New Long-Range Heteronuclear Shift Correlation Methods

NEW LONG-RANGE HETERONUCLEAR SHIFT CORRELATION METHODS 

HMBC data as well as some responses not observed in the conventional HMBC spectrum. Because of the long duration of the A intervals in the broadband HMBC experiment reported, in the opinion of this author losses due to spin-spin relaxation during the long delays would be problematic when dealing with either very small samples or in the acquisition of long-range data where signals are quite weak because of 

Another approach is to intentionally select a very small coupling optimization such that integer multiples of that coupling will be in phase and read out at the end of the experiment with maximal intensity. The author (GEM) and a co-worker reported this approach using a 1.75 Hz optimization in the acquisition of proton double quantum coherence of strychnine (1) many years ago with some degree of success. 

Shaped gradients are shown as described in the work of Sprang and Bigler but there is no reason why square gradients could not he used in this sequence. 

The available accordion-optimized long-range heteronuclear shift correlation experiments were surveyed in a recent chapter. No novel accordion-optimized methods have been reported, but following the author s initial report on the advantages of using the IMPEACH-MBC sequence for long-range studies, Kline and Cheatham have 

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New Long-Range Heteronuclear Shift Correlation Methods... 

A period of intense research effort devoted to the development of new long-range heteronucieus-detected heteronuclear shift correlation experiments followed Reynolds " first demonstration of the feasibility of performing long-range heteronuclear shift correlation experiments. These methods have been reviewed" and only a couple of salient points will be discussed here. 

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