Selective chemical shift assignment of bacteriochlorophyll a in uniformly [13C-15N]-labeled light-harvesting 1 complexes by solid-state NMR in ultrahigh magnetic field.

Magic-angle spinning (MAS) 13C−13C correlation NMR spectroscopy was used to resolve the electronic ground state characteristics of the bacteriochlorophyll a (BChl a) cofactors in light-harvesting 1 (LH1) complexes of Rhodopseudomonas acidophila (strain 10050). The BChl a 13C isotropic chemical shifts of the LH1 complexes are compared to the 13C chemical shifts for BChl a dissolved in acetone-d6 and to 13C NMR data that has been obtained for the B800 and B850 BChl molecules in Rps. acidophila peripheral light-harvesting complexes (LH2). Since both complexes contain BChl a cofactors, we can address the chemical shift variability for specific carbon responses between the two types of antennae. The global shift pattern of the LH1 BChl's resembles the shift patterns of the LH2 α- and β-B850 BChl's, while some carbon responses, in particular the C3 and C31, show significant deviations. A comparison with density functional theory (DFT) shift calculations provides insight into the BChl concomitant structural and ...