Near-ultraviolet circular dichroism of bovine high molecular weight alpha-crystallin

High molecular weight (HMW) alpha-crystallin isolated from cow nucleus has a molecular weight greater than 5 x 10(6) Daltons. Its particle dimensions have been reported to be over 500 nm. It is derived mainly from low molecular weight (LMW) alpha-crystallin. The conformational change as LMW alpha-crystallin is converted into HMW alpha-crystallin was studied by near-ultraviolet circular dichroism (NUV-CD). The main concern in measuring CD for protein aggregates with particle dimensions as high as HMW alpha-crystallin and with an irregular shape is the contribution of differential scattering. The differential scattering becomes increasingly more important for particles with dimensions greater than 1/20th the wavelength of light. This contribution was minimized by increasing the acceptance half-angle of detection. The present data indicate that bovine HMW alpha-crystallin has a different tertiary structure from LMW alpha-crystallin.