Following chemical shifts (2)

Close the existing popups and go to M: Data Analysis: Follow Shift Changes. In {Settings} ensure that the "Reference Peak List:" is set to H[N]-288K - this is the assigned, blue spectrum, from which the assignments will be propagated across to the other spectra. Check that the Fitting Function is set to "Ax +B" - a linear relationships. (You may like to browse the available options here to see the available types of curves that Analysis can fit to the data. This list is readily expanded upon request.) Check that the "NMR Experiment Series:" is set to "1:temperature", set the "Max Step Size:" for 1H (in the' Isotope Parameters' section) to 0.1:

Finally, click [Group Peaks].

You will note that after a brief pause assignments of the assigned spectrum will be transferred to the peaks of the other spectra in the series and that various function-fit parameters appear in the {Peak Groups & Analysis} table. This has been achieved by matching the chemical shift changes of the peaks across the related spectra to the linear "Ax+B" shift-distance expectation for the specified temperatures, bearing in mind the chemical shift weightings, step size limits and assuming a relatively straight peak 'trajectory'. Note that if we have any errors with the spreading of assignments across the spectra, then we can manually propagate assignments across selected peaks (which use different shift lists) via R: Assign: Propagate.

For one of the peak groups, select its row in the table, then click [Show Fit Graph], hopefully you will see a new window appear with a graph of how the chemical shift distance for a group of peaks varies according to experiment temperature. Check the boxes of "Follow in window?" and "Mark Ref Peak?", then click on [Next Set]. You will see that you can zoom around the spectra (you might have to reopen window1) of the series and check the positioning and assignment of each group of peaks to check for errors. If you find an understandably wonky graph you might like to adjust the peak position (and re-fit the graph) or remove the offending point.

Referring back to the Data Analysis: Follow Shift Changes popup, in the {Peak Groups & Analysis} table you now might like to extract the temperature coefficients for further analysis. You can [Export Shifts] as a text file, or generate a graph by selecting with the right mouse button over the table R: Graph: X Assign F1: Y Fit Param A, which will give you a graphical indication of how the temperature coefficient; the "A" in the "Ax+B" equation varies across the sequence. In this window, click R: Graph type: Bar Chart, for a more appropriate display of data in this instance:

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