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At least 109 records · Page 6Linked to original sources
PubMed1983

2-(Hydroxyphenyl)indoles: a new class of mammary tumor inhibiting compounds.

1-Alkyl-4-chloro-2-(2,6-dichloro-4-hydroxyphenyl)-6-hydroxyindoles (4, alkyl = CH3, C2H5, C3H7) were synthesized by thermolysis of the corresponding N,N'-dialkyl-1,2-diphenylethylenediamines and subsequent ether cleavage. They showed an affinity for the estrogen receptor (1% of 17 beta-estradiol) and inhibited the growth of the 9,10-dimethyl-1,2-benz[a]anthracene (DMBA) induced mammary carcinoma of the Sprague-Dawley (SD) rat. The best result was obtained by the ethyl compound (4b), which reduced the original tumor area by 50% after 4 weeks administration of 6 X 18 (mg/kg)/week. Since 4a and 4b show uterotrophic activity and cytostatic effects against hormone-independent cells, a dual mode of action has to be considered for the tumor inhibition.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1998

Fluorescent probes for adenosine receptors: synthesis and biology of N6-dansylaminoalkyl-substituted NECA derivatives.

New fluorescent ligands for adenosine receptors are described; these compounds were obtained by the insertion, in the N6 position of NECA (a potent adenosine agonist), of dansylaminoalkyl moieties with alkyl spacers of increasing carbon chain length (from 3 to 12). Among them, the compound with a C6 alkyl spacer proved to be the most interesting one, showing a marked selectivity for the A1 receptor subtype; furthermore, in fluorescence microscopy assays it proved to be able to visualize and localize this receptor subtype at the level of the molecular layer of the rate cerebellar cortex.

Adenosine-5'-(N-ethylcarboxamide)↗
PubMed1980

Effects of phosphonium compounds on Schistosoma mansoni.

A new series of phosphonium salts was examined for effects on the cholinergic nervous system of Schistosoma mansoni. Studies were conducted using both an activity-monitoring and fluorescent-labeling technique. The activity method gave more definitive results, indicating that some poly(methylene)bis(triphenylphosphonium) salts and some [3-(alkylamino)propyl]triphenylphosphonium salts have strong anticholinergic effects. Hexyltriphenylphosphonium bromide has very marked effects both in the motility and the fluorescence test, but these effects cannot immediately be ascribed to cholinergic actions.

Acetylcholine↗
PubMed1979

Determination of L-alanosine in plasma and urine by reversed-phase high-performance liquid chromatography of the Dns derivative.

L-Alanosine is an antitumour antibiotic that has recently been placed in clinical trial. We have developed a relatively rapid and specific assay for urinary and plasma alanosine, based on formation of the Dns derivative and separation of this from other Dns compounds by reversed-phase high-performance liquid chromatography. Dns-Alanosine is detected by its absorption at 254 nm, since alanosine is atypical in that it forms a Dns derivative with very low fluorescence. The lower limit of detection of alanosine in plasma is 0.1 microgram/ml. The assay has been used to measure the levels of alanosine in the plasma and urine of rabbits and of man.

Alanine↗
PubMed1995

Comparison of a novel ETA receptor antagonist and phosphoramidon in renal ischemia.

Infusion (0.46 mumol/kg/min) of the endothelin (ET)-converting-enzyme inhibitor, phosphoramidon (P), protected function and structure after 30 min renal ischemia in rats more than treatment (5 mumol/kg/min) with the ETA receptor antagonist, BMS-182874 (B). The glomerular filtration rate (GFR; 0.7 +/- 0.12 ml/min) and renal plasma flow (RPF) decreased approximately 40% at 2 h reflow versus controls (C: 1.2 +/- 0.12). B weakly protected the GFR (0.8 +/- 0.07 ml/min); P restored it (1.1 +/- 0.05). Both compounds reduced tubular injury at 2 h reflow; P ameliorated glomerular changes. At 24 h the GFR (0.6 +/- 0.06 ml/min) and RPF decreased 67% versus C (1.8 +/- 0.08). B did not protect the GFR and RPF. P partially protected the GFR (0.9 +/- 0.07 ml/min) but not RPF, and reduced tubular injury. The results suggest that both ETA and non-ETA receptors mediate ET-induced changes in ischemic renal failure.

