101
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de Kowalewski DG, Díez E, Esteban AL, Barone V, Peralta JE, Contreras RH. Substituent effects on scalar J(13C, 13C) couplings in pyrimidines. An experimental and DFT study. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2004; 42:938-943. [PMID: 15386555 DOI: 10.1002/mrc.1426] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
One- two- and three 13C, 13C (n = 1, 2, 3) scalar couplings, (n)J(C,C) in a set of pyrimidine derivatives were studied both experimentally at natural abundance and theoretically by their DFT calculation of all four contributions. Trends of non-contact terms are discussed and substituent effects are rationalized, comparing some of them with the corresponding values in benzene and pyridine. Although substituent effects on non-contact terms are relatively important, the whole trend is dominated by the Fermi contact term. According to the current literature, substituent effects on 1J(C,C) couplings in benzene derivatives are dominated by the inductive effect, which, apparently, is also the case in nitrogen heteroaromatic compounds. However, some differences observed in this work for substituent effects on 1J(C,C) couplings in pyrimidine derivatives suggest that in the latter type of compounds substituent effects can be affected by the orientation of the ring nitrogen lone pairs.
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Affiliation(s)
- Dora G de Kowalewski
- Departamento de Física, FCEyN, Universidad de Buenos Aires, Ciudad Universitaria, P. 1 and CONICET (C1428EHA), Buenos Aires, Argentina
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102
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Henckens A, Adriaensens P, Gelan J, Lutsen L, Vanderzande D. Synthesis and complete NMR spectral assignment of thiophene-substituted sulfinyl monomers. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2004; 42:931-937. [PMID: 15372616 DOI: 10.1002/mrc.1455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
This paper describes the synthesis of thiophene-substituted sulfinyl monomers. It comprises a four-step reaction by which the thiophene unit is built in via Suzuki coupling. These monomers could be used as building blocks for the preparation of conducting polymers via a new concept: the sulfinyl precursor route i.e. via thiophene substituted poly(p-phenylenevinylene) precursors. Furthermore, the complete 1H and 13C NMR signal assignment is presented. In addition to being essential for the characterization of the polymers concerned, it offers useful input information for further improvement of chemical shift prediction software. Furthermore, the T1C relaxation decay times are demonstrated to have the potential of being a fast and robust criterion for the spectral assignment of analogous monomers.
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Affiliation(s)
- Anja Henckens
- Laboratory for Organic and Polymer Chemistry, Limburgs Universitair Centrum, IMO, Division Chemistry, Universitaire Campus, B-3590 Diepenbeek, Belgium
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103
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Koźmiński W, Zhukov I. The DQ-HN[CACB] and DQ-HN(CO)[CACB] sequences with evolution of double quantum Calpha-Cbeta coherences. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2004; 171:186-191. [PMID: 15504699 DOI: 10.1016/j.jmr.2004.08.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2004] [Revised: 08/19/2004] [Indexed: 05/24/2023]
Abstract
The new variant of known HNCACB and HN(CO)CACB techniques is proposed that employs excitation and evolution of double quantum Calpha-Cbeta coherences. The most important features of the new method are: increased signal dispersion, lack of splittings due to 1J(Calpha-Cbeta) spin-spin couplings, and absence of accidental cancellations of positive and negative signals. The acquisition of both DQ-HN[CACB] and DQ-HN(CO)[CACB] techniques enables sequential assignment of protein backbone, using only Calpha-Cbeta DQ-frequencies. The determination of all Calpha and Cbeta chemical shifts requires, however, a comparison with HN(CO)CA or HNCA spectra. Examples of applications of the DQ-HN[CACB] and DQ-HN(CO)[CACB] experiments are presented, employing the 2D Reduced Dimensionality approach for 13C, 15N-labeled ubiquitin, and the 3D acquisition for 13C, 15N-double labeled Ca2+ -binding bovine S100A1 protein in the apo state (21 kDa) with overall correlation time of 8.1 ns.
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Affiliation(s)
- Wiktor Koźmiński
- Department of Chemistry, Warsaw University, ul. Pasteura 1, 02-093 Warszawa, Poland.
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104
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Eppers O, Fox T, Günther H. The6Li,6Li-INADEQUATE Experiment: A New Tool for 1D- and 2D-NMR Studies of Organolithium Compounds. Helv Chim Acta 2004. [DOI: 10.1002/hlca.19920750322] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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105
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Mueller LJ, Elliott DW, Leskowitz GM, Struppe J, Olsen RA, Kim KC, Reed CA. Uniform-sign cross-peak double-quantum-filtered correlation spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2004; 168:327-335. [PMID: 15140444 DOI: 10.1016/j.jmr.2004.03.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2003] [Revised: 03/18/2004] [Indexed: 05/24/2023]
Abstract
We detail the uniform-sign cross-peak double-quantum-filtered correlation spectroscopy (UC2QF COSY) experiment, a new through-bond correlation method for disordered solids. This experiment is a refocused version of the popular double-quantum-filtered correlation spectroscopy experiment in liquids. Its key feature is that it provides in-phase and doubly absorptive line shapes, which renders it robust for chemical shift correlation in solids. Both theory and experiment point to distinct advantages of this protocol, which are illustrated by several experiments under challenging conditions, including fast magic-angle spinning (30kHz), anisotropic molecular motion, and (13)C correlation spectroscopy at the natural abundance isotope level.
