NMR analyses of the cold cataract. II. Studies on protein solutions

Water proton relaxation studies were performed on total soluble protein (TSP) solutions and individual alpha-, beta-, and gamma-crystallin fractions derived from weanling rat lenses, 16 month, and 60- to 70-year-old normal human lenses. The effects of perturbants (temperature and acrylamide) were monitored in order to delineate further the mechanisms involved in the generation of the cold cataract phenomenon (in young lenses) and the role of acrylamide and age in preventing this phenomenon. The data demonstrate a relationship between the relative concentration of the alpha-, beta-, and gamma-crystallin fractions within the lens and the cold cataract phenomenon. It is possible that cross-linking between acrylamide and the gamma-crystallins within the lens alters one or more of the intracytoplasmic protein-water phases. The gamma-crystallin solution showed greater than 35% increase in T2 when 1% acrylamide was added; the young TSP solution T2 increased by approximately 20%. However none of the T2 values for the alpha, beta and old TSP solutions changed significantly when acrylamide was added. The unique response of gamma-crystallin in these experiments suggests a significant role for this protein fraction in the phenomenon associated with cold cataractogenesis. Our data indicate that most of the UVA radiation-induced acrylamide binding occurred with the gamma-crystallins within the lens. We have also noted that only the gamma-crystallin and the young lens TSP solutions become opaque at 4 C while the alpha, beta and "old" TSP solutions remain clear at this temperature. It is suggested that acrylamide exerts its role by cross-linking to one or more of the gamma-crystallins, thereby altering the normal protein water relationship and preventing cold opacification.