Calculate heteronuclear NOE values from peak intensities

It is possible in Analysis to calculate heteronuclear NOE values for amide resonances based upon a comparison of the peak intensities in spectra that derive from an NOE saturated experiment and an unsaturated (reference) experiment. This is done in the Data Analysis: Heteronuclear NOE popup, which is accessible from M: Data Analysis: Heteronuclear NOE:

The idea of this functionality is that three peak lists are chosen, two of which are for heteronuclear NOE experiments (H,N axes); unsaturated reference and saturated, and one which is the source of assignments and peak locations. This last “Assignment” peak list may be the same as one of the NOE peak lists, but may also be entirely separate. To calculate the heteronuclear values, do as follows:

• • Select the {Peak Lists & Settings} tab.

  • Set the “Assignment Peak List:” to specify which peak assignments and locations that should be used for the calculation of the heteronuclear NOE values, and thus can be used to specify only a subset of the resonances for measurement. For example, it is common to copy an HQSC peak list for use as the “Assignment” peak list but remove overlapped and NH2 peaks so that the NOE values are only calculated for separated backbone amides. The calculation process involves taking each of these assigned peaks and finding peaks with the same assignment in the NOE peak lists, or if that fails finding peaks with a similar position (within the stated tolerances); new peaks may be picked if the “Pick new peaks?” option is set.

  • Set “Ref Peak List:”, “Sat Peak List:” and other various options that will be used in the peak-finding and NOE calculation. The ‘Peaks’ table allows the peaks from each of the three peak list selections to be displayed when one of the [Show..] buttons is clicked. The [Separate Peak Table] function allows these peaks to be displayed in the main, separate Peak Lists table (M: Peak: Peak Lists), which has many more peak manipulation options. The options below the table may be used to locate selected peaks within the spectrum window displays.

  • Select the {Peak Intensity Comparison} tab, which is where the heteronuclear NOE values are actually calculated. Assuming that two NOE experiment peak lists have been chosen and that some of their peaks match the assigned peak positions then the peak intensities are extracted and NOE values automatically calculated when the tab is opened. Although, a refresh of the table can be forced with [Refresh Table] at the bottom.

If pairs of NOE saturated and reference peaks are found then the actual heteronuclear NOE value is displayed as the |Intensity Ratio| in the last, rightmost, column of the table:

To store these values as a NOE measurement list so that the data can be saved in the CCPN project without need for recalculation, the [Create Hetero NOE List] function can be used. The results are then available to view at any time in the Measurement Lists table (M: Data Analyses: Measurement Lists).

For more information about the Data Analysis: Heteronuclear NOE popup see the in-program documentation.