Additive gives improved mileage, less smog A chemical normally known for its role

in the manufacture of synthetic rubber may lead to cleaner-burning, more-fuelef- ficient cars and trucks.

Automobiles using the polymer addi- tive, called polyisobutylene, decrease their emissions by 70 percent, says Paul F. Waters of American University in Wash- ington, D.C. What’s more, mileage goes up 20 percent, while horsepower increas- es 10 percent, he says.

Due to the emissions improvements and fuel savings, Waters says, poly- isobutylene “reduces the number of gases that potentially lead to global warming.”

Waters reported the results in late August at the 220th national meeting of the American Chemical Society in Washington, D.C.

Gasoline is a menagerie of hydrocar- bon molecules that differ in size and shape. Short molecules generally burn very quickly, causing temperature and pressure inside an engine to rise in a dra- matic spike. That creates engine knock and emissions of nitrous oxide pollution. Meanwhile, longer hydrocarbons burn more slowly and incompletely, which raises exhaust temperature and leaves remnants of hydrocarbons that con- tribute to soot and other forms of pollu- tion.

Polyisobutylene appears to slightly de-

lay the burning of short hydrocarbon molecules, which then hasten the burn- ing of the longer hydrocarbons, Waters says. With the additive, therefore, the fu- el burns more completely and engine and exhaust temperatures drop significantly.

Waters suspects that polyisobutylene changes the surface tension of fuel droplets, preventing short hydrocarbons from immediately vaporizing when gaso- line is sprayed into the engine. The delay apparently is “long enough, so that . . . the two components evaporate more or less in the same physical region in space and then they burn more or less togeth- er,” says Waters.

“I think Paul has some intriguing results that could be very promising for the au te motive industry,” comments Graham Swift, a polymer chemist and independent con- sultant outside of Philadelphia. “It sounds delightfully simple and promising to me. We tend not to look for simple solutions.”

“What I like about his approach was that he looked at combustion, and he looked at what controls combustion, and then applied it to the internal combus- tion engine,” says Swift. With better con- trol over the fuel droplets, Swift says, “the better your combustion, the better

An experimentaal fuel additive reduces car emissions by 70 percent.

Gene find could vield decaffeinated plants An international team has succeeded

in cloning one of tea’s genes for making caffeine-a step toward creating decaf tea and coffee plants.

The gene, TCSI, codes for caffeine syn- thase, the enzyme that controls the final two steps in the molecule’s four-step syn- thesis, explain Misako Kato and Hiroshi Ashihara of Ochanomizu University in Tokyo and their colleagues in the Aug. 31 NATURE. When the researchers finally cloned TCSI, they found it had little simi- larity to other genes.

Important as caffeine has been to hu- manity-inspiring cuisine, commerce, and poetry, not to mention preventing the collapse of the industrialized world on Monday mornings-biologists have only recently begun unraveling nature’s own caffeine synthesis.

Some 40 species of plants make caf- feine, but “no function is really known” for the chemical, notes coauthor Alan Crozier of the University of Glasgow in Scotland. He acknowledges the theories that caffeine might repel pests or build up in soil to sabotage seeds from rival plants. However, he objects, “there are naturally low-caffeine plants that grow quite happily.”

Decaf now amounts to about 20 per- cent and 8 percent of the total U S . coffee

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and tea markets, respectively, Crozier notes. “To someone like me who likes good, strong [coffee], decaffeinated tastes like dishwater,” he grumbles.

Coffee and tea plants become caffeinat- ed by virtually the same chemistry, Crozi- er says. Finding the right gene to switch off in either plant could create full-flavor beverages without caffeine.

The report in NATURE ranks as the first published report of a gene associated with the synthesis of caffeine in tea, Crozier claims.

He says published because not every- thing on caffeine gets into print. The field isn’t exactly boiling. Funding is scarce and the number of labs known to be working in the field may be as small as three. Yet in June, the University of Hawaii in Honolulu received US. patent 6,075,184, involving a caffeinesynthesis gene in coffee. The gene sequence in the patent “is nothing like ours,” Crozier comments.

The Hawaiian biologists whose work led to the patent discussed findings in places with lower profiles than NATURE: ACTA HOR- TICULTURE and a 1999 coffee conference.

In the Tokyo-Glasgow collaboration, “the real donkey work and the part where no one thought we were getting anywhere was the 6 or 7 years of trying to purify enough enzyme to work with,”

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your fuel consumption, the better your automotive horsepower, the less incom- plete combustion you get, and that means you’ve got less noxious fumes coming out.”

So far, Waters and his colleagues have tested the additive on a dozen automo- biles in three states and several other countries. Waters points out that 50 other cars also have shown improved performance with the additive.

Waters says the mileage benefits could pay for the cost of the fuel additive- perhaps 10 cents a gallon, he says. Poly- isobutylene works well in diesel engines, too, he adds.

“This is of course useful for global warming, but it’s also useful for the vehi- cle and the engine itself,” says Waters. “When the engine operates at a lower overall temperature, there’s less wear and tear on all the parts. The less tem- perature that you impose on any of these devices, the longer they’re going to last, and in principle, the less your repair bill is going to be.” -1 Gorman

Crozier recalls. Last year, when the re- searchers determined caffeine synthase’s amino acid sequence, they then were able to create molecular probes for find- ing the gene encoding the enzyme.

To see whether they’d ferreted out the right gene, the researchers inserted it in- to Escherichia coli bacteria, which they fed precursors for caffeine. Bacteria with the new gene could pump out caffeine, but unmodified bacteria couldn’t.

John Stiles, one of the biologists behind the patent and now at the biotech firm In- tegrated Coffee Technologies in Honolulu, speaks admiringly of the Tokyo-Glasgow team’s triumph: “It was certainly a really good feat to purify that enzyme.’’

Stiles says his patented enzyme con- trols an earlier step in the synthesis than the gene reported in the NATURE paper. By modifymg the patented gene in plants, he hopes to avoid creating plants that build up half-finished caffeine, in the form of a chemical called 7-methylxanthine, which would require research on its potential effects on consumers.

Stiles already has coffee plants grow- ing, but he can’t yet say how things will turn out.

William Franke, vice president of scientif- ic and regulatory affairs for Lipton in Engle wood, Calif., says the company’s current teadecaffeinating process is “safe and effec- tive.” But he says if someone finds a good alternative, he’ll take a look. 4. Milius

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