tures. "This compound could provide a unique means of removing sulfur dioxide from stack gases," McAuliffe says. Infrared spectra indicate that the compounds absorb neutral oxygen, as distinct from superoxide or peroxide. Also, oxygen uptake is a two-stage process. Kinetic measurements show that the first 50 mole % is absorbed more rapidly than the second. And although visible light does not affect the uptake rate of the first 50 mole %, it increases substantially the uptake rate of the second. From evidence of magnetic measurements, McAuliffe concludes that two forms of neutral oxygen are involved. The first 50 mole % of the uptake, he believes, comprises neutral triplet oxygen, yielding a total of seven unpaired electrons when complexed to manganese(II). The second 50 mole % is the more highly energetic singlet oxygen giving a total of five unpaired electrons in MnLX2*02- Coexistence of the two forms of oxygen would explain the apparent presence of six unpaired electrons in the oxygenated system. Electron paramagnetic resonance data substantiate this hypothesis. "If such is the case," McAuliffe says, "this is yet another unique aspect of these complexes. Our evidence points to them as providing a means of isolating singlet oxygen." McAuliffe is convinced that the discrete properties of the individual members of the new family of complexes can have many industrial applications. One obvious outlet could be the bulk separation of oxygen from air by the pressure swing absorption (PSA) process, thereby replacing the conventional energy-intensive
% one possible drawback is that sucrose J- polyester also interferes with the ab| sorption of fat-soluble vitamins, especially g vitamins A and E. For that reason, people g who want to use the material to keep their cholesterol low also might have to resort to vitamin supplements, he suggests. Commenting on its mode of action, Mattson says that because sucrose polyester is not absorbed through the intestinal wall, it is not broken down by the enzymes that normally convert foods into fatty acids, which can act as precursors to cholesterol. In addition, any cholesterol present—whether it is produced in the body or added in the diet—is swept up by the sucrose polyester molecules and is removed unchanged from the body before it can be absorbed. P&G chemists began working on sucrose polyester about eight years ago when the company first saw it as a lowUMISTresearch workers (clockwise, fromcalorie food supplement, Mattson says. top left) McAuliffe, Edwards, Minten, Al-However, he admits that a lot more testing for efficacy will be required before it Khateeb, and McCullough hits the market as a cholesterol-reducing cryogenic method of air fractionation. agent, especially since the Food & Drug They also might be used for obtaining the Administration considers it a drug and D high-quality oxygen needed in certain not a food. steel-cutting operations. Several hundred variations of the complexes are theoretically possible. He foresees tailor-making specific compounds to perform specific tasks, many of which are yet to be fully developed. Others share his enthusiasm. To date, The human form of renin, an enzyme his research has been funded largely by believed to play a major role in high blood the U.K.'s National Research Develop- pressure, has been purified simultament Corp. Now, a major British indus- neously and independently by researchers trial concern is offering financial and at Massachusetts General Hospital in technical backing. • Boston and at Vanderbilt University in Nashville. The biochemical feat was described in Dallas at the recent meeting of the American Heart Association. Renin is an enzyme that is manufaca substance now believed to exert a pro- tured in the kidneys and released into the tective effect against atherosclerosis and bloodstream. Once in the blood, it converts a protein called hypertensinogen heart attack, he says. In other studies carried out at the into angiotensin II, the most powerful University of California and the Veterans constrictor of blood vessels known. With its purification, clinical reAdministration Hospital in San Diego, searchers now may be able to determine Dr. John Crouse and his coworkers found that sucrose polyester reduced cholesterol the exact role of the enzyme in high blood pressure, why it appears to be low in some in 11 obese men and women who were on individuals with hypertension and high in a strict weight-reduction program and others, and perhaps use it as a tool for that the material appeared to block the developing new types of antihypertensive absorption of cholesterol through the indrugs, suggests Dr. Eve Elizabeth Slater testines. of the Boston group. In the San Diego study, serum cholesterol levels dropped from 192 mg per 100 Purification of the enzyme at Boston ml to 175, whereas the percentage of was the culmination of a 10-year effort. cholesterol absorbed through the intesThat effort was constantly frustrated tines dropped from 39% to 17%. As in the because the enzyme is found in such small Cincinnati study, the sucrose polyester concentrations in human kidneys and appeared to have no adverse side effects because it breaks down chemically before other than "loosening up the stools" in it can be fully isolated and purified, Slater most patients, Crouse says. says. "Sucrose polyester appears to be the Both groups used essentially the same most effective cholesterol-lowering agent procedures to achieve the long-sought to come down the pike in a long time," purification of renin, starting with human Glueck asserts. He agrees that it does not cadaver kidneys. Other kidney enzymes appear to be beset by the sometimes sewere first removed with inhibitors that rious detrimental side effects associated acted on everything except renin. The with all of the other cholesterol-lowering enzyme was then further purified via ion drugs now on the hiarket. exchange chromatography and gel filtraHowever, Mattson of P&G says that tion. However, the key step for both
Sucrose polyester lowers cholesterol levels Sucrose polyester appears to be a safe and powerful cholesterol-reducing agent, judging from results of two clinical trials described at the recent 51st scientific session of the American Heart Association in Dallas. The substance, developed by Dr. Fred H. Mattson and his colleagues at Procter & Gamble's Miami Valley Laboratories in Cincinnati, can be either a vegetable-oillike liquid or a spreadable margarine-type solid, depending on whether the sucrose is esterified with an unsaturated or saturated fatty acid, Mattson says. In trials carried out with 24 male volunteers at the University of Cincinnati college of medicine, sucrose polyester "significantly lowered" cholesterol levels, whether it was added in high (800 mg per day) or low (300 mg per day) concentrations to the diet or was part of foods eaten in a regular diet, according to Dr. Charles J. Glueck of the University of Cincinnati. The sucrose polyester reduced total cholesterol, including low-density lipoprotein cholesterol, the form usually believed to be associated with the onset of atherosclerosis, or hardening of the arteries, Glueck explains. On the other hand, it did not affect high-density lipoprotein, 26
C&EN Dec. 4, 1978
Researchers purify human form of renin
