14N NQR Spectroscopy of Some Amino Acids and Nucleic Bases via Double Resonance in the Laboratory Frame

Abstract

The 14N nuclear quadrupole resonance spectra and spin-lattice relaxation times of the amino acids histidine, methionine, cystine, cysteine, and tyrosine as well as of the nucleic bases uracil, thymine, cytosine, and guanine have been determined by a 14N-proton double resonance technique in the laboratory frame. The experiments were performed on polycrystalline samples at 77°K or above this temperature. A theoretical estimate of the sensitivity of this method for a variety of experimental conditions is as well presented. It is shown that in contrast to usual double resonance techniques the method works even in the case of a short proton spin-lattice relaxation time if only the nitrogen relaxation time is long.

14N NQR study of nicotinamide and related compounds

“…[12] Nevertheless, such spectra show the approximate location of the NQR frequencies, which simplifies the application of the NQDR techniques with multiple frequency sweeps and two-frequency irradiation. The 14 N NQR frequencies, quadrupole coupling constants e 2 qQ/h, and asymmetry parameters η in picolinamide, nicoti- In all the substances, except for acetamide, we observe two significantly different nitrogen positions: one with the quadrupole coupling constant about 4.5 MHz and the other with the quadrupole coupling constant about 2.6 MHz.…”

Impact of structural differences in carcinopreventive agents indole-3-carbinol and 3,3′-diindolylmethane on biological activity. An X-ray, 1H–14N NQDR, 13C CP/MAS NMR, and periodic hybrid DFT study

“…Three complementary double resonance techniques were applied to search for three 14 N NQR frequencies for each nucleus. The first method was the 1 H-14 N cross relaxation spectroscopy (Blinc et al, 1972;Seliger et al, 1976) then the solid-effect technique (Seliger and Žagar, 2008a,b) and finally the two-frequency irradiation technique (Seliger and Žagar, 2012;Seliger et al, 1994a,b) A more detailed description of the experimental techniques can be found in our earlier papers (e.g. allopurinol (Latosiń ska et al, 2014c) or caffeine (Latosiń ska et al, 2014b)).…”

Nuclear quadrupole double resonance techniques for the detection of explosives and drugs

“…This is achieved in the "NQDR with multiple level crossing" experiment [10], in which the proton NMR levels and nitrogen NQR levels cross several times in between the rf irradiation period (see Fig. l).…”

“…The proton NMR signal is measured after the adiabatic demagnetization-remagnetization cycle. Nitrogen NQR transitions are saturated by rf irradiation in zero field, enabling energy flow between the two subsystems[10]. NQDR spectrum of TNT in zero external magnetic field asa function of frequency of the rf irradiation field v~[4].…”