[modeller_usage] making ideal alpha-helix

Dear all,

I am having a trouble with making an alpha helix example ( http://salilab.org/modeller/wiki/Make%20alpha%20helix).

It works fine for shorter helices, but if I increase helix length and do e.g. m.build_sequence('AAAAAAAAAAAAAAAAAA') then the resulting helix is far from perfect, has local distortions and largely is not recognized as helix by DSSP (it shows mixed H and T conformation), and not drawn as helical cartoon in pymol. The situation does not improve if I increase the number of conjugate gradient steps. The extent of distortions does seem to be somewhat sequence dependent.

Is there a better way of making an ideal alpha helix with Modeller ?

I tested on Modeler 9.11 and 9.12.

Thanks in advance for help, Jan