IMPROVEMENTS IN THE SENSITIVITY OF INVERSE-DETECTED HETERONUCLEAR CORRELATION SPECTRA USING MICRO INVERSE PROBES AND MICRO CELLS - HMQC ANDHMBC SPECTRA OF CARIBBEAN CIGUATOXIN - PRELIMINARY STRUCTURAL INFERENCES

Cignatoxins are extremely potent activators of voltage-dependent sodiu m channels and elicit gastrointestinal and neurologic dysfunction in h umans. Because they are present only at extremely low levels, the acqu isition of heteronuclear shift correlation nmr spectra has been very d ifficult Inverse-detected heteronuclear shift correlation experiments (HMQC and HMBC) have greatly increased sensitivity relative to older, heteronuclide-detected experiments. The use of micro inverse-detection probes has afforded a further dramatic increase in sensitivity relati ve to conventional 5 mm probe technology. Micro inverse-detection prob es employed in conjunction with Shigemi micro nmr cells are shown to a fford a further significant improvement in sensitivity which was neces sary to acquire spectra on a sample of <0.1 mu mole of Caribbean cigua toxin.