Thomas T. Nakashima

Biosynthesis of averufin by Aspergillus parasiticus: detection of 18O-label by 13C-N.M.R. isotope shifts.

The incorporation of oxygen-18 gas and doubly-labelled sodium [1-13C, 18O2]acetate into averufin (1) by an aflatoxin deficient mutant of Aspergillus parasiticus was detected by 18O-induced isotope shifts in 13C-n.m.r. spectra.

A Synthesizer‐Based 13C NMR Spectrometer with 19F Field/Frequency Lock

Described here is a modification of the Varian HA‐100 spectrometer which permits convenient observation of 13C NMR spectra at 25.1 MHz, with field/frequency stabilization based upon a 19F lock at 94.1 MHz. All radio frequencies are derived from a synthesizer. The resulting stability permits efficient storing of repetitive experiments.

Isotope shifts in 13C-n.m.r. spectra of 18O-labelled acetals; multiple labelling effects at β-carbons

Acetals which are isotopically mono- or disubstituted with 18O show 13C-n.m.r. isotope shifts, both at directly attached carbons and at β-carbons, which are dependent on the number of labelled oxygens in an additive fashion.

Biosynthesis of the aflatoxin precursor sterigmatocystin by Aspergillus versicolor; spin-echo resolution of 18O isotope shifts in 13C-n.m.r. spectroscopy

Locations of oxygen-18 label in an aflatoxin precursor, sterigmatocystin, derived from sodium [1-13C,18O2]-acetate were determined using a spin-echo pulse sequence [90°-τ-180°-τ-acquisition, where τ= 1/(2JC-C)] in 13C-n.m.r. spectroscopy to resolve isotope shifts from interfering carbon–carbon couplings(JC-C).