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Affiliation(s)
- Leonard J Mueller
- Department of Chemistry, University of California, Riverside, CA 92521, USA.
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106
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Brus J, Jegorov A. Through-Bonds and Through-Space Solid-State NMR Correlations at Natural Isotopic Abundance: Signal Assignment and Structural Study of Simvastatin. J Phys Chem A 2004. [DOI: 10.1021/jp0498163] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jiri Brus
- Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky sq. 2, 162 06 Prague 6, Czech Republic, and IVAX Pharmaceutical sro, Research Unit, Branisovska 31, 370 05 Ceske Budejovice, Czech Republic
| | - Alexandr Jegorov
- Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky sq. 2, 162 06 Prague 6, Czech Republic, and IVAX Pharmaceutical sro, Research Unit, Branisovska 31, 370 05 Ceske Budejovice, Czech Republic
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107
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Fayon F, King IJ, Harris RK, Evans JS, Massiot D. Application of the through-bond correlation NMR experiment to the characterization of crystalline and disordered phosphates. CR CHIM 2004. [DOI: 10.1016/j.crci.2003.10.019] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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108
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Kövér KE, Forgó P. J-modulated ADEQUATE (JM-ADEQUATE) experiment for accurate measurement of carbon-carbon coupling constants. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2004; 166:47-52. [PMID: 14675819 DOI: 10.1016/j.jmr.2003.09.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A new method for the accurate determination of carbon-carbon coupling constants is described. The method is based on a modified ADEQUATE experiment, where a J-modulated spin-echo sequence precedes the ADEQUATE pulse scheme. The J-modulation and scaling of carbon-carbon couplings is based on simultaneous incrementation of 13C chemical shift and coupling evolution periods. The time increment for the homonuclear carbon-carbon coupling evolution can be suitably scaled with respect to the corresponding increment for the chemical shift evolution. Typically a scaling factor of 2 to 3 is employed for the measurement of one-bond coupling constants, while multiplication by a factor of 10 to 15 is applied when small long-range couplings are determined. The same pulse scheme with coupling evolution period optimized for one-bond or long-range couplings allows the determination of the corresponding carbon-carbon coupling constants. The splittings of the ADEQUATE crosspeaks in the F1 dimension yield the appropriately multiplied coupling constants.
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Affiliation(s)
- Katalin E Kövér
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Egyetem tér 1, H-4010 Debrecen, Hungary.
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109
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Takafuji M, Fukui M, Ansarian HR, Derakhshan M, Shundo A, Ihara H. Conformational Effect of Silica-supported Poly(octadecyl acrylate) on Molecular-Shape Selectivity of Polycyclic Aromatic Hydrocarbons in RP-HPLC. ANAL SCI 2004; 20:1681-5. [PMID: 15636515 DOI: 10.2116/analsci.20.1681] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Poly(octadecyl acrylate) with a terminal reactive group was synthesized by radical telomerization in various solvents. The polymers were grafted onto porous silica for use in RP-HPLC, and the molecular recognition ability was investigated along with the selectivity for the structural isomers of polycyclic aromatic hydrocarbons. The mechanism of selectivity was also investigated with differential scanning calorimetry and NMR spectroscopic observations.
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Affiliation(s)
- Makoto Takafuji
- Department of Applied Chemistry & Biochemistry, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan
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110
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Advantages and disadvantages of nuclear magnetic resonance spectroscopy as a hyphenated technique. Anal Chim Acta 2003. [DOI: 10.1016/j.aca.2003.08.048] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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111
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Duma L, Hediger S, Lesage A, Emsley L. Spin-state selection in solid-state NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2003; 164:187-195. [PMID: 12932473 DOI: 10.1016/s1090-7807(03)00187-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Spin-state selection in solid-state NMR is demonstrated, using similar pulse sequences as used in liquid-state NMR. The different transitions of all three carbon resonances in fully 13C-labeled L-alanine are separated in different spectra. By selecting spin-states, the contribution of the J-coupling to the linewidth is removed, leading to a considerable enhancement in resolution. The spin-state-selective technique is demonstrated for magic-angle spinning frequencies from 6 to 35kHz. Other experimental conditions affecting the sensitivity of the experiments are discussed. Sensitivity losses due to the introduction of the spin-state-selective filter are shown to be acceptable. Finally, spin-state selection was used to experimentally confirm the differential broadening expected for the two transitions of the CH3 resonance.
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Affiliation(s)
- Luminita Duma
- Laboratoire de Chimie (UMR-5532 CNRS/ENS), Laboratoire de Recherche Conventionné du CEA (23V), Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, 69364 Lyon, France
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112
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Verdier L, Sakhaii P, Zweckstetter M, Griesinger C. Measurement of long range H,C couplings in natural products in orienting media: a tool for structure elucidation of natural products. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2003; 163:353-359. [PMID: 12914852 DOI: 10.1016/s1090-7807(03)00063-6] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In this paper we show that water insoluble compounds dissolved in poly-gamma-benzyl-glutamate are amenable to the measurement of a number of homo- and heteronuclear dipolar couplings. The sensitivity and experimental precision of dipolar couplings are sufficient to obtain a good match with the structure. In order to achieve the necessary precision for H,C dipolar couplings between protons and carbons that are not directly bound a new method for the measurement of heteronuclear long range couplings is introduced that allows a one-parameter fit to a HSQC-based experiment as reference experiment. The methodology is applied to menthol (1R, 3S, 4R).
