X-band electron paramagnetic resonance spectra of bovine serum albumin-copper(II) and bovine serum albumin-copper(II)-aminoacid systems.

X-band electron paramagnetic resonance (epr) spectra of the binary systems, BSA-copper(II) (1:1 and 2:1), and the ternary systems, BSA-Cu(II)-aminoacid (1:1:1), are described. In the binary system, two distinct epr features have been observed. One of the features (towards the low pH), showing broad and overlapping epr signals, has been attributed to non-specific bonding of copper(II) to the albumin and other feature (towards higher pH), showing sharp intense epr signals, has been attributed to the specific bonding. The change from non-specific to specific binding is favoured by increase in pH as well as by increase in protein concentration. Specific binding of copper(II) in BSA-Cu(II) has been suggested to be similar to that in HSA-Cu(II). Spectra of BSA-Cu(II)-aminoacid (1:1:1) show simultaneous presence of binary BSA-Cu(II) and ternary BSA-Cu(II)-aminoacid.