Interconversion of Cystine and Cysteine induced by X-rays


CYSTEINE is spontaneously oxidized to cystine at neutral pH1,2; at acid pH. this spontaneous reaction does not take place. Under the influence of ionizing radiation, cysteine is oxidized, even at acid pH.3–7. In the presence of oxygen this radiation conversion of cysteine to cystine is very fast, and a G value of 74 has been reported8, although the exact rate of conversion depends on the cysteine concentration and oxygen tension9. It has also been reported that, in the presence of hydrogen, radiation could induce the reduction of cystine to cysteine9. Markakis and Tappel10 analysed a number of products after irradiating cystine in oxygen-saturated and nitrogen-saturated solutions, and in both cases cysteine was one of the products. Yalow11 also reported the presence of cysteine after deuteron irradiation of dry cystine. However, Cavallini et al.12 invariably found that no SH was produced after irradiating a mixture of disulphides, including cystine.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Warburg, O., Biochem. Z., 187, 255 (1927).

  2. 2

    Gray, L. H., Progress in Radiobiology, 267 (Oliver and Boyd, Ltd., 1956).

  3. 3

    Kinsey, V. E., J. Biol. Chem., 110, 551 (1935).

  4. 4

    Barron, E. S. G., and Flood, V., J. Gen. Physiol., 33, 229 (1950).

  5. 5

    Fricke, H., Solvent-activated Radiation Reactions in Aqueous Solutions, Symposium 4, at Army Chemical Centre, 24 (1950).

  6. 6

    Lefort, M., Chimie des Radiations des Solutions Aqueuses: Aspects Actuels des Resultats Experimentaux. Actions Chimiques et Biologiques des Radiations, 95 (Masson et Cie., Paris, 1955).

  7. 7

    Dewey, D. L., Rad. Res., 19, 64 (1963).

  8. 8

    Hart, E. J., and Platzman, R. L., Mechanisms in Radiobiology, 1, 93 (1961).

  9. 9

    Swallow, A. J., J. Chem. Soc., 1334 (1952).

  10. 10

    Markakis, P., and Tappel, A. L., J. Amer. Chem. Soc., 82, 1613 (1960).

  11. 11

    Yalow, R. S., Proc. First National Biophysics Conference, 169 (Yale University Press, 1959).

  12. 12

    Cavallini, D., Mondovi, B., Giovanella, B., and De Marce, C., Science, 131, 1441 (1960).

  13. 13

    Ellman, G. L., Arch. Biochem. Biophys., 82, 70 (1959).

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

DEWEY, D., BEECHER, J. Interconversion of Cystine and Cysteine induced by X-rays. Nature 206, 1369–1370 (1965).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.