Morphological evidence for the folding of polyproline II helices

Spherulites of poly‐L‐proline II were grown by film casting from a dilute formic acid solution. Electron diffraction indicated that the molecular axis was parallel to the surface and essentially normal to the face of the lamellae. The molecular length was five times greater than the width of the lamellae. This is considered to he substantial evidence for the molecular folding of poly‐L‐proline II. A correlation between the molecular conformation of poly‐L‐proline in solution and the observed morphological form in the solid state has been determined. As the solution mutarotates from form I to form II, the solid morphology varies from an indistinetly shaped spherulite with little inner detail to a well formed crystalline spherulite complete with lamellae.