Rational modulation of N and O binding in Fe(III) complex formation derived from hydroxychloroquine: Synthesis, Spectroscopic, Computational, and Docking Simulation with Human Thrombin Plasma

2021 ◽  
pp. 132268
Author(s):  
Doaa S. El-Sayed ◽  
Hemmat A. El badawy ◽  
Tarek E. Khalil
Keyword(s):  
Complex Formation ◽  
Docking Simulation ◽  
Human Thrombin

scholarly journals Osmotic pressure effects identify dehydration upon cytochrome c–cytochrome c oxidase complex formation contributing to a specific electron pathway formation

2020 ◽  
Vol 477 (8) ◽  
pp. 1565-1578 ◽  
Author(s):  
Wataru Sato ◽  
Seiji Hitaoka ◽  
Takeshi Uchida ◽  
Kyoko Shinzawa-Itoh ◽  
Kazunari Yoshizawa ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Complex Formation ◽  
Osmotic Pressure ◽  
Cytochrome C Oxidase ◽  
Docking Simulation ◽  
Bulk Water ◽  
Pressure Effects ◽  
Hydration Water ◽  
Interaction Sites ◽  
Cyt C

In the electron transfer (ET) reaction from cytochrome c (Cyt c) to cytochrome c oxidase (CcO), we determined the number and sites of the hydration water released from the protein surface upon the formation of the ET complex by evaluating the osmotic pressure dependence of kinetics for the ET from Cyt c to CcO. We identified that ∼20 water molecules were dehydrated in complex formation under turnover conditions, and systematic Cyt c mutations in the interaction site for CcO revealed that nearly half of the released hydration water during the complexation were located around Ile81, one of the hydrophobic amino acid residues near the exposed heme periphery of Cyt c. Such a dehydration dominantly compensates for the entropy decrease due to the association of Cyt c with CcO, resulting in the entropy-driven ET reaction. The energetic analysis of the interprotein interactions in the ET complex predicted by the docking simulation suggested the formation of hydrophobic interaction sites surrounding the exposed heme periphery of Cyt c in the Cyt c–CcO interface (a ‘molecular breakwater'). Such sites would contribute to the formation of the hydrophobic ET pathway from Cyt c to CcO by blocking water access from the bulk water phase.

COMPLEX FORMATION,BETWEEN THROMBIN AND FIBRINOGEN OR FIBRINOGEN DEGRADATION PRODUCTS (FDP)

1987 ◽  
Author(s):  
E Kaczmarek ◽  
J McDonagh
Keyword(s):  
Complex Formation ◽  
Degradation Products ◽  
Amino Acid Residues ◽  
Amino Groups ◽  
Human Fibrinogen ◽  
Reducing Conditions ◽  
Lysine Residues ◽  
Human Thrombin ◽  
Sepharose 4B ◽  
Fibrinogen Molecule

To identify the part of the fibrinogen molecule which interacts with thrombin binding of human thrombin to plasmic FDP was analyzed.125I-thrombin was incubated with FDP, purified fibrinogen fragment D or fragment E in the presence of 0.2% glutaraldehyde. Incubation mixtures were analyzed by SDS-PAGE and autoradiography. Under non-reducing conditions, the autoradiogram from the thrombin and fibrinogen fragment D incubation showed only one dark band, the molecular weight (Mr) of which was identical to that of thrombin, indicating no complex formation between thrombin and fragment D. With thrombin and fibrinogen fragment E, two dark bands were observed: the electrophoretic mobility of the first was the same as that of thrombin and the Mr of the second was equal to the sum of the Mr of thrombin and fragment E. This shows that human thrombin Forms a complex with fibrinogen fragment E. Hence, we can conclude that only the N-terminal part of the fibrinogen molecule is necessary for interaction with thrombin. Under reducing conditions, the complex of thrombin with fragment E produced four bands on gel electrophoresis. One was thrombin; the remaining three were complexes of thrombin with fragment E chain remnants. To investigate this further, carboxymethylated human fibrinogen chains Aα, Bβ and γ were purified and coupled to Sepharose 4B. 125I-thrombin was applied on the three columns. Nearly all radioactivity was bound to the three affinity columns and was eluted with higher NaCl concentration. We can infer that complex formation between thrombin and fibrinogen requires interaction between thrombin and all three fibrinogen chains. To find which thrombin amino acid residues are responsible for interaction with fibrinogen, human thrombin was coupled to Affi-Gel 102 and Affi-Gel 202 through thrombin's carboxyl and amino groups, respectively. We observed binding of fibrinogen and fibrinogen fragment E only to Affi-Gel 102 column, indicating that lysine residues and perhaps the N-terminal of the thrombin molecule interact with fibrinogen. When thrombin was bound to the gel through its amino groups, there was no interaction between thrombin and fibrinogen or fragment E.

