Nuclear magnetic resonance spectrum of living tunicate blood cells and the structure of the native vanadium chromogen.

The 1-H nuclear magnetic resonance spectrum of living tunicate blood cells was examined in an attempt to develop a biophysical assay for the native vanadium chromogen. The living cell spectrum was found to exhibit a broad 21 ppm downfield Gaussian signal which, however, disappears immediately upon cell disruption. Examination of the properties of this extremely low field signal revealed that it corresponds to a labile vanadium (III) aquo complex contained in the cell vacuoles, that vanadium(III) concentrations are rigidly regulated within these vacuoles, and that artifact formation does occur in the hemolysate. The living cell spectrum also indicates the number of ligand-bound vanadium(III) coordination sites in the native blood pigment. Results are discussed relation to the possible functions of the vandium chromogen.