Oxidized modification of fragments D and E from fibrinogen induced by ozone

Abstract

Ozone-induced free-radical oxidation of fragments D and E from fibrinogen has been studied. The methods of elastic and dynamic light scattering in combination with electrophoresis of unreduced samples have shown the acceleration of enzymatic covalent crosslinking of molecules of oxidation-modified fragment D under the action of factor XIIIa. UV and IR spectroscopy shows that free-radical oxidation of amino acid residues of polypeptide chains catalyzed by ozone affects the cyclic and amino groups, giving rise to generation of mainly oxygen-containing products. Comparison of the IR spectra obtained for the oxidation-modified D and E fragments revealed more significant transformation of functional groups for the D fragment. EPR spectroscopy showed that the rotational correlation time of spin labels bound to the ozonized proteins decreased in comparison with the non-ozonized proteins. The rotation correlation time of the radicals covalently bound to the ozonized D and E fragments suggests that D fragment of fibrinogen is more sensitive to free-radical oxidation followed by local structural changes. Possible causes of different degrees of oxidation for fragments D and E are discussed.

Ozone-induced oxidative modification of fibrinogen: Role of the D regions

“…10 and 11 demonstrate that the D and E fragments isolated from oxidized fibrinogen exhibit a spectacular transformation of the molecular structure. Notably, the overall changes in the spectra are in good correlation with those observed earlier for the fibrinogen D and E fragments upon their oxidation [36] and also for oxidized whole fibrinogen [35]. Specifically, for both the D and the E fragments, there is observed a decrease in the content of N-H groups in the peptide (the bands at 3299 þ 3149 and 3265 þ 3157 cm À 1 , respectively).…”

“…oxidation than the E region. It was noted earlier [36,51] that this could be mainly brought to specific features of the primary structure of the D and E regions of fibrinogen. The D region contains a significantly greater number of aromatic and cyclic amino acid residues, which are more easily oxidized [36].…”

“…It was noted earlier [36,51] that this could be mainly brought to specific features of the primary structure of the D and E regions of fibrinogen. The D region contains a significantly greater number of aromatic and cyclic amino acid residues, which are more easily oxidized [36]. Thus, the content of tryptophan residues, which are the most sensitive to oxidation, in the D region is more than fivefold higher than in the E region, whereas the contents of tyrosine, phenylalanine, and histidine residues are higher by nearly threefold.…”

“…This points to ozone-induced modification of tryptophan, which in the series of other aromatic amino acid residues has the highest susceptibility to O 3 [29,31]. As has been shown earlier [36], the oxidative modification of Trp residues in fibrinogen under the influence of ozone is caused by formation of the quinoid structures from indole tryptophan rings.…”

“…Infrared spectra were run on a Tensor-27 (Bruker, Germany) FTIR spectrometer equipped with a DTGS detector, as was described in detail earlier [36]. The samples for measurement were prepared by placing 2-to 5-μl drops of aqueous sample solution onto the surface of a silicon wafer (2 Â 2 Â 0.02 cm) with subsequent drying of the sample at room temperature to constant weight.…”