1H NMR studies of proton transfer in Schiff base and carboxylic acid systems

1990 ◽  
Vol 68 (10) ◽  
pp. 1909-1916 ◽  
Author(s):  
Hoa Le-Thanh ◽  
D. Vocelle
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Schiff Base ◽  
Proton Transfer ◽  
Carboxylic Acids ◽  
Proton Nuclear Magnetic Resonance ◽  
Nmr Studies ◽  
H Nmr ◽  
Mineral Acids ◽  
Rapid Equilibrium

When the unconjugated Schiff base, isobutylidene isopropylamine (2), reacts with acids such as the mineral acids HCl, HBr, and HI, or the carboxylic acids trichloroacetic, monochloroacetic, and propionic acid, in CDCl3, several complexes are formed. In this study, 1H NMR allows us to differentiate between several possibilities. With the mineral acids, only 1:1 structures are seen and the chemical shift of the [Formula: see text] proton varies according to the strength of the hydrogen bond between the protonated Schiff base and its counterion. With the carboxylic acids, 1:1 and 1:2 structures are present in rapid equilibrium. In the presence of an excess of acid, protonation of the Schiff base increases considerably. Extrapolation of the results is given in terms of the molecular mechanism of vision. Keywords: protonation, proton nuclear magnetic resonance, proton transfer, rhodopsins, Schiff base.

scholarly journals Proton Nuclear Magnetic Resonance Metabolomics Corroborates Serine Hydroxymethyltransferase as the Primary Target of 2-Aminoacrylate in a ridA Mutant of Salmonella enterica

mSystems ◽  
2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Andrew J. Borchert ◽  
Goncalo J. Gouveia ◽  
Arthur S. Edison ◽  
Diana M. Downs
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Metabolic Stress ◽  
Metabolic Changes ◽  
Serine Hydroxymethyltransferase ◽  
Proton Nuclear Magnetic Resonance ◽  
Growth Defect ◽  
Nutrient Supplementation ◽  
Content Type ◽  
H Nmr

ABSTRACT The reactive intermediate deaminase RidA (EC 3.5.99.10) is conserved across all domains of life and deaminates reactive enamine species. When Salmonella enterica ridA mutants are grown in minimal medium, 2-aminoacrylate (2AA) accumulates, damages several pyridoxal 5′-phosphate (PLP)-dependent enzymes, and elicits an observable growth defect. Genetic studies suggested that damage to serine hydroxymethyltransferase (GlyA), and the resultant depletion of 5,10-methelenetetrahydrofolate (5,10-mTHF), was responsible for the observed growth defect. However, the downstream metabolic consequence from GlyA damage by 2AA remains relatively unexplored. This study sought to use untargeted proton nuclear magnetic resonance (1H NMR) metabolomics to determine whether the metabolic state of an S. enterica ridA mutant was accurately reflected by characterizing growth phenotypes. The data supported the conclusion that metabolic changes in a ridA mutant were due to the IlvA-dependent generation of 2AA, and that the majority of these changes were a consequence of damage to GlyA. While many of the metabolic differences for a ridA mutant could be explained, changes in some metabolites were not easily modeled, suggesting that additional levels of metabolic complexity remain to be unraveled. IMPORTANCE The accumulation of the reactive enamine intermediate 2-aminoacrylate (2AA) elicits global metabolic stress in many prokaryotes and eukaryotes by simultaneously damaging multiple pyridoxal 5′-phosphate (PLP)-dependent enzymes. This work employed 1H NMR to expand our understanding of the consequence(s) of 2AA stress on metabolite pools and effectively identify the metabolic changes stemming from one damaged target: GlyA. This study shows that nutrient supplementation during 1H NMR metabolomics experiments can disentangle complex metabolic outcomes stemming from a general metabolic stress. Metabolomics shows great potential to complement classical reductionist approaches to cost-effectively accelerate the rate of progress in expanding our global understanding of metabolic network structure and physiology. To that end, this work demonstrates the utility in implementing nutrient supplementation and genetic perturbation into metabolomics workflows as a means to connect metabolic outputs to physiological phenomena and establish causal relationships.

