OPTICAL SPECTROSCOPY OF A HIGHLY FLUORESCENT AGGREGATE OF BACTERIOCHLOROPHYLL-C

Bacteriochlorophyll (BChl) c and a similar model compound, Mg-methyl b acteriopheophorbide d, form several types of aggregates in nonpolar so lvents. One of these aggregates is highly fluorescent, with a quantum yield higher than that of the monomer. This aggregate is also unusual in that it shows a rise time in its fluorescence emission decay at cer tain wavelengths, which is ascribed to a change in conformation of the aggregate. An analysis of fluorescence depolarization data is consist ent with either a linear aggregate of four or five monomers or prefera bly a cyclic arrangement of three dimers.