Figure 3.

Jane Richardson's ribbon drawing process as of 1980.A, the different conventions for drawing α helix, β sheet, and loops. B, the pencil sketch for Staphyloccocal nuclease, done on tracing paper over the scaled Cα plot. C, two optical illusions compensated for to draw convincing ribbons. D, the pastel-colored ribbon for Cu,Zn superoxide dismutase (SOD) that corrects for both illusions in (C). E, page 270 from reference (7), including the Greek key folds of Staph. nuclease, of SOD, and of an immunoglobulin V_L domain.