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Affiliation(s)
- Laurent Verdier
- Max Planck Institute for Biophysical Chemistry, Abt. 030, Am Fassberg 11, 37077 Göttingen, Germany
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113
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Wang CZ, Maier UH, Keil M, Zenk MH, Bacher A, Rohdich F, Eisenreich W. Phenylalanine-independent biosynthesis of 1,3,5,8-tetrahydroxyxanthone. A retrobiosynthetic NMR study with root cultures of Swertia chirata. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:2950-8. [PMID: 12846828 DOI: 10.1046/j.1432-1033.2003.03669.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Root cultures of Swertia chirata (Gentianaceae) were grown with supplements of [1-13C]glucose, [U-13C6]glucose or [carboxy-13C]shikimic acid. 1,3,5,8-Tetrahydroxyxanthone was isolated and analysed by quantitative NMR analysis. The observed isotopomer distribution shows that 1,3,5,8-tetrahydroxyxanthone is biosynthesized via a polyketide-type pathway. The starter unit, 3-hydroxybenzoyl-CoA, is obtained from an early shikimate pathway intermediate. Phenylalanine, cinnamic acid and benzoic acid were ruled out as intermediates.
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Affiliation(s)
- Chang-Zeng Wang
- Biozentrum-Pharmazie, Universität Halle, Halle/Saale, Germany
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114
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Roy D, Basu PK, Raghunathan P, Eswaran SV. Novolak resins: structure elucidation by multidimensional NMR techniques and correlation with lithographic performance. POLYM INT 2003. [DOI: 10.1002/pi.1141] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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115
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Glawischnig E, Gierl A, Tomas A, Bacher A, Eisenreich W. Starch biosynthesis and intermediary metabolism in maize kernels. Quantitative analysis of metabolite flux by nuclear magnetic resonance. PLANT PHYSIOLOGY 2002; 130:1717-27. [PMID: 12481054 PMCID: PMC166686 DOI: 10.1104/pp.006726] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2002] [Revised: 05/22/2002] [Accepted: 09/02/2002] [Indexed: 05/20/2023]
Abstract
The seeds of cereals represent an important sink for metabolites during the accumulation of storage products, and seeds are an essential component of human and animal nutrition. Understanding the metabolic interconversions (networks) underpinning storage product formation could provide the foundation for effective metabolic engineering of these primary nutritional sources. In this paper, we describe the use of retrobiosynthetic nuclear magnetic resonance analysis to establish the metabolic history of the glucose (Glc) units of starch in maize (Zea mays) kernels. Maize kernel cultures were grown with [U-(13)C(6)]Glc, [U-(13)C(12)]sucrose, or [1,2-(13)C(2)]acetate as supplements. After 19 d, starch was hydrolyzed, and the isotopomer composition of the resulting Glc was determined by quantitative nuclear magnetic resonance analysis. [1,2-(13)C(2)]Acetate was not incorporated into starch. [U-(13)C(6)]Glc or [U-(13)C(12)]sucrose gave similar labeling patterns of polysaccharide Glc units, which were dominated by [1,2,3-(13)C(3)]- and [4,5,6-(13)C(3)]-isotopomers, whereas the [U-(13)C(6)]-, [3,4,5,6-(13)C(4)]-, [1,2-(13)C(2)]-, [5,6-(13)C(2)], [3-(13)C(1)], and [4-(13)C(1)]-isotopomers were present at lower levels. These isotopomer compositions indicate that there is extensive recycling of Glc before its incorporation into starch, via the enzymes of glycolytic, glucogenic, and pentose phosphate pathways. The relatively high abundance of the [5,6-(13)C(2)]-isotopomer can be explained by the joint operation of glycolysis/glucogenesis and the pentose phosphate pathway.
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Affiliation(s)
- Erich Glawischnig
- Lehrstuhl für Genetik, Technische Universität München, Am Hochanger 8, 85350 Freising, Germany
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116
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Fayon F, Le Saout G, Emsley L, Massiot D. Through-bond phosphorus-phosphorus connectivities in crystalline and disordered phosphates by solid-state NMR. Chem Commun (Camb) 2002:1702-3. [PMID: 12196957 DOI: 10.1039/b205037b] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
2D 31P refocused INADEQUATE NMR experiments have been used to determine through-bond P-O-P connectivities in crystalline and disordered phosphates.
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Affiliation(s)
- Franck Fayon
- Centre de Recherches sur les Matériaux à Haute Température, CNRS, 45071 Orléans, France.
