Micromolar Range (micromolar + range)

Distribution by Scientific Domains

Kinds of Micromolar Range

  • low micromolar range


  • Selected Abstracts


    Ischaemic preconditioning is related to decreasing levels of extracellular adenosine that may be metabolically useful in the at-risk myocardium: an experimental study in the pig

    ACTA PHYSIOLOGICA, Issue 1 2010
    A. Waldenström
    Abstract Aim:, ,Pre-treatment' with short repetitive periods of ischaemia (ischaemic preconditioning) has proved to be a powerful mechanism for modification of the extent of myocardial damage following acute coronary artery occlusion. The exact mechanism of protection induced by ischaemic preconditioning is not known. We herewith put forward a contributing component for protection with preconditioning involving a shift in the adenylate kinase (AK) equilibrium reaction in favour of adenosine triphosphate (ATP) formation. Methods:, A coronary artery was occluded in anaesthetized thoracotomized pigs to induce ischaemic preconditioning as well as a longer period of ischaemia. Microdialysis probes were inserted in ischaemic and control myocardium and were infused with 14C- adenosine with two different specific activities. 14C-lactate was identified and measured in the effluent. Results:,14C-adenosine was taken up by non-preconditioned and preconditioned myocardium during ischaemia. Significantly increased levels of 14C-lactate were recovered in preconditioned myocardium. 14C-adenosine with high specific activity resulted in a specific activity of lactate that was 2.7 times higher than that of lactate after administration of 14C-adenosine with low specific activity. Mass spectrography verified the identity of 14C-lactate. Conclusions:, Preconditioning up-regulates a new metabolic pathway (starting with 5,-nucleotidase and ending up with lactate) resulting in ATP formation in the micromolar range on top of another effect terminating in a useful shift in the AK equilibrium reaction in favour of ATP generation in the millimolar range. Although the up-regulation of the purine nucleoside phosphorylase pathway is clearly demonstrated, its biological relevance remains to be proved. [source]


    Important region in the ,-spectrin C -terminus for spectrin tetramer formation

    EUROPEAN JOURNAL OF HAEMATOLOGY, Issue 2 2002
    Bing-Hao Luo
    Abstract: Many hereditary hemolytic anemias are due to spectrin mutations at the C -terminal region of ,-spectrin (the ,C region) that destabilize spectrin tetramer formation. However, little is known about the ,C region of spectrin. We have prepared four recombinant ,-peptides of different lengths from human erythrocyte spectrin, all starting at position 1898 of the C -terminal region, but terminating at position 2070, 2071, 2072 or 2073. Native polyacrylamide gel electrophoresis showed that the two peptides terminating at positions 2070 and 2071 did not associate with an N -terminal region ,-peptide (Sp,1,156) in the micromolar range. However, the peptides that terminated at positions 2072 and 2073 associated with the ,-peptide. Circular dichroism results showed that the unassociated helices in both ,- and ,-peptides became associated, presumably to form a helical bundle, for those ,-peptides that formed an ,, complex, but not for those ,-peptides that did not form an ,, complex. In addition, upon association, an increase in the ,-helical content was observed. These results showed that the ,-peptides ending prior to residue 2072 (Thr) would not associate with ,-peptide, and that no helical bundling of the partial domains was observed. Thus, we suggest that the C -terminal segment of ,-spectrin, starting from residue 2073 (Thr), is not critical to spectrin tetramer formation. However, the C -terminal region ending with residue 2072 is important for its association with ,-spectrin in forming tetramers. [source]


    Interaction of the alpha-helical H6 peptide from the pro-apoptotic protein tBid with cardiolipin

    FEBS JOURNAL, Issue 21 2009
    Patrice X. Petit
    BH3 interacting domain death agonist (Bid), a pro-apoptotic member of the Bcl-2 family of proteins, is activated through cleavage by caspase-8. The active C-terminal fragment of Bid (tBid) translocates to the mitochondria where it interacts with cardiolipins at contact sites and induces the release of cytochrome c by a mechanism that is not yet fully understood. It has been shown that the alpha-helices ,H6 and ,H7 (which create the hairpin-forming domain of tBid) mediate the insertion of Bid into mitochondrial membranes and are essential for the cytochrome c -releasing activity. In the present study, we focused on the interaction between the ,H6 and the mitochondrial membrane. By the use of single-cell electropermeabilization associated with flow cytometric analysis of intact cells, we demonstrated that H6 is able to induce cell death when used in the micromolar range. We also studied the interactions of the ,H6 with artificial monolayers. We showed that the presence of negatively charged cardiolipins greatly enhances the insertion of ,H6 into the phospholipid monolayer. The modification of two charged amino acid residues in ,H6 abolished its insertion and also its in vivo effects. Furthermore, the negative values of the excess areas of mixing indicate that attractive interactions between cardiolipins and ,H6 occur in the mixed monolayers. Fluorescence microscopy observations revealed that ,H6 significantly disrupts cardiolipin packing and stabilizes the fluid lipid phase. These results suggest that cardiolipins at the contact sites between the two mitochondrial membranes could mediate the binding of tBid via ,H6. [source]


