A comparative small-angle X-ray scattering study of crystallin supramolecular structure in carp, frog, and rat lenses

The supramolecular structure of crystallins in intact ocular lenses of carp, frog and rat as well as in the interior (nuclear) and outer (cortical) parts of these lenses was studied by the small-angle X-ray scattering method. The results show that the supramolecular structure of crystallins substantially varies both in lenses of different vertebrate species and in various parts of the same lens. In carp lens and in the cortical part of rat lens, crystallins have an ordered supramolecular structure, as indicated by a small-angle X-ray diffraction maximum in the region of Bragg distances 15-20 nm, whereas in frog lens and in the nuclear part of rat lens, the supramolecular structure of these proteins is disordered. The power-law X-ray scattering by rat lens nucleus may be evidence of fractal structures in the lens. A comparison of these results with literary data indicates that there is no obvious correlation between the type of supramolecular structure of crystallins and; their polypeptide composition-in lenses of different vertebrate species. The results suggest that the supramolecular ordering (short-range order) of crystallins is not a necessary condition-for his transparency.