Interaction of Alpha-Crystallin with Membranes Extracted from a Single Bovine Lens Nucleus

With age and cataract formation, α-crystallin binding with lens membranes increases. This study investigates the binding of α-crystallin with bovine nucleus lens lipid (BNLL) and a model of bovine lens lipid (MBLL) membranes using the electron paramagnetic resonance (EPR) spin-labeling method. The rapid solvent exchange method and probe-tip sonication were used to prepare unilamellar BNLL and MBLL membranes using the total lipids isolated from a single bovine lens nucleus and the four major phospholipids of the bovine lens, respectively. The percentage of membrane surface occupied (MSO) and binding affinity (K _a ) is less for BNLL membranes than for MBLL membranes. The high cholesterol content with cholesterol bilayer domains (CBDs) within BNLL membranes likely decreases the hydrophobicity near the surface of BNLL membranes, decreasing the likely hydrophobic binding of α-crystallin with these membranes. With increased α-crystallin concentration, the mobility parameter decreases and maximum splitting does not change significantly for BNLL and MBLL membranes, implying that these membranes near the surface become less mobile with no significant change in order due to α-crystallin binding. Our study shows the feasibility that such experiments can be performed with membranes isolated from a single human lens.