    Structural and thermodynamic insights into the binding mode of five novel inhibitors of lumazine synthase from Mycobacterium tuberculosis

    FEBS JOURNAL, Issue 20 2006
    Ekaterina Morgunova
    Recently published genomic investigations of the human pathogen Mycobacterium tuberculosis have revealed that genes coding the proteins involved in riboflavin biosynthesis are essential for the growth of the organism. Because the enzymes involved in cofactor biosynthesis pathways are not present in humans, they appear to be promising candidates for the development of therapeutic drugs. The substituted purinetrione compounds have demonstrated high affinity and specificity to lumazine synthase, which catalyzes the penultimate step of riboflavin biosynthesis in bacteria and plants. The structure of M. tuberculosis lumazine synthase in complex with five different inhibitor compounds is presented, together with studies of the binding reactions by isothermal titration calorimetry. The inhibitors showed the association constants in the micromolar range. The analysis of the structures demonstrated the specific features of the binding of different inhibitors. The comparison of the structures and binding modes of five different inhibitors allows us to propose the ribitylpurinetrione compounds with C4,C5 alkylphosphate chains as most promising leads for further development of therapeutic drugs against M. tuberculosis. [source]


    Divalent metal cation binding properties of human prothymosin ,

    FEBS JOURNAL, Issue 15 2000
    Nina V. Chichkova
    The divalent cation binding properties of human prothymosin ,, an abundant nuclear protein involved in cell proliferation, were evaluated. By using prothymosin , retardation on a weak cation chelating resin charged with various divalent cations, specific binding of Zn2+ ions by prothymosin , was observed. This finding was further confirmed by the equilibrium dialysis analysis which demonstrated that, within the micromolar range of Zn2+ concentrations, prothymosin , could bind up to three zinc ions in the presence of 100 mm NaCl and up to 13 zinc ions in the absence of NaCl. Equilibrium dialysis analysis also revealed that prothymosin , could bind Ca2+, although the parameters of Ca2+ binding by prothymosin , were less pronounced than those of Zn2+ binding in terms of the number of metal ions bound, the KD values, and the resistance of the bound metal ions to 100 mm NaCl. The effects of Zn2+ and Ca2+ on the interaction of prothymosin , with its putative partners, Rev of HIV type 1 and histone H1, were examined. We demonstrated that Rev binds prothymosin ,, and that prothymosin , binding to Rev but not to histone H1 was significantly enhanced in the presence of zinc and calcium ions. Our data suggest that the modes of prothymosin , interaction with Rev and histone H1 are distinct and that the observed zinc and calcium-binding properties of prothymosin , might be functionally relevant. [source]


    Structure-Based Design and Synthesis of the First Weak Non-Phosphate Inhibitors for IspF, an Enzyme in the Non-Mevalonate Pathway of Isoprenoid Biosynthesis

