Two-Dimensional NMR Data-Processing Parameters

For the heteronucleus-detected FLOCK experiment, longer RT s are appropriate since the signals of nonprotonated nuclei are being recorded. 

The receiver gain cannot necessarily be set in 2D experiments in the manner described for ID experiments in Section 2-4g. For gradient, H-delected, correlation sequences, 

In order to minimize the overall time of a 2D experiment, one wishes to keep the number of scans per increment (ns//) at a value that is sufficient to observe the spectrum of that particular increment. For heteronucleus detection, this number usually is large, but for protons, adequate detection can often be accomplished in 1 to 4 scans. The minimum ns//, however, is determined by the phase cycle (Section 5-8) of the pulse sequence used and may be anywhere from 4 to 64 scans. As a general rule, 8 scans// is a minimum value for H-detected experiments. Longer experiments that require a large ns//, such as the study of dilute solutions (proton detection) or heteronucleus detection, can make good use of interleaved acquisition with a suitable block size (as described in the discussion of the DEPT experiment in Section 7-2b). 

In recent years, gradient versions of many of the basic 2D NMR experiments have become very popular. One of the main reasons is that the use of gradients eliminates the need for phase cycling in the selection of a coherence pathway. Experiments involving detection can, therefore, often be performed with one to two transients per increment. 

Steady-state scans (Section 2-4i) are used before the start of essentially all 2D experiments. They are particularly important in a number of pulse sequences in order to compensate for spin-lock (Sections 7-7b and 7-10b) and decoupler (Section 7-8) heating effects. Larger numbers of steady-state scans are employed in experiments that have either particularly long spin-lock times or X-nucleus decoupling over especially wide spectral widths. 

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Data processing parameters Tire deuterium NMR peak area was normalized to peak area percentage. Principal component analysis (PCA) was conducted using SPSS software package. The final results were presented as a two dimensional PCA plot using the first two principal components. 

NMR NMR Data Processing NMR Pulse Sequences NMR Relaxation Rates Nuclear Overhauser Effect Parameters in NMR Spectroscopy, Theory of Solvent Suppression Methods in NMR Spectroscopy Structural Chemistry Using NMR Spectroscopy, Peptides Two-Dimensional NMR, Methods. 

NMR samples contained 0.6 ml receptor (0.5-2.0 mM) dissolved in refolding buffer (vide supra) with 10% DjO. One-dimensional F NMR spectra were obtained at 470 mHz on a General Electric GN 500 spectrometer fitted with a 5 mm F probe. Parameters included 16K data points, 3.0 second relaxation delay and 25 Hz linebroadening for processing spectra. T, relaxation times were measured by the inversion recovery method. The two-dimensional F NOESY NMR spectrum was obtained on a Varian Unity Plus 500 using the standard Varian pulse sequence. A total of 128 experiments with a mixing time of 0.3 seconds were performed with collection of 1024 data points. Quadrature detection in the second dimension was obtained through the method of States and Haberkom. C ( H NMR spectra were obtained on a Varian 500 Unity Plus fitted with a 10 mm broadband probe. 

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