Minimization of polypeptide energy. 8. Application of the deflation technique to a dipeptide.

In minimizing the energy of a polypeptide, it is necessary to be able to move out of local minima in the search for the global minimum of the energy. For this purpose, the standard technique of deflation (in solving systems of nonlinear equations) is described and applied to the calculation of various stationary points on the energy surface of the "dipeptide" glycyl-L-alanine. The results compare favorably with a detailed contour map of the energy surface. Of special interest is a deep minimum near (varphi,Psi) approximately (240 degrees , 120 degrees ) which was found by the deflation technique but which had usually been overlooked in previous investigations.