Isotopic Labelling

It is possible to apply an isotopic labelling scheme to your protein which will then be automatically taken into account by the software at various stages, e.g. when providing assignment options or generating distance constraints. This is particularly useful if you are dealing with quite complicated labelling schemes such as sparse labelling from [1,3-13C]-glycerol etc.

Reference Isotope Schemes

A variety of labelling schemes are provided with the program, but you can also generate your own custom scheme. You can find the schemes by going to Molecule: Reference Isotope schemes. Details about generating your own scheme can be found in the version 2.1.5 Documentation here.

Generating a 'Labeled Sample' and associating it with an Experiment

Rather than linking an experiment directly to a labelling scheme, you actually link it to a 'Labelled Sample'. Your 'Labelled Sample' can then, for instance, consist of a mix of two molecules each with a different labelling scheme (e.g. 50% U-13C and 50% U-15N) and when you link your NC experiment to this, Analysis will automatically know that the experiment can only include inter-molecular correlations.

Go to Molecule: Isotope Labelling. In the {Labelled Molecules} tab click on [New Sample] below the 'Labelled Samples' table, making sure that the correct molecule is selected in the dropdown menu. With this sample selected you can now specify the 'Sample Composition' by selecting [New Pattern from Scheme] with the correct reference isotope scheme selected in the drop-down menu. If the sample contains molecules with several different labelling schemes, then select another pattern and specify the correct |Weight| for each.

In order to associate experiments with this sample, go back to the 'Labelled Samples' table and double-click in the |Experiments| column and select the desired experiments.

The {Labelling Patterns} tab can be used in order to customise a Labelling Pattern on a residue by residue or atom by atom basis. This is useful for the case where only part of a molecule has been isotopically labelled (e.g. through protein ligation), only certain residues or atomic sites have been labelled (e.g. using solid-phase peptide synthesis).