[Fibrin fragment beta 15-118. Inhibitory and complex-forming properties]. / Fibrinovyi fragment beta 15-118. Ingibitornye i kompleksoobrazuiushchie svoistva.

Peptide beta 15-118 isolated from desAABB-NDSK preserves fibrin polymerization active site "B", inhibits polymerization process at 12 degrees C, eliminates the inhibitory properties of plasmin D-D-fragment but does not influence inhibitory properties of a D-monomer fragment. Complex formation between peptide beta 15-118 and both D- and D-D fragments was electrophoretically demonstrated. Peptide beta 15-118 forms more stable complex with the D-D fragment which does not dissociate in the medium of polymerizing fibrin as the complex of the peptide with monomer D fragment does. Gel filtration data confirm dimerization of D-monomer fragments after their complexing with beta 15-118. This phenomenon suggests that mutual affinity of D-domains in fibrin increases after loci interactions of the "B"-"b" type.

[Study of the polymerization of fibrin using monoclonal antibodies 2D-2A and their Fab-fragments]. / Issledovanie polimerizatsii fibrina s pomoshch'iu monoklonal'nykh antitel 2D-2A i ikh Fab-fragmentov.

It has been shown that monAb's 2d-2a and their Fab-fragments are specific and effective inhibitors of fibrinogen clotting. Only one IgG molecule of monAb's 2d-2a can bind with one of their epitopes situated around peptide bond B beta Arg14-Gly15 in dimer fibrinogen molecule reducing the rate of protofibril lateral association and clot turbidity with only one fibrinopeptide B splitting off per fibrinogen molecule by thrombin. But two molecules of Fab-fragments of monAb's 2d-2a join to both of their epitopes and inhibit fibrinogen clotting dramatically without clot formation and with no fibrinopeptide B splitting off. These data suggest that the site of fibrin protofibril lateral coalescence is localized in NH2-terminal part of fibrin (ogen) B beta-chain, i.e. central E-domain of fibrin molecule takes part in protofibril lateral association. The mutual space orientation of NH2-terminal regions of fibrinogen B beta-chains is discussed.

[The effect of ionizing radiation on the structure of the hydrophobic fragment of Ca-ATPase in skeletal muscle sarcoplasmic reticulum]. / Vliianie ioniziruiushchei radiatsii na strukturu gidrofobnogo fragmenta Ca-ATFazy sarkoplazmaticheskogo retikuluma skeletnykh myshts.

Early (1 and 24 h) after X-irradiation with a dose of 0.21 C/kg changes occurred in the acceptability of the polypeptide chain parts of sarcoplasmic reticulum Ca-ATPase for the effect of trypsin. The analysis of the results of studying the structural and functional properties of a hydrophobic fragment of this enzyme in the control and after irradiation permitted to define the part of the Ca-ATPase polypeptide chain that provided ion selectivity of the fragment.

[Interaction of fibrinogen with two forms of fibrin differing in the degree of activation by thrombin]. / Vzaimodeistvie fibrinogena s dvumia formami fibrina, razlichaiushchimisia po stepeni aktivatsii trombinom.

The inhibitory effect of fibrinogen in the clotting of two fibrin monomer species--f-desAA and f-desAABB--was studied. The concentration dependence of this effect for two fibrin forms was found to be of the same character. This fact indicates that the modifying influence of fibrinogen proposed earlier in relation to f-desAABB also takes place in the case of f-desAA. However, an equal inhibitory effect is achieved for f-desAA at much higher fibrinogen concentrations than that for f-desAABB. The inhibitory effect of fibrinogen is greater at higher ionic strengths for both fibrin forms, but in the case of f-desAA this effect is more pronounced. The role of fibrin polymerization sites formed after fibrinopeptides B removal in initial fibrin polymerization and in F-f-desAABB interaction is discussed.

[Study of fibrinogen-fibrin cryocomplexes by a quantitative analysis of N-terminal amino acids]. / Issledovanie kriokompleksov fibrinogena i fibrina metodom kolichestvennogo analiza N-kontsevykh aminokislot.

The reaction between fibrinogen (F) and thrombin (0.003 NIH/ml) has been investigated under physiological conditions. The action of thrombin was inhibited in various time intervals including gel point (4 h), and the reaction mixtures were allowed to stand 0 degrees C. The F-to-des-AA-fibrin (f) ratios were determined both in the initial reaction mixtures and in corresponding cryoprecipitants by the method of N-terminal amino acids quantitative analysis. It is found that the F/f ratio in the cryoprecipitant depends on the F/f ratio in the initial mixture at 37 degrees C. The F/f = 1 ratio in cryoprecipitant previously found by Shainoff and Page is valid only for the initial F/f = 7 ratio. But the F/f value in cryoprecipitants varies in favour of F or f components, if the F/f ratio increases or decreases in the initial mixture at 37 degrees C, respectively. A possible mechanism of various fibrinogen-fibrin cryocomplexes formation is discussed.

