title: Fast acquisition of high-resolution NMR spectra in inhomogeneous fields via intermolecular double-quantum coherences.
abstract: A pulse sequence, IDEAL-II, is proposed based on the concept of intermolecular dipolar-interaction enhanced all lines [Z. Chen et al., J. Am. Chem. Soc. 126, 446 (2004)] for obtaining one-dimensional (1D) high-resolution liquid NMR spectra in inhomogeneous fields via two-dimensional acquisitions. With the new acquisition scheme, the range of magnetic field inhomogeneity rather than chemical shift is sampled in the indirect dimension. This enables a great reduction in acquisition time and amount of data, much improved over the original IDEAL implementation. It is applicable to both isolated and J-coupled spin systems in liquid. For the latter, apparent J coupling constants are magnified threefold in spectra obtained with this sequence. This allows a more accurate measurement of J coupling constants in the cases of small J coupling constants or large inhomogeneous fields. Analytical expression was derived based on intermolecular multiple-quantum coherence treatments. Solution samples that were purposely deshimmed and biological samples with intrinsic field inhomogeneities were tested. Experimental results demonstrate that this sequence retains useful structural information including chemical shifts, relative peak areas, and multiplet patterns of J coupling even when the field inhomogeneity is severe enough to almost erase all spectroscopic information with conventional 1D single-quantum coherence techniques. This sequence is more applicable to weakly coupled and uncoupled spin systems, potentially useful for studying metabolites in in vivo NMR spectroscopy and for characterizing technologically important new materials in combinatorial chemistry.
authors.affiliation: Department of Physics, Fujan Key Laboratory of Plasma and Magnetic Resonance, State Key Laboratory of Physical Chemistry of Solid Surface, Xiamen University, Xiamen 361005, China. chenz@xmu.edu.cn
authors.forename: Zhong
authors.initials: Z
authors.lastname: Chen
authors.forename: Shuhui
authors.initials: S
authors.lastname: Cai
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Chen
authors.forename: Jianhui
authors.initials: J
authors.lastname: Zhong
mesh_terms: D020650:Combinatorial Chemistry Techniques; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods; D008280:Magnetics; D008660:Metabolism; D013997:Time Factors