[Theoretic analysis of conformation of proteins. I. Minimization of potential energy of ribonuclease S].

Variation of ribonuclease S structure is analysed with the potential energy being minimized by a computer. The function of potential energy contains the potentials of bond and angle distortions, torsional and non-valent interactions. It is shown that after 100 iterations the potential energy is decreased from the value of 6500 kcal/mole to--1012 kcal/mole, 92% of complete change of energy fitting the first ten iterations. The root mean square deviation (r. ms. d.) of final structure from the initial one is 0.232 A (0.206 A for the backbone and 0.257 A for side groups). The forbidden non-valent contacts are completely removed after minimization. R. ms. d. of the equilibrium value is decreased from 0.097 to 0.006 A for bond lengths; from 7.660 to 3.65 degrees for valence an-les and from 9.44 to 6.95 degrees for rotation angles around the peptide bonds. Distribution of tensions along the protein chain after minimization is considerably changed, the tensions decreasing in average by 100 times.