Figure 1: 27.11 MHz 17O NMR spectra of 0.1 M solutions of glutamic acid in H2O containing 1 M NaCl, temperature = 40°C, pH = 3.1. (a) Natural abundance spectrum in 17O depleted water (*). , , total experimental time ca.4.2 h; ▼ transmitter’s residual peak. Glutamic acid resonances after (a) vertical expansion (8x); (b) exponential multiplication of the FID (LB = 100 Hz). (b) Spectrum of 1% enriched glutamic acid in ordinary water (●). , NS = 150,000, total experimental time ca. 19 min. Glutamic acid resonances after (c) vertical expansion (8x); (d) multiplication of the FID with a Gaussian-exponential function. (Reprinted, with permission, from Helv. Chim. Acta . Copyright 1982, by Swiss Chemical Society).