
PHYs as photochromic proteins can reversibly switch between two distinct states: a red light (Pr) and a far-red light (Pfr) absorbing form. Phytochromes (PHYs) are photoreceptor proteins first discovered in plants, where they control a variety of photomorphogenesis events. b) Authors to whom correspondence should be addressed: and

4 The University of Chicago, Center for Advanced Radiation Sources, 9700 South Cass Ave., Bldg 434B, Argonne, Illinois 60439, USA.3 Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden.

Maryland Ave., Milwaukee, Wisconsin 53211, USA 2 Physics Department, University of Wisconsin-Milwaukee, 3135 N.1 Department of Biology, Northeastern Illinois University, 5500 N.