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117
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Grasso G, de Swiet TM, Titman JJ. Electronic Structure of the Polymer Phase of CsC60: Refocused INADEQUATE Experiments. J Phys Chem B 2002. [DOI: 10.1021/jp026093j] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Giuseppe Grasso
- School of Chemistry, University of Nottingham, University Park, Nottingham, UK
| | - Thomas M. de Swiet
- School of Chemistry, University of Nottingham, University Park, Nottingham, UK
| | - Jeremy J. Titman
- School of Chemistry, University of Nottingham, University Park, Nottingham, UK
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118
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Meissner A, Winneche Sørensen O. Exercise in modern NMR pulse sequence design: INADEQUATE CR. ACTA ACUST UNITED AC 2002. [DOI: 10.1002/cmr.10024] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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119
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Brown SP, Pérez-Torralba M, Sanz D, Claramunt RM, Emsley L. The direct detection of a hydrogen bond in the solid state by NMR through the observation of a hydrogen-bond mediated (15)N [bond] (15)N J coupling. J Am Chem Soc 2002; 124:1152-3. [PMID: 11841267 DOI: 10.1021/ja0172262] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A new method for detecting hydrogen bonds in the solid state is presented. Using two-dimensional NMR correlation experiments, it is shown that a hydrogen-bond mediated J coupling can be observed in a powder under magic-angle spinning conditions, even though the J coupling is 2 orders of magnitude smaller than the dominant anisotropic interactions encountered in solid-state NMR. Specifically, the observation of a pair of peaks in a two-dimensional 15N-15N solid-state INADEQUATE experiment due to two nitrogens that have no covalent connectivity is attributed to the presence of a J coupling across a linking hydrogen bond.
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Affiliation(s)
- Steven P Brown
- Laboratoire de Stéréochimie et des Interactions Moléculaires, UMR 5532 CNRS/ENS, Laboratoire de Recherche Conventionné du CEA (no. 23V), Ecole Normale Supérieure de Lyon, 69364 Lyon, France
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120
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Brown SP, Spiess HW. Advanced solid-state NMR methods for the elucidation of structure and dynamics of molecular, macromolecular, and supramolecular systems. Chem Rev 2001; 101:4125-56. [PMID: 11740929 DOI: 10.1021/cr990132e] [Citation(s) in RCA: 320] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- S P Brown
- Max-Planck-Institut für Polymerforschung, Postfach 3148, D-55021 Mainz, Germany
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121
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Schulte-Herbrüggen T, Untidt TS, Nielsen NC, Sørensen OW. Broadband composite spin-state-selective rotations for NMR spectroscopy on partially aligned molecules. J Chem Phys 2001. [DOI: 10.1063/1.1408621] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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122
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Knaack M, Emig P, Bats J, Kiesel M, Müller A, Günther E. Synthesis and Characterization of the Biologically Active 2-[1-(4-Chlorobenzyl)-1H-indol-3-yl]-2-oxo-N-pyridin-4-yl Acetamide. European J Org Chem 2001. [DOI: 10.1002/1099-0690(200110)2001:20<3843::aid-ejoc3843>3.0.co;2-p] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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123
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Brittingham KA, Espenson JH. Thermodynamics, Kinetics, and Mechanism of the Reversible Formation of Oxorhenium(VII) Catecholate Complexes. Inorg Chem 2001; 40:2730-6. [PMID: 11375688 DOI: 10.1021/ic001188q] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mononuclear Re(V) compounds MeReO(mtp)NC(5)H(4)X, 3, where mtpH(2) is 2-(mercaptomethyl)thiophenol have been prepared from the monomerization of [MeReO(mtp)](2) by pyridines with electron-donating substituents in the para or meta position; X = 4-Me, 4-Bu(t), 3-Me, 4-Ph, and H. Analogous compounds, MeReO(edt)N(5)H(4)X, 4, edtH(2) = 1,2-ethanedithiol, were prepared similarly. The equilibrium constants for the reaction, dimer + 2Py = 2M-Py, are in the range (2.5-31.6) x 10(2) L mol(-1). Both groups of monomeric compounds react with quinones (phenanthrenequinone, PQ, and 3,5-tert-butyl-1,2-benzoquinone, DBQ), displacing the pyridine ligand and forming Re(VII) catecholate complexes MeReO(dithiolate)PCat and MeReO(dithiolate)DBCat. With PQ, the reaction MeReO(dithiolate)Py + PQ = MeReO(dithiolate)PCat + Py is an equilibrium; values of K(Q) for different Py ligands lie in the ranges 9.2-42.7 (mtp) and 3.2-11.2 (edt) at 298 K. These second-order rate constants (L mol(-1) s(-1)) at 25 degrees C in benzene were obtained for the PQ reactions: k(f) = (5.3-15.5) x 10(-2) (mtp), (6.6-16.4) x 10(-2) (edt); k(r) = (3.63-5.71) x 10(-3) (mtp), (14.7-22.0) x 10(-3) (edt). The ranges in each case refer to the series of pyridine ligands, the forward rate constant being the largest for C(5)H(5)N, with the lowest Lewis basicity. The reactions of MeReO(dithiolate)Py with DBQ proceed to completion. Values of k(f)/L mol(-1) s(-1) fall in a narrow range, 4.02 (X = Bu(t)) to 8.4 (X = H) with the dithiolate being mtp.
