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Titolo:
Double-quantum double-quantum MAS exchange NMR spectroscopy: Dipolar-coupled spin pairs as probes for slow molecular dynamics
Autore:
Schnell, I; Watts, A; Spiess, HW;
Indirizzi:
Max Planck Inst Polymerforsch, D-55021 Mainz, Germany Max Planck Inst Polymerforsch Mainz Germany D-55021 55021 Mainz, Germany Univ Oxford, Dept Biochem, Oxford OX1 3QU, England Univ Oxford Oxford England OX1 3QU Dept Biochem, Oxford OX1 3QU, England
Titolo Testata:
JOURNAL OF MAGNETIC RESONANCE
fascicolo: 1, volume: 149, anno: 2001,
pagine: 90 - 102
SICI:
1090-7807(200103)149:1<90:DDMENS>2.0.ZU;2-A
Fonte:
ISI
Lingua:
ENG
Soggetto:
SOLID-STATE NMR; NUCLEAR-MAGNETIC-RESONANCE; SIDE-BAND PATTERNS; PI-PI PACKING; ROTATING SOLIDS; TORSIONAL ANGLE; C-13 NMR; HOMONUCLEAR; HEXABENZOCORONENE; POLYETHYLENE;
Keywords:
dipolar-coupled spin pairs; double-quantum MAS spectroscopy; exchange spectroscopy; slow molecular dynamics; molecular jump angles and rates;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Physical, Chemical & Earth Sciences
Citazioni:
37
Recensione:
Indirizzi per estratti:
Indirizzo: Spiess, HW Max Planck Inst Polymerforsch, Postfach 3148, D-55021 Mainz, Germany Max Planck Inst Polymerforsch Postfach 3148 Mainz Germany D-55021
Citazione:
I. Schnell et al., "Double-quantum double-quantum MAS exchange NMR spectroscopy: Dipolar-coupled spin pairs as probes for slow molecular dynamics", J MAGN RES, 149(1), 2001, pp. 90-102

Abstract

By combining two dipolar double-quantum (DQ) MAS experiments, a homonuclear DO-DO MAS exchange experiment has been designed, which probes the reorientation of dipolar tensors and allows the observation of slow molecular dynamics, in particular the determination of reorientation angles and rates. The dipolar coupling between two distinct spins is used to generate a DQ coherence, and the orientation-dependent coupling is measured by means of the DQ MAS sideband pattern before and after a mixing time. In the course of a reduced three-dimensional experiment, the two DQ sideband patterns are correlated, resulting in a DO-DO sideband pattern which is sensitive to the reorientation angle. By referencing the DO-DO time signal, the information content of the pattern can be divided into the sidebands and the centerband, with the former reflecting only the moieties which have undergone a reorientation, and the latter predominantly containing contributions from moieties which have remained in, or returned to, their initial position. Hence, a single sideband pattern provides access to both the reorientation angle and the relative number of moieties subject to the motional process. As a first example, such DQ-DQ MAS experiments were performed on the C-13-C-13 spin pairs of an enriched poly(ethylene) sample. In its crystallites, the dynamics of a known chain-flip motion were investigated, yielding a C-13-C-13 reorientation angle of Delta theta (ij) = (70 +/- 5)degrees and an activation energy of E-A = (100 +/- 20) kJ mol(-1). (C) 2001 Academic Press.

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Documento generato il 03/04/20 alle ore 04:30:47