NMR measurement of signs and magnitudes of C-H dipolar couplings in lecithin

Journal Article · Wed Mar 22 04:00:00 EST 1995 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja00116a051· OSTI ID:35463

Hong, M; Schmidt-Rohr, K; Pines, A ^[1]

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1. Lawrence Berkeley Lab., CA (United States)

In this communication, we demonstrate the measurement of C-H dipolar coupling constants {delta}{sub D}, including the signs, for a number of sites in a liquid crystalline lipid, lecithin. 2D PDLF NMR with switched-angle spinning (SAS) provides the magnitudes of the couplings and their signs by comparison of spectra taken at different spinner axis orientations. More directly, the signs are observed as the signs of peak amplitudes in a novel 1D SAS technique using J couplings to make sign-dependent dipolar PDLF coherences observable. The dipolar couplings with their signs are summarized and compared with {sup 2}H NMR order parameters from the literature. Due to scaling factors from sample rotation and homonuclear decoupling, the dipolar couplings are less precise than the {sup 2}H results. The C-H couplings are hardly affected by the acyl chain composition, except in the double bond region and at the end of the acyl chains. This can be concluded from C-H dipolar couplings measured in DMPC, as well as from {sup 2}H data. The signs of the S{sub C{minus}H} values determined here are important for testing structural models of the lipid and providing complete order tensor information. 25 refs., 4 figs.

• Sponsoring Organization: USDOE
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 35463
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 11 Vol. 117; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
66 PHYSICS
COUPLING CONSTANTS
J-J COUPLING
LECITHINS
LIPIDS
LIQUID CRYSTALS
NMR SPECTRA