[Analysis of the stability of the intermediate fibrin polymers formed in a fibrinogen-thrombin system]. / Issledovanie stabil'nosti promezhutochnykh polimerov fibrina, obrazuiushchikhsia v sisteme fibrinogen-trombin.

Intermediate fibrin polymers formed from fibrinogen at low thrombin concentrations under physiological conditions are studied for their stability. Smith's statement that intermediate fibrin oligomers are inert molecules whose further self-assembly is possible only under additional thrombin activation was not supported. It is shown that the intermediate fibrin polymer stability at pH 7.4 is not high because of a strong tendency to aggregation and the higher molecular weight of the polymer the less its stability. The polymer stability in solution increases with pH. Stability of soluble fibrin complexes in solution depends on their size, defined by environmental conditions and on the quantity of fibrinogen present.

[Properties of 2 fibrin monomer forms which differ in the degree of thrombin activation. Relation of these 2 forms to specific polymerization inhibitors]. / Svoista dvukh form monomernogo fibrina, razlichaiushchikhsia po stepeni aktivatsii trombinom. Otnoshcnie polimerizatsii dvukh form fibrina k spetsificheskim ingibitoram.

The inhibitory effect of fibrinogen and its fragment D on the clotting of two fibrin monomer species has been studied. One of them (f0) lacks peptides A and B, the other (fB) preserves peptides B. The inhibitors retard the clotting of f0 but fail to influence fB polymerization. This means that the peptide B removal and appearance of the active site B in the central (E) domain of the fibrin molecule is a prerequisite for the inhibitory effect of fibrinogen or fragment D. The specificity of this effect suggests that fragment D and the periferal D-domains of fibrinogen possess a special site (B') which reacts selectively with the fibrin active site B to block polymerization. The present investigation has demonstrated the importance of the H-bond system formation for B-B' sites interaction.

[Properties of 2 fibrin monomer species which differ in the degree of thrombin activation. Characteristics of successively appearing active sites]. / Svoistvadvukh form monomernogo fibrina, razlichaiushchikhsia po stepeni aktivatsii trombinom. Kharakteristika posledovatel'no obrazuiushchikhsia aktivnykh tsentrov.

Some properties of intermediate and final products of fibrinogen activation by thrombin have been studied. The intermediate (fB) lacks peptide A, the final fibrin (fo)--A and B peptides. Peculiar pH-dependent differences have been observed when examining the effect of ionic strength on polymerization rate of fo and fB. Intermolecular links present in fo polymer are found to be stronger than those of fB polymer. Curves of clot turbidity vs pH for fo and Fb do not coincide. Considering these results together with the literature data on the fibrin-polymer H-bond system one may assume that there are much more H-bonds in fo polymer than in its fB variant. Polymerization of fB has been found to be practically unaffected by higher NaCl concentrations which activate fo polymerization. Our and literature evidence lead to the conclusion that the active site (contact region), generated by the release of the peptide A, effects polymerization through electrostatic and H-bonding, whereas on the removal of the peptide B another active site arises of which a system of H-bonds and hydrophobic interactions are characteristic.

[Electrophoretic fractions and NH2-terminal amino acids of high-molecular tryptic fragments of fibrinogen and fibrin]. / Doslidzhennia elektroforetychnykh fraktsii i NH2-kintsevykh aminokyslot vysokomolekuliarnykh tryptychnykh frahmentiv fibrinohenu i fibrynu

The electrophoretic and NH2-terminal analyses were performed for D and E fragments obtained by tryptic digestion of bovine fibrinogen and fibrin under various conditions. The preparations of fragment D were heterogeneous, they were separated by polyacrylamide gel electrophoresis into a number of electrophoretic components with molecular weight ranging from 65 000 to 85 000. NH2-terminal analysis revealed from 6 to 8 NH2-terminal amino acids: Ser, Gly, Thr, Asp, Gly, Lys, Gln, Asn. Their composition and quantitative ratios were found to vary depending on the conditions of the fragment D production. The electrophoregrams showed that with Ca++ in the medium the enzymatic splitting of fibrinogen was limited. Fragment D obtained from fibrinogen without Ca++ was electrophoretically rather similar to that obtained from fibrinogen at Ca++ optimal concentration. Taking into consideration a very high specific anti-coagulational activity of these two fragment D preparations, one may conclude that both the polymerized state of protein molecules and the presence of Ca++ stabilize the specific molecular structure, that favorus the preservation of specific inhibitory activity in fragment D. According to the NH2-terminal analysis data, fragment E derived from fibrinogen hydrolyzed in the presence of Ca++ optimal concentration is also heterogeneous. The following amino acids were found: Tyr, Lys, His (main ones) and Gly, Ser, Thr, Val (minor ones). As to molecular weight determined by electrophoresis, fragment E appears to be homogeneous.