The effect of water dynamics on conformation changes of albumin in pre-denaturation state:photon correlation spectroscopy and simulation

Water is essential for protein three-dimensional structure, conformational dynamics, and activity. Human serum albumin (HSA) is one of major blood plasma proteins, and its functioning is fundamentally determined by the dynamics of surrounding water. The goal of this study is to link the conformational dynamics of albumin to the thermal motions in water taking place in the physiological temperature range. We report the results of photon correlation spectroscopy and molecular dynamics simulations of HSA in aqueous solution. The experimental data processing produced the temperature dependence of the HSA hydrodynamic radius and its zeta potential. Molecular dynamics reproduced the results of experiments and revealed changes in the secondary structure caused by the destruction of hydrogen bonds in the macromolecule's globule

The fibrin Bβ125-135 site is involved in the lateral association of protofibrils

Earlier we reported that during the human fibrinogen to fibrin transition a neoantigenic determinant was exposed in the Bβ119-133 fragment, where a hinge locus is situated. The fibrin-specific mAb FnI-3c and its Fab-fragment with epitope in this fragment inhibited the lateral association of protofibrils. We suggested that the epitope coincided with a site involved in this process. In this work we investigated the epitope location more precisely and defined a functional role for its exposure in the hinge locus of the molecule. It was found that mAb FnI-3c bound to human, horse and rabbit fibrins, all of which have Lys in the position corresponding­ to human BβK130, but not to bovine and rat fibrins, which have other amino acid residues in this position, strongly suggesting that BβK130 provides the integral part of the epitope. This fact, homology data, and structural biological analysis of the amino acid sequences around BβK130 indicate that the site of interest is localized within Bβ125-135. The synthetic peptides Bβ121-138 and Bβ125-135, unlike their scrambled versions, bound to mAb FnI-3c in SPR analysis. Both peptides, but not their scrambled versions, inhibited the lateral association of protofibrils. The FnI-3c epitope is exposed after fibrinopeptide A cleavage and desA fibrin monomer formation. Structural biological analysis of the fibrinogen to fibrin transition showed a distinct increase of flexibility in the hinge locus. We propose that the structural transformation in the fibrin hinge regions leads to the conformation necessary for lateral association of protofibrils

Comparative analysis of the influence of chlorine and fluorine anions on the fibrin polymerization

The effect of NaCl and NaF salts in the range of 0.1-0.225 M concentrations on individual stages of fibrin polymerization was investigated, namely: the rate of fibrinogen activation by thrombin, the rate of protofibrils formation, the rate of lateral association of protofibrils, and the maximum clot absorbance value at 350 nm. It was found that the chlorine and fluorine anions equally inhibit the rate of formation of fibrin from fibrinogen and the formation of protofibrils activated with thrombin. Chlorine anions were shown to be significantly more effective than fluorine anions, inhibiting the rate of lateral association and maximal clot absorban­ce level from fibrin desA and desAB. A component of the inhibitory action of chlorine anions, not related to the ionic strength of the solution, was identified and its effect on the individual polymerization steps was shown. Chlorine anions were found to bind to a fibrin clot. Using the surface plasmon resonance method and fibrin-specific mAb FnI-3c, it was established that the rate of exposure of neoantigenic determinants of mAb in the hinge regions of the fibrinogen molecule during its transformation into fibrin under the action of thrombin is inhibited by chlorine anions in correlation with inhibition of the protofibril lateral association rate. It has been suggested that the inhibitory effect of chlorine anions consists of an ionic component and a component that blocks the conformational mobility of the molecule by the chlorine anions binding to its hinge regions and polymerization sites

COAGULATION AND FIBRINOLYTIC ACTIVITY INDICES IN PATIENTS WITH IHD AFTER PERCUTANEOUS CORONARY ANGIOPLASTY (PART I)

It is well known that restenosis/thrombosis in stent placement site is one of the commonest complications in patients with ischemic heart disease (IHD) and percutaneous coronary angioplasty (PCA), and activation of intravascular thrombogenesis can be one of pathogenetic factors of this process. Hence, determination of early and reliable biochemical markers in diagnosis of that complication is aimed at timely correction of hemostasis disturbances. Blood plasma overall hemostatic potential (OHP) is considered to be one of the informative biochemical markers of hemostasis. It is helpful in determining the balance between links of blood coagulation and fibrinolysis and is based on the study of light absorption time curve, being an index of formation and destruction of blood clot in the presence of thromboplastin and plasminogen tissue activator (t-PA). The aim of research work was to study coagulation and fibrinolytic activity indices in patients with IHD and PCA, and to determine probable markers of intravascular thrombogenesis. 91 patients (77 males and 14 females) with IHD and PCA were studied, 32 had late restenosis/thrombosis development after 6 months of stenting. Among those with no history of stent occlusion (59 individuals), 20 patients had FC ²²-²²² angina pectoris. Blood plasma hemostatic potential was determined by spectrophotometry, registering light absorption at 405 nm by fibrin clot, using microreader Multiscan (Finland). Statistical analysis was performed using variation methods and correlation analysis. Quantitative analysis of the curves of OHP and fibrinolytic potential (FP) as well as their components, obtained during the study, demonstrated all the patients of general group to have significant (ð 0.1). Determination of correlation relationships between the main components of OHP and FP in patient groups showed their one-direction positive character from moderate to strong (r=0.56?0.83). The strongest correlations between the parameters were observed in patients with angina, while the weakest ones in those with history of restenosis. Significant increase in OHP and FP indices can be indicative of disturbed balance between the processes of blood coagulation and fibrinolysis in that category of patients. The data received indicate also that activity of hemostasis components is higher in females than in males, and coagulation system potential tends to increase in the group of patients with history of restenosis and in those with angina because of decreased FP value