A New Method for Measuring Diffusion Constants of Biologically Active Substances


THE study of diffusion constants of proteins and other materials of high molecular weight has added much to our knowledge of the nature of these substances (Svedberg and Pederssen1, Polson2). These studies were made on materials which were obtained in the pure state. Unfortunately, when dealing with substances comprising several components, the usual optical method of diffusion (Lamm3) cannot be applied except with great difficulty. In such cases recourse must be made to analytical methods. The method of Northrop and Anson4, namely, diffusion through a porous plate, has been of great value, but this method too has its limitations. Bourdillon5 has proposed a method for the analytical determination of diffusion constants. His method, although theoretically sound, is very difficult to apply, especially when dealing with viruses. (For a criticism of the above-mentioned methods, see Markham, Smith and Lea6.)

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  1. 1

    Svedberg and Pederssen, "The Ultracentrifuge" (Oxford University Press, 1940).

  2. 2

    Polson, Koll. Z., 87, 149, and 88, 51 (1939).

  3. 3

    Lamm, Nova Acta Reg. Soc. Scient. Upsal., 4, 10, No. 6 (1937).

  4. 4

    Northrop and Anson, J. Gen. Physiol., 12, 543 (1928–29).

  5. 5

    Bourdillon, J. Gen. Physiol., 24, 459, and 25, 263 (1941).

  6. 6

    Markham, Smith and Lea, Parasitology, 34, 315 (1942).

  7. 7

    Polson, Onderstepoort J. Vet. Sci. and Animal Ind., 16, 33 (1941).

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