The James Keeler Group http://www-keeler.ch.cam.ac.uk/ Current and recent research topics: Spectra of solutes in weakly aligning media and MAS spectra of solutes in liquid crystal (Andrew Phillips) Fast and precise methods for the measurement of self diffusion coefficients (Michael Thrippleton) Rapid measurement of two-dimensional spectra (Michael Thrippleton) Methods for measuring long-range heteronuclear coupling constants (Richard Edden) Downloads: http://www-keeler.ch.cam.ac.uk/
Dr James Keeler Nuclear Magnetic Resonance (NMR) spectroscopy is undoubtedly one of the most powerful techniques available to the chemist for determining the structure and dynamics of molecules. In contrast to other kinds of spectroscopy, there is a direct and intuitively appealing relationship between the features observed in an NMR spectrum and structural elements in the molecule. Over the years, NMR spectroscopists have learnt how to exploit this relationship and developments of the techniques used to record NMR spectra have made it possible to improve the reliability of structure determination and to study larger and larger molecules.
The aim of our research is to devise elegant, efficient and sensitive ways of extracting structural information from NMR spectra. Just 'recording the spectrum' does not give access to the information required. More advanced techniques based on multiple pulse and multi-dimensional NMR are needed to make the information accessible. For example, we might record a three- dimensional spectrum in which each peak indicates the relationship between a particular carbon atom, the hydrogen atom attached to it and a second close-by hydrogen. Such a spectrum contains a great deal of information about the structure and, most importantly, this information is presented in a readily interpreted format. Our work involves the invention and development of such multiple pulse and multi- dimensional NMR experiments. These techniques are very much aimed at solving structural problems on a wide range of molecular systems that are presented to us by colleagues in Chemistry, Biochemistry and Molecular Biology - with whom we have close collaborations.
Examples of our recent work includes high-speed methods for the determination of diffusion constants, the measurement of long-range carbon-proton coupling constants and the development of highly effective 'z-filters' for use in two-dimensional experiments.
Application of our new z-filter: On the left is shown part of the two-dimensional TOCSY spectrum of strychnine. As is common in such spectra, the multiplets are distorted by the presence of dispersive contributions. On the right is the same spectrum recorded using our new z- filter - the improvement is dramatic; the multiplets now have clean lineshapes and the resolution is effectively improved.
Selected Publications
Elimination of Zero-Quantum Interference in Two-Dimensional NMR Spectra Angew. Chem., Int. Ed. Engl., 42, 3938-3941 (2003)
A fast method for the measurement of diffusion coefficients: one-dimensional DOSY Magn. Reson. Chem. 41, 441-447 (2003)
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