NMR Pulse Sequences (nmr + pulse_sequence)

Distribution by Scientific Domains

Selected Abstracts

Magnetization Transfer from Laser-Polarized Xenon to Protons with Spin-Diffusion Quenching

CHEMPHYSCHEM, Issue 4 2003
Hervé Desvaux
Position of the prisoner: Accurate location of xenon atoms in cage molecules (see picture) is derived by specific through-space magnetization transfer from laser-polarized gas to protons using a new NMR pulse sequence. [source]

High-resolution NMR correlation experiments in a single measurement (HR-PANACEA)

riks Kup
Abstract Three important NMR pulse sequences, INADEQUATE, HSQC and three-dimensional HMBC have been combined into a single entity called high-resolution Parallel Acquisition NMR: an All-in-one Combination of Experimental Applications (HR-PANACEA) to provide reliable structural information about a small molecule in a single measurement. This exploits a recent instrumental development that permits simultaneous acquisition of signals from several nuclear species, using multiple receivers. Where high-precision values of the long-range heteronuclear splittings are important, selected regions of a large experimental data matrix are extracted and examined with the highest possible resolution. The J -doubling technique is then applied to derive precise values for these couplings. As proof of principle, the method is applied to the molecule of methyl salicylate, confirming the expected conformation of the COH moiety. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Toward multipurpose NMR experiments

Judith Schlagnitweit
Abstract Standard phase cycled NMR pulse sequences were generalized such that for each individual step of the pulse phase cycle the free induction decay is stored separately without phase correction. This is in contrast to the usual practice, where pulse responses are phase shifted immediately (by applying a ,receiver phase') and co-added as they are stored. The approach used here allows one to extract different types of NMR information, which are usually referred to as different ,experiments', from the same raw data set a posteriori by using complex linear combinations. Storing the free induction decays of individual phase cycle steps separately and using specific linear combinations of these data to obtain a particular type of information increase the overall efficiency of a given set of NMR experiments substantially, because all information can be derived from a single multiplexed data set. This ,super-experiment' requires only as much time as the most complex of the derived specific experiments alone. The principle of this multipurpose approach was demonstrated by performing different multiple-quantum filtered COSY experiments. It also becomes possible to generate linear combinations, which differ from the conventionally acquired spectra a posteriori. For example, we implemented diagonal peak reduction by using zero- and single-quantum filtered COSY contributions without requiring additional experiment time. Copyright © 2009 John Wiley & Sons, Ltd. [source]

1H and 13C NMR assignments of abietane diterpenes from Aegiphila lhotzkyana

Maria Claudia Pinheiro Barros
Abstract An NMR study of one new and several known abietane diterpenes isolated from the roots of Aegiphila lhotzkyana is described. In addition to 1D NMR, several 2D shift-correlated NMR pulse sequences (1H,1H-COSY, NOESY, HMQC and HMBC) were used to establish all the structures, and unambiguously perform the 1H and 13C chemical shift assignments of the new natural diterpene and three derivatives, the NMR data for which have not been reported previously. Revision of current data assignment for teuvincenone H is also suggested. Copyright © 2003 John Wiley & Sons, Ltd. [source]