摘要:

AbstractPure absorption phase two‐dimensional nuclear Overhauser spectrocopy (NOESY), using a short cycle time protocol, has been used to study cross‐relaxation between protons of ligands bound to proteins. The 2D experiment is an accurate and efficient method for determining exchange transferred NOEs. Truncated NOESY data sets (obtained in less than 3 h) for the test systems—prostaglandin F2α bound to albumin and NAD+bound to three different dehydrogenase enzymes—provide NOE estimates within experimental error of those obtained by the more time‐consuming one‐dimensional experiments. The 2D data matrix has within it spin‐diffusion controls and cross‐relaxation spectra useful for the subtraction of unwanted signals including spin transfer from coincidentally perturbed protein resonances andt1st

ISSN:0749-1581    

DOI:10.1002/mrc.1260251202

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe rate of the degenerate 6,1‐hydride shift and rearrangement of the 2‐methyl‐2‐norbornyl cation has been determined using selective pulse transfer experiments and 2D NOESY experiments over the temperature range 200–220 K. Least‐squares analysis of the data gives a free energy of activation of 11.3 kcal mol−1. The results are compatible with the presence of σ‐delocalization in the 2‐methyl

ISSN:0749-1581    

DOI:10.1002/mrc.1260251203

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

Abstract13C NMR assignments have been made for a series of 36 α‐ and 3,4‐dehydroretinoids with different substituents (alcohol, ester, aldehyde and acid) and for their separatedEandZgeometrical isomers. The assignments were made by using 2D heteronuclear‐correlated NMR experiments. From the chemical shift data of 24 systematically related retinoids, empirical chemical shift changes due to four polar end groups (alcohol, aldehyde, carboxylic acids and esters), three chain configurations (all‐E, 9Zand 13Z), and two ring substitutions (2,6,6‐trimethyl‐cyclohex‐2‐enyl and 2,6,6‐trimethylcyclohexa‐1,3‐dienyl) were determined. All trends were found to be independent of each other, except for the dependence of the chemical shift change of the 13Z‐isomers on the polar end groups. The chemical shift changes were used to predict the chemical shifts of other retinoids based on two different ring structures (2,6,6‐trimethylcyclohexenyl and 4‐me

ISSN:0749-1581    

DOI:10.1002/mrc.1260251204

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractA simple procedure is proposed for increasing the size of NOEs in NMR studies of small molecules. The method involves the use of a mixed solvent (Me2SO‐d6‐D2O) to increase the viscosity of the solution such thatωtc>1. The advantages of this solvent system and approach are compared with other approaches currently in

ISSN:0749-1581    

DOI:10.1002/mrc.1260251205

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe31P and13C NMR spectra of all twelve phenoxychlorocyclotriphosphazenes of general formula N3P3Cl6‐n(OC6H5)n(n= 1‐6) were assigned in detail. With samples abundant in one homolog, but with a disparity between geometrical isomers, the signals due to thecisandtransisomers of N3P3Cl4(OC6H5)2and N3P3Cl2(OC6H5)4were also assigned. The31P chemical shifts and coupling constants correlate linearly with the level of substitution,n. The13C NMR spectra exhibit complex multiplets for theipso‐ andortho‐carbons. It is shown that each of these is the X part of one of the spin systems XAM2, XAA′M, XAA2′, XAB2and XAA′B. The13C chemical shifts of theipso‐ andpara‐carbons also exhibit correlations withn.The13C‐31P coupling constants, both2J(POC) and3J(POCC), are larger for the PCl(OC6H5) than for th

ISSN:0749-1581    

DOI:10.1002/mrc.1260251206

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe1H and13C chemical shifts in 5‐(2‐dimethylaminoethoxy)‐7‐oxo‐7H‐benzo[c]fluorene (1) and 5‐hydroxy‐7‐oxo‐7H‐benzo[c]fluorene (2) were assigned using H,H‐COSY, H,C‐COSY and selective INEPT spectra. It was found that the main phenolic metabolite of 1 and its hydrochloride corresponds to 9‐hydroxy‐5‐(2‐dimethylaminoetho

ISSN:0749-1581    

DOI:10.1002/mrc.1260251207

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe choice of standard compounds for setting up CP MAS NMR experiments on the nuclei77Se,119Sn,195Pt,199Hg and207Pb in organometallic compounds is discussed. Spectra of suitable compounds are presented, together with the relevant optimum acquisition parameters (contact times, recycle delays).

ISSN:0749-1581    

DOI:10.1002/mrc.1260251208

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractProton and13C line widths and13C spin‐lattice relaxation times (T1) were measured over a wide temperature region in liquid and solidtert‐butyl bromide (1) andtert‐butyl cyanide (2). A striking feature of the proton and13C NMR spectra of 1 is the abrupt line narrowing at the phase I → phase II transition point. In 2, however, the line width does not vary with temperature in phase I, indicating that the translational motion is too slow to affect the line width.An analysis of spin‐lattice relaxation times in both the liquid and solid phases is reported. It is shown that13CT1measurements can distinguish between internal methyl group reorientation (C3motion) and uniaxial molecular reorientation oftert‐butyl groups (C3′ motion) if these motions are independent and responsible for theT1relaxation over a large part of the temperature region. The13C spin‐lattice relaxation mechanism in the liquid and disordered phases of 1, and the liquid phase of 2, is governed by overall molecular tumbling with an activation energy of 8–11 kJ mol−1. The13CT1data show that the faster motion in the ordered phases of 1 and 2 is the C3′ reorientation with an activation energy of 15–18 kJ mol−1while the slower motion is the C3reorientation with an activati

ISSN:0749-1581    

DOI:10.1002/mrc.1260251209

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe solution structures of dimers consisting of negatively charged Zn[tetra(4‐carboxyphenyl)porphyrin], ZnTPPC, with positively charged Zn[tetra(4‐N‐methylpyridyl)porphyrin], ZnTMPyP, and with H2[tetra(4‐N‐methylpyridyl)porphyrin], H2TMPyP, were determined by1H NMR ring current shifts. The conformation is not affected by the presence of the metal in the centre of the TMPyP monomer. The dimers have a cofacial conformation with a plane‐to‐plane separation of 3.1 Å and an in‐plane translation of 4.2 Å along t

ISSN:0749-1581    

DOI:10.1002/mrc.1260251210

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY

摘要:

AbstractOne‐ and two‐dimensional NMR spectroscopy was used to determine the structure of the phenyldichloroarsine‐British anti‐lewisite adduct. The major component had the hydroxymethyl group in theantiorientation with respect to the phenyl ring on the arsenous atom. This structure was based on the chemical shifts of the1H and13C resonances and on the respective homonuclear coupling co

ISSN:0749-1581    

DOI:10.1002/mrc.1260251211

出版商:John Wiley&Sons, Ltd.    

年代:1987

数据来源: WILEY