34 research outputs found

    Defining the Putative Inhibitory Site for a Selective Negative Allosteric Modulator of Human α4β2 Neuronal Nicotinic Receptors

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    Neuronal nicotinic receptors (nAChRs) have been implicated in several diseases and disorders such as autism spectrum disorders, Alzheimer’s disease, Parkinson’s disease, epilepsy, and nicotine addiction. To understand the role of nAChRs in these conditions, it would be beneficial to have selective molecules that target specific nAChRs in vitro and in vivo. Our laboratory has previously identified a novel allosteric site on human α4β2 nAChRs using a series of computational and in vitro approaches. At this site, we have identified negative allosteric modulators that selectively inhibit human α4β2 nAChRs, a subtype implicated in nicotine addiction. This study characterizes the allosteric site via site-directed mutagenesis. Three amino acids (Phe118, Glu60, and Thr58) on the β2 subunit were shown to participate in the inhibitory properties of the selective antagonist KAB-18 and provided insights into its antagonism of human α4β2 nAChRs. SAR studies with KAB-18 analogues and various mutant α4β2 nAChRs also provided information concerning how different physiochemical features influence the inhibition of nAChRs through this allosteric site. Together, these studies identify the amino acids that contribute to the selective antagonism of human α4β2 nAChRs at this allosteric site. Finally, these studies define the physiochemical features of ligands that influence interaction with specific amino acids in this allosteric site

    Chemoproteomic Discovery of AADACL1 as a Regulator of Human Platelet Activation

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    A comprehensive knowledge of the platelet proteome is necessary for understanding thrombosis and for conceiving novel antiplatelet therapies. To discover new biochemical pathways in human platelets, we screened platelets with a carbamate library designed to interrogate the serine hydrolase subproteome and used competitive activity-based protein profiling to map the targets of active carbamates. We identified an inhibitor that targets arylacetamide deacetylase-like 1 (AADACL1), a lipid deacetylase originally identified in invasive cancers. Using this compound, along with highly selective second-generation inhibitors of AADACL1, metabolomics and RNA interference, we show that AADACL1 regulates platelet aggregation, thrombus growth, RAP1 and PKC activation, lipid metabolism and fibrinogen binding to platelets and megakaryocytes. These data provide the first evidence that AADACL1 regulates platelet and megakaryocyte activation and highlight the value of this chemoproteomic strategy for target discovery in platelets

    Impact of fermentation, drying, roasting and Dutch processing on flavan-3-ol stereochemistry in cacao beans and cocoa ingredients

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    This paper reports a systematic study of the level of flavan-3-ol monomers during typical processing steps as cacao beans are dried, fermented and roasted and the results of Dutch-processing. Methods have been used that resolve the stereoisomers of epicatechin and catechin. In beans harvested from unripe and ripe cacao pods, we find only (-)-epicatechin and (+)-catechin with (-)-epicatechin being by far the predominant isomer. When beans are fermented there is a large loss of both (-)-epicatechin and (+)-catechin, but also the formation of (-)-catechin. We hypothesize that the heat of fermentation may, in part, be responsible for the formation of this enantiomer. When beans are progressively roasted at conditions described as low, medium and high roast conditions, there is a progressive loss of (-)-epicatechin and (+)-catechin and an increase in (-)-catechin with the higher roast levels. When natural and Dutch-processed cacao powders are analyzed, there is progressive loss of both (-)-epicatechin and (+)-catechin with lesser losses of (-)-catechin. We thus observe that in even lightly Dutch-processed powder, the level of (-)-catechin exceeds the level of (-)-epicatechin. The results indicate that much of the increase in the level of (-)-catechin observed during various processing steps may be the result of heat-related epimerization from (-)-epicatechin. These results are discussed with reference to the reported preferred order of absorption of (-)-epicatechin > (+)-catechin > (-)-catechin. These results are also discussed with respect to the balance that must be struck between the beneficial impact of fermentation and roasting on chocolate flavor and the healthful benefits of chocolate and cocoa powder that result in part from the flavan-3-ol monomers

    Routes to N-glycinamide oxazolidinone derivatives: The reaction of 4-trityloxymethyl-3-oxa-1-azabicyclo[3.1.0]hexan-2-one with active halides

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    © ARKAT USA, Inc. N-Glycinamide oxazolidinones are key intermediates for the synthesis of a new class of peptidomimetics. We report, herein, the synthesis of a series of 3,4,5-trisubstituted oxazolidinones with a glycine residue at N-3 of the oxazolidinone ring. Substituents at C-4 and C-5 contain substitution capabilities which are amenable for the introduction of additional peptide chains. The synthesis of the key N-Glycinamide oxazolidinone is made possible through two reactions; a tandem aziridine ring opening/oxazolidinone alkylation and, subsequently, a fused-lactone ring opening by an amine which leads to the N-Glycinamide oxazolidinones

    Aziridine−Allylsilane-Mediated Total Synthesis of (−)-Yohimbane

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    Synthesis and cytotoxic activity of MOM-ether analogs of isosteviol

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    Lung cancer is one of the most common malignancies worldwide. In this Letter, novel MOM-ether analogs of isosteviol were designed and synthesized to be tested for anticancer activities against H1299 lung cancer cell lines. The effects of these derivatives were studied in H1299 human large cell lung carcinoma cells that are null for p53 and compared to normal counterparts NL-20 normal lung epithelial cells. The initial screening of twelve MOM-ether analogs of isosteviol derivatives on H1299 lung cancer cells by MTT assay revealed that two derivatives (an ester and a carbamate) were the most potent in reducing cell viability. The IC50 values for these derivatives were determined to be 14 and 21 ?M respectively. We compared the cytotoxicity of the best derivatives in H1299 lung cancer cells and NL-20 normal lung epithelial cells. Both derivatives showed lower cytotoxic effects on NL-20 normal lung epithelial cells. Moreover, both derivatives induced apoptosis in H1299 lung cancer cells more than NL-20 normal lung epithelial cells.U.S.-Egypt Joint Board on Scientific and Technological Cooperation and Science and Technology Development Fund (STDF) grant ID 3684Scopu

    Formation of Scalemic Aziridines via the Nucleophilic Opening of Aziridines

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