Search results for "binding site"

Sex differences in GABAA receptor binding in rat brain measured by an improved in vitro binding assay.

1990

The distribution of GABAA receptor sites was studied in female and male rat brain by an improved in vitro binding assay using 3H-muscimol and carefully washed membrane fractions. The binding studies revealed a single class of binding sites exhibiting the properties of GABAA receptors. The specific binding of 3H-muscimol was measured in four brain areas: the preoptic brain area, mediobasal hypothalamus, corticomedial amygdala and cerebral cortex. The equilibrium dissociation constants (KD) ranged from 11.2 to 23.3 nM in diestrous females and from 13.1 to 50.4 nM in males, the maximal number of binding sites (Bmax) from 3290 to 10240 fmol/mg protein in females and from 5495 to 17449 fmol/mg p…

Muscarinic inhibition of endogenous noradrenaline release from rabbit isolated trachea: receptor subtype and receptor reserve.

1994

The aim of the present study was to characterize putative muscarine receptors on sympathetic nerve terminals in the rabbit trachea. Release of endogenous noradrenaline from in vitro incubated rabbit trachea was evoked by electrical field stimulation (3 Hz, 540 pulses) and quantified by high performance liquid chromatography with electrochemical detection. The muscarine receptor agonist oxotremorine inhibited the evoked release of noradrenaline completely at 1 mumol/l (EC50: 64 nmol/l). The concentration response curve was very steep (Hill coefficient of 2.3). Scopolamine shifted the concentration response curve of oxotremorine to the right (-log KB 8.48) demonstrating specific, inhibitory m…

Inhibition by Fendiline of the Transient Outward Current in Rat Ventricular Cardiomyocytes

1999

The effects of fendiline on the transient outward current (Ito) were investigated in rat ventricular cardiomyocytes. Extracellularly applied fendiline reduced peak and steady-state current amplitude of Ito; the inactivation of Ito was accelerated by the drug, which reflects onset of block. The described effects were concentration dependent: half-maximal effects were achieved at approximately 3 microM fendiline. Intracellularly applied fendiline (3 microM) did not affect Ito within 5 min. The steady-state current amplitude of Ito was more efficiently suppressed by the drug at 22 +/- 1 degrees C than at 36 +/- 1 degrees C. The recovery of Ito was analyzed by the application of twin depolarizi…

Peripheral benzodiazepine binding sites on striated muscles of the rat: Properties and effect of denervation

1985

In order to test the hypothesis that peripheral benzodiazepine binding sites mediate some direct effects of benzodiazepines on striated muscles, the properties of specific 3H-Ro 5-4864 binding to rat biceps and rat diaphragm homogenates were investigated. In both tissues a single population of sites was found with a KD value of 3 nmol/l. The density of these sites in both muscles was higher than the density in rat brain, but was considerably lower than in rat kidney. Competition experiments indicate a substrate specificity of specific 3H-Ro 5-4864 binding similar to the properties already demonstrated for the specific binding of this ligand to peripheral benzodiazepine binding sites in many…

Correlation between the effects of retinoic acid and dexamethasone on liver tyrosine aminotransferase

1997

A single dose of 50 microg of trans-retinoic acid administered to rats significantly raised the level of hepatic tyrosine after a few hours. This effect was compared with that of dexamethasone and a possible correlation between these effectors was also investigated. An equal increase in enzyme activity level caused by retinoic acid was observed in adrenalectomized rats, leading to the suggestion that the effect of retinoic acid on liver tyrosine aminotransferase is independent of glucocorticoids. However, the study of the binding activity of the liver nuclear glucocorticoid receptors vs dexamethasone showed that this activity is favoured by retinoic acid, whereas no variation was evidenced …

Binding of urate and caffeine to hemocyanin of the lobster Homarus vulgaris (E.) as studied by isothermal titration calorimetry.

2000

Hemocyanin serves as an oxygen carrier in the hemolymph of the European lobster Homarus vulgaris. The oxygen binding behavior of the pigment is modulated by metabolic effectors such as lactate and urate. Urate and caffeine binding to 12-meric hemocyanin (H. vulgaris) was studied using isothermal titration calorimetry (ITC). Binding isotherms were determined for fully oxygenated hemocyanin between pH 7.55 and 8.15. No pH dependence of the binding parameters could be found for either effector. Since the magnitude of the Bohr effect depends on the urate concentration, the absence of any pH dependence of urate and caffeine binding to oxygenated hemocyanin suggests two conformations of the pigme…

Binding site of different tannins on a human salivary proline-rich protein evidenced by dissociative photoionization tandem mass spectrometry

2015

Abstract The sensation of astringency is thought to originate from the interaction occurring between tannins and the salivary proline-rich proteins (PRPs). Astringency perception can be modified by the structure of tannins. Herein, we study the interactions occurring between the human salivary PRP, IB5, and three model tannins with different structure, epigallocatechin gallate and the procyanidin dimers B2 and B2 3′ O -gallate, using the coupling of mass spectrometry and VUV-synchrotron radiation. The results obtained indicate that the structure of tannins, in particular the degree of polymerization and the galloylation, does not modify the binding site on IB5 involved in the interaction.

Influence of Binding-Site Density in Wet Bioadhesion

2008

A comparison of 3 H-cocaine binding on melanin granules and human hair in vitro

1997

The in vitro experiments on the interaction of 3H-cocaine and melanin from Sepia officinalis confirmed the existence of drug binding sites on melanin granules. The results suggested that the binding of 3H-cocaine to melanin could be analyzed by assuming that the binding to the surface of pigment granules is analogous to the adsorption of a drug on a solid and follows Langmuir adsorption isotherm type I. Scatchard analysis indicated heterogeneity of binding sites. Structural and chemical alterations caused by isolation of the melanoproteins, which are heterogeneous in nature and show different physico-chemical properties, are considered to be most crucial. The studies on hair samples confirm…

Structure-Guided, Single-Point Modifications in the Phosphinic Dipeptide Structure Yield Highly Potent and Selective Inhibitors of Neutral Aminopepti…

2014

Seven crystal structures of alanyl aminopeptidase from Neisseria meningitides (the etiological agent of meningitis, NmAPN) complexed with organophosphorus compounds were resolved to determine the optimal inhibitor–enzyme interactions. The enantiomeric phosphonic acid analogs of Leu and hPhe, which correspond to the P1 amino acid residues of well-processed substrates, were used to assess the impact of the absolute configuration and the stereospecific hydrogen bond network formed between the aminophosphonate polar head and the active site residues on the binding affinity. For the hPhe analog, an imperfect stereochemical complementarity could be overcome by incorporating an appropriate P1 side…