Amino acid/zwitterion equilibria II: vibrational and NMR studies of substituted thiazolidine-4-carboxylic acids

1991 ◽  
Vol 69 (11) ◽  
pp. 1721-1727 ◽  
Author(s):  
H. E. Howard-Lock ◽  
C. J. L. Lock ◽  
M. L. Martins
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Amino Acid ◽  
Carboxylic Acids ◽  
Infrared And Raman Spectra ◽  
Solid Samples ◽  
Nmr Studies ◽  
Nuclear Magnetic Resonance Spectra ◽  
Key Words Amino Acid ◽  
Methyl Derivatives ◽  
Derivatives Of

Infrared and Raman spectra (4000–100 cm) of solid samples of seven different 2-phenyl-, N-benzoyl-, and 2-ethyl-2 methyl derivatives of L-cysteine and D-penicillamine have been observed and assigned. Proton and 13C nuclear magnetic resonance spectra for the compounds have also been measured. Amino acid/zwitterion equilibria are discussed with reference to pK values and the vibrational spectra. Key words: amino acid/zwitterion equilibria, thiazolidine carboxylic acids.

scholarly journals Correlations between Proton Nuclear Magnetic Resonance Imaging and Retrospective Histochemical Images in Experimental Cerebral Infarction

1985 ◽  
Vol 5 (2) ◽  
pp. 267-274 ◽  
Author(s):  
Hiroyuki Kato ◽  
Kyuya Kogure ◽  
Hitoshi Ohtomo ◽  
Muneshige Tobita ◽  
Shigeru Matsui ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Spin Echo ◽  
Proton Nuclear Magnetic Resonance ◽  
Nmr Imaging ◽  
Resonance Imaging ◽  
H Nmr ◽  
Experimental Cerebral Infarction ◽  
Nuclear Magnetic

Evaluation of ischemic brain injury in experimental cerebral infarction in gerbils and rats was performed by means of both proton nuclear magnetic resonance imaging ([1H]NMR-CT) and various histochemical analyses. In vivo nuclear magnetic resonance (NMR) imaging was carried out employing saturation recovery, inversion recovery, and spin echo pulse sequences. Spatial resolution of the images was excellent. The ischemic lesions were detected with a remarkable contrast in inversion recovery and spin echo images within a few hours after insult. Those changes in NMR images consistently corresponded with the various retrospective histochemical observations, especially with methods related to brain edema (K+ staining) rather than structural (enzymatic) studies. Calculated T1 and T2 relaxation times indicated the evolution of the edema state in the brain in situ. They correlated excellently with the retrospective water content measurement. As a result, detailed characterization of the edema state induced by cerebral ischemia was possible in vivo using [1H]NMR imaging.

1H NMR studies on the solution conformation of contulakin-G and analogues

2002 ◽  
Vol 80 (8) ◽  
pp. 1022-1031 ◽  
Author(s):  
Lill Kindahl ◽  
Corine Sandström ◽  
A Grey Craig ◽  
Thomas Norberg ◽  
Lennart Kenne
Keyword(s):  
Hydrogen Bond ◽  
Chemical Shifts ◽  
Torsional Rigidity ◽  
Peptide Chain ◽  
Random Coil ◽  
Amide Proton ◽  
Solution Conformation ◽  
Nmr Studies ◽  
H Nmr ◽  
Intramolecular Hydrogen

The conformation of contulakin-G, a bioactive 16 amino acid O-linked glycopeptide (ZSEEGGSNAT*KKPYIL) with the disaccharide β-D-Gal(1[Formula: see text]3)α-D-GalNAc attached to the threonine residue in position 10, has been investigated by 1H NMR spectroscopy. The 1H NMR data for the non-glycosylated peptide and for two glycopeptide analogues, one with the monosaccharide α-D-GalNAc at Thr10 and one with the disaccharide β-D-Gal(1–>3)α-D-GalNAc at Ser7, all of lower bioactivity than contulakin-G, have also been collected. The chemical shifts, NOEs, temperature coefficients of amide protons, and 3JNH,αH-values suggest that all four compounds exist mainly in random coil conformations. Some transient populations of folded conformations are also present in the glycopeptides and turns, probably induced by the sugars, are present in the peptide chain around the site of glycosylation. In the two peptides O-glycosylated at Thr10, the rotation of α-D-GalNAc around the linkage between the sugar and the peptide is restricted. There is evidence for a hydrogen bond between the amide proton of α-D-GalNAc and the peptide chain that could contribute to this torsional rigidity. An intramolecular hydrogen bond between the carbohydrate and the peptide chain does not exist in the peptide O-glycosylated at the Ser7 residue. Key words: conformation, contulakin-G, NMR, O-linked glycopeptide.