    HELVETICA CHIMICA ACTA, Issue 6 2007
    Corinne Baumgartner
    Abstract In this paper, we describe the structure-based design, synthesis, and biological evaluation of cytosine derivatives and analogues that inhibit IspF, an enzyme in the non-mevalonate pathway of isoprenoid biosynthesis. This pathway is responsible for the biosynthesis of the C5 precursors to isoprenoids, isopentenyl diphosphate (IPP, 1) and dimethylallyl diphosphate (DMAPP, 2; Scheme,1). The non-mevalonate pathway is the sole source for 1 and 2 in the protozoan Plasmodium parasites. Since mammals exclusively utilize the alternative mevalonate pathway, the enzymes of the non-mevalonate pathway have been identified as attractive new drug targets in the fight against malaria. Based on computer modeling (cf. Figs.,2 and 3), new cytosine derivatives and analogues (Fig.,1) were selected as potential drug-like inhibitors of IspF protein, and synthesized (Schemes,2,5). Determination of the enzyme activity by 13C-NMR spectroscopy in the presence of the new ligands showed inhibitory activities for some of the prepared cytosine and pyridine-2,5-diamine derivatives in the upper micromolar range (IC50 values; Table). The data suggest that it is possible to inhibit IspF protein without binding to the polar diphosphate binding site and the side chain of Asp56,, which interacts with the ribose moiety of the substrate and substrate analogues. Furthermore, a new spacious sub-pocket was discovered which accommodates aromatic spacers between cytosine derivatives or analogues (binding to ,Pocket III') and rings that occupy the flexible hydrophobic region of ,Pocket II'. The proposed binding mode remains to be further validated by X-ray crystallography. [source]


    A Novel Synthesis of Highly Substituted Perhydropyrrolizines, Perhydroindolizines, and Pyrrolidines: Inhibition of the Peptidyl-Prolyl cis/trans Isomerase (PPIase) Pin1

    HELVETICA CHIMICA ACTA, Issue 2 2007
    Romain Siegrist
    Abstract In this paper, we describe the synthesis and biological evaluation of highly substituted perhydropyrrolizines that inhibit the peptidyl-prolyl cis/trans isomerase (PPIase) Pin1, an oncogenic target. The enzyme selectively catalyzes the cis/trans isomerization of peptide bonds between a phosphorylated serine or threonine, and proline, thereby inducing a conformational change. Such structural modifications play an important role in many cellular events, such as cell-cycle progression, transcriptional regulation, RNA processing, as well as cell proliferation and differentiation. Based on computer modeling (Fig.,2), the new perhydropyrrolizinone derivatives (,)- 1a,b, decorated with two substituents, were selected and synthesized (Schemes,1,3). While enzymatic assays showed no biological activity, 15N,1H-HSQC-NMR spectroscopy revealed that (,)- 1a,b bind to the WW recognition domain of Pin1, apparently in a mode that does not inhibit PPIase activity. To enforce complexation into the larger active site rather than into the tighter WW domain of Pin1 and to enhance the overall binding affinity, we designed a perhydropyrrolizine scaffold substituted with additional aromatic residues (Fig.,5). A novel, straightforward synthesis towards this class of compounds was developed (Schemes,4 and 5), and the racemic compounds (±)- 22a,22d were found to inhibit Pin1 with Ki values (Ki,=,inhibition constant) in the micromolar range (Table,2). To further enhance the potency of these inhibitors, the optically pure ligands (+)- 22a and (+)- 33b,c were prepared (Schemes,6 and 7) and shown to inhibit Pin1 with Ki values down to the single-digit micromolar range. According to 15N,1H-HSQC-NMR spectroscopy and enzymatic activity assays, binding occurs at both the WW domain and the active site of Pin1. Furthermore, the new synthetic protocol towards perhydropyrrolizines was extended to the preparation of highly substituted perhydroindolizine ((±)- 43; Scheme,8) and pyrrolidine ((±)- 48a,b; Scheme,9) derivatives, illustrating a new, potentially general access to these highly substituted heterocycles. [source]


    Synthetic dsDNA-Binding Peptides Using Natural Compounds as Model

    HELVETICA CHIMICA ACTA, Issue 6 2006
    Filip Borgions
    Abstract We have developed a series of short DNA-binding peptides containing newly synthesized, unnatural as well as natural amino acid building blocks. By a combinatorial-library approach, oligopeptides were developed with moderate dsDNA-binding affinities. Two strategies were used to further enhance the binding affinity of the lead peptides: Ac-Arg-Ual-Sar-Chi-Chi-Chi-Arg-NH2 and Ac-Arg-Cbg-Cha-Chi-Chi-Tal-Arg-NH2. Site-selective amino acid substitutions increased the binding affinities up to 2,×,10,5,M. Further enhancement of the binding affinities could be achieved by coupling of an acridine intercalating unit, using linker arms of different length and flexibility. With the introduction of a new lysine-based acridine unit, different types of oligopeptide,acridine conjugates were designed using known dsDNA-binding ligands as model compounds. The binding capacities of these new oligopeptide,acridine conjugates have been investigated by a fluorescent intercalator (ethidium bromide) displacement (FID) assay. With the synthesis of the dipeptide,acridine conjugates, binding affinities in the low micromolar range were obtained (6.4,×,10,6,M), which is similar to the binding strength of the well-known DNA binder Hoechst 33258. [source]


