Application of Raman spectroscopy to study the high pressure effect on the secondary structure of bean [Phaseolus vulgaris] and pea [Pisum sativum] proteins

The effect of high pressure on the secondary structure of bean and pea proteins was studied using Raman spectroscopy. The proteins were pressurized at 300 and 600 MPa. Raman spectra were obtained for samples both in the solid state and dissolved in D 2 O. The results indicated that the contributions of unordered structure in pressurized proteins increased at the expense of the contributions of the α-helix and β-structure. High pressure denaturation produced more changes in β-structure of pea proteins than bean proteins. Intensity analysis of band at 853 and 828 cm -1 showed that the residues of tyrosine were buried in the pressurized bean proteins, whereas in pea proteins the residues of tyrosine were exposed on the surface of protein molecules by high pressure. The results indicated that upon pressure processing the proteins of bean and pea folded and unfolded respectively. The Raman spectra of bean proteins in solid state revealed differences in comparison with the proteins solution in D 2 O. These changes were observed in the intensity of the bands in the region of 1000 to 1350 cm -1 . The extent of changes in the secondary structure of proteins in the solid state was smaller in comparison with the deuterated samples after denaturation by high pressure.