Pyruvic Acid Adds Pep To Prebiotic Chemistry In a pressurized reaction vessel designed to simulate conditions at hydrothermal vents deep below the ocean surface, a team of geochemists and biochemists at Carnegie Institution of Washington, D.C., led by senior staff scientist George D. Cody has cooked up some surprising chemistry. An experiment designed to better understand how transition-metal sulfides help catalyze the synthesis of simple organic acids yielded an unexpected product: very small amounts of pyruvic acid [Science, 289,1337 (2000)]. Pyruvic acid, CH3COCOOH, is one of the more elusive of the molecules that would have been needed for life to arise in the high-pressure world of subocean hydrothermal vents, as some theorists propose. An energetic and relatively unstable molecule, it functions in living cells today as the entry point for a major energysupplying metabolic pathway known as the tricarboxylic acid cycle. It's important, as well, as an intermediate in the synthesis of some amino acids and sugars. Demonstrating that this molecule could form completely nonbiologically in a ventlike environment "provides key support" for proposals that lifefirstarose in such an environment, aided by catalysts forged from elements like sulfur, iron, and possibly other transition metals, according to Gunter Wâchtershàuser, a German patent attorney and organic chemist who is one of the chief proponents of a hydrothermal origin of life. 'The newfinding,if it holds,fillsa critical gap in the experimental picture of the iron-sulfur world," Wâchtershàuser writes in a commentary accompanying publication of the work. "All individual reaction steps for a conversion of carbon monoxide to peptides have now been demonstrated." Kiochiro Matsuno, professor of bioengineering at Nagaoka University of Technology in Japan and an active researcher in thefield,also calls the work "an important discovery." Chemical evolution leading to the origin of life on Earth would have required simple forms of DNA-like molecules, protein-like molecules, and "compact energy packages that could be exploited by various energy consumers there at the time," Matsuno explains. In these experiments, Cody and his colleagues have demonstrated one way those early energy transactions could have been "financed," Matsuno says.
But that's not what the Carnegie ous healthrisksin urban areas. These inchemists started out to do. The work is clude a number of organic chemicals and part of an ongoing study investigating metal compounds. EPA plans to add inthe ability of a broad range of transition- formation on the outdoor concentrations metal sulfides to catalyze the carbon in- of dioxins and particulate matter from sertion reactions that are at the heart of diesel exhaust after scientific review of the hydrothermal vent theory of the ori- these substances is completed. A second phase of NATA, expected gin of life. Iron monosulfide, the researchers found, is particularly suscep- in early 2001, will estimate human expotible to reaction in the presence of or- sure to these air toxics and the health ganic thiols and fluids rich in carbon risks posed by that exposure. NATA differs from the Toxics Remonoxide to produce soluble and potentially catalytic organometallic phases. lease Inventory—the annual compilaBecause iron-sulfur clusters are impor- tion of industry-generated estimates of tant throughout biology in energy con- large releases to air, water, and land—in version systems, Cody explains, uncov- that it is based on an inventory of emisering a nonbiological way to begin to as- sions of air toxics from a broad array of semble such clusters is chemically sources, including vehicles and small interesting all by itself. That one of the businesses. EPA fed numbers from the reactions these clusters seem to cata- inventory into a computer model to estilyze is the formation of pyruvate was an mate the ambient concentrations of toxics in outdoor air. unexpected bonus, he says. Rebecca Rawls The just-released NATA estimates are based on 1996 data. EPA says it plans to update the assessment every three years. EPA Assesses State According to EPA, the NATA data will Of Nation's Outdoor Air help identify air toxics of the greatest potential concern. Also, the assessment will For the first time, estimates of the out- help characterize the relative contribudoor air concentrations of 32 toxic com- tions to air toxics concentrations from pounds across the U.S. are available various emission sources such as large from the Environmental Protection factories, cars and trucks, and small commercial facilities like dry cleaners. Agency. The American Chemistry Council Released in mid-August, the estimates make up thefirstpart of EPA's National- (ACC, formerly the Chemical ManufacturScale Air Toxics Assessment (NATA), ers Association) calls NATA "an important which focuses on air pollutants known or first step toward improving public undersuspected of causing cancer or other seri- standing of trends in air emissions." Ted Cromwell Sr., director of ACCs air program, says, "Once EPA is assessing urban emissions completed, NATA can of more than 3 0 chemicals be a valuable tool for evaluating trends, Acetaldehyde Ethylene oxide identifying remaining Acrolein Formaldehyde problems, and highHexachlorobenzene Acrylonitrile lighting where reducHydrazine Arsenic compounds ing risks from emisLead compounds Benzene sions will make the Manganese compounds Beryllium compounds biggest difference." Mercury compounds 1,3-Butadiene Cromwell notes, Cadmium compounds Methylene chloride however, that "NATA Nickel compounds Carbon tetrachloride Chloroform Particulate matter3 is a snapshot and Chromium compounds Perchloroethylene does not reflect the Polychlorinated biphenyls (PCBs) Coke oven emissions most recent years of Polycyclic organic matter (POM) 1,3-Dichloropropene our industry's continDioxinsa Quinoline ued progress in re1,1,2,2-Tetrachloroethane Ethylene dibromide ducing emissions Trichloroethylene Ethylene dichloride and improving air Vinyl chloride Propylene dichloride quality." a Expected to be added to NATA after scientific review. Alaska and Hawaii are not now included AUGUST 28,2000 C&EN
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