Pulse Excitation Method Research Articles

31P-NMR studies of tRNA

Unlike other spectroscopic methods, 31P-NMR provides direct information on the state of the phosphate residues of nucleic acids. Cueron [l] measured the 31P-NMR spectra of two individual tRNAs by routine techniques; the time of accumulation was 4 to 8 hr. The pulse excitation method combined with Fourier transformation makes it possible to obtain rapidly NMR spectra of tRNA characterized by good signal-to-noise ratio. Thus, the techniques enable one to study the processes of tRNA transformation in the course of chemical or enzymatic reactions, as well as to study the effects of higher structure in solutions of low concentrations. The present communication is concerned with the possibilities of the pulse-excitation 31PNMR spectroscopy as a means of investigation of tRNA higher structure, chemical modification and enzymatic hydrolysis.

Nuclear magnetic resonance Fourier spectroscopy with pulse and stochastic excitation controlled by an IBM 1800 computer.

Utilization of a general purpose computer in controlling pulses and data collection in NMR Fourier spectroscopy is described. Coherent addition of free induction decay signals can be achieved for analogue-to- digital conversion rates up to 20 kHz with an IBM 1800 computer. Stochastic excitation and signal detection are time-shared in order to suppress leakage. The benefits of this procedure, compared with the pulse excitation method, are low peak power requirements and the fact that resolution and sensitivity can be set independently. However, contrary to the pulse experiment, care must be taken with the receiver system in commercially available high-resolution NMR spectrometers. For high conversion rates, ringing and saturation of the narrow band detector might necessitate the exchange for a broad band amplifier.