Radiation-induced transformations of methanol molecules in low-temperature solids: a matrix isolation study.

The effect of X-ray irradiation on methanol molecules (CHOH, CDOH, and CHOH) isolated in solid noble gas matrices (Ne, Ar, Kr, and Xe) was studied by FTIR spectroscopy at 6 K. CHOH˙, HCO, HCO˙ and CO were found to be the main degradation products. Somewhat unexpectedly, the production of CO is quite prominent, even at low doses, and it strongly predominates in low-polarizable matrices (especially, in neon).

[Effect of nanodispersed manganese oxide (III, IV) on morphological properties of various tissues and body systems].

The study of morphological features of tissue organs of experimental animals after a single intragastric administration of an aqueous suspension nanodis-dispersed manganese (III, IV) at doses of 2000, 3500 and 5000 mg/kg showed complex of morphological changes in the form of circulatory disorders up to hemostasis and bleeding which lead to changes in the structure of organs, enhanced apoptosis, activation of macrophage system by proliferation and macrophage phagocytosis of degradation products of cells, hypertrophy of lymphoid tissue of immune system; development of histiocytic infiltrates in parenchymal organs and central nervous system. With the introduction of microsized analogues in the same doses of the morphological changes in the circulatory system, macrophage system and immune organsfound predominantly in a dose of 5000 mg/kg. Changes were less significant and were presented as activation of macrophages in the liver in the form of activation of Kupffer cells, proliferation of lymphoid tissue in the spleen, lymph histiocytic infiltrates in the liver, kidney, medium size.

Communication: stabilization of radical anions with weakly bound electron in condensed media: a case study of diacetonyl radical anion.

The radical anion resulting from electron capture by diacetonyl molecule has been characterized by EPR and optical absorption spectroscopy in glassy ether matrices at 77 K. In non-polar alkane glasses this species was not observed under the same conditions, which confirms the crucial role of matrix interactions in stabilizing this species. Calculations at the MP2 level show the vertical detachment energy to increase gradually from roughly zero for a bare anion to ∼1 eV for the complex involving six ether molecules.

Inhibitors in hemophilia A: advances in elucidation of inhibitory mechanisms and in inhibitor management with bypassing agents.

Development of inhibitory antibodies (inhibitors) to factor VIII (FVIII) is the most serious adverse event in replacement therapy of hemophilia A patients. The etiology and management of this condition remain major challenges for both researchers and clinicians. In the present review, we discuss recent advances in understanding the molecular mechanisms by which inhibitors inactivate FVIII and experimental approaches used for the mapping of inhibitor epitopes.

Identification of a protein S-interactive site within the A2 domain of the factor VIII heavy chain.

We have recently demonstrated that protein S impairs the intrinsic tenase complex, independent of activated protein C, in competitive interactions between the A2 and A3 domains of factor VIIIa and factor IXa. In the present study, we have identified a protein S-interactive site in the A2 domain of factor VIIIa. Anti-A2 monoclonal antibody recognising a factor IXa-functional region (residues 484-509) on A2, and synthetic peptide inhibited the A2 binding to protein S by approximately 60% and approximately 70%, respectively, in solid-phase binding assays.

Identification of plasmin-interactive sites in the light chain of factor VIII responsible for proteolytic cleavage at Lys36.

We have recently reported that plasmin likely associates with the factor VIII light chain to proteolyze at Lys36 within the A1 domain. In this study, we determined that the rate of plasmin-catalyzed inactivation on the forms of factor VIIIa containing A1-(1-336) and 1722A3C1C2, reflecting Lys36 cleavage, was reduced by approximately 60%, compared with those containing 1649A3C1C2 and 1690A3C1C2. SDS-PAGE analysis revealed that Lys36 cleavage of factor VIIIa with 1722A3C1C2 was markedly slower than those with 1649A3C1C2 and 1690A3C1C2.

Mechanisms of action of recombinant activated factor VII in the context of tissue factor concentration and distribution.

Supraphysiological concentrations of recombinant activated factor VII (rVIIa, NovoSeven) are used to control bleeding in hemophilia. Current experimental evidence suggests that rVIIa may increase thrombin generation via two pathways: one being tissue factor (TF)-dependent and another being activated platelet-dependent. Contribution of TF to the rVIIa action may justify different administration profiles of rVIIa.

Protein S down-regulates factor Xase activity independent of activated protein C: specific binding of factor VIII(a) to protein S inhibits interactions with factor IXa.

Protein S functions as an activated protein C (APC)-independent anticoagulant in the inhibition of intrinsic factor X activation, although the precise mechanisms remain to be fully investigated. In the present study, protein S diminished factor VIIIa/factor IXa-dependent factor X activation, independent of APC, in a functional Xa generation assay. The presence of protein S resulted in an c.

Interaction of coagulation factor VIII with members of the low-density lipoprotein receptor family follows common mechanism and involves consensus residues within the A2 binding site 484-509.

Coagulation factor VIII interacts with several members of the low-density lipoprotein receptor family including low-density lipoprotein receptor-related protein, low-density lipoprotein receptor, and very low-density lipoprotein receptor. The present study was aimed to compare the mechanisms of factor VIII interaction with low-density lipoprotein receptor-related protein, megalin, low-density lipoprotein receptor, and very low-density lipoprotein receptor in order to reveal a general mode of these interactions. Binding of plasma-derived factor VIII and its fragments to recombinant soluble ligand-binding domain of low-density lipoprotein receptor (sLDLR1-7) and purified megalin was studied in solid phase and surface plasmon resonance assays.

Identification of a plasmin-interactive site within the A2 domain of the factor VIII heavy chain.

