CHLOROPHYLL ORIENTATION IN CRYSTALS OF BACTERIOCHLOROPHYLL-PROTEIN FROM GREEN PHOTOSYNTHETIC BACTERIA

Optical properties of single crystals of a bacteriochlorophyll-protein complex from Chloropseudomonas ethylicum were investigated. The absorption spectrum of these crystals is essentially the same as that of the complex in solution. The crystals are weakly dichroic at both the 603-nm (D = 1 1.21) and the 809-nm (D = 1.30) absorbances. This dichroism is confirmed by selective dispersion of birefringence: Negative at 603 nm and positive at 809 nm with respect to the optic axis. The sites of bacteriochlorophyll binding are therefore oriented with respect to the crystal axes. A radial arrangement of the porphyrin sites within each macromolecule is proposed and evaluated. © 1969.