Hello,

I have performed PCA analysis, without mass weighting, on a peptide using g_covar and g_anaeig. The first principal component generally corresponds to the stretching of the peptide. I understand that each eigenvalue represents the variance in the motion along the associated eigenvector. However, the square root of the variance for the first eigenvalue is ~20 nm while the maximum extended length of any peptide is ~3 nm. I have tried normalizing the eigenvalues by the number of atoms used for the analysis (73) but this gives the standard deviation of the motion to be ~2.2 nm, still much too large. I would like to know how to normalize the eigenvalues to obtain reasonable standard deviations from the eigenvalues.

Thank you,

Tyler


 ________________________________________________________________
(_    Tyler Luchko                           Ph.D. Candidate    _)
 _)   Department of Physics            University of Alberta   (_
(_    Edmonton, Alberta, Canada                                 _)
 _)   780-492-1063                       [EMAIL PROTECTED]   (_
(________________________________________________________________)



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