Spectroscopy of individual LH2 complexes of Rhodopseudomonas acidophila:localized excitations in the B800 band

Using single-molecule detection techniques, fluorescence-excitation spectra from the B800 absorption band of individual light-harvesting complexes (LH2) of purple bacteria at 1.2 K were recorded. The spectra show distributions of narrow absorption lines that originate from excitations that are mainly localized on individual B800 bacteriochlorophyll a molecules. Spectroscopic details normally hidden under the inhomogeneous broadening, such as the degree of disorder in the pigment rings, the excited state dynamics and the energy transfer can be obtained