Raman study of the cleavage of disulphide bonds in albumin, chymotrypsin, and thrombin

The structural changes resulting from the reduction of disulphide bonds in three globular proteins (albumin, chymotrypsin and thrombin) in aqueous solutions are investigated using Raman spectroscopy. Changes in SS and SH vibrational bands are used for direct observation of the disulphide bond reduction. The corresponding changes in secondary structure and H-bonding of tyrosines are observed. It is shown that the unfolding pathway after the reduction of disulphide bridges in albumin depends on the reducing agent. The most developed changes are observed for the band assigned to the ggg conformation of the disulphide bridge in two similar serine proteases (thrombin and chymotrypsin) but the secondary structure of thrombin is much more stable against the reduction of the disulphide bonds.