Animals↗
PubMed1992

Fluorescence probes in biochemistry: an examination of the non-fluorescent behavior of dansylamide by photoacoustic calorimetry.

Photoacoustic calorimetry is shown to be a simple, precise, and accurate method for the quantification of the photophysics of a fluorescence probe, e.g., dansylamide, in a variety of solvents. This technique, which is described in detail, provides a direct measurement of the energy that is released nonradiatively following photostimulation, and can therefore be used to indirectly determine the amount of energy released via luminescent pathways. Photoacoustic calorimetry combined with established absorption and fluorescence methodologies provides a complete arsenal for characterizing the photophysical properties of many systems. Comparison of the photoacoustic signal for dansylamide versus standard compounds (ferrocene, tetraphenylethylene, 8-anilinonaphthalene-1-sulfonate, and/or 5,5'-dithiobis(2-nitrobenzoic acid) in 12 different solvents gave fh values (fraction of each absorbed 337.1-nm photon returned as heat) from a low of 0.530 in 1,4-dioxane to a high of 0.973 in water. The trend noted with solvent polarity is different and more revealing than that determined by the more classical approach of examining either the wavelength of the emission maximum or the fluorescence quantum yield.

Calorimetry↗
PubMed1990

Preparation and utilization of fluorescent synthetic peptides.

In this study, several methods for controlled labelling of synthetic peptides by the use of fluorescent compounds (fluorescein isothiocyanate and dimethylaminonaphthalene sulfonyl chloride) were investigated. The first reagent yielded monofluoresceinated, active compounds only when the peptides lacked lysine residues. Monolabelling of peptides in solution with dimethylaminonaphthalenesulphonyl chloride was hindered by the broad reactivity of the reagent, but was achieved by reacting the fluorochrome on protected resin-bound peptides in solid-phase synthesis. The remarkable stability of the linkage allowed the cleavage of the peptide from the resin and deprotection of side-chain functions without hydrolysis of the labelled group. The binding of antipeptide antibodies to the labelled fragments was then estimated using different techniques.

Amino Acid Sequence↗
PubMed1996

Crystal structures of thrombin with thiazole-containing inhibitors: probes of the S1' binding site.

Structures of the blood clotting enzyme thrombin complexed with hirugen and two active site inhibitors, RWJ-50353 10080(N-methyl-D-phenylalanyl-N-[5-[(aminoiminomethyl)amino]-1- [[(2-benzothiazolyl)carbonyl]butyl]-L-prolinamide trifluoroacetate hydrate) and RWJ-50215 (N-[4-(aminoiminomethyl)amino-1-[2- (thiazol-2-ylcarbonylethyl)piperidin- 1-ylcarbonyl]butyl]-5-(dimethylamino)naphthalenesulfonamide trifluoroacetate hydrate), were determined by x-ray crystallography. The refinements converged at R values of 0.158 in the 7.0-2.3-A range for RWJ-50353 and 0.155 in the 7.0-1.8-A range for RWJ-50215. Interactions between the protein and the thiazole rings of the two inhibitors provide new valuable information about the S1' binding site of thrombin. The RWJ-50353 inhibitor consists of an S1'-binding benzothiazole group linked to the D-Phe-Pro-Arg chloromethyl ketone motif. Interactions with the S1-S3 sites are similar to the D-phenylalanyl-prolyl-arginyl chloromethylketone structure. In RWJ-50215, a S1'-binding 2-ketothiazole group was added to the thrombin inhibitor-like framework of dansylarginine N-(3-ethyl-1,5-pentanediyl)amide. The geometry at the S1-S3 sites here is also similar to that of the parent compound. The benzothiazole and 2-ketothiazole groups bind in a cavity surrounded by His57, Tyr60A, Trp60D, and Lys60F. This location of the S1' binding site is consistent with previous structures of thrombin complexes with hirulog-3, CVS-995, and hirutonin-2 and -6. The ring nitrogen of the RWJ-50353 benzothiazole forms a hydrogen bond with His57, and Lys60F reorients because of close contacts. The oxygen and nitrogen of the ketothiazole of RWJ-50215 hydrogen bond with the NZ atom of Lys60F.

