On The Mechanisms Regulating Alpha-crystallin Activity

a-crystallin is a protein that plays several relevant physiological roles (i.e is the major constituent of human lens or help in maintain the correct folding of several protein) all of them affected by the occurrence of aggregation. a-crystallin supramolecular aggregation, induced by generating heat-modified a-crystallin forms, has been investigated over a range of temperature between 30 C and 60 C by means of static and dynamic light scattering and atomic force microscopy. Aggregation, after the formation of first clusters or basic aggregation units, can be described as a cluster-cluster aggregation similar to that of colloidal particles. Below a temperature TC ¼ 45 C, after a large lag time needed to form the first clusters, a fast, diffusion limited, aggregation can be observed. Above TC we observe a faster lag time followed by a slow aggregation. Correspondingly the temperature dependence of aggregation rates display an abrupt discontinuity at TC . This discontinuity and the different kinetics of aggregation shed new light in the pathogenesis of the human eye lens cataract assigning a key role to the heat modified form of a-crystallin that markedly protect from aggregation preserving the transparency of the lens.