Acetonitrile can promote formation of different structural intermediate states on aggregation pathway of immunoglobulin G from human and bovine

A sequential addition of acetonitrile to human and bovine immunoglobulin G induces molten globule-like state at 50% (v/v) and 60% (v/v) respectively having secondary structure similar to native protein as evident from far-UV circular dichroism and Fourier transform infra red spectroscopy. Further addition of acetonitrile up to 80% forms aggregate of IgG as confirmed by increase in thioflavin T, loss of signals in near-UV CD spectra, decrease in ANS and tryptophan fluorescence. Thus at high acetonitrile concentration, a relatively large amount of partially unfolded intermediates of IgG are present which result in aggregates formation.