Physicochemical studies on bovine eye lens proteins. II. Comparative physical study of the low-molecular-weight alpha-crystallins from calf lens cortical and nuclear fiber cells.

The alpha L of cortical and nuclear fiber cells have been studied using hydrodynamical and physicochemical techniques. From the sedimentation and the diffusion coefficients in identical conditions, it can be concluded that alpha L,N is appreciably larger than alpha L,C but both have a similar structure in solution: a spherical particle with a high hydration. The alpha L,N not only contains several degraded alpha A- and alpha B-peptides but also a typical pattern of beta-peptides. The fluorescence spectrum indicates a shift of the hydrophobic tryptophan residues from a hydrophobic environment in alpha L,C to a more solvent-exposed and polar neighbourhood for alpha L,N. Also solubility studies on alpha L,C and alpha L,N in different solvent conditions and temperatures, indicate more apolar interactions between the peptides of the nuclear alpha L, than its cortical counterpart. The more hydrophobic interaction pattern of the peptides in alpha L,N can also be reconciled with a lower mean hydration potential, indicative of a higher hydrophobicity of the degraded alpha A-peptides.