pure-shift

pure-shift

During the interpretation of NMR-experiments signal overlap frequently is a critical issue. It complicates signal assignment, leads to increasingly complex signal lineshapes and usually impedes the extraction of the signal volumes via integration. These problems arise particularly frequently in proton detected spectra as the difference in resonance frequencies induced by chemical shift is rather small for this nucleus and because homonuclear scalar couplings often significantly broaden the observed signals. A simultaneous suppression of the effect of all homonuclear scalar couplings therefore offers the opportunity to significantly reduce the problem of signal overlap and simplify the observed signal lineshapes. These simplifications can be achieved when using so called pure-shift experiments, which may reveal information usually obscured in spectra due to signal overlap. Experiments not aiming at the extraction of scalar coupling effects in between protons may therefore profit from such techniques. Possible applications are for example the investigation of dynamic processes, the determination of interatomic distances using the nuclear overhauser effect (NOE) and the observation of diffusion processes.

In the field of pure-shift techniques we are working in coperation with the Morris group (University of Manchester) in experiments aiming at the measurement of exchange rates in dynamic processes and interatomic distances using the NOE without the interference of scalar couplings. With these techniques we hope to make the examination of molecular structure and dynamic a feasible task for structures which can currently not be studied due to strong signal overlap.

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