RSC - Advancing the Chemical Sciences


Chemistry World

 

News in brief



Fish scales hold dazzling secret 

For us humans, iridescence is associated with superficial prettiness but for water-dwelling creatures it's a fundamental survival tool: predators can be dazzled and confused by a scaly metallic sheen. The effect in some fish is caused by photonic crystals made of guanine, shining through from the skin below. Those crystals contain a surprising structural secret, researchers in Israel have discovered. 

Lia Addadi and colleagues from the Weizmann Institute of Science in Rehovot, used electron microscopy to show that guanine crystals in fish skin formed thin plates - unlike the prism shapes they normally adopt when grown in the test tube. The thin plates stack into layers that interfere with light to give the skin a metallic lustre. 

'The fish must expend energy to actively interfere with the natural growth of the crystals,' explained Addadi. 'We can predict that there are inhibitory factors within the skin cells that interact with crystals while they're growing.' The researchers, publishing in Crystal Growth & Design  (DOI: 10.1021/cg0704753), hope to work out this mechanism to produce the same iridescent sheen in the laboratory.

Acute toxicity test redundant 

A European pharmaceutical company initiative has concluded that the single-dose acute toxicity test - used before human clinical trials to identify a medicine's lethal dose in animals - is redundant.  

The four-year study, published in Regulatory Toxicology and Pharmacology(DOI: 10.1016/j.yrtph.2007.11.009), also noted that many of the 18 pharmaceutical companies involved in the initiative had cut down on acute toxicity animal testing anyway.  

'We hope that the regulators will accept the evidence and no longer require this test prior to testing in man,' said Brian Ager, director general of the European Federation of Pharmaceutical Industries and Associations.

Amber molecule hints at Paris's tropical past 

Chemists based in France think that a newly-discovered natural product, isolated from a 55 million-year-old sample of Parisian amber (fossilised tree resin), may have been formed from a chemical precursor now found only in rainforest trees. The research suggests that ancient Parisian trees were tropical - agreeing with plate tectonics theory which places France's land mass in the tropical zone 55 million years ago. 

The researchers, publishing in the Journal of Organic Chemistry( DOI: 10.1021/jo701544k), say their new compound, christened quesnoin, is related to diterpene molecules but was most likely formed from isoozic acid - today found in Amazon rainforest trees. But other scientists told Chemistry World  that quesnoin, though certainly structurally unusual, could more likely have been formed from other precursors, such as furans.  

Acrylamide's second cancer link 

Danish scientists have found an epidemiological link between the chemical acrylamide - found in bread, crisps, potato chips and coffee - and breast cancer. 

A previous study (Chemistry World, January 2008, p24), which quizzed women on their dietary intake, had found a link between acrylamide in foods and the rare ovarian and endometrial cancers, but not breast cancer. 

The new study, published in the International Journal of Cancer  (DOI: 10.1002/ijc.23359), checked for biological markers (adducts of acrylamide and haemoglobin) in women's blood, and showed that higher levels of these were linked to greater incidence of breast cancer - though it was not clear whether the acrylamide came from sources other than food, or whether both biological markers and breast cancer might be correlated with some other food-derived chemical.  

Ranking challenge 

A new open-access internet database provides a free alternative to Thomson Scientific's traditional 'Impact Factor' that ranks journals' importance by calculating how many citations their papers attract.  

SCImago (scimagojr.com), created by Spanish data-mining researchers, allows any user to immediately analyse citation statistics for journals or countries. It takes its data from Scopus, the database of Amsterdam-based science publisher Elsevier who are collaborators on the project. It also introduces a new metric, the SCImago Journal Rank (SJR), based on a Google ranking algorithm. This weights the citations received by journal papers, so that some citations are worth more than others.  

Comparisons between the SJR and the Impact Factor are ongoing - they are complicated by the use of different metrics and different underlying databases. 

Green light for UK nuclear power 

The UK government's long-awaited formal support for a new generation of nuclear power stations has been broadly welcomed by scientists. They warned that the government still needed to concentrate on commitments to renewable energy, decisions on radioactive waste disposal, and maintaining a high level of skilled nuclear scientists (Chemistry World, October 2007, p56). 

Nuclear plants could, in theory, be constructed in the UK whatever the government's view. But political support reassures private investors that business plans will not be confounded by obstacles such as delays in planning permission. Despite this confidence boost, new nuclear plants are still a decade away in the UK (Chemistry World, October 2007, p52). 

US takes climate action 

US president George Bush signed energy legislation in December that raises fuel efficiency standards in cars, expands ethanol production, and demands domestic appliances that consume less energy.  

Though the bill, which should reduce the country's dependence on oil, was historic (vehicle fuel economy was last increased in 1975), environmentalists complained that it was too little, too late. A Democrat proposal to shift tax breaks from oil companies to renewable energy producers was removed before the bill was signed. 

By 2020, cars' standard fuel efficiency should increase by 40 per cent to 35 miles per gallon, and ethanol production should increase to 36 billion gallons a year (currently 6 billion gallons), with 21 billion gallons obtained from alternatives to corn. Energy-intensive light bulbs will be phased out by 2014. 

Butterflies' chemical con trick

Blue Alcon (Maculinea alcon) butterflies can fool ants into neglecting their own young and raising butterfly larvae instead, because the larvae have an outer coating whose hydrocarbon chemistry mimics that of the ants' surface chemicals, chemists based in the UK and Denmark have discovered. 

The Alcon grubs give off vapours, whose profile the scientists studied with gas chromatography, that persuade ants to take the larvae back to their nests and feed them. Once there, the larvae become parasites, eating some of the ants. 

Publishing in Science  (DOI: 10.1126/science/1149180), the researchers describe an 'arms race' where ants and larvae surface chemicals co-evolve. Only in Denmark does the Alcon butterfly enjoy this chemical dominance; elsewhere, it is an endangered species. The scientists suggest that the ant-larvae surface chemical match should be considered when reintroducing the threatened butterfly into the wild. 

Canada fires head of nuclear safety 

The Canadian government has sacked the head of its nuclear safety agency over a dispute about the reopening of a nuclear reactor that produces more than half of the world's medical isotopes.  

Linda Keen was dismissed as president of the Canadian Nuclear Safety Commission, though she will stay on as a full-time member of the CNSC. Keen had refused to reopen the 50-year old Chalk River plant, based in Ontario, after it was shut down for routine maintenance in November 2007, because a CNSC inspection found back-up safety upgrades had not been carried out. But the prolonged closure caused shortages in the worldwide supply of nuclear isotopes for medical imaging and diagnostic scans, according to media reports. So Canadian MPs pushed through emergency legislation to start the reactor up again in December 2007.  

'Had we not acted, there is no question in my mind that people would die,' said Natural Resources minister Gary Lunn. The head of Atomic Energy Canada Ltd, who operate the reactor, resigned last month.