title: Q.E.COSY: determining sign and size of small deuterium residual quadrupolar couplings using an extended E.COSY principle.
abstract: Residual quadrupolar couplings contain important structural information comparable with residual dipolar couplings. However, the measurement of sign and size of especially small residual quadrupolar couplings is difficult. Here, we present an extension of the E.COSY principle to spin systems consisting of a Spin 1 coupled to a spin ½ nucleus, which allows the determination of the sign of the quadrupolar coupling of the Spin 1 nucleus relative to the heteronuclear coupling between the spins. The so-called Q.E.COSY approach is demonstrated with its sign-sensitivity using variable angle NMR, stretched gels and liquid crystalline phases applied to various CD and CD3 groups. Especially the sign-sensitive measurement of residual quadrupolar couplings that remain unresolved in conventional deuterium 1D spectra is shown.
authors.affiliation: Institute of Organic Chemistry and Institute for Biological Interfaces 4 - Magnetic Resonance, Fritz-Haber-Weg 6, 76131, Karlsruhe, Germany.
authors.forename: Pavleta
authors.initials: P
authors.lastname: Tzvetkova
authors.affiliation: Institute of Organic Chemistry and Institute for Biological Interfaces 4 - Magnetic Resonance, Fritz-Haber-Weg 6, 76131, Karlsruhe, Germany.
authors.forename: Burkhard
authors.initials: B
authors.lastname: Luy
keywords: 13C; 2H; E.COSY; NMR; Spin 1; deuterium; quadrupolar couplings; sign sensitivity; small coupling constants