17O NMR Studies of Solid Amino Acids
17O nmr quadrupolar echo experiments have been performed of polycrystalline 1-leucine in order to gain better insight into its crystalline structure and dynamics of molecular motion primarily of the structural aspects of N – H…O hydrogen bonds. The central transition (m-1/2 < — > -1/2) NMR spectrum was derived by Fourier transforming the second half of the quadrupolar echo signal. The spectrum was further analyzed by a numerical method. L-leucine was enriched to about 20% in 17 O and studies were carried out in a magnetic field of 4.23 T (17O Larmor frequency 24.4 MHz). The measurements were performed in the temperature range of -50°C to 80°C. The room temperature (26°C) spectrum consists of two lines, each having a shape typical to NMR powder pattern of a central transition in the case when second order quadrupolar perturbation is significant.