Absorption and fluorescence of chlorophyll a in particle fractions from different plants.

Density-gradient centrifugation of disintegrated cells from a variety of plants gave two kinds of chlorophyll particles from all except the blue-green algae. As in previous procedures using detergents, the lighter Fraction 1 particles usually had greater absorption at longer wavelengths; they always had a lower ratio of short to long wavelength fluorescence at low temperature, and a lower fluorescence yield per chlorophyll than the denser Fraction 2 particles. Although only one kind of particle fraction was found in each blue-green alga, the fine structure of the chlorophyll a absorption band differed significantly among the three species measured.