Biomolecular Structure and Design Program, University of Washington, Seattle, WA 98195-5013, USA.|Biomolecular Structure and Design Program, University of Washington, Seattle, WA 98195-5013, USA.|Biomolecular Structure and Design Program, University of Washington, Seattle, WA 98195-5013, USA.|Biomolecular Structure and Design Program, University of Washington, Seattle, WA 98195-5013, USA.