The influence of heparin on the reaction between thrombin and plasminogen activator inhibitor-l (PAI-1) has been examined. With a 50-fold excess of PAI-1, the rate constant for the inhibition of thrombin was 458 mol/L"s", which increased to 5,000 mol/L"s" in the presence of 25 pg/mL unfractionated heparin or heparin with low affinity for antithrombin. The effect of low affinity heparin was then...

Protein specific aptamers are highly applicable affinity ligands in different fields of research and clinical applications. They have been developed against various targets, in particular, bio-macromolecules such as proteins. Among human proteins, the coagulation factors are the most attractive targets for aptamer selection and their specific aptamers have valuable characteristics in therapeuti...

Protein-protein interactions are essential in diverse cellular processes including signal transduction. It is not uncommon for protein-protein the transmembrane signaling to exhibit low binding affinities with a dissociation constant μM range or higher. Presumably, membrane proteins can selectively bind their partners via low-affinity because they only diffuse laterally plane and interact withi...

Protein Z is a vitamin K-dependent protein of unknown function present in normal bovine plasma at a concentration of approximately 0.1 microM. Quantitative affinity chromatographic studies using diisopropylphosphoryl (DIP)-thrombin-Affi-Gel 10 as the affinity matrix and free DIP-thrombin as the competitor demonstrated that protein Z interacts with DIP-thrombin with a dissociation constant of 0....

We have studied the ligand-binding reactions of lamprey (Petromyzon marinus and Petromyzon fluviatitis) hemoglobin with O2 and CO in the pH range 9.0 to 5.6 by means of both rapid reaction and equilibrium techniques. All the data can be accurately described by a model in which it is assumed that there are two forms of hemoglobin, a high affinity monomer and a lower affinity dimer, and that the ...

The binding of oxygen by the haemocyanin of the gastropod Lymnaea stagnalis was studied by equilibrium and kinetic methods. The studies were performed under conditions in which the haemocyanin molecule was in the native state. Over the pH range 6.8-7.6, in the presence of 10mM-CaCl2 the haemocyanin bound O2 cooperatively. Over this pH range the haemocyanin molecule displayed a normal Bohr effec...

The binding of human alpha-thrombin (IIa) to fibrin polymer (FnIIp) was studied in the presence and absence of a high affinity 20,300 Mr heparin (H) at pH 7.4, I 0.15, and 23 degrees C. In the absence of heparin, thrombin interacts with a high affinity class of binding sites on fibrin polymer with a dissociation constant of 301 +/- 36 nM in a manner which is independent of the enzyme active sit...

The binding of human cr-thrombin (IIa) to fibrin polymer (FnIIp) was studied in the presence and absence of a high affinity 20,300 M, heparin (H) at pH 7.4,10.15, and 23 “C. In the absence of heparin, thrombin interacts with a high affinity class of binding sites on fibrin polymer with a dissociation constant of 301 f 36 nM in a manner which is independent of the enzyme active site. Studies of ...

We estimated the unliganded opening and closing rate constants of neuromuscular acetylcholine receptor-channels (AChRs) having mutations that increased the gating equilibrium constant. For some mutant combinations, spontaneous openings occurred in clusters. For 25 different constructs, the unliganded gating equilibrium constant (E(0)) was correlated with the product of the predicted fold-increa...

Radioiodinated R- and S-Quinuclidinyl derivatives of RS-benzilate (R- and S-125IQNB) have been synthesized for quantitative evaluation of muscarinic acetylcholine receptor binding in vivo. Two sets of experiments were performed in rats. The first involved determining the metabolite-corrected blood concentration and tissue distribution of tracer R-IQNB (active enantiomer) and S-IQNB (inactive en...