Fourier transform Raman spectroscopy study of heat-induced gelation of plasma proteins as influenced by pH

Fourier transform ( FT) Raman spectroscopy was used to elucidate heat-induced structural changes of albumin, globulins, serum, and plasma protein solutions ( 15% w/w) as affected by pH ( 4.5, 6.0, and 7.5). Reduction of alpha-helix and formation of beta-sheet, disulfide bond reactions, and exposure and buriedness of hydrophobic groups and amino acid residues were observed. All of these features contributed to the formation of strong, irreversible heat-induced gels. The application of a dimensionality reducing technique such as principal component analysis proved to be useful to determine the most influential qualities of protein samples, as well as the pH-dependent behavior of some of the attributes of both unheated and heated solutions. Analysis of Raman spectra in terms of differences demonstrated the interactions of albumin and globulins in co-occurrence and the significant role of fibrinogen on the gel's attributes.