Electron microscopic and hydrodynamic studies of protein A-immunoglobulin G soluble complexes.

摘要: The soluble complexes formed by reacting staphylococcal protein A (SpA) with rabbit immunoglobulin G (IgG) antibodies were characterized hydrodynamic and electron microscopic methods. In moderate SpA excess, equilibrium mixtures of IgG four discrete that sedimented at approximately 7, 10, 13, 15S. putative visible microscopy appeared to contain one, two, three, five molecules IgG. Probably because its elongated shape, was not clearly in these or control preparations alone. Both native modified cleavage single-hinge disulfide bond similar on interaction SpA. It possible resolve heterogeneous IgG-SpA using an analytical ultracentrifuge equipped a photoelectric scanner interfaced small computer. relative concentrations sedimentation velocities different mixture determined from computer-generated integral derivative plots. methods revealed the distribution sensitive molar ratio. amounts faster increased as ratio increased. Surprisingly, when greater than equal 2, converted into unique 17S complex. This rather unprecedented transformation reversible: addition excess caused dissociation complex 15S structures. average translational diffusion coefficient 2.62 +/- 0.13 Ficks. microscope, be exceptionally compact diameter 287 A. stoichiometry complex, together equilibrium, diffusion, measurements, indicated it is composed two