Binding Sites↗
PubMed2000

Dipeptide binding to the extended active site of the Streptomyces R61 D-alanyl-D-alanine-peptidase: the path to a specific substrate.

Bacterial cell walls are cross-linked in the final step of biosynthesis by specific D-alanyl-D-alanine(DD)-peptidases/transpeptidases. The natural substrates of these enzymes should therefore be segments of peptidoglycan, but high specificity for such structures has yet to be demonstrated. The binding of dipeptides to the extended substrate binding site of the Streptomyces R61 DD-peptidase has been studied by means of a fluorescent beta-lactam probe. It was found that dipeptides of structure Gly-L-Xaa have affinity for a subsite adjacent to the beta-lactam binding site. Hydrophobic peptides such as Gly-L-Met and Gly-L-aminocaprylic acid had the greatest affinity for this site, with dissociation constants in each case of 0.19 mM. A combination of this motif with the C-terminal D-alanyl-D-alanine moiety required of a DD-peptidase substrate yielded a new substrate, glycyl-L-alpha-amino-epsilon-pimelyl-D-alanyl-D-alanine. Steady-state kinetic measurements established this compound as the most specific peptide substrate yet discovered for a DD-peptidase by at least 3 orders of magnitude (k(cat) = 69 s(-1), K(m) = 7.9 microM, k(cat)/K(m) = 8.7 x 10(6) s(-1) M(-1)); acylation was rate-determining at saturation. This substrate, presumably not coincidentally, contains the acyl donor and acceptor moieties, appropriately separated, of the Streptomyces peptidoglycan structure. This general method of approach should be of value in the search for specific substrates and inhibitors (antibiotics) of other DD-peptidases.

Binding Sites↗
PubMed1972

Induction of immunity and tolerance in vitro by hapten protein conjugates. 3. Hapten inhibition studies of antigen binding to B cells in immunity and tolerance.

The capacity of dissociated spleen cell suspensions to be immunized by dinitrophenylated polymeric flagellin (DNP POL), in the absence of thymus-dependent lymphocytes or macrophages, provided a simple experimental system to investigate the mechanism of binding of antigen molecules to nonthymus-dependent lymphocyte (B cell) receptors during the induction of immunity or tolerance. Various nonimmunogenic DNP compounds were used to inhibit the anti-DNP response to DNP POL. By performing inhibition experiments of brief duration at 4 degrees C, it was established that the inhibition of the anti-DNP response by nonimmunogenic compounds was due to competitive blockade of receptors, and not tolerance or receptor modulation. It was found that univalent DNP compounds were much less efficient inhibitors of the antibody response than multivalent DNP conjugates. The difference in inhibitory capacity between univalent and multivalent DNP human globulin (DNP HgG) suggested the importance of interaction with both combining sites of a single receptor antibody molecule. Nonimmunogenic highly conjugated DNP(3)POL was a more efficient inhibitor of the anti-DNP response to immunogenic DNP(1)POL than DNP(12)HgG, indicating that interactions at more than one receptor molecule are involved in immunization of B cells. Recent demonstrations of the rapid metabolic turnover of receptor antibody molecules suggests that the requirement for multipoint binding (to different receptors) may simply be to maintain the antigen at the cell surface in a dynamic system. Competitive inhibition experiments were also performed to investigate the mechanism of binding of DNP(3)POL in the induction of B cell tolerance. It was found that monovalent DNP compounds or multivalent DNP(12)HgG did not prevent the induction of tolerance, unlike their capacity to inhibit immunity, suggesting that a tolerance-inducing antigen binds more avidly to the cell membrane than an immunogen. The inhibition data obtained here, together with prior results describing the differential immunogenicity of DNP conjugates of different structure, and the importance of epitope density on DNP POL conjugates, permit certain conclusions about the details of antigen-receptor interaction in immunity and tolerance. Distinctions between the mechanisms of immune and tolerance induction are discussed.

Animals↗
PubMedDate not supplied

High performance liquid chromatographic strategy for the analysis of exopolysaccharides extracted from pathogenic bacteria.