    High-resolution real-time recording with microelectrode biosensors reveals novel aspects of adenosine release during hypoxia in rat hippocampal slices

    JOURNAL OF NEUROCHEMISTRY, Issue 6 2003
    B. G. Frenguelli
    Abstract We have used improved miniaturized adenosine biosensors to measure adenosine release during hypoxia from within the CA1 region of rat hippocampal slices. These microelectrode biosensors record from the extracellular space in the vicinity of active synapses as they detect the synaptic field potentials evoked in area CA1 by stimulation of the afferent Schaffer collateral-commissural fibre pathway. Our new measurements demonstrate the rapid production of adenosine during hypoxia that precedes and accompanies depression of excitatory transmission within area CA1. Simultaneous measurement of adenosine release and synaptic transmission gives an estimated IC50 for adenosine on transmission in the low micromolar range. However, on reoxygenation, synaptic transmission recovers in the face of elevated extracellular adenosine and despite a post-hypoxic surge of adenosine release. This may indicate the occurrence of apparent adenosine A1 receptor desensitization during metabolic stress. In addition, adenosine release is unaffected by pharmacological blockade of glutamate receptors and shows depletion on repeated exposure to hypoxia. Our results thus suggest that adenosine release is not a consequence of excitotoxic glutamate release. The potential for adenosine A1 receptor desensitization during metabolic stress implies that its prevention may be beneficial in extending adenosine-mediated neuroprotection in a variety of clinically relevant conditions. [source]


    Synthesis and in-vitro antitumour activity of new naphthyridine derivatives on human pancreatic cancer cells

    JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 8 2009
    Irene Banti
    Abstract Objectives The aim of the study was to evaluate the antitumour effect in vitro of newly synthesized 7-substituted 2,3-dihydro-1,8-naphthyridines. Methods Characterization tools included cell viability assay, caspase 3/7 induction, DNA fragmentation, fibroblast growth factor type 1 receptor kinase inhibition, and in-vitro antiangiogenic analysis. Key findings Treatment of MIA PaCa-2 human pancreatic cancer cells with test compounds showed time- and concentration-dependent cytotoxicity with IC50 values in the micromolar range. Compounds with an aminoalkyl or a diaminoalkyl side chain at the 7-position exhibited remarkable cytotoxicity, whereas the presence of a methyl group or a cyclic amine in the same position led to a significant decrease in their biological activity. Cytotoxicity screening demonstrated that the most active was compound 11 (mean 50% inhibition of cell proliferation (IC50) 11 ,M). This compound had an in-vitro antitumour efficacy superior to 5-fluorouracil (the lowest cell viability value after treatment (Emax) 0.2% and 19%, respectively) and proved to be less toxic than 5-fluorouracil against non-cancerous human oral epithelial cells. In addition, compound 11 induced apoptosis in MIA PaCa-2 cells and it was able to promote antiangiogenic effects in vitro. Finally, its cytotoxicity was enhanced in pancreatic cancer cells stimulated with fibroblast growth factor, while no substantial effect was observed on human bronchial smooth muscle cells stimulated with the same growth factor. Conclusions These findings suggest that 1,8-naphthyridine derivatives are a promising class of compounds in cancer research. In particular, the antitumour activity of compound 11 is worth further investigation. [source]


    House cleaning, a part of good housekeeping

    MOLECULAR MICROBIOLOGY, Issue 1 2006
    Michael Y. Galperin
    Summary Cellular metabolism constantly generates by-products that are wasteful or even harmful. Such compounds are excreted from the cell or are removed through hydrolysis to normal cellular metabolites by various ,house-cleaning' enzymes. Some of the most important contaminants are non-canonical nucleoside triphosphates (NTPs) whose incorporation into the nascent DNA leads to increased mutagenesis and DNA damage. Enzymes intercepting abnormal NTPs from incorporation by DNA polymerases work in parallel with DNA repair enzymes that remove lesions produced by modified nucleotides. House-cleaning NTP pyrophosphatases targeting non-canonical NTPs belong to at least four structural superfamilies: MutT-related (Nudix) hydrolases, dUTPase, ITPase (Maf/HAM1) and all-, NTP pyrophosphatases (MazG). These enzymes have high affinity (Km's in the micromolar range) for their natural substrates (8-oxo-dGTP, dUTP, dITP, 2-oxo-dATP), which allows them to select these substrates from a mixture containing a ,1000-fold excess of canonical NTPs. To date, many house-cleaning NTPases have been identified only on the basis of their side activity towards canonical NTPs and NDP derivatives. Integration of growing structural and biochemical data on these superfamilies suggests that their new family members cleanse the nucleotide pool of the products of oxidative damage and inappropriate methylation. House-cleaning enzymes, such as 6-phosphogluconolactonase, are also part of normal intermediary metabolism. Genomic data suggest that house-cleaning systems are more abundant than previously thought and include numerous analogous enzymes with overlapping functions. We discuss the structural diversity of these enzymes, their phylogenetic distribution, substrate specificity and the problem of identifying their true substrates. [source]


