Stability – Instability Index

The Stability – Instability Index track estimates the stability of the protein in a test tube. The Instability Index is calculated using the approach of Guruprasad et al., 1990,, which predicts regional instability by calculating the weighted sum of dipeptides that occur more frequently in unstable proteins when compared to stable proteins. Detailed information about this method is available on the ExPASY website. An instability index less than 40 predicts a stable protein, whereas values higher than 40 denote a potentially unstable protein.

To apply this track to the sequence:

In the Tracks panel, expand Stability and check the box next to Instability Index. The track will now be visible in the Sequences view.

To edit track options:

Select the track in the Tracks panel. Open the Track Options section, which appears as follows:

• Residues to Average – number of residues to be averaged when constructing each point in the plot. The default is 19. The closer a calculation is to this value, the more likely the chance of aggregation. Over small windows, this method gives an idea of the potential for local instability.

Click if you wish to return to the default value.