Magn. Reson. Chem. (MRC) up to July 30, 2008

Magn. Reson. Chem. up to July 30, 2008

Correlating sideband patterns with powder patterns for accurate determination of chemical shift parameters in solid-state NMR
from Magnetic Resonance in Chemistry by M. S. Ironside, D. G. Reid, M. J. Duer

Powder patterns and sideband patterns have different strengths when it comes to using them to determine chemical shift parameters. Here, we show that chemical shift parameters can be determined with high accuracy by analysing the correlation pattern from a 2D experiment which correlates a powder pattern in the indirect dimension with a sideband pattern in the direct dimension. The chemical shift parameters so determined have greater accuracy than those obtained by analysing a sideband or powder pattern alone, for the same signal-to-noise ratio. This method can be applied for both resolved correlation patterns and to cases where two components share similar isotropic chemical shifts. The methodology is demonstrated in this paper, both theoretically and experimentally, on the 31P signals of the bis-phosphonate drug, pamidronate. Copyright © 2008 John Wiley & Sons, Ltd.
Digital Object Identifier (DOI)
10.1002/mrc.2262

Swept-frequency two-pulse phase modulation (SWf-TPPM) sequences with linear sweep profile for heteronuclear decoupling in solid-state NMR
from Magnetic Resonance in Chemistry by C. Vinod Chandran, P. K. Madhu, Narayanan D. Kurur, Thomas Bräuniger

Recently, a pulse scheme for heteronuclear spin decoupling in solid-state NMR, called swept-frequency two-pulse phase modulation (SWf-TPPM), was introduced which outperforms the standard TPPM and small phase incremental alteration (SPINAL) schemes. It has also been shown that the frequency-sweep profile can be varied to achieve optimal efficiency for crystalline and liquid-crystalline samples, respectively. Here we present a detailed comparison of the proton decoupling performance for SWf-TPPM sequences with tangential sweep profiles (SWftan-TPPM) and linear sweep profiles (SWflin-TPPM). Using the 13CH2 resonance of crystalline tyrosine as a model system, it is shown that linear profiles have a decoupling performance which is at least as good and in some instances slightly better than that obtained from tangential sweep profiles. While tangential sweep profiles require a tangent cut-off angle as an additional parameter, the lack of that parameter makes linear sweep profiles easier to implement and optimise. Copyright © 2008 John Wiley & Sons, Ltd.
Digital Object Identifier (DOI)
10.1002/mrc.2285