Comparative Labelling and Biokinetic Studies of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn)

1977 ◽  
Vol 16 (01) ◽  
pp. 30-35 ◽  
Author(s):  
N. Agha ◽  
R. B. R. Persson
Keyword(s):  
Complex Formation ◽  
Significant Influence ◽  
Room Temperature ◽  
Ph Value ◽  
Maximum Activity ◽  
Reduction Step ◽  
Labelling Yield ◽  
Different Temperatures ◽  
Kinetics Of

SummaryGelchromatography column scanning has been used to study the fractions of 99mTc-pertechnetate, 99mTcchelate and reduced hydrolyzed 99mTc in preparations of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn). The labelling yield of 99mTc-EDTA(Sn) chelate was as high as 90—95% when 100 μmol EDTA · H4 and 0.5 (Amol SnCl2 was incubated with 10 ml 99mTceluate for 30—60 min at room temperature. The study of the influence of the pH-value on the fraction of 99mTc-EDTA shows that pH 2.8—2.9 gave the best labelling yield. In a comparative study of the labelling kinetics of 99mTc-EDTA(Sn) and 99mTc- DTPA(Sn) at different temperatures (7, 22 and 37°C), no significant influence on the reduction step was found. The rate constant for complex formation, however, increased more rapidly with increased temperature for 99mTc-DTPA(Sn). At room temperature only a few minutes was required to achieve a high labelling yield with 99mTc-DTPA(Sn) whereas about 60 min was required for 99mTc-EDTA(Sn). Comparative biokinetic studies in rabbits showed that the maximum activity in kidneys is achieved after 12 min with 99mTc-EDTA(Sn) but already after 6 min with 99mTc-DTPA(Sn). The long-term disappearance of 99mTc-DTPA(Sn) from the kidneys is about five times faster than that for 99mTc-EDTA(Sn).

Inactivation of α- and β-Thrombin by Antithrombin-III and Heparin

1976 ◽  
Vol 36 (03) ◽  
pp. 503-508 ◽  
Author(s):  
Raymund Machovich ◽  
György Blaskó ◽  
Anna Borsodi
Keyword(s):  
Heat Treatment ◽  
Complex Formation ◽  
Blood Circulation ◽  
Antithrombin Iii

SummaryInactivation of α- and β-thrombin by antithrombin-III and heparin was studied, since it had been suggested that two forms of thrombin exist with respect to heparin sensitivity (Machovich 1975b).It was found that the inactivation rates of α- and β-thrombin by antithrombin were different, namely α-thrombin was more sensitive to antithrombin than β-thrombin. Heparin facilitated the complex formation between α-thrombin and antithrombin-III, whereas β-thrombin inactivation was only slightly affected.Furthermore, heparin protected α-thrombin against the inactivating effect of heat, while β-thrombin lost its activity during the heat treatment.These findings suggest that the formation of β-thrombin in blood circulation may have an important role in thrombosis predisposition.

Factor VIII Inhibitor Antibodies with C2 Domain Specificity Are Less inhibitory to Factor VIII Complexed with von Willebrand Factor

1996 ◽  
Vol 76 (05) ◽  
pp. 749-754 ◽  
Author(s):  
Suzuki Suzuki ◽  
Morio Arai ◽  
Kagehiro Amano ◽  
Kazuhiko Kagawa ◽  
Katsuyuki Fukutake
Keyword(s):  
Complex Formation ◽  
Factor Viii ◽  
Von Willebrand Factor ◽  
Domain Specificity ◽  
Factor Viii Inhibitor ◽  
C2 Domain ◽  
Recombinant Fviii ◽  
Von Willebrand ◽  
A2 Domain ◽  
Willebrand Factor

SummaryIn order to clarify the potential role of von Willebrand factor (vWf) in attenuating the inactivation of factor VIII (fVIII) by those antibodies with C2 domain specificity, we investigated a panel of 14 human antibodies to fVIII. Immunoblotting analysis localized light chain (C2 domain) epitopes for four cases, heavy chain (A2 domain) epitopes in five cases, while the remaining five cases were both light and heavy chains. The inhibitor titer was considerably higher for Kogenate, a recombinant fVIII concentrate, than for Haemate P, a fVIII/vWf complex concentrate, in all inhibitor plasmas that had C2 domain specificity. In five inhibitor plasmas with A2 domain specificity and in five with both A2 and C2 domain specificities, Kogenate gave titers similar to or lower than those with Haemate P. The inhibitory effect of IgG of each inhibitor plasma was then compared with recombinant fVIII and its complex with vWf. When compared to the other 10 inhibitor IgGs, IgG concentration, which inhibited 50% of fVIII activity (IC50), was remarkably higher for the fVIII/vWf complex than for fVIII in all the inhibitor IgGs that had C2 domain reactivity. Competition of inhibitor IgG and vWf for fVIII binding was observed in an ELISA system. In 10 inhibitors that had C2 domain reactivity, the dose dependent inhibition of fVIII-vWf complex formation was observed, while, in the group of inhibitors with A2 domain specificity, there was no inhibition of the complex formation except one case. We conclude that a subset of fVIII inhibitors, those that bind to C2 domain determinants, are less inhibitory to fVIII when it is complexed with vWf that binds to overlapping region in the C2 domain.

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