1XFN:
reference: The solution structure of a transient photoreceptor intermediate: Delta25 photoactive yellow protein., Bernard C, Houben K, Derix NM, Marks D, van der Horst MA, Hellingwerf KJ, Boelens R, Kaptein R, van Nuland NA, Structure (Camb) 2005 Jul;13(7):953-62. PMID: 16004868

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).