    Inhibition of Porphyromonas gingivalis proteinases (gingipains) by chlorhexidine: synergistic effect of Zn(II)

    MOLECULAR ORAL MICROBIOLOGY, Issue 4 2006
    C. A. Cronan
    Background/aims:, Gingipains, proteolytic enzymes produced by the periodontal pathogen Porphyromonas gingivalis, are regarded as virulence factors in the pathogenesis of periodontitis. Inhibition of gingipain activity therefore may have therapeutic potential, and it has been suggested that chlorhexidine may inhibit the activities of these enzymes. The purposes of the present study were to examine systematically the inhibitory effects of chlorhexidine on three purified gingipains and to determine the effect of Zn(II) on chlorhexidine inhibition. Methods:, The activities of lys-gingipain (Kgp) and two forms of arg-gingipain (RgpB and HRgpA) were measured in the presence of varying concentrations of chlorhexidine and with chlorhexidine supplemented with Zn(II). Inhibition constants (Ki's) were determined for chlorhexidine alone and in the presence of Zn(II). Fractional inhibitory constant indices were calculated to assess the synergy of the chlorhexidine,Zn(II) inhibition. Results:, RgpB, HRgpA, and Kgp were all inhibited by chlorhexidine with Ki's in the micromolar range. For RgpB and HRgpA, the inhibitory effects of chlorhexidine were enhanced 3,30-fold by Zn(II). The chlorhexidine,Zn(II) interaction was synergistic for inhibition of HRgpA and RgpB. For Kgp, the effect of Zn(II) on chlorhexidine inhibition was antagonistic. Conclusions:, Chlorhexidine is an effective inhibitor of gingipains, and the inhibition of R-gingipains is enhanced by Zn(II). A mixture of chlorhexidine and Zn(II) may be useful as an adjunct in the treatment of periodontitis and in the post-treatment maintenance of periodontitis patients. [source]


    Effect of otilonium bromide on contractile patterns in the human sigmoid colon

    NEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2010
    D. Gallego
    Abstract Background, The mechanism of action of the spasmolytic compound otilonium bromide (OB) on human colonic motility is not understood. The aim of our study was to characterize the pharmacological effects of OB on contractile patterns in the human sigmoid colon. Methods, Circular sigmoid strips were studied in organ baths. Isolated smooth muscle cells from human sigmoid colon were examined using the calcium imaging technique. Key Results, Otilonium bromide inhibited by 85% spontaneous non-neural rhythmic phasic contractions (RPCs), (IC50 = 49.9 nmol L,1) and stretch-induced tone (IC50 = 10.7 nmol L,1) with maximum effects at micromolar range. OB also inhibited by 50% both on- (IC50 = 38.0 nmol L,1) and off- contractions induced by electrical stimulation of excitatory motor neurons. In contrast, the inhibitory latency period prior to off -contractions was unaffected by OB. OB inhibited acetylcholine-, substance P-, and neurokinin A-induced contractions. The L-type Ca2+ channel agonist BayK8644 reversed the effects of OB on RPCs, on- and off -contractions. Hexamethonium, atropine, the NK2 antagonist, or depletion of intracellular Ca2+ stores by thapsigargin did not prevent the inhibitory effect of OB on RPCs and electrical contractions. KCl-induced calcium transients in isolated smooth muscle cells were also inhibited by OB (IC50 = 0.2 ,mol L,1). Conclusions & Inferences, Otilonium bromide strongly inhibited the main patterns of human sigmoid motility in vitro by blocking calcium influx through L-type calcium channels on smooth muscle cells. This pharmacological profile may mediate the clinically observed effects of the drug in patients with irritable bowel syndrome. [source]


