I now enter into a speculative mode about Dr. Petkau and SOD. What I though I heard through the grapevine, was that Abe had suggested to AECL that it should donate SOD to help fight the radiation exposures to which cleanup crews at Chernobyl were being subjected. I can only guess that his suggestion was ignored.
Then in 1986 the “unthinkable” occurred. Chernobyl literally exploded on the nuclear scene. This time there were casualties, many of them.
Up until 1979 all power reactors were being touted by reactor scientists as safer than most of the then available sources of energy. Then, in 1979, a meltdown occurred at Three Mile Island in Pennsylvania. Although there were no radiation-induced injuries, this incident opened a new perspective in the nuclear industry. I remember having gone to early seminars featuring “human factors engineering” by experts from MIT who had claimed that the possibility of having a reactor accident was less than one in a million.
Our paper came out in 1983. It was one of the few papers that caused a flutter in the company hierarchy. I even received calls from on high asking for a simplified summary if the work we’d done.
The smallest entity we observed was the dimer. Our measurements therefore ruled out isolated monomer exchange by way of subunit diffusion in solution. On the other hand, what we did observe was significant numbers of whole SOD molecules lying side by side. It became obvious that exchange was taking place by some “docking mechanism”. The Whiteshell Lab then carried out HPLC (High Performance Liquid Chromatography) on irradiated solutions that showed that nothing smaller than whole SOD molecules were present.
The results presented by Abe indicated that at high concentrations, SOD seemed to undergo a reversal of radiation-induced inactivation after storage for a few days. Noting that each SOD molecule is made up of two identical short cylinders joined end to end by weak bonds, the tendency of any thinking chemist would be to initially interpret SOD’s return to viability in terms of a concentration-dependent model where damaged short cylinders (monomers) in a pool of damaged SOD are exchanged with undamaged ones to make up healthy cylinder pairs (called dimers). However, our neutron measurements yielded no evidence of isolated monomers.
In the best of all worlds a desirable property of an enzyme that confers radiation protection would be that it itself would be relatively insensitive to radiation. Such insensitivity was suggested by experiments on SOD carried out by researchers at another of AECL’s Labs (Whiteshell) located near Winnipeg, Manitoba. The researchers involved there were a medical doctor, Abe Petkau, and a biochemist, W.S. Chelack. As chance would have it I met Dr. Petkau at a meeting of the American Biophysical Society. After looking over the results he was presenting, I suggested that small angle scattering could help to elucidate the theory he and Chelack were advancing for SOD’s effectiveness as a protective enzyme against negatively charged oxygen molecules.
One of the more damaging products of radiation in living matter is a negatively charged oxygen molecule called a superoxide anion. This anion is an oxidant that also is produced in living beings undergoing ordinary metabolic processes. To counteract the deleterious effects of negatively charged oxygen molecules nature has given us an enzyme called superoxide dismutase (SOD).
One of the more damaging products of radiation in living matter is a negatively charged oxygen molecule called a superoxide anion. This anion is an oxidant that also is produced in living beings undergoing ordinary metabolic processes. To counteract the deleterious effects of negatively charged oxygen molecules nature has given us an enzyme called superoxide dismutase (SOD).
Another interesting experiment involved mechanisms radiation protection in humans—a topic especially important for the nuclear industry.
