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Light-harvesting complex II; State of association; Analytical ultracentrifugation; (R. molischianum)
Abstract:
The molar mass of the light-harvesting complex II (LH II) from Rhodospirillum molischianum in solutions of two nonionic detergents (N,N-dimethyldodecylamine N-oxide, nonaethyleneglycol lauryl ether) was studied by sedimentation equilibrium experiments in the analytical ultracentrifuge. To account for the contribution of protein-bound detergent to the effective particle mass, solvent density was varied by addition of D<sub>2<(sub>O. In both detergents, the relative molar mass of the protein/pigment complex was found to be 114 500 ± 7% (maximum error), corresponding to the (8.0 ± 0.6)-fold of that of the monomeric unit. The complex is thus the octamer of the basic unit.