Plotting 2D spectra

As already outlined for ID spectra, plotting of NMR data is by no means a task of secondary importance. The choice of suitable expansions, the completeness of additional data, including the relevant acquisition, processing and plot parameters, an appropriate title and a structural formula if available facilitate the subsequent spectral analysis. 

This section gives an overview of the most important options for plotting spectra available in the Output pull-down menu of 2D WIN-NMR (Fig. 4.30). These options affect the output of the 2D spectrum, its projection spectra in Fl and F2, the title text and the parameter lists. The 2D spectrum and corresponding projection spectra, either calculated from the 2D data itself or separately measured as a standard 1D spectrum can be displayed on the screen in the 2D WIN-NMR window or sent directly to a hardcopy device. 

An additional feature, the Preview window, accessible with the Preview button from within the Page Setup... sub-menu in the Output pull-down menu, displays an exact copy of your plot (WYSIWYG). It is recommended that you exploit this useful option and inspect the layout in this Preview window prior to plotting your 2D NMR spectra in order to avoid a waste of paper and time. 

To prepare a plot layout the corresponding spectrum must first be displayed on the 

Compared to ID WIN-NMR the scope of the output options available with 2D WIN-NMR is less comprehensive. The inclusion of graphics elements (e.g. structural formulae), additional text files (e.g. pulse programs) and the interactive drawing of lines and rectangles is limited or not possible with 2D WIN-NMR. However the more powerful layout capabilities of ID WIN-NMR may also be exploited by 2D data sets (section 4.10.5). 

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Note that for plotting 2D spectra up to 14 contour levels may be used. They can be defined with the Page Layout option in the Output pull-down menu (see 4.10.2). 

For comparison, the calculated linear and 2D spectra using ft = 12.3 cm-1 and 6 = 52°, which correspond to an a-helical structure (see the contour plot Fig. 19) for the isotopomer Ala -Ala-Ala are shown in Figure 21. The observed spectra for Ala -Ala-Ala are strikingly different from the calculated spectra for a molecule in an a-helical conformation. We emphasize here an important point In contrast to the NMR results on oligo(Ala), in which averaging of different backbone conformations might be present because measurements are made on a time scale that is slow compared to that of conformational motions, these vibrational spectroscopy results are detected on a very fast time scale (Hamm et al, 1999 Woutersen and Hamm, 2000, 2001). This rules out conformational averaging. 

Figure 7 (a) 2D spectral-spatial perspective plot of nitroxide biradicals derived from HAS doped in HPEC on one side of the plaque (left), and in a transparent film attached to the plaque on the opposite side (right), (b) Spectral slices determined nondestructively from 2D plot ESR spectra of biradicals located in two amorphous phases in the polymer (upper), and dispersed in a film (bottom). 

Fig. 4. Two-dimensional (2D) spectra of cyclo(Pro-Gly), 10 mM in 70/30 volume/volume DMSO/H2O mixture at CLio/27r = 500 MHz and T = 263 K. (A) TCX SY, t = 55 ms. (B) NOESY, Tm = 300 ms. (C) ROESY, = 300 ms, B, = 5 kHz. (D) T-ROESY, Tin = 300 ms, Bi = 10 kHz. Contours are plotted in the exponential mode with the increment of 1.41. Thus, a peak doubles its intensity every two contours. All spectra are recorded with 1024 data points, 8 scans per ti increment, 512 fi increments repetition time was 1.3 s and 90 = 8 ps 512x512 time domain data set was zero filled up to 1024 x 1024 data points, filtered by Lorentz to Gauss transformation in u>2 domain (GB = 0.03 LB = -3) and 80° skewed sin" in u), yielding a 2D Fourier transformation 1024 x 1024 data points real spectrum. (Continued on subsequent pages)...

This allows you to store your layout (Save layout...) and to reload it (Load layout...) for later use in order to get standardised plots of your 2D spectra. With these commands the kind of windows (spectrum, title, parameter), their position and size and additional features (axis, units, projections, parameters,...) are stored and loaded respectively. After loading a layout, these layout parameters may be inspected and if necessary modified in the Page Setup dialog box opened with the Page Setup... command (section 4.10.2) before a data set is loaded and plotted. 

Finally, the preparation of the plot layout is determined by the problem under investigation, the type of experiment performed and your own preferences. Suitable expansions for both ID and 2D spectra not only simplify the analysis, but make signal assignments and the evaluation of small coupling constants more reliable. 

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