A high performance liquid chromatographic (HPLC) method has been developed to permit the rapid comparison of acidic polysaccharides of diverse compositions and the sensitive determination of their constituents. It is based on two combined analyses of the polysaccharide hydrolysates--a separation of the released compounds by ion-moderated partition chromatography with UV detection at two wavelengths and a separation of the sugar dansylhydrazine derivatives by reversed phase chromatography. The former permits identification and quantitation of uronic and carboxylic acids, the latter permits more sensitive and specific determination of the neutral aldoses. Some bacterial exopolysaccharides have been used to demonstrate the validity of this HPLC procedure for the chemical characterization of uronic acid-containing polysaccharides. This method appears to be useful for studying capsular polysaccharides, which are involved in the evasion of phagocytosis by pathogenic bacteria.

Carboxylic Acids↗
PubMed1996

High-performance liquid chromatographic evaluation of biogenic amines in foods. An analysis of different methods of sample preparation in relation to food characteristics.

Biogenic amines are compounds formed by amino acid decarboxylation in fermented foods. Most of the methods for amine determination involve acid extraction followed by a liquid-liquid purification step. The different parameters which can influence amine recoveries are considered; experience with different foods such as cheese, fish and meat preserves are reported and for each of them the optimized analytical procedure is described. Data concerning recovery and repeatability of the method are also reported and the various factors that influence amine extraction are discussed. The possibility of applying direct derivatization without any other purification step is also considered.

Biogenic Amines↗
PubMed1988

Rapid and simple dansylation of phenolic steroids using a two-phase system and phase transfer catalysis.

Dansylation of phenolic steroids was carried out in chloroform-water and hexane-water two-phase systems with a tetrabutylammonium salt as phase transfer catalyst. Derivatization was complete within a few minutes on shaking at room temperature. Direct injection of part of the organic phase into a normal-phase liquid chromatography system was possible. The calibration graph of ethinyl estradiol, dansylated in a chloroform-water two-phase system, was linear over three orders of magnitude with a correlation coefficient of 0.993 (n = 8). The detection limit of dansylated ethinyl estradiol was 100 pg (signal-to-noise ratio = 2). The reproducibility of the derivatization at an analyte concentration of 200 ng/ml in chloroform was 4.1% (relative standard deviation; n = 5). A mechanism is proposed for the phase transfer catalysed dansylation of phenolic compounds.

Catalysis↗
PubMed2000

Contribution of dithiol ligands to in vitro and in vivo trypanocidal activities of dithiaarsanes and investigation of ligand exchange in an aqueous solution.

Twelve new dithiaarsanes were evaluated for their in vitro and in vivo trypanocidal properties in regard to their three parent molecules, 4-amino-phenylarsenoxide, melarsenoxide, and 4-dansylamino-phenylarsenoxide. The most potent dithiaarsane, compound 2b, had a minimum effective concentration of 1.5 nM after 48 h of incubation and at a dose of 0.39 micromol/kg of body weight (0.2 mg/kg) administered subcutaneously cured 100% of mice acutely infected with Trypanosoma brucei brucei CMP. With this model, the chemotherapeutic index of compound 2b was 512, compared to 256 for melarsamine dihydrochloride (Cymelarsan) under the same conditions. With a chronic infection produced by T. brucei brucei GVR, compound 2b cured 100% of mice after treatment at a dose of 25 micromol/kg (12.5 mg/kg) for 4 consecutive days, whereas melarsamine dihydrochloride and potassium melarsonyl (Trimelarsan) cured less than 50% mice at this dose. For both acute and late-stage infections, dithiaarsanes having a melaminophenyl ring exhibited the most-potent trypanocidal activity. Compound 2b is thus one of the most active organoarsenicals described in a mouse trypanosomiasis model. Considering that the main intracellular targets of organoarsenicals are thiol groups, we studied the possibility of ligand exchange between Cymelarsan and several dithiols. In aqueous solution, we observed a rapid exchange of cysteamine from melarsamine with free cysteamine and also with various dithiols always in favor of more stable cyclic derivatives. These ligand exchanges suggest the ability of trivalent organoarsenicals to react with targets such as trypanothione and dihydrolipoic acid. Among several ligands, a 1,3-dimercaptopropane moiety appeared the most suitable for trypanocidal activity.

