reasoning process consists of now is nar rowing the possibilities, the last of which in the minds of most Viking scientists is life. Indeed, the possibilities appeared to narrow considerably early last week with the first results from a fresh soil sample in the lander's GC/MS instrument. When heated to 350° C in the instrument's sample oven, the Martian soil again lib erated "copious" amounts of water, but "little or no" organic compounds. The instrument is sensitive in the low partsper-billion range. "It is certainly difficult to reconcile the absence or extremely low level of organic molecules with the pres ence of appreciable numbers of actively living microorganisms," says Klaus Biemann, head of Viking's molecular analysis team. The sample will be heated again to 500° C to see if any organic mol ecules are driven off at the higher tem perature. But even if all subsequent data are negative, this doesn't rule out life on Mars. As Cornell University astronomer and sometimes exobiologist Carl Sagan likes to point out, Viking might just be looking in the wrong place. Viking scien tists may get a second look on Sept. 3. Viking II, the sister ship to the one now on Mars, is slated to land on the opposite side of the planet in a region closer to Mars' north pole that, NASA scientists believe, contains more water and thus a better chance of sustaining life. D
Unit offers continuous biological separation Electrophoresis is the basis of new equipment designed for continuous sep aration and recovery of a variety of com pounds of biological importance. Devel oped at the U.K. Atomic Energy Author ity's Harwell Research Establishment, a prototype model, unveiled at the 10th International Congress of Biochemistry in Hamburg late last month, now is being evaluated with a view toward possible commercial production. The system has great potential for preparative fractionation of blood plasma, enzymes, cells, and the like, as well as pharmaceuticals and fine chemicals, ac cording to Dr. Alan R. Thomson, head of Harwell's biochemistry group. It is the outgrowth of a concept originally pro posed by John Philpot of the U.K. Medi cal Research Council. The principle of electrophoretic sepa ration is that molecules in solution mi grate at different rates in an electrical field. It provides a high degree of resolu tion under mild operating conditions. However, although electrophoresis has played an important role in bench-scale work during the past 30 years or so, until now it has never been adapted to largescale continuous fractionation. A number of special features are claimed for the Harwell unit including:
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• Production-scale operation with day-to-day reproducibility. • Fractionation capability for macromolecules and subcellular particles. • Continuous performance providing up to 30 fractions simultaneously. • Minimal contamination by electrol ysis by-products. The unit consists of two cylinders, one within the other. The solution containing the items to be fractionated and a buff ered carrier fluid are fed into the narrow annulus between the two cylinders. As the solution flows upward, it passes through an electrical field. This causes the com ponents to migrate different distances across the annulus and separate as dis crete zones. The components emerge through channels at the top of the central cylinder. During operation, the outer cylinder revolves at about 150 rpm. The rotation provides stability by maintaining laminar flow of the solution in the annulus even in the presence of heat generated by the voltage gradient. As it is, the temperature rise is limited to between 15° and 20° C. "The system gives excellent recoveries of biological materials owing to the mild treatment and short exposure time of less than a minute," Thomson says. "Up to 30 grams of protein have been fractionated in an hour on our prototype unit." An outline design of a larger one has been drawn up that should be capable of coping with 10 times that amount, he adds. D
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for they shall give fast, accurate test results. Spectroquality® Solvents Without exception, MC/B Spectroquality Sol vents specifications are more stringent than any published or recommended specifica tions for solvents to be used in spectrophoto metry. This includes absorbance characteris tics, water and evaporation residues. Our catalogue lists 44 such solvents — more than anyone else in the industry. Pesticidequality Solvents MO/B Pesticidequality Solvents are specially purified for use in the determination of pesti cide residues by GLC utilizing electron cap ture and flame photometric detections. These solvents contain no interfering substance greater than that equivalent to: 5 nanograms/ liter chlorinated pesticide (5 ppt), 50 nanograms/liter Parathion (50 ppt), 0.2 meg/liter phosphorus (200 ppt). AH MC/B Spectroquality and Pesticidequality Solvents are competitively priced and come in any quantity. Please write or call for catalog.
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