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Search results for: organophosphorus chemistry
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Stereostructure of mycoheptin A2
PublicationThe absolute configurations of all the stereogenic centers of the antibiotic mycoheptin A2 were established upon previously elaborated general procedure, consisting of DQF-COSY, NOESY, ROESY, HSQC and HMBC experiments as major tools. The structure of mycoheptin A2 without stereochemistry of its aglycone has been reported before.
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Similar concentration of surfactants in rural and urban areas
PublicationSince surfactants are used in various products, they end up in surface and wastewater. Surfactants may therefore impact ecosystems and living organisms. Actually, only few anionic surfactants and some alkylphenols are regulated. There is no comprehensive evaluation of surfactants in the atmosphere, surfaces and waters of areas of increasing anthropic levels. Here, we measured the levels of cationic, anionic and nonionic surfactants...
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Structural Variety of Cobalt(II), Nickel(II), Zinc(II), and Cadmium(II) Complexes with 4,4′-Azopyridine: Synthesis, Structure and Luminescence Properties
PublicationSelf-assembled bi- and polymetallic complexes of CoII, NiII, ZnII, and CdII were obtained by the reaction of 4,4′-azopyridine (azpy) with metal tri-tert-butoxysilanethiolates (Co, 1; Cd, 2), acetylacetonates (Ni, 3; Zn, 4), and acetates (Cd, 5). All compounds were characterized by single-crystal X-ray structure analysis, elemental analysis, FTIR spectroscopy, and thermogravimetry. Complexes 1, 2 and 4, 5 exhibit diverse structural...
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Inhibitors of angiogenesis in cancer therapy – synthesis and biological activity
PublicationAngiogenesis is the process of formation of new capillaries from preexisting blood vessels. Angiogenesis is involved in normal physiological processes, and plays an important role in tumor invasion and development of metastases. Vascular endothelial growth factor (VEGF) plays a key role in angiogenesis. VEGF is a mitogen for vascular endothelial cells and stimulates their proliferation. By inhibiting the biological activity of...
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Implication of the disulfide bridge in trypsin inhibitor SFTI-1 in its interaction with serine proteinases
PublicationFourteen monocyclic analogues of trypsin inhibitor SFTI-1 isolated from sunflower seeds were synthesized by the solid-phase method. The purpose of this work was to establish the role of a disulfide bridge present in inhibitor's side chains of Cys3 and Cys11 in association with serine proteinases. This cyclic fragment was replaced by the disulfide bridges formed by L-pencillamine (Pen), homo-L-cysteine (Hcy), N-sulfanylethylglycine...
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Troubleshooting of the determination of bisphenol A at ultra-trace levels by liquid chromatography and tandem mass spectrometry
PublicationDetermination of trace amounts of bisphenol A (BPA) may cause problems mainly related to the presence of BPA in solvents (even in LC-MS grade), laboratory vessels, and plastic equipment used for sample preparation. Variable and sometimes significant amounts of BPA present in the background cause problems in obtaining good repeatability of measurements at the ultra-trace levels. Such observations (i.e., poor repeatability of results)...
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Observation of the Hydrogen Migration in the Cation-Induced Fragmentation of the Pyridine Molecules
PublicationThe ability to selectively control chemical reactions related to biology, combustion, and catalysis has recently attracted much attention. In particular, the hydrogen atom relocation may be used to manipulate bond-breaking and new bond-forming processes and may hold promise for far-reaching applications. Thus, the hydrogen atom migration preceding fragmentation of the gas-phase pyridine molecules by the H+, H2+, He+, He2+, and...
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The structure, including stereochemistry, of levorin A1
PublicationThe constitution and stereostructure of levorin A1 1, an aromatic heptaeneantifungal antibiotic, was established on the basis of NMR studies, which contained DQFCOSY,ROESY, HSQC and HMBC experiments. Mycosamine moiety was used as an internalchiral probe to determine the absolute configuration of levorin A1 stereogenic centers: 13S,15R, 17S, 18R, 19S, 21R. The relative configuration of the remaining stereogenic centers wasassigned...
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Absolute configurations of C34 and C35 of antibiotic niphimycin A
PublicationThe relative configurations of four stereogenic centers of the C33-C42 fragment of niphimycin A were assigned as 2S*, 3R*, 4S* and 6S*, based upon 1H NMR analysis with double-quantum filtered COSY and nuclear Overhauser spectroscopy experiments. These data were then correlated with absolute configurations at C36 and C38 of niphimycin A, which were declared previously as 36S and 38S [3]. This allowed for the assignment of the absolute...