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Affiliation(s)
- K A Brittingham
- Ames Laboratory and the Department of Chemistry, Iowa State University of Science and Technology, Ames, Iowa 50011, USA
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124
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Abstract
Bicyclic aziridines formed by the irradiation of pyridinium salts in basic solution have recently been recognized to have great synthetic potential. We have undertaken a joint computational and experimental investigation of the mechanism of this photoreaction. We have computationally determined the structures and relative energies of the relevant stationary points on the lowest potential energy surface (PES) of the pyridinium and methylpyridinium ions. Two important intermediates are shown to be bound minima on the ground-state PES: azoniabenzvalene and a 6-aza[3.1.0]bicyclic ion with an exo-oriented substituent (analogous to prefulvene). We advance a mechanism which involves initial formation of this exo-bicyclic ion, followed by nitrogen migration around the ring via the azoniabenzvalene intermediate. Thus, the barrier separating the two intermediates is the factor that determines the degree of scrambling observed in the photoproducts when the carbon atoms are labeled with deuterium or substituted with additional methyl groups. For N-methylpyridinium, the exo-methyl bicyclic ion was computed to be approximately 1 kcalmol(-1) lower in energy than N-methyl-azoniabenzvalene. The transition state was computed to lie several kcal mol(-1) above the exo-methyl bicyclic ion (+8.4kcalmol(-1), 6-31G* RHF; +3.7kcalmol(-1), 6-31G* B3LYP), but still well below the energy available from the 254 nm excitation of the N-methylpyridinium ion. The computed relative energies correspond splendidly with several experimental findings which include the preference for exo products, the results of deuterium labeling, and the impact of additional substituent methyl groups on the product distribution.
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Affiliation(s)
- R A King
- Laboratorium für Physikalische Chemie, ETH Zentrum, Zürich, Switzerland
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125
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Heindrichs AS, Geen H, Giordani C, Titman JJ. Improved scalar shift correlation NMR spectroscopy in solids. Chem Phys Lett 2001. [DOI: 10.1016/s0009-2614(01)00018-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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126
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Hoek AC, Hermans-Lokkerbol AC, Verpoorte R. An improved NMR method for the quantification of alpha-acids in hops and hop products. PHYTOCHEMICAL ANALYSIS : PCA 2001; 12:53-57. [PMID: 11704962 DOI: 10.1002/1099-1565(200101/02)12:1<53::aid-pca550>3.0.co;2-e] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A new and independent method for the quantification of alpha-acids in hops and hop products has been developed. NMR was used as a qualitative method for the complete assignment of all 1H- and 13C-NMR signals of the three main alpha-acids, cohumulone (1), humulone (2) and adhumulone (3). In a 13C two-dimensional INADEQUATE experiment, the 13C-NMR spectrum of 1 was unambiguously assigned via the carbon-carbon connectivities. Use of NMR as a quantitative method allowed quantification of the pure and individual alpha-acids 1 and 2, and the determination of the absolute concentration of solutions of these compounds. Quantification of alpha-acids by NMR is less complicated and more reliable than the methods used until now.
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Affiliation(s)
- A C Hoek
- Department of Pharmacognosy, Leiden/Amsterdam Center for Drug Research, Gorlaeus Laboratories, PO Box 9502, 2300 RA Leiden, The Netherlands.
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127
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Bringmann G, Rischer H, Wohlfarth M, Schlauer J. Biosynthesis of Antidesmone in Cell Cultures of Antidesma membranaceum (Euphorbiaceae): An Unprecedented Class of Glycine-Derived Alkaloids. J Am Chem Soc 2000. [DOI: 10.1021/ja001391k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Gerhard Bringmann
- Contribution from the Institute of Organic Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Heiko Rischer
- Contribution from the Institute of Organic Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Michael Wohlfarth
- Contribution from the Institute of Organic Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Jan Schlauer
- Contribution from the Institute of Organic Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
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128
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Hartmann P, Zwanziger JW, Jäger C. Through-bond connectivity in solids by continuous-wave spin lock. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2000; 16:189-197. [PMID: 10868571 DOI: 10.1016/s0926-2040(00)00074-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A simple two-dimensional correlation experiment that enables determination of through-bond connectivity in the solid state is described. The experiment is performed under fast magic angle spinning (MAS) conditions. After the initial pi/2 pulse, the magnetization develops freely under the MAS Hamiltonian. The t1-period is followed by a strong spin locking pulse used as mixing period. The dipolar coupling is averaged out by magic angle spinning, and the chemical shifts and r.f.-offsets are scaled by the applied spin locking field. Hence, for strong locking conditions, the isotropic J-coupling is the dominant interaction. The mixing Hamiltonian is thus identical to the well-known TOCSY-Hamiltonian, resulting in a net through-bond magnetization transfer. The mixing-time dependence of the exchange rates is investigated. Applications to crystalline P4S7 and MgP4O11 are shown.
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Affiliation(s)
- P Hartmann
- Institut für Optik und Quantenelektronik, Friedrich-Schiller Universität Jena, Germany.
