High Binding Selectivity Research Articles

Design and synthesis of a piperazinylalkylisoxazole library for subtype selective dopamine receptor ligands

A piperazinylbutylisoxazole libary was designed, synthesized and screened for the binding affinities to dopamine D 2, D 3, and D 4 receptors. Several ligands were identified to possess high binding affinity and selectivity for the D 3 and D 4 receptors over the D 2 receptor. Compounds 6s and 6t showed K i values of 2.6 nM and 3.9 nM for the D 3 receptor with 46- and 50-fold selectivity over the D 2 receptor, respectively.

3-Heteroaryl-2-pyridones: benzodiazepine site ligands with functional delectivity for alpha 2/alpha 3-subtypes of human GABA(A) receptor-ion channels.

A novel series of 3-heteroaryl-5,6-bis(aryl)-1-methyl-2-pyridones were developed with high affinity for the benzodiazepine (BZ) binding site of human gamma-aminobutyric acid (GABA(A)) receptor ion channels, low binding selectivity for alpha 2- and/or alpha 3- over alpha 1-containing GABA(A) receptor subtypes and high binding selectivity over alpha 5 subtypes. High affinity appeared to be associated with a coplanar conformation of the pyridone and sulfur-containing 3-heteroaryl rings resulting from an attractive S.O intramolecular interaction. Functional selectivity (i.e., selective efficacy) for alpha 2 and/or alpha 3 GABA(A) receptor subtypes over alpha1 was observed in several of these compounds in electrophysiological assays. Furthermore, an alpha 3 subtype selective inverse agonist was proconvulsant and anxiogenic in rodents while an alpha 2/alpha 3 subtype selective partial agonist was anticonvulsant and anxiolytic, supporting the hypothesis that subtype selective BZ site agonists may provide new anxiolytic therapies.

Molecular Recognition Studies on Supramolecular Systems. Part 38. Inclusion Complexation of Organic Dyes by Organoselenium Bridged Bis(β-cyclodextrin)s with a Short Linker

In order to further explore the inclusion complexation behavior with β-cyclodextrin dimers, the binding constants (KS) of three organoselenium bridged bis(β-cyclodextrin)s (2ndash;4) tethered with a short linker were determined with some representative dye molecules in aqueous phosphate buffer solution (pH 7.20) at 25 °C by fluorescence and UV-vis spectrometry. As compared with the parent β-cyclodextrin (1), the bridged bis(β-cyclodextrin)s (2ndash;4) can not only significantly enhance the original binding affinity of the parent β-cyclodextrin by the cooperative binding of one guest molecule in the closely located two β-cyclodextrin cavities but also remarkably extend its molecular recognition abilities towards the different size/shape or substituent of model substrates. The higher binding ability and selectivity of dye molecules by bridged bis(β-cyclodextrin)s (2ndash;4) are discussed from the viewpointof the size/shape-fit concept and multiple recognition mechanism.

Evaluation of the origins of the selectivity of polymers imprinted with a HIV protease inhibitor using infrared spectroscopy and high performance liquid chromatography.

This work investigates the origins of enantioselectivity of polymers imprinted with the HIV protease inhibitor, Indinavir. For the preparation of imprints of the drug, the critical interactions between the functional monomer, methacrylic acid, and Indinavir were characterized by infrared (IR) spectroscopy to explore the optimum functional monomer concentration for the polymerization. It was shown that a polymer with high selectivity and minimum non-selective binding for Indinavir was obtained when prepared with enough functional monomer to hydrogen bond with all of the functional groups of the drug without using an excess of monomer. This observation is explained in terms of a balance that is achieved in the monomer-template equilibrium during the polymerization that yields a polymer with highly selective sites and minimal non-selective sites. This paper further demonstrates that IR spectroscopy can be a valuable tool in the design and syntheses of molecular imprinted polymers.

Triplex formation involving 2',4'-BNA with 2-pyridone base analogue: Efficient and selective recognition of C:G interruption

We examined the thermodynamic properties of 2',4'-bridged nucleic acid containing 2-pyridone as a nucleobase (PB) to recognize a C interruption in the homopurine strand of the target duplex for pyrimidine motif triplex formation at neutral pH. The triplex formation involving triplex-forming oligonucleotide with PB is highly sequence-selective to specifically recognize C:G target base pair rather than the other G:C, T:A, or A:T base pairs. PB.C:G triad gives significantly larger binding constant than T.C:G triad, which has been known to be the most stable combination in natural base.C:G triad. Our results certainly support the idea that PB could be a key nucleoside to recognize a C interruption in the homopurine strand of the target duplex with high binding affinity and selectivity, and reduce the restriction of target sequences for triplex formation.