    Time-resolved Microspectrofluorimetry and Fluorescence Lifetime Imaging of Hypericin in Human Retinal Pigment Epithelial Cells,

    PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2005
    Paola Taroni
    ABSTRACT Hypericin is the active ingredient of the off-the-shelf antidepressant St. John's Wort. It is an effective phototoxic agent and its systemic administration at therapeutic doses could induce particular damage in the eye due to continuous light exposure. Hypercin is strongly fluorescent and its fluorescence properties can be monitored to investigate noninvasively its localization and interactions. To this aim, time-resolved microspectrofluorimetry and fluorescence life-time imaging were used to assess the spectral and temporal properties as well as the spatial distribution of the fluorescence emitted by retinal pigment epithelium (RPE) cells treated with Hyp at concentrations in the micromolar range (0.5,10 ,M). In the presence of hypericin, the emission peaks at 600-605 nm and the fluorescence decay is best fitted with three lifetimes (5.5-7 ns, 1.9-2.5 ns and < 0.8 ns). Spectral and temporal differences were observed between high (,5 ,M) and low hypericin concentrations. In particular, upon increasing concentration, the emission spectrum of the slow component broadens and its lifetime shortens. The latter change is observed also when high concentrations are reached locally, due to more efficient localization within the cell. [source]


    Copper binding to octarepeat peptides of the prion protein monitored by mass spectrometry

    PROTEIN SCIENCE, Issue 2 2000
    Randy M. Whittal
    Abstract Electrospray ionization mass spectrometry (ESI-MS) was used to measure the binding of Cu2+ ions to synthetic peptides corresponding to sections of the sequence of the mature prion protein (PrP). ESI-MS demonstrates that Cu2+ is unique among divalent metal ions in binding to PrP and defines the location of the major Cu2+ binding site as the octarepeat region in the N-terminal domain, containing multiple copies of the repeat ProHisGlyGlyGlyTrpGlyGln. The stoichiometries of the complexes measured directly by ESI-MS are pH dependent: a peptide containing four octarepeats chelates two Cu2+ ions at pH 6 but four at pH 7.4. At the higher pH, the binding of multiple Cu2+ ions occurs with a high degree of cooperativity for peptides C-terminally extended to incorporate a fifth histidine. Dissociation constants for each Cu2+ ion binding to the octarepeat peptides, reported here for the first time, are mostly in the low micromolar range; for the addition of the third and fourth Cu2+ ions to the extended peptides at pH 7.4, KD's are <100 nm. n-terminal acetylation of the peptides caused some reduction in the stoichiometry of binding at both ph's. cu2+ also binds to a peptide corresponding to the extreme N-terminus of PrP that precedes the octarepeats, arguing that this region of the sequence may also make a contribution to the Cu2+ complexation. Although the structure of the four-octarepeat peptide is not affected by pH changes in the absence of Cu2+, as judged by circular dichroism, Cu2+ binding induces a modest change at pH 6 and a major structural perturbation at pH 7.4. It is possible that PrP functions as a Cu2+ transporter by binding Cu2+ ions from the extracellular medium under physiologic conditions and then releasing some or all of this metal upon exposure to acidic pH in endosomes or secondary lysosomes. [source]


    ,-Latrotoxin increases spontaneous and depolarization-evoked exocytosis from pancreatic islet ,-cells

    THE JOURNAL OF PHYSIOLOGY, Issue 3 2005
    Amelia M. Silva
    ,-Latrotoxin (,-LT), a potent excitatory neurotoxin, increases spontaneous, as well as action potential-evoked, quantal release at nerve terminals and increases hormone release from excitable endocrine cells. We have investigated the effects of ,-LT on single human, mouse and canine ,-cells. In isolated and combined measurements, ,-LT, at nanomolar concentrations, induces: (i) rises in cytosolic Ca2+, into the micromolar range, that are dependent on extracellular Ca2+; (ii) large conductance non-selective cation channels; and (iii) Ca2+ -dependent insulin granule exocytosis, measured as increases in membrane capacitance and quantal release of preloaded serotonin. Furthermore, at picomolar concentrations, ,-LT potentiates depolarization-induced exocytosis often without evidence of inducing channel activity or increasing cytosolic Ca2+. These results strongly support the hypothesis that ,-LT, after binding to specific receptors, has at least two complementary modes of action on excitable cells. (i) ,-LT inserts into the plasma membrane to form Ca2+ permeable channels and promote Ca2+ entry thereby triggering Ca2+ -dependent exocytosis in unstimulated cells. (ii) At lower concentrations, where its channel forming activity is hardly evident, ,-LT augments depolarization-evoked exocytosis probably by second messenger-induced enhancement of the efficiency of the vesicle recruitment or vesicle fusion machinery. We suggest that both modes of action enhance exocytosis from a newly described highly Ca2+ -sensitive pool of insulin granules activated by global cytosolic Ca2+ concentrations in the range of ,1 ,m. [source]


