A Spectroscopic Study of a Photosystem I Antenna Complex

  • Ishita Mukerji
  • Kenneth Sauer


The unusual long wavelength fluorescent behavior of Photosystem I (PSI) has been well documented (1) This study investigates the origin and temperature dependence of this emission using an intact peripheral antenna preparation isolated from a PSI complex originally extracted from spinach. This antenna complex (LHCP-I) contains polypeptides in the 19–24 kDa range and exhibits a red shift in emission maximum from 685nm (F685) to 735nm (F735) as the temperature is lowered. Fluorescence excitation spectra demonstrate that chlorophyll b (chl b) preferentially stimulates the long wavelength emission at both room temperature and 77K and also indicate the presence of a long wavelength absorber in the 703–708nm range. Excitation polarization scans show a rising polarization value reaching a maximum of 0.3 from 705nm to 725nm, confirming the presence of a long wavelength pigment or pigments which are primarily responsible for emission at 735nm (F735). Absorption spectra demonstrate that this species comprises a small percentage of the total pigment population in the light harvesting antenna. The overall fluorescence yield of the complex increases as the temperature is lowered suggesting the presence of a quenching mechanism which does not involve the reaction center, P700.


Reaction Center Excitation Spectrum Fluorescence Yield Antenna Complex Fluorescence Excitation Spectrum 
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Copyright information

© Springer Science+Business Media New York 1990

Authors and Affiliations

  • Ishita Mukerji
    • 1
  • Kenneth Sauer
    • 1
  1. 1.Department of Chemistry and Chemical Biodynamics Division, Lawrence Berkeley LaboratoryUniversity of CaliforniaBerkeleyUSA

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