Solution scattering studies of dimeric and tetrameric spectrin

The structure of spectrin dimers and tetramers in solution has been examined by light, low-angle X-ray and neutron scattering. The results show a good correspondence between the solution dimensions of these molecules and their appearance in the electron microscope after shadowing. The scattering profiles are not compatible with an extended rod-like character, but reflect the presence of a considerable degree of bending. The radii of gyration of the dimer and tetramer were determined to be 170 and 375 A and the cross-section radii of gyration 14 and 12.3 A, respectively. Both are thus long, thin, rather bent molecules, and the tetramer is twice the length of the dimer.