    N -(Indazolyl)benzamido Derivatives as CDK1 Inhibitors: Design, Synthesis, Biological Activity, and Molecular Docking Studies

    ARCHIV DER PHARMAZIE, Issue 5 2009
    Demetrio Raffa
    Abstract A series of N -1H -indazole-1-carboxamides has been synthesized and their effects on both CDK1 / cyclin B and the K-562 (human chronic myelogenus leukemia) cell line were evaluated. Using a computational model, we have observed that all the most active compounds 9e, f, i,n exhibited the same binding mode of purvanalol A in the ATP-binding cleft. Although they were able to moderately inhibit the leukemic cell line K-562 and to show inhibitory activity against the Cdc2-Cyclin B kinase in the low micromolar range, they turned out to be non-cytotoxic against HuDe (IZSL) primary cell cultures from human derm. These preliminary results are quite encouraging in view of the low toxicity demonstrated by the above-mentioned compounds. [source]


    An Efficient Method for the Synthesis of Peptide Aldehyde Libraries Employed in the Discovery of Reversible SARS Coronavirus Main Protease (SARS-CoV Mpro) Inhibitors

    CHEMBIOCHEM, Issue 7 2006
    Samer I. Al-Gharabli Dr.
    Abstract A method for the parallel solid-phase synthesis of peptide aldehydes has been developed. Protected amino acid aldehydes obtained by the racemization-free oxidation of amino alcohols with Dess,Martin periodinane were immobilized on threonyl resins as oxazolidines. Following Boc protection of the ring nitrogen to yield the N-protected oxazolidine linker, peptide synthesis was performed efficiently on this resin. A peptide aldehyde library was designed for targeting the SARS coronavirus main protease, SARS-CoV Mpro(also known as 3CLpro), on the basis of three different reported binding modes and supported by virtual screening. A set of 25 peptide aldehydes was prepared by this method and investigated in inhibition assays against SARS-CoV Mpro. Several potent inhibitors were found with IC50 values in the low micromolar range. An IC50 of 7.5 ,M was found for AcNSTSQ-H and AcESTLQ-H. Interestingly, the most potent inhibitors seem to bind to SARS-CoV Mpro in a noncanonical binding mode. [source]


    Interaction of the Catalytic Domain of Inositol 1,4,5-Trisphosphate 3-Kinase A with Inositol Phosphate Analogues

    CHEMBIOCHEM, Issue 8 2005
    Alexandra Poinas Dr.
    Abstract The levels of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] in the cytoplasm are tightly regulated by two enzymes, Ins(1,4,5)P3 3-kinase and type I Ins(1,4,5)P3 5-phosphatase. The catalytic domain of Ins(1,4,5)P3 3-kinase (isoenzymes A, B and C) is restricted to approximately 275 amino acids at the C-terminal end. We were interested in understanding the catalytic mechanism of this key family of enzymes in order to exploit this in inhibitor design. We expressed the catalytic domain of rat Ins(1,4,5)P3 3-kinase A in Escherichia coli as a His- and S-tagged fusion protein. The purified enzyme was used in an Ins(1,4,5)P3 kinase assay to phosphorylate a series of inositol phosphate analogues with three or four phosphate groups. A synthetic route to D -2-deoxy-Ins(1,4,5)P3 was devised. D -2-Deoxy-Ins(1,4,5)P3 and D -3-deoxy-Ins(1,4,6)P3 were potent inhibitors of the enzyme, with IC50 values in the micromolar range. Amongst all analogues tested, only D -2-deoxy-Ins(1,4,5)P3 appears to be a good substrate of the Ins(1,4,5)P3 3-kinase. Therefore, the axial 2-hydroxy group of Ins(1,4,5)P3 is not involved in recognition of the substrate nor does it participate in the phosphorylation mechanism of Ins(1,4,5)P3. In contrast, the equatorial 3-hydroxy function must be present in that configuration for phosphorylation to occur. Our data indicate the importance of the 3-hydroxy function in the mechanism of inositol trisphosphate phosphorylation rather than in substrate binding. [source]


    A Novel Cytotoxic Cerium Complex: Aquatrichloridobis(1,10-phenanthroline)cerium(III) (KP776).

