William Lehman1, Yuichiro Maéda2. 1. Department of Physiology & Biophysics, Boston University School of Medicine, Boston, MA, 02118, USA. wlehman@bu.edu. 2. Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan.