Dear modeller users, I have a question concerning the phi/psi distribution in the alpha region. The homology models which I generate seem to have a curious phi/psi distribution within the allowed alpha region. Almost all the residues within procheck's red region are sharply clustered into two peaks (one at the classical alpha helical angles of around -60, -40) and the other at the gamma region ( -90, 0). I often get a couple of minor lateral peaks as well. This is very different from crystal structures (including my template), where there is a more homogenous spread within the allowed region, although obviously showing a greater density of points towards -60, -40. I wonder why this happens and if I am doing something obviously stupid. It would seem that the sigmas on binormal restrainsts for phi/psis are very small. Can I easily adjust these values and what is the easiest way? This question is related to a similar one concerning proline phis angles which I note have a tendancy to drift away from -65. I have in the past used special restraints on all prolines in order to reduce sigma(phi) for which the default value seems to be rather generous. I would be most grateful for any comments/suggestions/help. Thanks, Richard Garratt University of Sao Paulo