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CP/MAS Experiments (ma + experiment)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Setting up 13C CP/MAS experiments

CONCEPTS IN MAGNETIC RESONANCE, Issue 1 2004
R.E. Taylor
Abstract The 13C cross-polarization (CP) technique combined with magic angle spinning (MAS) has become one of the more commonly performed solid-state nuclear magnetic resonance (NMR) experiments. The basics of initially setting up the experiment are given and used to illustrate such NMR phenomena as rotational echoes, homogeneous and inhomogeneous interactions, continuous wave 1H decoupling, and coupling of quadrupolar 14N nuclei to 13C nuclei. The polarization transfer from the protons to the carbons is described briefly with the usual thermodynamic and quantum mechanical models. The setup and use of the experiment for routine analyses are discussed. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 22A: 37,49, 2004. [source]

TOWARD A REALISTIC MODEL OF MUTATIONS AFFECTING FITNESS

EVOLUTION, Issue 3 2003
Peter D. Keightley
Abstract Analysis of a recent mutation accumulation (MA) experiment has led to the suggestion that as many as one-half of spontaneous mutations in Arabidopsis are advantageous for fitness. We evaluate this in the light of data from other MA experiments, along with molecular evidence, that suggest the vast majority of new mutations are deleterious. [source]

High-resolution 1H NMR spectroscopy in rat liver using magic angle turning at a 1 Hz spinning rate

MAGNETIC RESONANCE IN MEDICINE, Issue 5 2002
Jian Zhi Hu
Abstract It is demonstrated that a high-resolution 1H NMR spectrum of excised rat liver can be obtained using the technique of magic angle turning (MAT) at a sample spinning rate of 1 Hz. A variant of the phase-corrected MAT (PHORMAT) pulse sequence that includes a water suppression segment was developed for the investigation. The spectral resolution achieved with PHORMAT approaches that obtained from a standard magic angle spinning (MAS) experiment at a spinning rate of several kHz. With such ultra-slow spinning, tissue and cell damage associated with the standard MAS experiment is minimized or eliminated. The technique is potentially useful for obtaining high-resolution 1H spectra in live animals. Magn Reson Med 47:829,836, 2002. © 2002 Wiley-Liss, Inc. [source]

Solid-state 1H , 19F/19F , 1H CP/MAS NMR study of poly(vinylidene fluoride)

MAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2002
Shinji Ando
Abstract Solid-state 1H , 19F and 19F , 1H cross-polarization magic angle spinning (CP/MAS) NMR spectra have been investigated for a semicrystalline fluoropolymer, namely poly(vinylidene fluoride) (PVDF). The 1H , 19F CP/MAS spectra can be fitted by five Lorentzian functions, and the amorphous peaks were selectively observed by the DIVAM CP pulse sequences. Solid-state spin-lock experiments showed significant differences in T1,F and T1,H between the crystalline and amorphous domains, and the effective time constants, THF* and T1,*, which were estimated from the 1H , 19F CP curves, also clarify the difference in the strengths of dipolar interactions. Heteronuclear dipolar oscillation behaviour is observed in both standard CP and 1H , 19F inversion recovery CP (IRCP) experiments. The inverse 19F , 1H CP-MAS and 1H , 19F CP-drain MAS experiments gave complementary information to the standard 1H , 19F CP/MAS spectra in a manner reported in our previous papers for other fluoropolymers. The value of NF/NH (where N is a spin density) estimated from the CP-drain curve is within experimental error equal to unity, which is consistent with the chemical structure. Copyright © 2001 John Wiley & Sons, Ltd. [source]