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129
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Brinkmann A, Edén M, Levitt MH. Synchronous helical pulse sequences in magic-angle spinning nuclear magnetic resonance: Double quantum recoupling of multiple-spin systems. J Chem Phys 2000. [DOI: 10.1063/1.481458] [Citation(s) in RCA: 177] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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130
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Bringmann G, Wohlfarth M, Rischer H, Grüne M, Schlauer J. Ein neuer Biosyntheseweg zu Alkaloiden in Pflanzen: acetogenine Isochinoline. Angew Chem Int Ed Engl 2000. [DOI: 10.1002/(sici)1521-3757(20000417)112:8<1523::aid-ange1523>3.0.co;2-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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131
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Strobel G, Li JY, Sugawara F, Koshino H, Harper J, Hess WM. Oocydin A, a chlorinated macrocyclic lactone with potent anti-oomycete activity from Serratia marcescens. MICROBIOLOGY (READING, ENGLAND) 1999; 145 ( Pt 12):3557-3564. [PMID: 10627053 DOI: 10.1099/00221287-145-12-3557] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A unique chlorinated macrocyclic lactone, termed oocydin A, was isolated from a strain of Serratia marcescens growing as an epiphyte on Rhyncholacis pedicillata, an aquatic plant native to the Carrao river of the Venezuelan-Guyanan region of South America. The lactone has a molecular mass of 470 Da, and contains one atom of chlorine, a carboxyl group and a tetrahydrofuran ring internal to a larger macrocyclic ring. MICs of approximately 0.03 microg ml(-1) were noted for oocydin A against such phytopathogenic oomycetes as Pythium ultimum, Phytophthora parasitica, Phytophthora cinnamomi and Phytophthora citrophora. With regard to the true fungi, oocydin A had either minimal or no effect against certain Fungi Imperfecti (including several pathogens of humans), two ascomycetes and a basidiomycete. Oocydin A may have potential as an antimycotic in agricultural applications and especially for crop protection.
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Affiliation(s)
- Gary Strobel
- Department of Plant Sciences, Montana State University, Bozeman, MT 59717, USA1
| | - Jia-Yao Li
- Department of Plant Sciences, Montana State University, Bozeman, MT 59717, USA1
| | - Fumio Sugawara
- Department of Applied Biological Science, Science University of Tokyo, Noda, Chiba 278-8510, Japan2
| | - Hiroyuki Koshino
- The Institute of Physical and Chemical Research, Wako, Saitama 351- 0198, Tokyo, Japan3
| | - James Harper
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA4
| | - W M Hess
- Department of Botany and Range Science, Brigham Young University, Provo, UT 84602, USA5
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132
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Untidt TS, Schulte-Herbrüggen T, Sørensen OW, Nielsen NC. Nuclear Magnetic Resonance Coherence-Order- and Spin-State-Selective Correlation in I2S Spin Systems. J Phys Chem A 1999. [DOI: 10.1021/jp990968l] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- T. S. Untidt
- Laboratory for Biomolecular NMR Spectroscopy, Department of Molecular and Structural Biology, University of Aarhus, DK-8000 Aarhus C, Denmark, and Department of Chemistry, Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-2500 Valby, Denmark
| | - T. Schulte-Herbrüggen
- Laboratory for Biomolecular NMR Spectroscopy, Department of Molecular and Structural Biology, University of Aarhus, DK-8000 Aarhus C, Denmark, and Department of Chemistry, Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-2500 Valby, Denmark
| | - O. W. Sørensen
- Laboratory for Biomolecular NMR Spectroscopy, Department of Molecular and Structural Biology, University of Aarhus, DK-8000 Aarhus C, Denmark, and Department of Chemistry, Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-2500 Valby, Denmark
| | - N. C. Nielsen
- Laboratory for Biomolecular NMR Spectroscopy, Department of Molecular and Structural Biology, University of Aarhus, DK-8000 Aarhus C, Denmark, and Department of Chemistry, Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-2500 Valby, Denmark
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133
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Verel R, van Beek JD, Meier BH. INADEQUATE-CR experiments in the solid state. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 1999; 140:300-303. [PMID: 10479577 DOI: 10.1006/jmre.1999.1880] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Through-bond connectivity can be probed by J couplings. For effective two-spin systems, the INADEQUATE experiment is highly valuable in liquid-state spectroscopy. It is the purpose of this Communication to show that in-phase INADEQUATE-CR spectra, where the intensity is concentrated in only one line of the J splitted doublet, can be obtained from solid-state samples. The problem of the cancellation of nonresolved multiplet lines, as experienced typically in INADEQUATE spectra in the solid, is resolved and the (13)C spectra become simpler because the number of resonance lines is reduced. Furthermore, a gain in signal intensity by 2 can, theoretically, be achieved. We limit the discussion to two-spin systems. In the present context, a two-spin system is defined considering the J coupling only. When the dipolar coupling is also taken into account, the two-spin system will usually become a many-spin system, but in the present context this is not relevant.
