NMR Spectroscopic Study (nmr + spectroscopic_study)

Distribution by Scientific Domains

Selected Abstracts

Solution-State 15N NMR Spectroscopic Study of ,-C-Phycocyanin: Implications for the Structure of the Chromophore-Binding Pocket of the Cyanobacterial Phytochrome Cph1

CHEMBIOCHEM, Issue 18 2007
Janina Hahn
Abstract The detailed structure of the chromophore-binding pocket in phytochrome proteins and the structural changes associated with its photocycle are still matters of debate. Insight into the structure and dynamics of the binding pocket has been gained through the comparison of a 15N NMR spectrum of ,-C-phycocyanin, which is often used as a model system for the study of phytochromes, with the previously described 15N NMR spectrum of the cyanobacterial phytochrome Cph1. The former spectrum supports the hypothesis that all four nitrogen atoms of the ,-C-phycocyanin chromophore are protonated, in analogy with the proposed protonation state for the Pr and Pfr forms of Cph1. The spectra show that the chromophores in both proteins exhibit a distinct dynamic behavior, as also indicated by a NOESY spectrum of Cph1. Finally, stereochemical arguments and a Cph1 homology model support the hypothesis that the chromophore in Cph1 is most likely in the ZZZssa conformation in the Pr form of the protein. [source]

ChemInform Abstract: A 119Sn Moessbauer and 45Sc Solid State NMR Spectroscopic Study of the Stannides ScTSn (T: Ni, Pd, Pt).

CHEMINFORM, Issue 4 2009
Thomas Harmening
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

NMR Spectroscopic Study of Xenon Fluorides in the Gas Phase and XeF2 in the Solid State.

CHEMINFORM, Issue 37 2004
Michael Gerken
No abstract is available for this article. [source]

Phosphine Ligands in the Palladium-Catalysed Methoxycarbonylation of Ethene: Insights into the Catalytic Cycle through an HP,NMR Spectroscopic Study

Verónica de, la Fuente Dipl.-Chem.
Abstract Novel cis -1,2-bis(di- tert -butyl-phosphinomethyl) carbocyclic ligands 6,9 have been prepared and the corresponding palladium complexes [Pd(O3SCH3)(L-L)][O3SCH3] (L- L=diphosphine) 32,35 synthesised and characterised by NMR spectroscopy and X-ray diffraction. These diphosphine ligands give very active catalysts for the palladium-catalysed methoxycarbonylation of ethene. The activity varies with the size of the carbocyclic backbone, ligands 7 and 9, containing four- and six-membered ring backbones giving more active systems. The acid used as co-catalyst has a strong influence on the activity, with excess trifluoroacetic acid affording the highest conversion, whereas excess methyl sulfonic acid inhibits the catalytic system. An in operando NMR spectroscopic mechanistic study has established the catalytic cycle and resting state of the catalyst under operating reaction conditions. Although the catalysis follows the hydride pathway, the resting state is shown to be the hydride precursor complex [Pd(O3SCH3)(L- L)][O3SCH3], which demonstrates that an isolable/detectable hydride complex is not a prerequisite for this mechanism. [source]

Synthesis and Characterization of the D5h Isomer of the Endohedral Dimetallofullerene Ce2@C80: Two-Dimensional Circulation of Encapsulated Metal Atoms Inside a Fullerene Cage

Michio Yamada Dr.
Abstract Herein we show the synthesis and characterization of the second known Ce2@C80 isomer. A 13C,NMR spectroscopic study revealed that the structure of the second isomer has D5h symmetry. Paramagnetic NMR spectral analysis and theoretical calculation display that the encapsulated Ce atoms circulate two-dimensionally along a band of ten contiguous hexagons inside a D5h -C80 cage, which is in sharp contrast to the three-dimensional circulation of two Ce atoms in an Ih -C80 cage. The electronic properties were revealed by means of electrochemical measurements. The D5h isomer of Ce2@C80 has a much smaller HOMO,LUMO gap than cluster fullerenes (M3N@C80, M=Sc, Tm, and Lu) with the same D5h -C80 cages. The chemical reactivity was investigated by using disilirane as a chemical probe. The high thermal reactivity toward 1,1,2,2-tetramesityl-1,2-disilirane is consistent with the trends of the redox potentials and the lower LUMO level of the D5h isomer of Ce2@C80 compared with that of C60. [source]