    CHEMISTRY & BIODIVERSITY, Issue 12 2009
    Antiproliferative Activity, Behavior in H2O, Binding towards Biomolecules, Characterization, Synthesis
    Abstract The lanthanide complex aquatrichloridobis(1,10-phenanthroline)cerium(III) [Ce(phen)2(H2O)Cl3] (KP776) was fully characterized by elemental analysis, IR-, and 1H- and 13C-NMR spectroscopy, as well as TG/DTA measurements, and its behavior in H2O, important for the application as a chemotherapeutic, was studied. In addition, the binding of KP776 to nucleotides and single serum proteins was investigated by capillary electrophoresis, whereas binding to proteins in human plasma was observed by ICP-MS. The compound shows promising anticancer properties in vitro: proliferation of human cancer cell lines is strongly inhibited with IC50 values in the very low micromolar range. [source]


    Design, Synthesis, and Biological Evaluation of New Territrem B Analogues

    CHEMISTRY & BIODIVERSITY, Issue 4 2005
    Xiangrui Jiang
    Some 23 analogues of the potent acetylcholinesterase (AChE) inhibitor territrem B (1) were designed, synthesized, and tested for their biological activities. Some of the new synthetic derivatives exhibited IC50 values for AChE inhibition in the upper micromolar range. Molecular-modeling studies indicated that a planar conformation seems to be crucial for AChE inhibition. The two N-atoms of the piperazine moieties in 5o, 5p, and 5r might further enhance the inhibitory effects. The cytotoxicities of selected compounds against six human tumor cell lines were also determined. [source]


    Thiazolopyrimidine Inhibitors of 2-Methylerythritol 2,4-Cyclodiphosphate Synthase (IspF) from Mycobacterium tuberculosis and Plasmodium falciparum

    CHEMMEDCHEM, Issue 7 2010
    Julie
    Abstract A library of 40,000 compounds was screened for inhibitors of 2-methylerythritol 2,4-cyclodiphosphate synthase (IspF) protein from Arabidopsis thaliana using a photometric assay. A thiazolopyrimidine derivative resulting from the high-throughput screen was found to inhibit the IspF proteins of Mycobacterium tuberculosis, Plasmodium falciparum, and A.,thaliana with IC50 values in the micromolar range. Synthetic efforts afforded derivatives that inhibit IspF protein from M.,tuberculosis and P.,falciparum with IC50 values in the low micromolar range. Several compounds act as weak inhibitors in the P.,falciparum red blood cell assay. [source]


    Virtual Screening and Biological Characterization of Novel Histone Arginine Methyltransferase PRMT1 Inhibitors

    CHEMMEDCHEM, Issue 1 2009
    Ralf Heinke
    Abstract Lysine and arginine methyltransferases participate in the posttranslational modification of histones and regulate key cellular functions. Protein arginine methyltransferase,1 (PRMT1) has been identified as an essential component of mixed lineage leukemia (MLL) oncogenic complexes, revealing its potential as a novel therapeutic target in human cancer. The first potent arginine methyltransferase inhibitors were recently discovered by random- and target-based screening approaches. Herein we report virtual and biological screening for novel inhibitors of PRMT1. Structure-based virtual screening (VS) of the Chembridge database composed of 328,000 molecules was performed with a combination of ligand- and target-based in,silico approaches. Nine inhibitors were identified from the top-scored docking solutions; these were experimentally tested using human PRMT1 and an antibody-based assay with a time-resolved fluorescence readout. Among several aromatic amines, an aliphatic amine and an amide were also found to be active in the micromolar range. [source]


    A Cryptophane Biosensor for the Detection of Specific Nucleotide Targets through Xenon NMR Spectroscopy

    CHEMPHYSCHEM, Issue 14 2007
    Vincent Roy Dr.
    DNA sensor: A xenon host composed of a cryptophane structure with a DNA strand (see picture) serves to detect its complementary strand in the micromolar range through laser-polarized 129Xe NMR spectroscopy. [source]