LASER RAMAN-SPECTROSCOPY STUDY OF BOVINE FIBRINOGEN AND FIBRIN

The Raman spectra of bovine fibrinogen and fibrin are presented. A tentative assignment of the main bands is proposed. The study of the Amide I and Amide III regions showed an important increase in the β-sheet form of fibrin, compared with that of fibrinogen. The reorganization of the protein which takes place during the fibrinoformation is confirmed by the noticeable variations in the bands characteristic of the skeletal Cα-C and Cα-N stretching modes at about 1000 cm-1 and in the bands characteristic of aromatic chromophores. The intensity ratio of the tyrosine doublet I(850)/I(830) has a value of approx. 1.5 in fibrinogen. This would indicate that the majority of the tyrosine hydroxyl groups interact freely with the solvent. Therefore, the high pK values observed elsewhere by ultraviolet spectroscopy for 70% of the fibrinogen tyrosine residues, are indicative of local barriers rather than strong interactions with other residues. Precise intensity measurements below 900 cm-1 are difficult in fibrin where the value of the ratio seems to be somewhat lower (1.2-1.4). The study of the characteristic frequencies of the S-S bonds in the 510-540 cm-1 region showed that the majority of the 29 disulfide bridges of fibrinogen or fibrin have probably very similar geometry and that the C-C-S-S-C-C sequence is in the gauche-gauche-gauche form. © 1979.