Solvent-mediated pseudo-quadruple hydrogen-bond motifs in three lamotrigine–carboxylic acid complexes

2013 ◽  
Vol 69 (10) ◽  
pp. 1164-1169 ◽  
Author(s):  
Balasubramanian Sridhar ◽  
Jagadeesh Babu Nanubolu ◽  
Krishnan Ravikumar
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Carboxylic Acid ◽  
Proton Transfer ◽  
Antiepileptic Drug ◽  
Carboxylic Acids ◽  
Solvent Interactions ◽  
Partial Transfer ◽  
Quadruple Hydrogen Bonding ◽  
Quadruple Hydrogen Bond

Lamotrigine, an antiepileptic drug, has been complexed with three aromatic carboxylic acids. All three compounds crystallize with the inclusion ofN,N-dimethylformamide (DMF) solvent,viz.lamotriginium [3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazin-2-ium] 4-iodobenzoateN,N-dimethylformamide monosolvate, C9H8Cl2N5+·C7H4IO2−·C3H7NO, (I), lamotriginium 4-methylbenzoateN,N-dimethylformamide monosolvate, C9H7Cl2N5+·C8H8O2−·C3H7NO, (II), and lamotriginium 3,5-dinitro-2-hydroxybenzoateN,N-dimethylformamide monosolvate, C9H8Cl2N5+·C7H3N2O7−·C3H7NO, (III). In all three structures, proton transfer takes place from the acid to the lamotrigine molecule. However, in (I) and (II), the acidic H atom is disordered over two sites and there is only partial transfer of the H atom from O to N. In (III), the corresponding H atom is ordered and complete proton transfer has occurred. Lamotrigine–lamotrigine, lamotrigine–acid and lamotrigine–solvent interactions are observed in all three structures and they thereby exhibit isostructurality. The DMF solvent extends the lamotrigine–lamotrigine dimers into a pseudo-quadruple hydrogen-bonding motif.

1H NMR studies on the solution conformation of the [L-Ser10] and [D-Ser10] analogues of contulakin-G

2005 ◽  
Vol 83 (2) ◽  
pp. 156-165 ◽  
Author(s):  
Lill Kindahl ◽  
Lennart Kenne ◽  
Corine Sandström
Keyword(s):  
Hydrogen Bond ◽  
Biological Data ◽  
Random Coil ◽  
Solution Conformation ◽  
Nmr Studies ◽  
Peptide Backbone ◽  
H Nmr ◽  
Nmr Data ◽  
Nmr Study ◽  
C Terminus

The synthesis of the O-glycosylated serine-10 analogue of contulakin-G yielded both the [L-] and the [D-Ser10] analogues. The 1H NMR study indicated that the sugars of the two Ser10-glycosylated peptides lacked the hydrogen bond to the peptide backbone that exists in contulakin-G. NOEs showed that the glycan part of the [D-Ser10] analogue had a different orientation to the peptide backbone than that of the [L-Ser10] analogue. The peptide backbones in the two compounds were found to exist mainly in random coil conformations, with transient turns at the site of glycosylation. A transient turn was also found at the C-terminus of the [D-Ser10] glycopeptide. The NMR data indicated that the average conformation of the [D-Ser10] analogue resembles the conformation of contulakin-G more than the [L-Ser] does. Since biological data showed that the [D-Ser10] glycopeptide was as active as contulakin-G, while the [L-Ser10] glycopeptide was only slightly active at more than 100 times the dose, it is possible that it is the orientation of the glycan relative to the peptide chain that is actually recognized by the proteolytic enzyme.Key words: conformation, contulakin-G analogues, NMR, O-linked glycopeptide.

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