Animals↗
PubMed2005

High-throughput solution-based medicinal library screening against human serum albumin.

High-throughput screening of combinatorial libraries has evolved from studying large diverse libraries to analyzing small, structurally similar, focused libraries. This paradigm shift has generated a need for rapid screening technologies to screen both diverse and focused libraries in a simple, efficient, and inexpensive manner. We have proactively addressed these needs by developing a high-throughput, solution-based method combining size exclusion (SEC), two-dimensional liquid chromatography (2-D LC), and mass spectrometry (MS) for determining the relative binding of drug candidates in small, focused medicinal libraries against human serum albumin (HSA). Two types of libraries were used to evaluate the performance of the system. The first consisted of five diverse ligands with a wide range of hydrophobicities and whose association constants to HSA cover 3 orders of magnitude. A beta-lactam library composed of structurally similar compounds was used to further confirm the validity of the methodology. The ability to distinguish site-specific interactions of drugs competing for individual domains of the HSA receptor is also demonstrated. Comparison of chromatographic profiles of the library components before and after incubation with the receptor using multiple reaction monitoring allowed a ranking of the ligands according to their relative binding affinities. The observed rankings correlate closely with literature values of the association constants between the respective ligands and HSA. This simple, rugged methodology can screen a wide spectrum of chemical entities from combinatorial mixtures in less than 6 min.

Acecainide↗
PubMed1992

Thieno[2,3-b]furan-2-sulfonamides as topical carbonic anhydrase inhibitors.

Novel 5-[(alkylamino)methyl]thieno[2,3-b]furan-2-sulfonamides were prepared and evaluated in vitro for inhibition of human carbonic anhydrase II (CA II) and ex vivo for their ability to inhibit Ca II in the albino rabbit eye after topical administration. Compound 11a was found to lower intraocular pressure (IOP) in both the alpha-CT ocular hypertensive albino rabbit and the normal albino rabbit, but was ineffective at lowering IOP in a hypertensive, pigmented monkey model. Since 11a was highly bound to ocular pigment, a series of less basic analogs was prepared. Examples in this series were both less extensively bound to ocular pigment and more active at reducing IOP in pigmented rabbits after topical dosing. Key examples displayed moderate reactivity toward glutathione.

Administration, Topical↗
PubMedDate not supplied

Activity of some natural and modified (fluorescent) cyclosporins on T cells.

A simple test system for comparing the proliferation inhibition properties of cyclosporins (Cs) on susceptible T cells is described. This test was applied to a number of natural and chemically altered Cs-compounds, the latter from inactive, hypo-active and hyper-active Cs. These cyclosporins constituted standards for further comparison of the activities of new Cs such as fluorescent derivatives of the molecules, and especially for determining their mechanism of action. The use of Cs-sensitive (CsS) and Cs-resistant (CsR) cell lines permitted the distinction between specific cytostatic and generalized cytotoxic effects. Active--but not inactive--Cs were found to cause the appearance of refractive globular bodies in both CsS and CrR lymphocytes and in macrophages. When active fluorescent Cs were used, Cs detectable by fluorescence after one or several days was found to be concentrated within these globular bodies.

Animals↗
PubMed1979

S-(N-dansylaminoethyl)-6-mercaptoguanosine as a fluorescent probe for the uridine transport system in human erythrocytes.

A fluorescent derivative of 6-mercaptoguanosine, S-(N-dansylaminoethyl)-6-mercaptoguanosine, was synthesized, and found to be a strong inhibitor of the uridine transport system of erythrocyte (Ki approximately 0.3 microM). The emission spectrum of this compound has peaks at 400 and 550 nm. The emission at 550, but not that a 400 nm, in environment-sensitive. A method was devised for preparing a suspension of erythrocyte-membrane fragments with sufficiently low light scattering so that a detailed study could be made of the fluorescence of the probe when bound to membranes. Direct binding measurements showed the existence of a tight binding site, with a dissociation constant of the same order of magnitude as the inhibition constant. Binding of probe and substrate are not mutually exclusive, but the fluorescence and affinity of the bound probe are sensitive to the presence of uridine. The emission spectrum suggests that the bound probe penetrates into the bilayer region of the membrane.

Binding Sites↗