chl) b molecules of the complex could thus be studied separately. The analysis of our data showed that the "blue" Chl b (absorption around 640 nm) transfers excitation to a "red" Chl a with a time constant of 350 +/- 100 fs, while the 'red' Chl b (absorption at 650 nm) transfers on a picosecond time scale (2.2 +/- 0.5 ps) toward a "blue" Chl a. Furthermore, both fast (280 +/- 50 fs) and slow (10-13 ps) equilibration processes among the Chl a molecules were observed, with rates and associated spectra very similar to those of the major antenna complex, LHC-II. Based on the protein sequence homology between CP29 and LHC-II, a basic modelling of the observed kinetics was performed using the LHC-II structure and the Förster theory of energy transfer. Thus, an assignment for the spectral properties and orientation of the two Chl's b, as well as for their closest Chl a neighbors, is put forward, and a comparison is made with the previous assignments and models for LHC-II and CP29.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chlorophyll / metabolism*
  • Chlorophyll / radiation effects
  • Chlorophyll A
  • Energy Transfer*
  • Lasers
  • Light
  • Light-Harvesting Protein Complexes*
  • Models, Chemical
  • Models, Molecular
  • Photosynthetic Reaction Center Complex Proteins / isolation & purification
  • Photosynthetic Reaction Center Complex Proteins / metabolism*
  • Photosynthetic Reaction Center Complex Proteins / radiation effects
  • Photosystem II Protein Complex*
  • Spectrophotometry
  • Spinacia oleracea
  • Time Factors

Substances

  • CP29 light harvesting complex
  • Light-Harvesting Protein Complexes
  • Photosynthetic Reaction Center Complex Proteins
  • Photosystem II Protein Complex
  • Chlorophyll
  • chlorophyll b
  • Chlorophyll A