Purpose
To extract crystalline proteins from porcine eye lenses and to evaluate their relation with oxidative stress.

Methods
10 lenses were extracted from porcine eyes. The lenses were washed with phosphate-buffered saline (PBS) and homogenized in extraction buffer (20 mM Tris HCl, 5 mM EDTA, 2.6 ml/g of lenses) using Polytron homogenizer. The water insoluble residues were eliminated from the homogenate by subsequent centrifugations at 12000 rpm for 10 minutes. Crystalline proteins concentration of the extract was assessed with Bradford assay using Bradford reagent (Sigma Aldrich) and HPLC using Jupiter 5 μm C18 300 Å column.
The reactive oxygen species (ROS) probe Dihydrorhodamine-123 (DHR123, Sigma Aldrich) was added to the lens homogenate solution containing 3 mg/ml of crystalline proteins and irradiated by UV light (254 nm) for 0, 5, 10, 15 minutes. Irradiated samples were analyzed both by HPLC for protein characterization
and fluorimetry recording emission fluorescence spectra from 510 to 700 nm, using a Perkin Elmer luminescence spectrophotometer with excitation at 505 nm to determine ROS production.

Results
HPLC analysis showed the presence of a specific peak pattern of crystalline proteins in the porcine eye lens extract corresponding to 21% of α, 66% of β, and 13% of γ crystalline proteins. The concentration of each crystalline protein decreased after 15 minutes of UV irradiation. The emission fluorescence spectra showed a peak at 527 nm corresponding to the presence of Rhodamine 123, as a result of the oxidation of DHR123 probe induced by the presence of ROS.

Conclusions
α, β and γ crystalline proteins were extracted from porcine eye lens and quantified. UV irradiation of crystalline proteins solution induced the protein degradation that could be related to ROS production.
Additional studies are necessary to evaluate the oxidative stress mechanism that induce crystalline proteins degradation.