The optical properties of α2-macroglobulin from normal and from cystic fibrosis plasma

Abstract

The α2-macroglobulin (α2-M) was purified from the plasma of normal individuals and from that of cystic fibrosis patients. The proteins exhibited identical optical properties. Both proteins have an absorbance coefficient of A = 1060 g∙cm−2 at 280 nm. The circular dichroism spectra are identical and indicate about 45% β-sheet structure and almost no α-helix. The spectra of solutions at pH 8.0 do not change when trypsin is added.The fluorescence spectra of the α2-M measured at pH 8.0 have contributions by tyrosine and tryptophan residues. The fluorescence intensities are identical and are enhanced about 30% when trypsin is added in 2:1 molar ratios.