DETERMINATION OF SECONDARY STRUCTURE OF NORMAL FIBRIN FROM HUMAN PERIPHERAL-BLOOD

The secondary structure of human fibrin from normal donors and from bo vine and suilline plasma was studied by Fourier transform ir spectrosc opy and a quantitative analysis of its secondary structure was suggest ed. For this purpose, a previously experimented spectrum deconvolution procedure based on the use of the Conjugate Gradient Minimisation Alg orithm with the addition of suitable constraints was applied To the an alysis of conformation-sensitive amide bands. This procedure was appli ed to amide I and III analysis of bovine and suilline fibrin, obtained industrially, and to amide III analysis of human fibrin clots. The an alysis of both amide I and III in the first case was useful in oi der to test the reliability of the method. We Sound bovine, suilline, and human fibrin to contain about 30% alpha-helix (amide I and III compone nts at 1653 cm(-1), and 1312 and 1284 cm(-1), respectively), 40% beta- sheets (amide I and III components at 1625 and 1231 cm(-1), respective ly) and 30% turns (amide I and III components at 1696, 1680, 1675 cm(- 1), and 1249 cm(-1), respectively). The precision of the quantitative determination depends on the amount of these structures in the protein . Particularly, the coefficient of variation is < 10% for percentage v alues of amide I and III components > 15 and 5%, respectively. The goo d agreement of our quantitative data, obtained separately by amide I a nd amide III analysis, and consistent with a previous fibrinogen (from commercial sources) study that reports only information about fibrin beta-sheet content obtained by factor analysis, leads us to believe th at the amounts of secondary structures found (alpha-helix, beta-sheets , and turns) are accurate. (C) 1997 John Wiley & Sons, Inc.