No abstract

alpha-Crystallin was isolated from calf lens periphery by chromatography on DEAE-cellulose and gel filtration. Three distinct populations of macromolecules have been isolated with molecular weights in the ranges approx. 6x10(5)-9x10(5), 0.9x10(6)-4x10(6) and greater than 10x10(6). The concentration of macromolecules at the molecular-weight limits of a population are very low. The members of the different populations do not appear to be in equilibrium with each other. Further, in those molecular-weight fractions investigated, no equilibrium between members of the same population was observed. The population of lowest molecular weight comprises 65-75% of the total material. The amino acid and subunit composition of the different-sized fractions appear very similar, if not identical. The only chemical difference observed between the fractions is the presence of significant amounts of sugar in the higher-molecular-weight fractions. Subunit molecular weights of approx. 19.5x10(3) and 22.5x10(3) were observed for all alpha-crystallin fractions.

No abstract

Several observations suggest that three tyrosyl and carboxyl residues may be interacting with each other in ribonuclease. Accepting the hypothesis that such interactions may exist, and making use of the knowledge that the buried tyrosyl and carboxyl groups of ribonuclease are Tyr 25, 92, 97 and Asp 14, 38, 83, it is possible to pair these residues on the basis of studies with ribonuclease derivatives. Blocking of Asp 38

The water soluble (WS), urea soluble (US) and urea insoluble (UI) fractions from individual human lenses 1.8 to 65 years of age were isolated from concentric fiber layers. In lenses younger than 19 years, a uniform distribution in the amount of WS, US and UI fractions was found throughout the entire lens. These fractions represent 83, 11.5 and 5.5%, respectively, of the lens dry weight. This composition was observed with the cortical fibers of all lenses examined up to the 65-year old. In the nuclear fiber layers, the proportion of US protein gradually increases in the third to fourth decade of lens growth and appears to have reached a maximum representing 22-24% of the nuclear fiber mass in 50-year and older lenses. A large increase in the amount of the UI fraction to 30% of the fiber mass was observed in lenses between the 5th and 6th decade of lens growth. The change from the cortical to nuclear composition occurs in a narrow region of the lens which becomes more peripheral with aging. The cortical WS fractions were characterized by well defined polyacrylamide gel bands in sodium dodecyl sulfate (SDS). Those of the nuclear fibers were broadened, especially in the 27/29 and 16/18 kilodalton (KD) region. The disappearance of the 20/22 KD bands in the inner cortical and nuclear fibers cannot be accounted for by the small increase in protein insolubilization in these regions of lenses 40 years or younger.