Pulse angle width

Figure 4. Proton decoupled 19F-NMR spectrum of pABG5 /7-glucosidase inactivated with 2F/ GluF (conditions as described in text). This spectrum was recorded on a 270 MHz Bruker/Nicolet instrument using gated proton decoupling (decoupler on during acquisition only) and a 90° pulse angle with a repetition delay of 2s. A spectral width of 40,000 Hz was employed and signal accumulated over 10,000 transients.

Fig. 2.5. (a) FID signal of hexadeuteriodimethyl sulfoxide neat liquid natural 13C abundance 22.63 MHz 30 C pulse width 10 qs for about 30 as pulse angle observation time 0.8 s 0.2 s of the decay are shown 2048 accumulated scans ... 

In Fig. 2 we show a flow chart of the simulation program. Apart from the specification of the m.p. sequence, that is, of the spacings t of the pulses, their widths their flip angles /3 = (o tp, and phases a, the program requires as input parameters the dipole-dipole coupling strengths b.k, the chemical shifts and the offset Aw. 

The length of time in which the radiofrequency pulse excites the nuclei is the pulse width, which is measured in p,s but usually expressed in terms of pulse angles. Pulse angles between 30° and 90° are used... 

All NMR experiments were performed on a Varian XL-200 spectrometer at 50.31 MHZ. Relevant instrument settings include 90 degree pulse angle, 1.0 second acquisition time, 0.5 second pulse delay, 238.5 ppm spectral width, and broad band proton decoupling. About 40,000 transients were collected for each spectrum. Temperature was maintained at 40 C. Spin-lattice relaxation time (Tl) and Nuclear Overhauser Enhancement (NOE) values for all C-13 NMR resonances were carefully measured to determine the optimum NMR experimental conditions. The spectral intensity data thus obtained were assured of having quantitative validity. 

To conclude, each spectrum consisted of 64 scans of 32K data points with a spectral width of 6.000 Hz and an acquisition time of 5.3 s, a recycle delay of 25 second per scan and a pulse angle of 90°. The analysis of each solid extract was performed using D2O as an internal lock. Spectra were acquired under an automation procedure (automatic shimming and automatic sample loading) requiring about 33 min per sample. 

Figure 1. The proton decoupled 9.12 IWz NNR spectra at 27 of N-enriched cells (left) and cell envelopes (right). Spectra of 1.5 cc of packed cells ( 3(X) ng. dry wt.) or cell nenbranes and walls ( 100 ng. dry wt.) were obtained on a Brucker HFX-90 spectroneter using 30 000-60/000 accumulations/ 90 pulse angle/ 4K data points/ 3000 Hz spectral width/ 0.94 Hz exponential decay filter.

Figure 3.- The proton decoupled 9.12 MHz NMR spectra at 27 C of five ISig-enriched intact gram positive bacterial cells. Spectra of 1.5 cc packed cells ( 300 mg. dry wt.) were obtained on a Brucker UH-90 spectrometer using 10,000 accumulations, 90° pulse angle, 4 K data points, 2000 Hz spectral width, 2 Hz exponential filter, with quadrature and alternating phase detection.

Determination of PHA polymer composition by nuclear magnetic resonance (NMR). Twenty mg of each polymer was dissolved in 1 ml of CDCI3 and subjected to both H and C NMR analysis. H NMR spectra were recorded using a JEOL a-400 spectrometer with a 5.0 ps pulse width (45 pulse angle), 3-s pulse repetition, 7500-Hz spectra width, and 16K data points. For C NMR analysis, ta were collected using a JEOL ECP-500 spectrometer with a 7.0-ps pulse width (45° pulse angle), 5-s pulse repetition, 25000-Hz spectra width, and 64K data points. Tetramethylsilane (Me4Si) was used as an internal chemical shift standard. 

Figure 10. Effects of increasing pulse width on the magnetization vector M in the rotating frame, (a) Axis conventions (b) steady state (c) pulse angle a (d) njl pulse (e) n pulse.

Since there is a slight delay between when a pulse is switched on and when it reaches full power, an error may be introduced when measuring 90° or smaller pulses directly. If the 90° pulse width is required with an accuracy of better than 0.5 fi, then it may be determined more accurately by using self-compensating pulse dusters that produce accurate flip angles even when there are small (<10%) errors in the setting of pulse widths. 

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