[Preliminary electron microscopic and x-ray study of the crystalline protein of diphtheria toxin]

The authors present the results of the electron microscopic and roentgenological study of the crystalline protein of diphtheria toxin. On the basis of direct measurements of the crystal image and diffraction pictures it was possible to calculate the interplane distances of the placement of molecules in the crystal. Examination in polarization microscope showed that the crystals were optically uniaxial with a direct extinction and a positive character of elongation. Molecular aggregates revealed in the protein molecules resembled the caudal part of the bacteriophage by structure.