N-[3-(2-Dimethylaminoethyl)-2-methyl-1H- indol-5-yl]-4-fluorobenzamide: a potent, selective, and orally active 5-HT(1F) receptor agonist potentially useful for migraine therapy.

Recent studies have demonstrated that selective 5-HT(1F) receptor agonists inhibit neurogenic dural inflammation, a model of migraine headache, indicating that these compounds may be effective therapies for the treatment of migraine pain. This communication describes the synthesis and discovery of a novel compound, N-[3-(2-(dimethylamino)ethyl)-2-methyl-1H-indol-5-yl]-4-fluorobenzamide (4), which possesses high binding affinity and selectivity at the 5-HT(1F) receptor relative to more than 40 other serotonergic and nonserotonergic receptors examined.

Caffeine selectivity of divinylbenzene crosslinked polymers in aqueous media

AbstractThe selective binding of caffeine to polymers is of interest in developing caffeine‐specific sensors. The influence of the nature and quantity of crosslinking agents and functional monomers on the selectivity and binding affinity of a polymer to caffeine is reported. A high binding affinity and selectivity of divinylbenzene (DVB) crosslinked polymers toward caffeine was exhibited by the binding competition of caffeine with several dimethylated and chlorinated xanthines and N‐methylated uric acids in aqueous media. To understand the nature of the caffeine–polymer interaction, we performed binding studies with solvents of different polarities and ionic strengths. The binding properties of DVB‐based polymers containing different functional monomers were compared with Amberlite® XAD resins. Analytes with hydrophilic and electron‐withdrawing groups lowered their binding affinity with the polymer in comparison with caffeine and its dimethylated derivatives. The caffeine–polymer interaction appeared to be predominantly a hydrophobic π–π interaction but partly due to the presence of caffeine‐specific sites. The reversibility of the caffeine–polymer binding was investigated, and the dissociation constants were approximated to be 27 and 6 mM. Dipole moments of caffeine and related molecules were estimated theoretically and were correlated with their corresponding B/T ratio, which is defined as the fraction of caffeine bound to the polymer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 195–205, 2001

Serotonin receptor and transporter ligands - current status.

The serotonin (5-HT) receptor system has 14 different subtypes classified by pharmacology and function. Many ligands are widely used for therapeutic and diagnostic purposes in some severe human diseases. Most of the ligands that are specific for each 5-HT receptor have distinctive chemical structures with regard to pharmacophore elements including 4-arylpiperazine, benzimidazole, benzamide, chroman, aminopyridazine, tetralin, and polycycles. However, their affinity and selectivity for 5-HT, dopamine and alpha1 receptors depend on their substituents and linker spacers. 5-HT transporter inhibitors have also been developed as potential antidepressants. In contrast to classical tricyclic compounds, newly developed secondary amine derivatives such as paroxetine and tetralin show high binding affinity and selectivity. Radioisotope-labeled ligands have also been developed, including [carbonyl-(11)C]WAY 100635 for 5-HT1A receptor, [(11C) or (18)F]ketanserine derivatives for 5-HT(2) receptor, [(125)I]DAIZAC for 5-HT(3) receptor, and [123I]IDAM for 5-HT transporter, and these are accumulated in brain regions that are rich in the respective receptors. This review summarizes the recent development of 5-HT receptor- and transporter-specific ligands and their pharmacological properties on the basis of their chemical structures.

The Mechanism of DNA Cytosine-5 Methylation: KINETIC AND MUTATIONAL DISSECTION OF HhaI METHYLTRANSFERASE

