Dextran and Levan Molecules Studied with the Electron Microscope

Abstract

THE fundamentally improved designs for the electron microscope made in recent years by different workers have led to such an improvement in the resolving power that a direct study of giant molecules with the aid of this instrument may contribute in a certain degree to our knowledge of their appearance. If we except the researches on viruses, the following investigations already performed in this direction should be mentioned: M. von Ardenne¹ and W. M. Stanley and Th. F. Anderson² have succeeded in photographing hæmo-cyanin and edestin; E. Husemann and H. Ruska have also photographed glycogen³ and iodobenzoyl-glycogen⁴. All these molecules, however, are more or less spherical (Φ ˜ 100–300 A.). They therefore appear on the plates as small diffuse dots. The electron-microscopical investigation of these molecules is facilitated by their more compact structure, which gives a good contrast with the substrate. In the case of iodobenzoylglycogen, this contrast has been further improved by the introduction of heavy atoms into the molecule.