Editor's note: Science Scan is a roundup of recently published biotechnology-relevant research.
Should anthrax have to move over and make room for cyanide as a bioweapon?
As recently as Friday, the New York Times reported, "Antidote kits for treating the victims of cyanide poisoning and nerve gas attacks had just been delivered to all New York City hospitals as security preparations continued to be tightened in response to the heightened alert that the city has been on since last week."
Also Friday, the journal Science, dated Feb. 14, 2003, carried a paper titled: "Taming of a poison: Biosynthesis of the NiFe-Hydrogenase Cyanide Ligands."
As a co-senior author of that article, chemist Richard Glass at the University of Arizona in Tucson, explained: "The enzyme hydrogenase is being primed for use in industry to generate hydrogen. In this process, platinum is the favored catalyst, but contaminating sulfur poisons it, which means," he added, "its enzymatic activity goes down, and it's no longer a good catalyst."
Microbiologist August Böck is emeritus professor at the University of Munich, and also a co-senior author of the Science article.
"Our paper," Böck told BioWorld Today, "analyzes the pathway of cyanide synthesis. The other study is the chemistry, which was done by Richard Glass. That chemistry is a really relevant thing for biotechnology, because it synthesizes a catalyst that produces hydrogen.
"The immediate source of the cyanide," Böck continued, "is carbon dioxide and ammonia. The bacteria synthesize it. In our work we use Escherichia coli, because there's such a fantastic genetic system in E. coli. Its genome is known, so we can manipulate that bacterium by biochemistry very well. But many other bacteria have this system. Almost all anaerobic bacteria, which live without oxygen, have hydrogenases. And it's a very important energy source in the bioworld, and also important for ecology, to know how this hydrogen is used.
"The hydrogen must come from somewhere," Böck observed. "In nature it comes from other organisms which produce hydrogen, such as cyanobacteria - blue-green algae. They produce some hydrogen during photosynthesis. So illuminate them with light and give them CO2 to grow, along with metal ions and salts, and they produce a little bit of hydrogen. It's a very important molecule for the microbial world living together. One organism meets the other. One produces hydrogen; the other uses it. And they may be interdependent."
Glass described biosynthesis - without liberating dangerous-free cyanide - of the cyanide component of a microbial enzyme, E. coli. "It may bring the world closer to incorporating hydrogen into a nonpolluting energy scenario," he suggested. "Those cyanide ligands modify the reactivity of the iron atom - in an iron-nickel hydrogenase cluster. So the bacterial enzymes can catalyze the controlled conversions of hydrogen gas into protons and electrons, under mild conditions compatible with life on earth.
"Two of the things that interest people," Glass recounted, "are the origin of life, and whether there's life on other planets. Part of that story is that these bacteria may have originated back when there wasn't any oxygen around, and cyanide was present in the actual living environment, which ordinarily would kill species. But their precursors have learned how to live with cyanide, tame it and use it to their advantage. This may be a sort of relic.
"What's unusual about the hydrogenase enzyme," Glass pointed out, "is that it has cyanide and carbon monoxide components, both very toxic, attached to the metals in these active sites. If you add cyanide it will kill the bacteria; the same with carbon monoxide. The most conclusive thing we showed is how the cyanide gets attached to the iron. It's never free. You never have free cyanides floating around. Nature has devised ways of passing that baton. Hemoglobin has iron, and it's an oxygen-carrying protein. But it's poisoned by CO2 and CO."
Glass recalled an article in Science dated Nov. 29, 2002, titled: "Molecular hydrogen as an energy source by Helicobacter pylori." He noted, "The medical significance is that this organism is believed to be the causative agent in a number of human problems - gastritis, peptic ulcers and the development of certain types of gastric cancer."
Small Kids Put To Sleep For Surgery Court Lifelong Memory, Learning Deficits As Adults
Anesthesiologists should think twice before putting very small children to sleep while surgery is being performed. Drugs commonly used to anesthetize children can cause brain damage, long-term learning and memory disturbances in infant rats, which pinch-hit as very young human infants. A paper in the Journal of Neuroscience dated Feb. 1, 2003, reports that: "Early exposure to common anesthetic agents causes widespread neurodegeneration in the developing rat brain and persistent learning defects."
The investigators, neuropsychopharmacologists at Washington University in, St. Louis, put 7-day-old rats to sleep with a combination of three anesthetic drugs commonly used in pediatric surgery. They found that moderately severe cell death had occurred in several brain regions in every rat brain examined, including the hippocampus.
Less Virulent Pre-Venom' Has Jobs To Do Before Scorpion Releases True Venom'
Scorpions secrete a poisonous "pre-venom" with unique molecular properties and a mechanism of action that differs from that of true venom. Entomologists at the University of California at Davis studied one of several dozen scorpion species that yield medically important venoms.
They observed that a droplet of transparent fluid formed on the critters' stinger immediately before they released venom. The fluid proved more effective than true venom at causing paralysis in insects and pain in mice, although true venom was lethal to both.
Their paper, in the Proceedings of the National Academy of Sciences (PNAS) dated Jan. 21, 2003, is titled: "One scorpion, two venoms: prevenom of Parabuthus transvaalicus acts as an alternate type of venom with distinct mechanism of action."