Long-wavelength-absorbing forms of bacteriochlorophyll a in solutions of Triton X-100.

At least three forms of Triton X-100-solubilized bacteriochlorophyll a (BChl a) have been characterized by UV/visible/near-IR absorption and CD spectra. One, absorbing at 770 nm, is similar to a monomeric solution in methanol. The two others have strongly red-shifted absorption peaks (860 nm and 930, 835 nm) and intense and complex CD bands in this region, indicative of strong interaction of at least two and three molecules of BChl a, respectively.