Kinetic and binding studies involving a model DNA cytosine-5-methyltransferase, M.HhaI, and a 37-mer DNA duplex containing a single hemimethylated target site were applied to characterize intermediates on the reaction pathway. Stopped-flow fluorescence studies reveal that cofactor S-adenosyl-l-methionine (AdoMet) and product S-adenosyl-l-homocysteine (AdoHcy) form similar rapidly reversible binary complexes with the enzyme in solution. The M.HhaI.AdoMet complex (k(off) = 22 s(-)1, K(D) = 6 microm) is partially converted into products during isotope-partitioning experiments, suggesting that it is catalytically competent. Chemical formation of the product M.HhaI.(Me)DNA.AdoHcy (k(chem) = 0.26 s(-)1) is followed by a slower decay step (k(off) = 0.045 s(-)1), which is the rate-limiting step in the catalytic cycle (k(cat) = 0.04 s(-)1). Analysis of reaction products shows that the hemimethylated substrate undergoes complete (>95%) conversion into fully methylated product during the initial burst phase, indicating that M.HhaI exerts high binding selectivity toward the target strand. The T250N, T250D, and T250H mutations, which introduce moderate perturbation in the catalytic site, lead to substantially increased K(D)(DNA(ternary)), k(off)(DNA(ternary)), K(M)(AdoMet(ternary)) values but small changes in K(D)(DNA(binary)), K(D)(AdoMet(binary)), k(chem), and k(cat). When the target cytosine is replaced with 5-fluorocytosine, the chemistry step leading to an irreversible covalent M.HhaI.DNA complex is inhibited 400-fold (k(chem)(5FC) = 0.7 x 10(-)3 s(-)1), and the Thr-250 mutations confer further dramatic decrease of the rate of the covalent methylation k(chem). We suggest that activation of the pyrimidine ring via covalent addition at C-6 is a major contributor to the rate of the chemistry step (k(chem)) in the case of cytosine but not 5-fluorocytosine. In contrast to previous reports, our results imply a random substrate binding order mechanism for M.HhaI.

Direct triazine herbicide detection using a self-assembled photosynthetic reaction center from purple bacterium

In this study, a direct detection system for triazine derivative herbicides was developed using the photosynthetic reaction center (RC) from the purple bacterium,Rhodobacter sphaeroides, and surface plasmon resonance (SPR) apparatus. The histidine-tagged RCs were immobilized on an SPR gold chip using nickel-nitrilotriacetic acid groups as a binder for one of the triazine herbicide, atrazine. The SPR responses were proportional to the sample concentrations of atrazine in the range 0.1–1 μg/mL. The sensitivity of the direct detection of atrazine using the RC-assembled sensor chip was higher than that using the antibody-immobilized chip. The other types of herbicides, DCMU or MCPP, were not detected with such high sensitivity. The results indicated the high binding selectivity of the RC complex.

Beta-Turned dipeptoids as potent and selective CCK(1) receptor antagonists.

To improve our knowledge of the bioactive conformation of CCK(1) antagonists, we previously described that replacement of the alpha-MeTrp residue of dipeptoids with the (2S,5S, 11bR)-2-amino-3-oxohexahydroindolizino[8,7-b]indole-5-carbox ylate (IBTM) skeleton, a probed type II' beta-turn mimetic, led to restricted analogues (2S,5S,11bR,1'S)- and (2S,5S,11bR, 1'R)-2-(benzyloxycarbonyl)amino-5-[1'-benzyl-2'-(carboxy)ethyl]carbam oyl-3-oxo-2,3,5,6,11,11b-hexahydro-1H-indolizino[8,7-b]indole, 1a,b, showing high binding affinity and selectivity for CCK(1) receptors. In this report, we describe the synthesis and binding profile of new analogues of compounds 1 designed to explore the importance of the C-terminal residue and of the type of beta-turn on the receptor binding affinity and selectivity. Structure-affinity relationship studies show that a C-terminal free carboxylic acid and an S configuration of the Phe and betaHph residues are favorable for CCK(1) receptor recognition. Moreover, selectivity for this receptor subtype is critically affected by the beta-turn type. Thus, while compounds 15a and 16a, containing the (2S,5S,11bR)- and (2R,5R, 11bS)-IBTM frameworks, respectively, are both endowed with nanomolar affinity for CCK(1) receptors, restricted dipeptoid derivative 15a, incorporating the type II' IBTM mimetic, shows approximately 6-fold higher CCK(1) selectivity than analogue 16a, with the type II mimetic. From these results, we propose that the presence of a beta-turn-like conformation within the peptide backbone of dipeptoids could contribute to their bioactive conformation at the CCK(1) receptor subtype. Concerning functional activity, compounds 15a and 16a behave as CCK(1) receptor antagonists.

X-ray studies of recombinant anti-testosterone Fab fragments: the use of PEG 3350 in crystallization.

