More precise details about the conformer population are gained by means of a GROMOS cluster analysis (Fig. ), performed according to the differences in the root mean square deviation (RMSD) values of individual conformers, computed only for the peptide backbone with a cut-off of 2.0 Å (Fig. ). The RMSD values confirm the variability of sampled structures in the REST ground trajectory, ranging from less than 0.2 Å to around 10.5 Å, with an average of 4.2 Å separating the structures. This variability results in the mostpopulated cluster containing only 9 % of the conformers, and to a smooth distribution of 20 clusters with conformer populations larger than 1 %. Almost 50 % of the conformers do not belong to these clusters and are grouped together in the histogram in Fig. (grey bar labelled 'Other').