News of the Week bership would be limited. Fellows of the academy would be chosen from those who are active in their fields of research. In this the proposed academy would differ from the European Sci ence Foundation, which came into being 10 years ago. ESF, headquar tered in Strasbourg, France, consists of the national bodies responsible for supporting basic research in its 18 member states—16 West Europe an countries together with Turkey and Yugoslavia. It is hoped that core funding
its success as a herbicide will de pend on discovery of cheaper ways to make it. The mechanism of action of the compound depends on its conver sion to tetrapyrroles within plants after application in darkness. The six tetrapyrroles especially impor tant for this effect are magnesium mono- and divinylprotoporphyrin IX, their monoesters, and mono- and divinylprotochlorophyllide. At sunrise, the excess concentra tions of tetrapyrroles act as photosensitizers, converting triplet oxy gen to the potently oxidizing sin glet form. Singlet oxygen oxidizes phospholipids of membranes with in plant cells in free-radical chain problem. Furthermore, Carbide and reactions. Damaged membranes be McGraw-Edison say, for transform come leaky, the plant loses sap, and ers containing more than 500 ppm death occurs in one to four hours. PCBs (and some contain as much as Susceptibility to tetrapyrrole pho 60 to 70%), no previous PCB remov tosensitizing reactions is greater for al process could reduce contamina dicotyledons than for monocotyle tion below 50 ppm. dons. "Dicots" are plants whose Carbide, for competitive reasons, seeds have two leaves and include isn't disclosing how its process many weed plants. "Monocots" have works. It does say that Unison will one seed leaf and include grasses, guarantee that the transformers it wheat, barley, and corn. Rebeiz says services will achieve the below- that the different sensitivities of mo 50-ppm standard—thus becoming nocots and dicots are related to dif eligible for reclassification to un ferent amounts of mono- and divinyl regulated status—and that the ser pathways used in chlorophyll bio vice will cost only about half as synthesis. much as replacing and disposing of In addition, Rebeiz and Hopen PCB-containing transformers. D distinguish a third class of interme diate sensitivity in such dicots as soybeans and kidney beans. If plants are only 1 to 1.5 inches high and primary leaves have not appeared, spraying with δ-aminolevulinic acid leaves them unharmed. If primary Researchers at the University of leaves have appeared, those leaves Illinois, Urbana, have developed use die within an hour, but they are of δ-aminolevulinic acid, an inter regenerated, and the healthy plant mediate of chlorophyll biosynthesis, continues growing. The molecular to kill weeds but spare crop plants, basis for this intermediate sensitivi with no harm to humans or other ty is the basis of further research. animals [Enzyme & Microbial Technol., The Urbana scientists obtained 36, 390 (1984)]. This research com good results by spraying at only 75 pound is now very expensive, plant g per acre with the use of such biochemistry professor Constantin activators as α,α'-dipyridyl. These A. Rebeiz and horticulture profes additives stimulate biosynthesis of sor Herbert J. Hopen point out, and δ-aminolevulinic acid. The hydro chloride of the acid is available from Biosynth International, Skokie, 111., at about $6.00 to $7.00 per g. Ο II The Illinois research was sup H2NCH2CCH2CH2C02H ported by the National Science δ-Aminolevulinic acid Foundation and the Illinois Agricul tural Experiment Station. D would come from private sources. Such sources would include existing foundations and major industrial concerns. In addition, the academy might receive government support toward specific activities. Much obviously remains to be done before the new body could come into being. As a first step, a framework document will be drawn up as a basis for its constitution. Brooke has offered the services of the U.K. scientific community to shoulder much of the work that this will entail. D
Carbide, McGraw-Edison join to clean up PCBs Union Carbide and McGraw-Edison have formed a joint venture to re move polychlorinated biphenyls (PCBs) from electrical transformers. The two firms say they can reduce PCB contamination to less than 50 ppm, and thus allow the transformers to escape regulatory requirements. The new firm, called Unison, will be based in Columbus, Ohio. It will market its services under the name Reclass 50. Union Carbide will fur nish proprietary chemical engineer ing technology and also replacement fluids for the treated transformers. McGraw-Edison, a major purveyor to the electric utility industry, will provide high-voltage expertise and a nationwide marketing, distribu tion, and service network. According to the two companies, there are, across the U.S., some 150,000 transformers containing a total of about 300 million lb of PCBs. In food and feed processing opera tions, use of transformers contain ing more than 500 ppm of PCBs is banned after Oct. 1,1985. Otherwise, in general, PCB transformers may continue to be used. However, the utilities must inspect them period ically, keep records and render re ports on them, and, eventually, dis pose of them, all in accordance with federal regulations. Optionally, the utilities can re place PCB-containing transformers with new ones. But that's expensive, and the old ones still present a dis posal problem. Or, they can drain them and refill them with a nonPCB cooling fluid, in which case the PCB still presents a disposal 8
September 24, 1984 C&EN
Photosensitivity basis of herbicide mechanism
