Hot Silk

The big, green silkworms crawling around the Harvard laboratory of Assistant Professor (of zoology) Carroll Milton Williams look like normal specimens, but when Professor Williams tests them with a Geiger counter, they make it rattle like a cornpopper. The caterpillars are radioactive. Soon they will spin cocoons of radioactive silk and will eventually emerge, if not disturbed, as radioactive moths.

Professor Williams and his associate, Paul Charles Zamecnik, Harvard associate in medicine, have a serious purpose. They are trying to study the structure of protein, the basic substance of living creatures. Fibroin, the principal constituent of silk, is a protein. Scientists know that it is made of certain amino acid molecules linked together in chains. What they do not know is how the chains are put together. The plan is to find out how the silkworms do it. Professor Williams is injecting mature worms with various amino acids which are made radioactive by carbon 14. After a while the worms start spinning their cocoons. If their silk turns out radioactive, it may prove that the particular amino acids injected by Professor Williams were used to form its protein.

Last year the Harvardmen produced two cocoons whose silk was "hot" enough to impress their images on a photographic film. This year they hope to grow a kilo (2.2 lbs.) of the stuff for themselves and colleagues to study. The hot silk, even in this quantity, will not be a menace. Even if it should escape from the laboratory and get itself woven into underwear, it is not strong enough to damage the most sensitive skin.

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