Factor VIII is activated and inactivated by plasmin by limited proteolysis. In our one-stage clotting assay, these plasmin-catalyzed reactions were inhibited by the addition of isolated factor VIII A2 subunits and by Glu-Gly-Arg-active-site modified factor IXa. SDS-PAGE analysis showed that an anti-A2 monoclonal antibody, recognizing the factor IXa-interactive site (residues 484-509), blocked the plasmin-catalyzed cleavage at Arg(336) and Arg(372) but not at Arg(740).

The binding sites for the very low density lipoprotein receptor and low-density lipoprotein receptor-related protein are shared within coagulation factor VIII.

Coagulation factor VIII (FVIII) is a ligand for two members of the low-density lipoprotein receptor family, low-density lipoprotein receptor-related protein (LRP) and low-density lipoprotein receptor, which cooperate in regulating clearance of FVIII from the circulation. This study was aimed to explore the mechanism of interaction of FVIII with very low density lipoprotein receptor (VLDLR), another member of the family, and map receptor-binding sites. Binding of plasma-derived FVIII and its fragments to recombinant soluble ectodomain of VLDLR (sVLDLR) was studied in solid-phase and surface plasmon resonance assays.

Efficient factor VIII affinity purification using a small synthetic ligand.

Background: Hemophilia A is currently treated by infusions of the coagulation factor (F) VIII, of which production and purification remain a challenging task. Current purification procedures using immunoaffinity chromatography are cumbersome, expensive, and suffer from the instability of the applied antibody ligands, which elute along with the product and contaminate it. Recently, FVIII was purified using octapeptide ligands, but their use is limited due to the low resistance to proteases.

Factor VIII bypasses CD91/LRP for endocytosis by dendritic cells leading to T-cell activation.

Background: The development of factor VIII (FVIII) inhibitors remains the major hurdle in the clinical management of patients with hemophilia A. FVIII uptake by professional antigen-presenting cells (APC) is the first step involved in initiation of immune responses to FVIII. Studies on FVIII catabolism have highlighted the role played by CD91/LRP as a potential target for increasing FVIII half-life in patients and prolonging treatment efficiency.

Identification of a thrombin-interactive site within the FVIII A2 domain that is responsible for the cleavage at Arg372.

FVIII is activated by cleavage at Arg(372), Arg(740), and Arg(1689) by thrombin. This study showed that an anti-A2 monoclonal antibody, with a specific epitope for residues 484-509, and anti-FVIII inhibitor alloantibodies with similar A2 epitopes, inhibited thrombin-catalyzed FVIII activation. Sodium dodecyl sulphate polyacrylamide gel electrophoresis analysis showed that cleavage at Arg(372) but not at Arg(740) occurred at approximately fourfold decreased rate in the presence of anti-A2 antibody.

Localization of the low-density lipoprotein receptor-related protein regions involved in binding to the A2 domain of coagulation factor VIII.

Catabolism of coagulation factor VIII (FVIII) is mediated by low-density lipoprotein receptor-related protein (LRP). The ligand-binding sites of LRP are formed by complement-type repeats (CR), and CR clusters II and IV bind most of LRP ligands. FVIII contains two major LRP-binding sites located in the A2 and A3 domains.

Development of a peptidomimetic ligand for efficient isolation and purification of factor VIII via affinity chromatography.

Hemophilia A, one of the most severe bleeding disorders, results from an inherited deficiency of factor VIII (FVIII) function. Treatment by injection of FVIII has been a common procedure for decades. Nevertheless, the production and purification of FVIII remains a challenging task.

Mathematical models of blood coagulation and platelet adhesion: clinical applications.

At present, computer-assisted molecular modeling and virtual screening have become effective and widely-used tools for drug design. However, a prerequisite for design and synthesis of a therapeutic agent is determination of a correct target in the metabolic system, which should be either inhibited or stimulated. Solution of this extremely complicated problem can also be assisted by computational methods.

Catalytic IgG from patients with hemophilia A inactivate therapeutic factor VIII.

Factor VIII (FVIII) inhibitors are anti-FVIII IgG that arise in up to 50% of the patients with hemophilia A, upon therapeutic administration of exogenous FVIII. Factor VIII inhibitors neutralize the activity of the administered FVIII by sterically hindering its interaction with molecules of the coagulation cascade, or by forming immune complexes with FVIII and accelerating its clearance from the circulation. We have shown previously that a subset of anti-factor VIII IgG hydrolyzes FVIII.

Role of the B domain in proteolytic inactivation of activated coagulation factor VIII by activated protein C and activated factor X.

Hereditary deficiency of factor VIII (FVIII), haemophilia A, is treated by plasma-derived FVIII (pd-FVIII) or recombinant FVIII (rFVIII) infusions. B-domain-deleted FVIII (BDD-rFVIII), although generally safe and effective, was less effective than pd-FVIII in prophylaxis -- evidenced by a 2.5-fold higher bleeding incidence.

Factor V C2 domain contains a major thrombin-binding site responsible for thrombin-catalyzed factor V activation.

Factor (F)V is converted into its active form, FVa, by limited proteolysis. Thrombin-catalyzed activation of FV is essential for its full cofactor activation. Previously, we reported that thrombin was bound to the C2 domain in the light chain of FVIII.

Strategies towards a longer acting factor VIII.

The reduced mortality, improved joint outcomes and enhanced quality of life, which have been witnessed in the developed world for patients with haemophilia, have been an outstanding achievement. Advancements in biotechnology contributed significantly through the development of improved pathogen screening, viral inactivation techniques and the development of recombinant clotting factors. These were partnered with enhanced delivery of care through comprehensive haemophilia centres, adoption of home therapy and most recently effective prophylaxis.