Biochemical features of the grey squirrel lens.

The ocular lens of the grey squirrel (Sciurus carolinensis) is an excellent model for studies of eye-light interactions that apply to the human system. In this diurnal animal, lens size, shape, yellow pigmentation, and light absorption properties have important similarities to those of young children. This article describes the observations of soluble to insoluble protein conversion with chronological aging, and the loss of heavier lens crystallins in the internal as compared to the external layers of the lens. Such changes are related to aging, as the older lens material is present in the nuclear core, while the younger lens material is superficial. It describes the subunit peptides of the soluble crystallins and of the extrinsic and instrinsic proteins associated with fiber cell membranes. Squirrel lens fiber membranes release most of their extrinsic peptides in 8 M urea, as do those of other young animals. Due to the presence of near-UV absorbing species of low molecular weight, the squirrel lens has great potential for studies of the effects of near-UV radiation on the lens.