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Preferential Binding (preferential + binding)
Selected AbstractsCation,, complexes of a bowl-shaped polycyclic aromatic hydrocarbonJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 9 2004Ronald B. M. Ansems Abstract Circumtrindene (1), a C36H12 geodesic polyarene that represents 60% of fullerene-C60, forms cation,, complexes with both silver ion (1·Ag+) and tetramethylammonium ion [(Me)4N+·1] in chloroform solution at room temperature (Ka>20,M,1 for both cations). Preferential binding in the concave pocket of 1 is predicted by DFT calculations for both cations; however, this stereochemical assignment has not yet been confirmed experimentally. Copyright © 2004 John Wiley & Sons, Ltd. [source] Cis -preferential recruitment of duck hepatitis B virus core protein to the RNA/polymerase preassembly complexHEPATOLOGY, Issue 1 2002Fritz von Weizsäcker M.D. Hepadnaviral replication requires the concerted action of the polymerase and core proteins to ensure selective packaging of the RNA pregenome into nucleocapsids. Virus assembly is initiated by cis -preferential binding of polymerase to the encapsidation signal ,, present on pregenomic RNA. Using the duck hepatitis B virus (DHBV) model, we analyzed how core protein is recruited to the RNA/polymerase preassembly complex. Two sets of trans-complementation assays were performed in cotransfected hepatoma cells. First, a replication-competent DHBV construct was tested for its ability to rescue replication of genomes bearing mutations within the core region. Self-packaging of wild-type pregenomes was more efficient than cross-packaging of core-deficient pregenomes, and this bias was strongly enhanced if mutant pregenomes coded for self-assembly,competent, but packaging-deficient, core proteins. Second, the site of wild-type core protein translation, i.e., pregenomic RNA (cis) or separate messenger RNA (trans), was analyzed for its effect on the phenotype of a previously described dominant-negative (DN) DHBV core protein mutant. This mutant forms chimeric nucleocapsids with wild-type core proteins and blocks reverse transcription within most, but not all, mixed particles. Strikingly, suppression of viral DNA synthesis by the mutant increased 100-fold when wild-type core protein was provided in trans. Our results suggest that recruitment of core protein to the DHBV preassembly complex occurs in a cis -preferential manner. This mechanism may account for the leakiness of DN DHBV core protein mutants targeting reverse transcription. [source] Brain region binding of the D2/3 agonist [11C]-(+)-PHNO and the D2/3 antagonist [11C]raclopride in healthy humansHUMAN BRAIN MAPPING, Issue 4 2008Ariel Graff-Guerrero Abstract The D2 receptors exist in either the high- or low-affinity state with respect to agonists, and while agonists bind preferentially to the high-affinity state, antagonists do not distinguish between the two states. [11C]-(+)-PHNO is a PET D2agonist radioligand and therefore provides a preferential measure of the D2high receptors. In contrast, [11C]raclopride is an antagonist radioligand and thus binds with equal affinity to the D2 high- and low-affinity states. The aim was to compare the brain uptake, distribution and binding characteristics between [11C]-(+)-PHNO and [11C]raclopride in volunteers using a within-subject design. Both radioligands accumulated in brain areas rich in D2/D3 -receptors. However, [11C]-(+)-PHNO showed preferential uptake in the ventral striatum and globus pallidus, while [11C]raclopride showed preferential uptake in the dorsal striatum. Mean binding potentials were higher in the putamen (4.3 vs. 2.8) and caudate (3.4 vs 2.1) for [11C]raclopride, equal in the ventral-striatum (3.4 vs. 3.3), and higher in the globus pallidus for [11C]-(+)-PHNO (1.8 vs. 3.3). Moreover [11C]-(+)-PHNO kinetics in the globus pallidus showed a slower washout than other regions. One explanation for the preferential binding of [11C]-(+)-PHNO in the globus pallidus and ventral-striatum could be the presence of a greater proportion of high- vs. low-affinity receptors in these areas. Alternatively, the observed distribution could also be explained by a preferential binding of D3 -over-D2 with [11C]-(+)-PHNO. This differential binding of agonist vs. antagonist radioligand, especially in the critically important region of the limbic striatum/pallidum, offers new avenues to investigate the role of the dopamine system in health and disease. Hum Brain Mapp 2008. © 2007 Wiley-Liss, Inc. [source] The Interaction of Bromide Ions with Graphitic Materials,ADVANCED MATERIALS, Issue 1 2009Apurva Mehta The detailed interactions between hydrated bromine ions and a number of graphene-like surfaces are elucidated for the first time. A common edge site that exhibits preferential binding of bromide is observed for all materials. The local structure around the hydrated bromide in this interaction region is that of the ion binding to a zigzag, convex site on the graphene sheet edge, consistent with predictions of a recent theoretical model. [source] Structural basis for preferential binding of non- ortho -substituted polychlorinated biphenyls by the monoclonal antibody S2B1JOURNAL OF MOLECULAR RECOGNITION, Issue 4 2005Jean-Luc Pellequer Abstract Polychlorinated biphenyls (PCBs) are a family of 209 isomers (congeners) with a wide range of toxic effects. In structural terms, they are of two types: those with and those without chlorines at the ortho positions (2, 2,, 6 and 6,). Only 20 congeners have no ortho chlorines. Three of these are bound by the aryl hydrocarbon receptor and are one to four orders of magnitude more toxic than all others. A monoclonal antibody, S2B1, and its recombinant Fab have high selectivity and nanomolar binding affinities for two of the most toxic non- ortho -chlorinated PCBs, 