The interactions between bacteriochlorophyll c and amphiphilic peptides

Absorption, fluorescence, photoacoustic and delayed luminescence spectra of bacteriochlorophyll c with and without peptides located in dimethyl sulfoxide were measured. For most molecules, the hydrophobic interactions between peptide and pigment in the ground state seems not to be very strong, as it follows from the absorption spectra of the samples with and without peptides. From photoacoustic spectra, it seems that at least part of the illuminated pigment molecules are forming complexes with peptides. These complexes are very efficient in thermal deactivation of excitation. The occurrence of the interactions between peptides and bacteriochlorophyll c follows also from delayed luminescence spectra, which are different for the sample with and without peptides. The observed delayed luminescence is so-called delayed fluorescence or E-type delayed luminescence because it is generated by thermal activation from the triplet to first excited state followed by emission from this state. (C) 1998 Elsevier Science S.A. All rights reserved.