Effect of urea on the cold precipitation of protein in the lens of the dogfish.

Abstract

WHEN lenses of young rats are cooled below 10° C they become reversibly opaque due to the precipitation of a cold-precipitable protein. This fraction is prepared by homogenizing rat lenses in several volumes of water and cooling the 105,000g supernatant to 0° C. Repeated solubilization at 20° C and precipitation at 0° C serves as a means of purification1. The cold-precipitation phenomenon is thought to be caused by changes in protein conformation due to a disturbance of the balance between hydrogen and hydrophobic bonding of protein chains at lower temperatures.