Separate quantification of doubly and singly C-13-labeled metabolites by HSQC-filtered J spectroscopy

NMR detection of multiply labeled compounds in biological samples is often used to follow metabolic pathways. Detection of protons bound to C-13 atoms offers a more sensitive approach than direct C-13 detection, but generally results in the loss of carbon-carbon coupling information. We have modifie d an HSQC sequence to refocus the carbon chemical shifts in order to obtain a proton-correlated C-13 homonuclear J spectrum, which allows us to measur e singly and doubly labeled compounds in the same spectrum. (C) 1999 Academ ic Press.