Exciting NMR Applications with Selective Excitation
A very powerful and useful general NMR technique is to use selective excitation to focus directly on a resonance frequency or region to allow acquisition of very specific information to efficiently answer a specific question. Many experiments have been developed that are in essence 1-dimensional analogues of 2-dimensional experiments. In particular NOESY-1D1 and TOCSY-1D have gained wide spread use and acceptance in the NMR community. The NOESY-1D and TOCSY-1D experiments can provide specific answers to questions in a fraction of the time needed for a full 2D result even with NUS techniques. In this Applications Note, we will explore the StepNoesy1D2 experiment, which can yield information typically obtained by performing time consuming 3D experiments.
The StepNoesy experiment is really back-to-back TOCSY1D and NOESY1D pulse programs combined into a single sequence. We can use the TOCSY1D to reveal a fairly complete spin system for all resonances which are coupled to the selected peak. In this way a signal desired for nOe studies that might be buried under other resonances can be revealed and then selectively excited itself for the NOESY1D part. We will use Brucine as an example molecule to illustrate StepNoesy in action.