A sulfur‐33 nuclear quadrupole resonance study of 33S2‐labeled L‐cystine

Abstract

AbstractThe sulfur electric‐field‐gradient tensor for a disulfide bond in 33S2‐labeled L‐cystine has been investigated by 33S nuclear quadrupole resonance (NQR). 33S2‐labeled L‐cystine is synthesized by introduction of disulfide ions prepared from elemental 33S‐sulfur into an amino acid derivative, the side chain of which is iodinated. In its NQR spectrum, sharp single peaks are observed at between 24.63 and 24.90 MHz in the temperature range from 80 to 298 K. The two‐dimensional nutation echo 33S NQR experiment is carried out at 160 K, and the quadrupole coupling constant, CQ, and the asymmetric parameter, ηQ, are obtained to be 46.9(9) MHz and 0.6(1), respectively. The calculated 33S electric‐field‐gradient tensor components with respect to the molecular frame is briefly discussed.