1FLX:
reference: De novo design, expression, and characterization of Felix: a four-helix bundle protein of native-like sequence., Hecht MH, Richardson JS, Richardson DC, Ogden RC, Science 1990 Aug 24;249(4971):884-91. PMID: 2392678

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