Louis Harold Gray was a physicist and radiation biologist who specialized in the application of radiation to cancer therapy.
Franklin had sought his advice regarding the tendency of viruses to break down during long exposures to x-rays, one of the
many challenges in her virus work. In this letter, she responded to his suggestions, noting that she would try them when her
x-ray apparatus was repaired.
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1957-03-14 (March 14, 1957)
Gray, L. H.
Mount Vernon Hospital
Original Repository: Churchill Archives Centre. The Papers of Rosalind Franklin
Reproduced from the Franklin Collection at the Churchill Archives Centre with the permission of the copyright holder.
Thank you very much for your letter of 25th February, and for taking so much trouble to answer all my questions.
I regret to say that my estimate of 100 r was due to a misunderstanding of the definition of r - a unit which we do not normally
use. A re-calculation shows that a 20 hour exposure of the crystal gives approximately 5 x 10[to the fifth] r, and that this
corresponds to 10 to 20 ionisations per virus particle. The effect of such an exposure is appreciable.
At the moment our apparatus is under repair. When it is working again we shall try adding cysteine, as you suggest. We cannot
use dry virus, as the regularity of the crystal is greatly decreased on drying.
I shall write to you again if the combined effect of cysteine, nitrogen atmosphere, and reduced temperature give results that
are of any interest.