Excelsin, edestin, and tobacco seed globulin crystals. Preparation, density, and X‐ray measurements

Abstract

Abstract The vegetable proteins excelsin, edestin, and tobacco seed globulin were obtained from seeds, and the purity of the preparations was tested. Crystals were grown from solutions by dialysis against water. Their optical properties were examined and their densities were measured at different water contents. Single‐crystal X‐ray photographs were obtained from excelsin equilibrated with air of various relative humidities, and from tobacco seed globulin and edestin in both the dry and the wet state. The photographs were rather poor, except for excelsin, which, in a certain range of water content, shows reflections corresponding to spacings down to 4 Å. Its Laue symmetry is R 3m. A more detailed X‐ray investigation of excelsin, involving the introduction of heavy atoms into the structure, is in progress. The structures of the three proteins may be represented by approximate close packings of spheres. The molecular weights as calculated from the unit cell dimensions and densities of the dry crystals are 303,000 (± 10,000), 360,000 (± 20,000) and 350,000 (± 20,000) for excelsin, edestin, and tobacco seed globulin respectively. The relationship between the specific volume of excelsin and its water content is discussed.

Keywords

Affiliated Institutions

• University of Groningen NL

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