Recombinant anti-testosterone wild-type Fab fragment and mutant Fab fragments with high binding selectivity developed by protein engineering have been crystallized with and without ligands. Crystals of these Fab fragments were obtained by the vapour-diffusion technique at room temperature using solutions of PEG 3350 with various biological buffers and with a wide pH range. So far, five data sets have been collected from crystals of three Fab-antigen complexes and from two uncomplexed Fab fragments, with resolutions ranging from 2.10 to 3.1 A. Crystallization conditions for Fab fragments were found by using modifications of the low ionic strength PEG 3350 series. Suitable concentrations of PEG 400, MPD and glycerol solutions for use as cryoprotectants in PEG 3350 solutions have been determined. One useful observation was that PEG 3350 is able to work alone as a cryoprotectant. The screening protocol used requires a smaller amount of protein material to achieve auspicious pre-crystals than previously. Results support the claim that PEG 3350 is more suitable for the crystallization of Fab fragments than higher molecular weight PEGs.

Molecular recognition of nucleic monomers by self-assembled films contained polycytidylic acid

Different types of multilayer films fabricated by self-assembled (SA) technique were examined on the binding of different nucleosides and nucleotides from water solutions. They contained polycytidylic acid (poly(C)) as specific sensor molecules. All the nucleosides, 5′mononucleotides and cyclonucleotides studied were found to penetrate into the inner layers of SA-films and bind with poly(C) molecules in the whole volume of the film. The SA-film with polycation cover layer binds negatively charged nucleotides 3–10 times better than neutral nucleosides. This type of film shows the high selectivity of binding of complementary guanylic monomers from the mixtures of nucleotides or nucleosides. The row of monomer binding preference depends on the type of polycation which is presented in the film. SA-film with poly(C) cover layer do not demonstrate any selectivity of nucleotide or nucleoside binding.

Novel 2-phenylimidazo[1,2-a]pyridine derivatives as potent and selective ligands for peripheral benzodiazepine receptors: synthesis, binding affinity, and in vivo studies.

The substituent effects at positions 6 and 8 (compounds 17-31) as well as at the amide nitrogen (compounds 32-40) of a series of 2-phenylimidazo[1,2-a]pyridineacetamides were evaluated at both central (CBR) and peripheral (PBR) benzodiazepine receptors. The structure-activity relationship studies detailed herein indicate the key structural features required for high affinity and selectivity for PBR. Substitution on the imidazopyridine nucleus at position 8 with lipophilic substituents and the presence of one chlorine atom at the para position of the phenyl ring at C(2) are crucial features for high binding affinity and selectivity toward PBR. A small subset of active ligands (i.e., 17, 20, 26, 34, and 35) were evaluated in vitro in Xenopus oocytes expressing cloned human GABA(A) receptors for their effects at CBR and in vivo for their ability to stimulate the synthesis of neurosteroids such as pregnenolone, progesterone, allopregnanolone, and allotetrahydrodeoxycorticosterone (THDOC). Compounds 17, 20, 26, and 34 markedly increased the levels of neuroactive steroids in plasma and cerebral cortex, unlike compound 35.

Highly constrained dipeptoid analogues containing a type II′ β-turn mimic as novel and selective CCK-A receptor ligands

Conformationally constrained dipeptoid analogues containing the type II′ β-turn mimic (2 S,5 S,11b R)-2-amino-3-oxohexahydroindolizino[8,7- b]indole-5-carboxylate framework in place of the α-MeTrp residue, show high binding affinity and selectivity for CCK-A receptors, suggesting that a turn-like conformation could contribute to the bioactive conformation at this CCK receptor subtype.

A Combinatorial Approach to Synthetic Receptors

Antibodies, the workhorses of every living organisms immune system, are characterized by their extraordinarily high binding affinity and selectivity for a particular antigen. Despite numerous efforts to mimic these binding properties in synthetic molecules, chemists have so far not been able to produce adequate synthetic substitutes for antibodies. Problems associated with biodegradability and thermal stability (and also batch-to-batch variability) of (polyclonal) antibodies, however, prompt the quest for more robust and reliable alternatives. Are chemists able to circumvent the long and difficult pathway of biological evolution by making use of the synthetic tools at their disposal? This article summarizes recent activities in the field of combinatorial chemistry that promise more efficient strategies leading towards synthetic receptors with binding properties rivaling those of their natural counterparts.

