Absorption spectra of chlorophyll a and b in Lhcb protein environment

Gianfelice Cinque*, Roberta Croce, Roberto Bassi

*Corresponding author for this work

Research output: Contribution to JournalArticle

Abstract

The spectral forms of the two chlorophyll species in higher plant Photosystem II antenna proteins have been experimentally determined within their protein environment. Recombinant CP29 and LHC II antenna proteins missing individual chromophores were obtained by over-expression in bacteria without any changing of the primary protein sequence and in vitro reconstitution. Difference absorption spectroscopy with respect to the corresponding proteins binding the complete pigment complement yielded the spectral shape and extinction of single chlorophyll a and b. A functional relation of their absorption was given by Gaussian subband decomposition covering the entire Qx and Qy optical region together with the absolute value of the molar extinction coefficient. With respect to analogous determinations reported in the literature for organic solvents, this information is valuable for further understanding the in-protein chlorophyll excited states and excited state dynamics: in particular, for the calculation of Förster transfer rates by means of chlorophyll-chlorophyll overlap integral employing the Stepanov relation for emission and single chromophore transition energies according to the results of mutational analysis of chlorophyll binding sites.

Original languageEnglish
Pages (from-to)233-242
Number of pages10
JournalPhotosynthesis Research
Volume64
Issue number2-3
DOIs
Publication statusPublished - 2000

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Keywords

  • Chlorophylls
  • LHC II and CP29 spectroscopy
  • Molar extinction coefficient
  • Spectral form

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