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Amide Hydrogen (amide + hydrogen)
Selected AbstractsA nitrogen-15 NMR study of hydrogen bonding in 1-alkyl-4-imino-1,4-dihydro-3-quinolinecarboxylic acids and related compoundsMAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2006Laurence Carlton Abstract The title compounds contain groups (amine, amide, imine, carboxylic acid) that are capable of forming intramolecular hydrogen bonds involving a six-membered ring. In compounds where the two interacting functional groups are imine and carboxylic acid, the imine is protonated to give a zwitterion; where the two groups are imine and amide, the amide remains intact and forms a hydrogen bond to the imine nitrogen. The former is confirmed by the iminium 15N signal, which shows the coupling of 1J(15N,1H) ,85 to ,86.8 Hz and 3J(1H,1H) 3.7,4.2 Hz between the iminium proton and the methine proton of a cyclopropyl substituent on the iminium nitrogen. Hydrogen bonding of the amide is confirmed by its high 1H chemical shift and by coupling of the amide hydrogen to (amide) nitrogen [(1J(15N,1H) ,84.7 to ,90.7 Hz)] and to ortho carbons of a phenyl substituent. Data obtained from N,N -dimethylanthranilic acid show 15N1H coupling of (,)8.2 Hz at 223 K (increasing to (,)5.3 Hz at 243 K) consistent with the presence of a N··· HO hydrogen bond. Copyright © 2006 John Wiley & Sons, Ltd. [source] Understanding Promiscuous Amidase Activity of an Esterase from Bacillus subtilisCHEMBIOCHEM, Issue 1 2008Robert Kourist Water works. Bacillus subtilis esterase BS2 is a promiscuous esterase that shows amidase activity. This amidase activity was shown to depend on a hydrogen-bond network with the substrate amide hydrogen (indicated by arrow). When this stabilising hydrogen bond network was removed by a point mutation, the amide activity was significantly lowered in comparison with the esterase activity. [source] A Cyclam Core Dendrimer Containing Dansyl and Oligoethylene Glycol Chains in the Branches: Protonation and Metal CoordinationCHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2006Barbara Branchi Dr. Abstract We have synthesized a dendrimer (1) consisting of a 1,4,8,11-tetraazacyclotetradecane (cyclam) core, appended with four benzyl substituents that carry, in the 3- and 5-positions, a dansyl amide derivative (of type 2), in which the amide hydrogen is replaced by a benzyl unit that carries an oligoethylene glycol chain in the 3- and 5-positions. All together, the dendrimer contains 16 potentially luminescent moieties (eight dansyl- and eight dimethoxybenzene-type units) and three distinct types of multivalent sites that, in principle, can be protonated or coordinated to metal ions (the cyclam nitrogen atoms, the amine moieties of the eight dansyl units, and the 16 oligoethylene glycol chains). We have studied the absorption and luminescence properties of 1, 2, and 3 in acetonitrile and the changes taking place upon titration with acid and a variety of divalent (Co2+, Ni2+, Cu2+, Zn2+), and trivalent (Nd3+, Eu3+, Gd3+) metal ions as triflate and/or nitrate salts. The results obtained show that: 1) double protonation of the cyclam ring takes place before protonation of the dansyl units; 2) the oligoethylene glycol chains do not interfere with protonation of the cyclam core and the dansyl units in the ground state, but affect the luminescence of the protonated dansyl units; 3) the first equivalent of metal ion is coordinated by the cyclam core; 4) the interaction of the resulting cyclam complex with the appended dansyl units depends on the nature of the metal ion; 5) coordination of metal ions by the dansyl units follows at high metal-ion concentrations; 6) the effect of the metal ion depends on the nature of the counterion. This example demonstrates that dendrimers may exhibit complete functionality resulting from the integration of the specific properties of their component units. [source] Structure of the 21,30 fragment of amyloid ,-proteinPROTEIN SCIENCE, Issue 6 2006Andrij Baumketner Abstract Folding and self-assembly of the 42-residue amyloid ,-protein (A,) are linked to Alzheimer's disease (AD). The 21,30 region of A,, A,(21,30), is resistant to proteolysis and is believed to nucleate the folding of full-length A,. The conformational space accessible to the A,(21,30) peptide is investigated by using replica exchange molecular dynamics simulations in explicit solvent. Conformations belonging to the global free energy minimum (the "native" state) from simulation are in good agreement with reported NMR structures. These conformations possess a bend motif spanning the central residues V24,K28. This bend is stabilized by a network of hydrogen bonds involving the side chain of residue D23 and the amide hydrogens of adjacent residues G25, S26, N27, and K28, as well as by a salt bridge formed between side chains of K28 and E22. The non-native states of this peptide are compact and retain a native-like bend topology. The persistence of structure in the denatured state may account for the resistance of this peptide to protease degradation and aggregation, even at elevated temperatures. [source] Glycerol-induced folding of unstructured disulfide-deficient lysozyme into a native-like conformationBIOPOLYMERS, Issue 8 2009Keiko Sakamoto Abstract 2SS[6-127,64-80] variant of lysozyme which has two disulfide bridges, Cys6-Cys127 and Cys64-Cys80, and lacks the other two disulfide bridges, Cys30-Cys115 and Cys76-Cys94, was quite unstructured in water, but a part of the polypeptide chain was gradually frozen into a native-like conformation with increasing glycerol concentration. It was monitored from the protection factors of amide hydrogens against H/D exchange. In solution containing various concentrations of glycerol, H/D exchange reactions were carried out at pH* 3.0 and 4°C. Then, 1H- 15N-HSQC spectra of partially deuterated protein were measured in a quenching buffer for H/D exchange (95% DMSO/5% D2O mixture at pH* 5.5 adjusted with dichloroacetate). In a solution of 10% glycerol, the protection factors were nearly equal to 10 at most of residues. With increasing glycerol concentration, some selected regions were further protected, and their protection factors reached about a 1000 in 30% glycerol solution. The highly protected residues were included in A-, B-, and C-helices and ,3-strand, and especially centered on Ile 55 and Leu 56. In 2SS[6-127,64-80], long-range interactions were recovered due to the preferential hydration by glycerol in the hydrophobic box of the ,-domain. Glycerol-induced recovering of the native-like structure is discussed from the viewpoint of molten globules growing with the protein folding. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 665,675, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Investigation of Protein,Ligand Interactions by Mass SpectrometryCHEMMEDCHEM, Issue 4 2007Andrea Sinz Prof. Abstract The rate of drug discovery is greatly dependent on the development and improvement of rapid and reliable analytical methods that allow screening for protein,ligand interactions. The solution-based methods for investigating protein,ligand interactions by mass spectrometry (MS), which are discussed in this paper, are hydrogen/deuterium exchange of protein backbone amide hydrogens, and photoaffinity labeling. Moreover, MS analysis of intact noncovalent protein,ligand complexes is described. Fourier transform ion cyclotron resonance mass spectrometry (FTICR,MS) with its ultra-high resolution and excellent mass accuracy is also considered herein as it is gaining increasing popularity for a mass spectrometric investigation of protein,ligand interactions. [source] | ||||||||||