New iodinated progestins as potential ligands for progesterone receptor imaging in breast cancer. part 2: in vivo pharmacological characterization

On the basis of the observed high selective binding to both the human and rat progesterone receptor (PR) in vitro, three 17α-iodovinyl-substituted nortestosterone derivatives, i.e., the Z-isomer of 17α-iodovinyl-19-nortestosterone ( Z-IVNT; Z-IPG1) and both the stereoisomers of 17α-iodovinyl-18-methyl-11-methylene-19-nortestosterone ( E-and Z-IPG2), were selected for radio-iodination and subsequently evaluated as potential radioligands for PR imaging in human breast cancer. Their target tissue uptake, retention, and uptake selectivity were studied in female rats. The distribution studies revealed that PR-mediated uptake in the uterus and ovaries could only be demonstrated for Z-[ 123I]IPG2. The target tissue uptake selectivity was, however, low, with the highest uterus-to-nontarget tissue uptake ratios observed at 2–4 h postinjection (p.i.), being 4.4, 1.8, and 7.4 for the uterus-to-blood, -fat, and -muscle ratio, respectively. For Z-[ 123I]IPG2, distribution was also studied in dimethylbenzanthracene (DMBA)-induced mammary tumour-bearing rats and in normal rabbits. Mammary tumour uptake of Z-[ 123I]IPG2 in the mammary tumour-bearing rat was also found to be PR-specific. In rabbits, higher selective target tissue uptake of Z-[ 123I]IPG2 was observed than in rats, resulting in uterus-to-blood, -fat, and -muscle ratios of 6.6, 2.2, and 21.3 at 2–4 h p.i., respectively. In conclusion, Z-[ 123I]IPG2, which displayed high binding affinity for both the human and rat PR in vitro, showed specific PR-mediated target tissue uptake in rats and rabbits in vivo, the uptake selectivity being highest in the latter. Because the binding characteristics appeared to vary between species, a pilot study in breast cancer patients may be needed to decide whether Z-[ 123I]IPG2 can be of potential use as PR imaging agent in breast cancer.

25 脳内中枢型IP2受容体高親和性PGの創製と生物活性(口頭発表の部)

25 脳内中枢型IP2受容体高親和性PGの創製と生物活性(口頭発表の部)

Specificity clusters of MUC1-reactive mouse monoclonal antibodies.

The ISOBM TD-4 Workshop antibodies 122-177 were grouped according to their reactivity with: (a) monomeric MUC1 peptide (TAP25); (b) the pentameric tandem repeat peptide (TR-5), both unglycosylated or as their GalNAc-substituted derivatives, and (c) the lactation or tumor-associated glycoforms of MUC1. The antibodies were grouped into nine clusters: Clusters 1-4 comprise those antibodies that bind to MUC1 tandem repeat peptide (monomeric) and define sequential epitopes differentially affected by glycosylation (GalNAc substitution) in the peptide motifs VTSA and GSTA. The ISOBM-163 antibody in cluster 5 defines Tn antigen as a site-specific glycotope within the tandem repeat peptide. The antibodies in clusters 6 and 7A recognize peptide epitopes within the tandem repeats, although these seem to be conformationally dependent on complex glycosylation or on oligomeric peptide repetition. Antibodies in clusters 7B bind to a conformational epitope not related to the tandem repeat peptide or to a carbohydrate epitope (cluster 7BC). Antibodies in cluster 8 showed a high selective binding to tumor-associated epitopes on MUC1 from mammary carcinoma cells. Cluster 9 antibodies were not reactive on any of the tested antigens and may be argued to lack MUC1 specificity. Alternatively, these antibodies could have a carbohydrate specificity not expressed by the MUC1 glycoforms tested in our studies.

Molecular Imprint Membranes Prepared by the Phase Inversion Precipitation Technique. 2. Influence of Coagulation Temperature in the Phase Inversion Process on the Encoding in Polymeric Membranes

Molecular imprinting membranes of theophylline (THO) were prepared by phase inversion with poly(acrylonitrile-co-acrylic acid) (P(AN-co-AA)). The copolymer−dimethyl sulfoxide solution with THO template was coagulated in water at various temperatures. It was found that the decrease of coagulation temperature caused an increase in THO binding to the THO-imprinted sites of the resultant membrane. The results for the 1H-NMR of the membrane before template extraction showed that the template amount in the membrane coagulated at 10 °C is higher than that at 40 °C. The IR analysis of P(AN-co-AA) membranes indicated that the effective binding of THO is due to hydrogen bonds between the THO and OH group of nondimerized carboxylic acid segments. For caffeine, which is structurally close to the THO template, less effective binding to the membranes was obtained. It was discussed that the high binding selectivity of THO solute to the copolymer membrane arises from the formation of the imprinted sites, which consist of...