1. Steacie Institute for Molecular Sciences, National Research Council of Canada, Theory and Computation Program, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada, Computational Chemistry Logic Ltd., Madach. u. 20, 8900 Zalaegerszeg, Hungary, Institute for Biological Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada, and The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351, Japan