Figure 2. The lenticular proteins generally had longer life times than the vitreoretinal and sclera/choroid proteins.

(A) Inter-tissue comparison of protein longevity showing numbers of proteins based on ¹⁴N-peptides only, ¹⁵N-peptides only, or ¹⁴N/¹⁵N ratios calculated (hatched pie). While in the lens a large number of protein had a greater proportion of ¹⁴N, other ocular tissues had a faster protein turnover with more proteins completely labeled with ¹⁵N within 12 weeks. (B) A list of the most abundant proteins that were only detected by ¹⁴N peptides with the absence of ¹⁵N. (C) Among the proteins identified with both ¹⁴N and ¹⁵N peptides—248, 362 and 398 proteins in the lens, the vitreoretinal and the sclera/choroid, respectively, the distribution of ¹⁴N-to-¹⁵N ratios of the lens proteins was different than those of the other tissues. As expected, the lens had the highest proportion of its ¹⁴N-proteins remaining. (D) The distribution of ¹⁴N/¹⁵N ratios from low to high as in Figure 2C. There is a long list of 278 proteins with only their ¹⁴N-proteins detected (dotted blue line to upper right), indicating possibly less ¹⁴N to ¹⁵N conversion of these proteins than those measured with ¹⁴N/¹⁵N ratios. Proteins that are implicated in cataract including structural proteins, gap junction and water channels, and metabolic enzymes are listed with arrows pointing to their corresponding values. The family of Crystallin proteins are listed below. Benchmark Histones H3.3 and H3.1/3.2 are also listed, representing transcription vs. cell proliferation activities, respectively.