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Excess Electron Attachment to Disulfide-Bridged l,l-Cystine. An ab Initio Study
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High-symmetry compact structures are preferred equilibrium configurations of Li n F n+1 − ( n = 2–5) superhalogen anions
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Negatively Charged Xanthine. I. Anions Formed by Canonical Isomers
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Temperature Dependence of the Dissociative Electron Attachment to 2-Thiothymine
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The acid strength of the HClO4/n(AlF3) and HClO4/n(SbF5) (n = 1–3) Lewis–Brønsted superacids containing the excess of the Lewis acid component
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First Evidence of Rhombic (NaCl)2-. Ab Initio Reexamination of the Sodium Chloride Dimer Anion
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Coulomb-Assisted Dissociative Electron Attachment: Application to a Model Peptide
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Why Are SiX5– and GeX5– (X = F, Cl) Stable but Not CF5– and CCl5–?
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Inverse Potassium Hydride: A Theoretical Study
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Ab initio studies of the structure, physicochemical properties and behavior of lead chlorides and chloroplumbate anions in gaseous and aqueous phases
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Unusual and Conventional Dative Bond Formation by s2 Lone Pair Donation from Alkaline Earth Metal Atoms to BH3, AlH3, and GaH3
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Possible Formation of H3O+ Cations Due to Aluminum Fluoride Interactions with Water
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The Only Stable State of O2- Is the X 2Πg Ground State and It (Still!) Has an Adiabatic Electron Detachment Energy of 0.45 eV
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Negative Ion Formation in Sodium Chloride TrimerAn ab Initio Study
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Nanosized zinc, epigenetic changes and its relationship with DMBA induced breast cancer in rats
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Bound-Excited Electronic States of the Anion of 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane
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Chemical Reduction of 2,4,6-Tricyano-1,3,5-triazine and 1,3,5-Tricyanobenzene. Formation of Novel 4,4‘,6,6‘-Tetracyano-2,2‘-bitriazine and Its Radical Anion
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Toward an Understanding of the Chemiluminescence Accompanying the Reaction of 9-Carboxy-10-methylacridinium Phenyl Ester with Hydrogen Peroxide
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Simulating Electron Transfer Attachment to a Positively Charged Model Peptide
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Caralumane Superacids of Lewis and Brønsted Character
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Formation of Enormously Strongly Bound Anionic Clusters Predicted in Binary Superacids
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Theoretical Study of Damage to DNA by 0.2−1.5 eV Electrons Attached to Cytosine
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Prediction of Thymine Dimer Repair by Electron Transfer from Photoexcited 8-Aminoguanine or Its Deprotonated Anion
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A metastable [(MgF3)2]2− dianion composed of two superhalogen anions
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Mechanism for Repair of Thymine Dimers by Photoexcitation of Proximal 8-Oxo-7,8-dihydroguanine
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Fate of Dipole-Bound Anion States when Hydrated
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Mechanism of the ethanol-based (C2H5OH2)+(SbF6)− salt formation by the superacid-catalyzed acetaldehyde hydrogenation
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An Excess Electron Bound to Magnesium Halides and Basic Grignard Compounds (RMgX and RMgR, R = Me, Et, Ph; X = F, Cl, Br)
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Electron Binding Capabilities of Some Silylenes Having Small Singlet−Triplet Splittings or Triplet Ground States
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Dipole and Coulomb Forces in Electron Capture Dissociation and Electron Transfer Dissociation Mass Spectroscopy
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Strength of the Lewis–Brønsted Superacids Containing In, Sn, and Sb and the Electron Binding Energies of Their Corresponding Superhalogen Anions
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Effects of Base π-Stacking on Damage to DNA by Low-Energy Electrons
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A Theoretical Model for Indirect Dissociative Electron Attachment
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Theoretical Search for Alternative Nine-Electron Ligands Suitable for Superhalogen Anions
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Backbone and Side-Chain Cleavages in Electron Detachment Dissociation (EDD)
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The Reason Why HAlCl4 Acid Does Not Exist
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The formation of formaldehyde via the carbon monoxide hydrogenation catalyzed by the HSbF6 superacid
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Effect of hybrid TiO2 nanoparticles with controlled morphology on rheological properties of poly(styrene-co-acrylonitrile) nanocomposites
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Facile synthesis of porous iron oxide/graphene hybrid nanocomposites and potential application in electrochemical energy storage
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The in situ construction of three-dimensional core–shell-structured TiO2@PPy/rGO nanocomposites for improved supercapacitor electrode performance
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One-pot synthesis of core/shell Co@C spheres by catalytic carbonization of mixed plastics and their application in the photo-degradation of Congo red
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