Search results for "binding site"
showing 10 items of 856 documents
Water Structure Recovery in Chaotropic Anion Recognition: High-Affinity Binding of Dodecaborate Clusters to γ-Cyclodextrin
2015
Dodecaborate anions of the type B12X12(2-) and B12X11Y(2-) (X=H, Cl, Br, I and Y=OH, SH, NH3(+), NR3(+)) form strong (K(a) up to 10(6) L mol(-1), for B12Br12(2-)) inclusion complexes with γ-cyclodextrin (γ-CD). The micromolar affinities reached are the highest known for this native CD. The complexation exhibits highly negative enthalpies (up to -25 kcal mol(-1)) and entropies (TΔS up to -18.4 kcal mol(-1), both for B12I12(2-)), which position these guests at the bottom end of the well-known enthalpy-entropy correlation for CDs. The high driving force can be traced back to a chaotropic effect, according to which chaotropic anions have an intrinsic affinity to hydrophobic cavities in aqueous …
Polyfunctional recognition of pyridinedicarboxylate anions with macrocyclic polyamine receptors containing heteroaromatic groups.
2008
The interaction of the biologically relevant anions deriving from the six pyridinedicarboxylic acids (H2PDC) with two macrocyclic receptors containing a pentamine chain and a bipyridine (1) or a phenanthroline (2) moiety, as well as with the aliphatic analogue [21]aneN7 (3), was studied by means of spectroscopic methods (UV-vis, NMR) and potentiometric titrations affording the stability constants of the adducts formed. All three receptors form stable complexes with the substrates thanks to the formation of several salt bridges and hydrogen bond contacts, as observed in the crystal structure of the H8[3(2,6-PDC)4] x H2O x 0.5 EtOH solid compound. Additional pi-stacking interactions between t…
Anion Recognition by a Bioactive Diureidodecalin Anionophore: Solid-State, Solution, and Computational Studies
2018
Recent work has identified a bis-(p-nitrophenyl)ureidodecalin anion carrier as a promising candidate for biomedical applications, showing good activity for chloride transport in cells yet almost no cytotoxicity. To underpin further development of this and related compounds, a detailed structural and binding investigation is reported. Crystal structures of the transporter as five solvates confirm the diaxial positioning of urea groups while revealing a degree of conformational flexibility. Structures of complexes with Cl−, Br−, NO3 −, SO4 2− and AcO−, supported by computational studies, show how the binding site can adapt to accommodate these anions. 1H NMR binding studies revealed exception…
Polyclonal antibodies to mannan from yeast also recognize the carbohydrate structure of gp120 of the AIDS virus: an approach to raise neutralizing an…
1990
This study initiates a new method of developing an antigen which might be useful in the prevention of HIV-1 infection. Using a mannan preparation from Saccharomyces cerevisiae neutralizing antiserum was raised in rabbits which prevents HIV-1 infection in vitro up to a titre of 1:128. The corresponding antibody preparation neutralized the in vitro infectivity down to a concentration of 5 micrograms/ml. Analytical studies suggest that the antibodies are directed against the mannose residues of the HIV-1 glycoprotein (gp) 120 and its precursor gp 160.
Synthesis and characterization of complexes of trialkyl- and triarylphosphine gold(I) with thiolated purines and pyrimidines. A class of bifunctional…
1991
Abstract New complexes of the type R 3 PAuL or (R 3 PAu) 2 (μ-L) where R=ethyl or phenyl and L=6-thioguanine, 2, 6- dithioxanthine, 2, 4-dithiouracil and/or dithioerythritol have been prepared. These complexes have been identified by using elemental analysis, 1 H, 13 C and 31 P NMR spectroscopy. The structures have been proposed based on these spectroscopic studies. Sulfur appears to be the binding site in disubstituted complexes of 2, 4-dithiouracil and 1, 4-dithioerythritol, while the phosphine gold( I ) moieties appear to be S and N bonded in 2, 6-dithioxanthine and 6-thioguanine. The potential use of these complexes as antitumor drugs is discussed.
