α-螺旋的四种图示（Four different graphic representations of the α-Helix）

(a) As it originally appeared in Pauling’s 1960 The Nature of the Chemical Bond.
(b) Showing the arrangement of peptide planes in the helix.
(c) A space-filling computer graphic presentation.
(d) A “ribbon structure” with an inlaid stick figure, showing how the ribbon indicates the path of the polypeptide backbone. (Irving Geis)