Three different heparin-catalyzed inhibitor/protease reactions were studied: antithrombin III/thrombin, heparin cofactor II/thrombin, antithrombin III/factor Xa. The three reactions were saturable with respect to both inhibitor and protease. The initial reaction velocity, for each reaction, could be described by the general rate equation for a random-order bireactant enzyme-catalyzed reaction. ...

The binding affinity to hemoglobin of 2 ,J-bisphosphoglycerate, ATP, and some other phosphorylated red cell metabolites has been measured at pH 7.2 in 0.12 M KC1 to simulate physiological conditions. The dissociation constant with 2,3-bisphosphoglycerate is independent of hemoglobin concentration in the range 0.06 to 4 mM. There is one binding site per deoxyhemoglobin tetramer. Phosphorylated c...

Recently we found that Ca2+ within chromaffin vesicles is largely bound [Bulenda, D., & Gratzl, M. (1985) Biochemistry 24, 7760-7765]. In order to explore the nature of these bonds, we analyzed the binding of Ca2+ to the vesicle matrix proteins as well as to ATP, the main nucleotide present in these vesicles. The dissociation constant at pH 7 is 50 microM (number of binding sites, n = 180 nmol/...

Lipid metabolites, free fatty acids and lysophospholipids, modify the function of membrane proteins including ion channels. Such alterations can occur through signal transduction pathways, but may also result from "direct" effects of the metabolite on the protein. To investigate possible mechanisms for such direct effects, we examined the alterations of gramicidin channel function by lysophosph...

Bovine retinal vessels have sites that specifically bind 3H-p-aminoclonidine (3H-PAC) with an apparent dissociation constant of 0.12 nM and a capacity of binding of 0.15 pmol/g. In addition, these vessels have 3H-prazosin binding sites bearing a dissociation constant of 5 nM and a binding capacity of 5 pmol/g. To understand the implications for retina-optic nerve vascular physiology and pathoph...

In this study, the direct determination of cefixime as an anti-bacterial agent, in pharmaceutical formulations, urine and human blood plasma was conducted based on spectrophotometric measurements using parallel factor analysis (PARAFAC) and partial least squares (PLS). The calibration set was composed of fourteen solutions in the range of 0.50- 9.00 µg mL-1. PLS models were calculated at each p...

A trivalent derivative of vancomycin, tris(vancomycin carboxamide), [C6H3-1,3,5-(CONHC6H4-4CH2NHCOV)3 (RtV3; V ) vancomycin)], binds an analogous trivalent derivative of D-Ala-D-Ala, R′tL′3, (C6H31,3,5-[CON H(N-Ac)-L-Lys-D-Ala-D-Ala]3) in water with a dissociation constant that is approximately 4 × 10-17 M, as estimated by HPLC using a competitive assay against NR, -diacetyl-L-Lys-D-Ala-D-Ala (...

Human hemoglobin has been studied in parallel experiments on structure and function. Structure has been examined in terms of the extent of dissociation into subunits in very dilute solutions by sedimentation velocity and equilibrium experiments with a scanning ultracentrifuge. Functional properties of the hemoglobin solutions have been evaluated by two rapid kinetic approaches, stopped flow mix...