Mechanism of vascular relaxation by thaligrisine
2000
Abstract In the present study we examine the mechanism by which thaligrisine, a bisbenzyltetrahydroisoquinoline alkaloid, inhibits the contractile response of vascular smooth muscle. The work includes functional studies on rat isolated aorta and tail artery precontracted with noradrenaline or KCl. In other experiments rat aorta was precontracted by caffeine in the presence or absence of extracellular Ca 2 +. In order to assess whether thaligrisine interacts directly with calcium channel binding sites or with α-adrenoceptors we examined the effect of the alkaloid on [ 3 H]-(+)- cis diltiazem, [ 3 H]-nitrendipine and [ 3 H]-prazosin binding to cerebral cortical membranes. The functional studi…
Azapropazone binding to human serum albumin
1980
Azapropazone, a new non-steroidal antiinflammatory drug, is strongly bound to human serum albumin. As revealed by Scatchard analysis, one high-affinity binding site with an association constant of about 1.2 x 10(6)M-1 and two low-affinity binding sites with association constants of about 0.05 x 10(6)M-1 were found. While the high-affinity binding site of azapropazone is clearly not identical with the diazepam or digitoxin binding sites of human serum albumin, contradictory evidence was found by optical measurements and displacement studies for the similarity of the azapropazone and the warfarin binding site of human serum albumin. At present, it is suggested that both drugs bind to differen…
Vascular Activity of (-)-Anonaine, (-)-Roemerine and (-)-Pukateine, Three Natural 6a(R)-1,2-Methylenedioxyaporphines with Different Affinities for α1…
2004
We have studied the mechanism of action of three 6a( R)-1,2-methylenedioxyaporphines as vasorelaxant compounds. The alkaloids assayed showed different affinities for the three human cloned alpha (1)-adrenoceptor (AR) subtypes stably expressed in rat-1 fibroblasts, showing lower affinity for alpha(1B)-AR with regard to the alpha(1A)- or alpha(1D)-subtypes. These three natural compounds are more potent inhibitors of [ (3)H]-prazosin binding than of [ (3)H]-diltiazem binding to rat cerebral cortical membranes. As all these alkaloids inhibited noradrenaline (NA)-induced [ (3)H]-inositol phosphate formation in cerebral cortex and rat tail artery, they may be safely viewed as alpha (1)-AR antagon…
A possible structural determinant of selectivity of boldine and derivatives for the alpha 1A-adrenoceptor subtype.
1996
1. The selectivity of action of boldine and the related aporphine alkaloids, predicentrine (9-O-methylboldine) and glaucine (2,9-O-dimethylboldine) and alpha 1-adrenoceptor subtypes was studied by examining [3H]-prazosin competition binding in rat cerebral cortex. WB 4101 and benoxathian were used as selective alpha 1A-adrenoceptor antagonists. 2. In the competition experiments [3H]-prazosin (0.2 nM) binding was inhibited by WB 4101 and benoxathian. The inhibition curves displayed shallow slopes which could be subdivided into high and low affinity components (pKi = 9.92 and 8.29 for WB 4101, 9.35 and 7.94 for benoxathian). The two antagonists recognized approximately 37% of the sites with h…
Binding of 11-cis retinaldehyde to the partially purified cellular retinaldehyde binding protein from bovine retinal pigment epithelium.
1987
11-cis retinaldehyde binding analysis was performed on a bovine retinal pigment epithelium preparation of cellular retinaldehyde binding protein (CRALBP), whose purity degree was estimated as 75%. Equilibrium binding studies were carried out measuring the replacement of tritium-labeled with unlabeled 11-cis retinaldehyde at 25 degrees C. Analysis of the experimental data both by a direct curve-fitting procedure utilizing a non linear least square regression analysis and by a conventional Scatchard plot revealed a single non-interacting binding site with an apparent equilibrium constant of 0.9 X 10(-7) M. A binding stoichiometry of approximately 1 mol of 11-cis retinaldehyde/mol of binding p…