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Affiliation(s)
- R Verel
- Laboratorium für Physikalische Chemie, Zürich, ETH-Zentrum, CH-8092, Switzerland
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134
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Bohman DW, Li Z, Li D, Owen NL. The analysis of mixtures using the 2-D INADEQUATE NMR technique. J Mol Struct 1999. [DOI: 10.1016/s0022-2860(98)00625-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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135
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Köck M, Junker J, Maier W, Will M, Lindel T. A C
OCON
Analysis of Proton‐Poor Heterocycles – Application ofCarbon Chemical Shift Predictions for the Evaluation of Structural Proposals. European J Org Chem 1999. [DOI: 10.1002/(sici)1099-0690(199903)1999:3<579::aid-ejoc579>3.0.co;2-#] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
| | - Jochen Junker
- Institut für Organische Chemie, Johann Wolfgang Goethe‐Universität, Marie‐Curie‐Straße 11, D‐60439 Frankfurt, Germany Fax: (internat.) +49(0)69‐798‐29128
| | - Walter Maier
- ZHV‐Molekülspektroskopie, BASF AG, D‐67056 Ludwigshafen, Germany
| | - Martin Will
- ZHV‐Molekülspektroskopie, BASF AG, D‐67056 Ludwigshafen, Germany
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136
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Nakai T, Fujimori H, Kuwahara D, Miyajima S. Complete Assignment of 13C NMR Spectra and Determination of Orientational Order Parameter for Antiferroelectric Liquid-Crystalline MHPOBC. J Phys Chem B 1999. [DOI: 10.1021/jp982996u] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Toshihito Nakai
- Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan, Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei 184-8588, Japan, and College of Humanities and Sciences, Nihon University, Sakurajosui, Setagaya-ku, Tokyo 156-8550, Japan
| | - Hiroki Fujimori
- Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan, Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei 184-8588, Japan, and College of Humanities and Sciences, Nihon University, Sakurajosui, Setagaya-ku, Tokyo 156-8550, Japan
| | - Daisuke Kuwahara
- Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan, Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei 184-8588, Japan, and College of Humanities and Sciences, Nihon University, Sakurajosui, Setagaya-ku, Tokyo 156-8550, Japan
| | - Seiichi Miyajima
- Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan, Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei 184-8588, Japan, and College of Humanities and Sciences, Nihon University, Sakurajosui, Setagaya-ku, Tokyo 156-8550, Japan
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137
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138
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139
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Mattiello DL, Freeman R. Blood, sweat, and tears. Toward a rehabilitation of the INADEQUATE experiment. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 1998; 135:514-521. [PMID: 9878478 DOI: 10.1006/jmre.1998.1589] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The double-quantum-filtered carbon-carbon correlation experiment (INADEQUATE) can be accelerated significantly through a reduction in the spin-lattice relaxation times by dissolving oxygen gas in the solution. The effect is enhanced by lowering the temperature and by pressurizing the sample tube with oxygen. This offers a fourfold reduction in the relaxation times of the carbon-13 resonances in the 125-MHz spectrum of methyl salicylate. The addition of perfluorotertiarybutanol (related to the artificial blood substitutes) increases the amount of oxygen that can be dissolved, so that without oxygen pressurization, similar reductions in the relaxation times can be achieved. The nuclear Overhauser enhancements are only slightly reduced by addition of oxygen. Polarization transfer from the directly attached protons (INEPT) further increases the sensitivity if at least one of the two coupled carbon sites is protonated, principally because the proton spin-lattice relaxation times of oxygenated samples are shortened by the relaxation agent. These modest improvements in sensitivity are in general complementary to existing enhancement schemes.
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Affiliation(s)
- D L Mattiello
- Varian NMR Instruments, 3120 Hansen Way, Palo Alto, California, 94304, USA
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140
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Bourdonneau M, Ancian B. Rapid-Pulsing Artifact-Free Double-Quantum-Filtered Homonuclear Spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 1998; 132:316-327. [PMID: 9632558 DOI: 10.1006/jmre.1998.1392] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Rapid pulsing artifacts are observed in the conventional phase-cycled carbon-13 2D INADEQUATE experiment. By using the product operator formalism, it is shown that they result from the effects of imperfect 90 degrees and 180 degrees excitation pulses on the most abundant molecules containing only one isolated carbon-13 nucleus. The labeled longitudinal magnetization remaining at the end of one scan is recycled by the subsequent acquisition, giving rise to multiple-quantum (p = 0, +/-1, +/-2, ellipsis) artifacts in the F1 dimension. By considering pairs of scans instead of single scans, a new phase cycle is proposed. It is based on a scheme for compensating for imperfections in the excitation cluster by a proper combination of the pulse phases in two consecutive scans. Because the artifacts are 90 degrees out of phase compared to the desired signal, a concomitant rearrangement of the receiver phase achieves suppression of all unwanted signals. Experiments are presented on menthol dissolved in CDCl3 as a test compound. Improvements in spectrum quality as well as increased sensitivity are discussed. Copyright 1998 Academic Press.
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Affiliation(s)
- M Bourdonneau
- CNRS, Université Louis Pasteur, UMR 50, 34, rue de l'Industrie, Wissembourg Cedex, F-67166, France
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141
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Qiu F, Rivera M, Stark RE. An 1H-13C-13C-edited 1H NMR experiment for making resonance assignments in the active site of heme proteins. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 1998; 130:76-81. [PMID: 9469900 DOI: 10.1006/jmre.1997.1276] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
In paramagnetic heme proteins, it is often problematic to make proton resonance assignments for heme substituents that do not have large isotropic shifts and consequently lie under the large envelope of polypeptide resonances. Furthermore, assignments that would normally be performed with the aid of HMBC experiments in diamagnetic molecules can prove difficult in the active site of paramagnetic heme proteins if T2(-1) > 2JCH. To circumvent this problem, a new method is presented to selectively detect 1H in 1Hn-13C-13C fragments biosynthetically introduced into the active site of heme proteins. The pulse sequence combines well-known building blocks such as INEPT to transfer 1H spin magnetization to bonded 13C nuclei, followed by INADEQUATE to generate 13C-13C double-quantum coherence that is selected with pulsed field gradients, and finally reverse-INEPT to transfer magnetization back to 1H nuclei for subsequent observation. The new 1Hn-13C-13C edited experiment takes advantage of the relatively large values of 1JCH and 1JCC, avoiding the long interpulse delays in HMBC that compromise the detectability of rapidly relaxing nuclei. The potential applicability of the pulse sequence is demonstrated by its contribution to the unambiguous assignment of the carbonyl carbons in the heme propionates of ferricytochrome b5.
