2(4)-SEMA as a sensitive and offset compensated SLF sequence

Jayanthi, S and Sinha, N and Ramanathan, KV (2010) 2(4)-SEMA as a sensitive and offset compensated SLF sequence. In: Journal of Magnetic Resonance, 207 (2). pp. 206-212.

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Abstract

Separated Local Field (SLF) spectroscopy is a powerful tool for the determination of structure and dynamics of oriented systems such as membrane proteins oriented in lipid bilayers and liquid crystals. Of many SLF techniques available, Polarization Inversion Spin Exchange at Magic Angle (PISEMA) has found wide application due to its many favorable characteristics. However the pulse sequence suffers from its sensitivity to proton resonance frequency offset. Recently we have proposed a new sequence named 2(4)-SEMA (J. Chem. Phys. 132 (2010) 134301) that overcomes this problem of PISEMA. The present work demonstrates the advantage of 2(4)-SEMA as a highly sensitive SLF technique even for very large proton offset. 2(4)-SEMA has been designed for obtaining reliable dipolar couplings by switching the magic-angle spin-lock for protons over four quadrants as against the use of only two quadrants in PISEMA. It is observed that for on-resonance condition, 2(4)-SEMA gives rise to signal intensity comparable to or slightly higher than that from PISEMA. But under off-resonance conditions, intensities from 2(4)-SEMA are several fold higher than those from PISEMA. Comparison with another offset compensated pulse sequence, SAMPI4, also indicates a better intensity profile for 2(4)-SEMA. Experiments carried out on a single crystal of N-15 labeled N-acetyl-DL-valine and simulations have been used to study the relative performance of the pulse sequences considered. (C) 2010 Elsevier Inc. All rights reserved.

Item Type:	Journal Article
Publication:	Journal of Magnetic Resonance
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	2(4)-SEMA; PISEMA; SAMPI4; Transverse spin-lock; Sensitivity enhancement and offset compensation
Department/Centre:	Division of Chemical Sciences > NMR Research Centre (Formerly Sophisticated Instruments Facility) Division of Physical & Mathematical Sciences > Physics
Date Deposited:	12 Jan 2011 10:59
Last Modified:	12 Jan 2011 10:59
URI:	http://eprints.iisc.ac.in/id/eprint/34905

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