Biophysical Insights into Implications of PEG-400 on the α-Crystallin Structure: Multispectroscopic and Microscopic Approach

Aggregation and precipitation of alpha-crystallin play a vital role in the cataract development. This study was targeted to delineate the effect of PEG-400 on the structural integrity of alpha-crystallin employing a multispectroscopic and microscopic approach. Intrinsic fluorescence and UV-vis spectroscopy suggested alterations in the tertiary structure of alpha-crystallin, namely global transition of native alpha-crystallin to a non-native form in the presence of PEG-400. Circular dichroism spectroscopy suggested secondary structural transition in a native conformation of alpha-crystallin in the presence of PEG-400. Loss in the native conformation of alpha-crystallin is implicated in cataract developments, thus highlighting the clinical significance of this work. Further, a significant increase in ANS fluorescence of PEG-400-incubated alpha-crystallin (7 days) suggested this non-native form to be molten globule (MG)-like state. Increased Thioflavin T fluorescence (ThT) and congo red (CR) absorbance along with transmission electron microscopy (TEM) confirmed the formation of the aggregates of alpha-crystallin after prolonged incubation with PEG-400. Insights into PEG-400-induced structural alterations can provide a platform to search for new therapeutic molecules that can combat alpha-crystallin-directed eye diseases.