3,4,3,,4,-tetrachlorobiphenyl and 3,4,3,,4,,5,-pentachlorobiphenyl. To investigate the basis for these properties, we built a three-dimensional structure model of the S2B1 variable fragment (Fv) based on the high-resolution crystallographic structures of antibodies 48G7 and N1G9. Two plausible conformations for the complementarity-determining region (CDR) H3 loop led to two putative PCB-binding pockets with very different shapes (models A and B). Docking studies using molecular mechanics and potentials of mean force (PMF) indicated that model B was most consistent with the selectivity observed for S2B1 in competition ELISAs. The binding site in model B had a deep, narrow pocket between VL and VH, with a slight constriction at the top that opened into a wider pocket between CDRs H1 and H3 on the antibody surface. This binding site resembles those of esterolytic antibodies that bind haptens with phenyl rings. One phenyl ring of the PCB fits into the deep pocket, and the other ring is bound in the shallower one. The bound PCB is surrounded by the side chains of TyrL91, TyrL96 and TrpH98, and it has a ,-cation interaction with ArgL46. The tight fit of the binding pocket around the ortho positions of the bound PCBs indicates that steric hindrance of ortho chlorines in the binding site, rather than induced conformational change of the PCBs, is responsible for the selectivity of S2B1. Copyright © 2005 John Wiley & Sons, Ltd. [source] Nuclear factor-,b activation is associated with glutamate-evoked tissue transglutaminase up-regulation in primary astrocyte culturesJOURNAL OF NEUROSCIENCE RESEARCH, Issue 6 2005Daniela Caccamo Abstract We have previously demonstrated that alterations of cell redox state, evoked by glutamate, are associated with tissue transglutaminase increases in primary astrocyte cultures. Furthermore, glutamate exposure activated the nuclear factor (NF)-,B pathway, and its effects were significantly reduced by antioxidants. Here, we investigated the possible involvement of activated NF-,B pathway in glutamate-evoked tissue transglutaminase up-regulation in primary astrocytes. The presence of DNA binding activity by NF-,B in nuclear extracts of astrocytes, treated for 24 hr with glutamate (500 ,M) or untreated, was assessed by EMSA, using an oligonucleotide probe containing the NF-,B consensus sequence present in the tissue transglutaminase promoter. Supershifting with monoclonal antibodies revealed that activated NF-,B dimer complexes were composed of p50 and p65 subunits. Interestingly, the specific NF-,B inhibitor SN50 (but not its inactive analogue SN50M), when added to cell cultures 30 min prior to glutamate treatment, was able gradually to reduce glutamate-induced NF-,B activation. Western blot analysis confirmed the reduction of the p50 amount in nuclear extracts. Notably, the preincubation with SN50 also diminished glutamate-increased tissue transglutaminase expression, as showed by both RT-PCR and Western blotting. Competition experiments, carried out with an excess of a probe containing the NF-,B consensus sequence present in the ,-light-chain promoter, demonstrated a preferential binding of the tissue transglutaminase specific NF-,B probe in the nuclear extracts of glutamate-treated astrocytes compared with untreated astrocytes. These preliminary data suggest that NF-,B activation, which has been demonstrated to be involved in astrocyte response to glutamate, could also be associated with the molecular pathway leading to glutamate-evoked tissue transglutaminase up-regulation. © 2005 Wiley-Liss, Inc. [source] Behavioural dynamics in the biological control of pests: role of silicon complexesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2008Savita Belwal Abstract The complexes of silicon (IV) with Schiff base ligands (L1H and L2H of isatin derivatives) having a sulfur and oxygen donor system were prepared by the reactions in methanol environment. These were isolated and characterized by elemental analysis, molecular weight determinations and conductance measurements. On the basis of electronic, infrared, 1H, 13C and 29Si NMR spectral studies, trigonal bipyramidal geometry was suggested for the resulting complexes. These data support preferential binding of sulfur and oxygen atom to the silicon atom. The disease resistance activities of the ligands and their corresponding complexes were examined successfully in in vitro and in vivo experiments, against pathogenic fungi and bacteria. Results were quite encouraging and these were compared with the standard pesticides Bavistin and Streptomycin. Copyright © 2008 John Wiley & Sons, Ltd. [source] Stereoselective binding of human serum albuminCHIRALITY, Issue 3 2006Victor Tuan Giam Chuang Abstract Stereoselectivity in binding can have a significant effect on the drug disposition such as first-pass metabolism, metabolic clearance, renal clearance, and protein and tissue binding. Human serum albumin (HSA) is able to stereoselectively bind a great number of various endogenous and exogenous compounds. Various experimental data suggested that the two major drug-binding cavities, namely, site I and site II, do not seem to be the stereoselective binding sites of HSA. Stereoselective binding of HSA under disease conditions such as renal and hepatic diseases was found to be enhanced. In addition, site-to-site displacement of a site II-specific drug by another site II-specific drug was found to be stereoselective, too. Endogenous compounds such as long-chain fatty acids and uremic toxins are likely to cause combined direct and cascade effects that contribute to the preferential binding of a particular drug enantiomer. Taking together the findings of other studies, it is highly possible that the stereoselective binding site exists at the interface of the subdomains. © 2006 Wiley-Liss, Inc. Chirality [source] | |||||||||||||