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Affiliation(s)
- F Qiu
- Department of Chemistry, College of Staten Island, New York, USA
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142
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Ernst L, Hopf H, Savinsky R. Cyclophanes, XLII. The Acid-Catalyzed Isomerization of Perhydro[2.2]paracyclophane – A Surprising Out-In Hydrogen Transfer Process. ACTA ACUST UNITED AC 1997. [DOI: 10.1002/jlac.199719970917] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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143
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Lesage A, Auger C, Caldarelli S, Emsley L. Determination of Through-Bond Carbon−Carbon Connectivities in Solid-State NMR Using the INADEQUATE Experiment. J Am Chem Soc 1997. [DOI: 10.1021/ja971089k] [Citation(s) in RCA: 182] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Anne Lesage
- Laboratoire de Stéréochimie et des Interactions Moléculaires UMR-117 CNRS/ENS, Ecole Normale Supérieure de Lyon 69364 Lyon, France
| | - Céline Auger
- Laboratoire de Stéréochimie et des Interactions Moléculaires UMR-117 CNRS/ENS, Ecole Normale Supérieure de Lyon 69364 Lyon, France
| | - Stefano Caldarelli
- Laboratoire de Stéréochimie et des Interactions Moléculaires UMR-117 CNRS/ENS, Ecole Normale Supérieure de Lyon 69364 Lyon, France
| | - Lyndon Emsley
- Laboratoire de Stéréochimie et des Interactions Moléculaires UMR-117 CNRS/ENS, Ecole Normale Supérieure de Lyon 69364 Lyon, France
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144
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Herberhold M, Dörfler U, Wrackmeyer B. The first 1,2-dibora-[2]ferrocenophane and its dynamic behaviour in solution. J Organomet Chem 1997. [DOI: 10.1016/s0022-328x(96)06470-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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145
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Harrison JJ, Young DC, Mayne CL. 2D-INADEQUATE Structural Assignment of Polybutene Oligomers. J Org Chem 1997; 62:693-699. [PMID: 11671466 DOI: 10.1021/jo961851l] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structure of polybutene oligomers has been unambiguously determined using NMR techniques. We used 2D-INADEQUATE to show that the major polybutene isomer synthesized via BF(3) catalysis has the expected structure with a tert-butyl group at the beginning of the chain and the expected methylvinylidene double bond at the other end. Surprisingly, we found that the main isomer of polybutene synthesized from AlCl(3) catalysis has an isopropyl group at the beginning of the chain. A trisubstituted double bond structure has been assigned at the other end of the chain. Structural information about several minor polybutene isomers has also been determined. Formation of an isopropyl group can be rationalized by assuming a protonated cyclopropane intermediate in the propagation step. Previously, the mechanism of formation of polybutene via AlCl(3) catalysis was thought to involve exclusively the tert-butyl carbenium ion. It now appears that the mechanism is more complicated than previously thought.
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Affiliation(s)
- James J. Harrison
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112
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146
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Chauret DC, Durst T, Arnason JT, Sanchez-Vindas P, Roman LS, Poveda L, Keifer PA. Novel steroids from Trichilia hirta as identified by nanoprobe INADEQUATE 2D-NMR spectroscopy. Tetrahedron Lett 1996. [DOI: 10.1016/0040-4039(96)01803-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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147
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Nielsen NC, Tho/gersen H, So/rensen OW. A systematic strategy for design of optimum coherent experiments applied to efficient interconversion of double‐ and single‐quantum coherences in nuclear magnetic resonance. J Chem Phys 1996. [DOI: 10.1063/1.472269] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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148
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Structure determination using the NMR “INADEQUATE” technique. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s1087-3295(96)80020-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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149
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Cordell GA, Lin LZ, Gil RR. Proton and carbon-13 NMR studies of steroids and triterpenes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1996; 405:281-97. [PMID: 8910713 DOI: 10.1007/978-1-4613-0413-5_25] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- G A Cordell
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago 60612, USA
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150
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Likhodii SS, Cunnane SC. Utilization of carbon from dietary polyunsaturates for brain cholesterol synthesis during early postnatal development in the rat: a 13C NMR study. Magn Reson Med 1995; 34:803-13. [PMID: 8598807 DOI: 10.1002/mrm.1910340605] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Incorporation of 13C from a dietary precursor into cholesterol was studied in neonatal rats. Rats were given uniformly 13C-enriched polyunsaturated fatty acids intragastrically and total lipid extracts of liver and brain were analyzed by 13C-NMR 1, 4, 8, and 15 days later. 13C-enrichment was detected in brain but not in liver cholesterol. Maximal 13C-labeling was observed 4 days after injection of the label. Spectra revealed that 70% of newly incorporated 13C had 13C as an adjacent neighbor, the other 30% had 12C as the neighbor. Double quantum NMR revealed the arrangement in the cholesterol skeleton of the 13C-13C pairs transferred from precursors to cholesterol. Desmosterol, an intermediate of cholesterol synthesis, was identified in the spectra of brain lipids. Comparison of 13C-13C unit arrangements in both cholesterol and desmosterol allowed carbons 26 and 27 of desmosterol to be unambiguously assigned.
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Affiliation(s)
- S S Likhodii
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Canada
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