POLARIZED SPECTRA OF ORIENTED PIGMENT‐LIPOPROTEIN COMPLEXES FROM THE PURPLE BACTERIUM: Chromatium minutissimum

Danuta Frackowiak, Ismail Abdourakhmanov, Roman Cegielski, Roger M. Leblanc

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

Abstract— Polarized absorption, fluorescence and photoacoustic spectra of bacteriochlorophyll (BChl)‐lipoprotein complexes from the purple bacterium Chromatium minutissimum oriented in stretched polyvinylalcohol films were measured at room temperature and 85 K. The preparations contain large amounts of the B800‐820 antenna complexes. From polarized absorption spectra taken under various light beam incidence angles with respect to the film plane, conclusions concerning arrangement of pigment molecules in B800‐820 complex are obtained. The transition moments of the BChl Qy band are not exactly parallel to the membrane plane. It seems that there are pools of differently oriented BChl chromophores absorbing in both 800 nm and 820 nm regions. Change in temperature strongly influences linear dichroism of carotenoids and BChl Qy bands. The reversible changes in absorption, linear dichroism and photoacoustic spectra caused by the variation in sample temperature suggest strongly the reversible twisting of carotenoid molecules, related probably to modification of the interactions between carotenoids and proteins. Various carotenoids exhibit different yield of thermal deactivation and this yield is also temperature dependent.

Original languageEnglish (US)
Pages (from-to)877-884
Number of pages8
JournalPhotochemistry and Photobiology
Volume57
Issue number5
DOIs
StatePublished - May 1993

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry

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