A 2D correlation Raman spectroscopy analysis of a human cataractous lens

• Cataract progress induces the changes of lens composition and macromolecular order.
• Both opaque phases of lens, white- and yellow-, are degenerate forms of the protein.
• The 2D correlation method was allowed to distinguish between the two selected phases.
• Both the white- and yellow-phases of the human eye lenses are arranged in a different way.

This work is a continuation of our study of a cataractous human eye lens removed after phacoemulsification surgery. There are clear differences in the lens colors that allowed for distinguishing two opaque phases in the obtained biological material: the white- and yellow-phase. The Raman spectroscopy and 2D correlation spectroscopy method were used to trace a pathologically altered human cataract lens at a molecular level. Although the Raman spectra of these two phases are relatively similar, taking advantage of 2D correlation, and considering time as an external perturbation, the synchronous and asynchronous spectra were obtained showing completely different patterns. Prominent synchronous auto-peaks appear at 3340, 2920, 1736, 1665 and 1083 cm−1 for the white-, and at 2929 and 1670 cm−1 for the yellow phase. The white phase is characterized by intensive asynchronous peaks at −(2936, 3360), −(1650, 1674) and +(1620,1678). The modifications in the water contained in the white phase structure are ahead of the changes in the protein (CH3-groups), furthermore changes in β-conformation are asynchronous with respect to the α-structure.The yellow phase demonstrates asynchronous peaks: +(2857, 2928), +(1645,1673), +(1663, 1679), and +(1672,1707). These illustrate concomitant modifications in the β- and unordered conformation. Both forms of cataractous human eye lens, white- and yellow-phases, are degenerate forms of the eye lens proteins, both are arranged in a different way. The main differences are observed for the amide I, methyl, methylene and OH vibrational band region. The effect of Asp, Glu and Tyr amino acids in cataractous lens transformations was observed.