ChemWeb Newsletter

Not a subscriber? Join now.July 25, 2006


The latest on the origins of life is reported in the Alchemist this week as well as the heady subject of the European ban on chemicals used in hair dyes. Also, discussed this week, US researchers have made "ice cubes full of crumpled paper" on the microscopic scale while others have built an organic transistor that has environmental potential. Finally, this week, for chemists under pressure, cellulose is really cooking.

Working out whether proteins or nucleic acids came first was a chicken and egg puzzle that vexed scientists for decades. Genes made of nucleic acids (DNA or RNA) contain the instructions for making proteins, but enzymes made of proteins are needed to replicate genes. The discovery of the catalytic activity of RNA seemed to solve the paradox. Now, William Scott of the University of California, Santa Cruz, and colleagues have obtained an image of the ribosome with almost atomic resolution, which they explain sheds new light on the workings of this enigmatic nucleic enzyme mimic. "The structure illustrates unambiguously how functional groups of the RNA mediate acid-base chemical catalysis, permitting us to suggest that acid-base chemistry is so fundamental to enzyme catalysis that it predates the origin of protein enzymes," Scott says. In other words, he and his colleagues have perhaps cracked the chicken and egg of the RNA world once and for all.

Long-term use of certain hair dyes has an increased risk of bladder cancer, according to European Commission scientists. As such, 22 hair dye chemicals are to be banned across the European Union. There is conflicting evidence that suggests such a stance should not be taken, but the Commission nevertheless insists the ban will improve consumer safety. The Commission says that safety data have not been submitted for these 22 chemicals, which include 4-hydroxyindole, 2,3-naphthalenediol, Acid Orange 24, and 3,4-diaminobenzoic acid. The ban is likely to have a rapid commercial impact as the hair dye market in the European Union was E 2.6 billion (about $3.3billion) in 2004 which accounts for some 8% of the value of output of the cosmetics industry in Europe. European Commission Vice-President Günter Verheugen, responsible for enterprise and industry policy, said: "Substances for which there is no proof that they are safe will disappear from the market. Our high safety standards do not only protect EU consumers, they also give legal certainty to European cosmetics industry."

Forget buckyballs and carbon nanotubes, graphene is the next big thing in carbon chemistry. Graphene sheets just one atom thick are electrically conducting and could be used to make new kinds of microelectronic devices. Now, Rodney Ruoff and colleagues at Northwestern University, Evanston, Illinois, have found a novel way to convert regular graphite into graphene embedded in a polymer matrix to form an electrically-conducting composite. The team has circumvented the issue of newly formed graphene sheets sticking together by devising a sonication technique to turn graphite oxide into a graphene-polymer composite. A reduction step introduced prior to polymer-graphene coagulation leads to the formation of the electrically conducting product. The researchers say that under the microscope their composite materials look like ice cubes full of pieces of crumpled paper.

A molecular transistor that responds to the presence of specific analytes has been developed by Colin Nuckolls and colleagues at Columbia University, New York. The transistor's wires are composed of a monolayer of a polycyclic aromatic hydrocarbon, and are formed in single file by self-assembly along a narrow gap in a carbon nanotube. The researchers found that the molecules are good electrical conductors with large current modulation and high gate efficiency. Such electrical characteristics change significantly when the device is exposed to electron-deficient molecules. The researchers say this could allow them to operate the device as an ultrasensitive chemical detector. When a molecule of interest is detected by the hydrocarbons, the current passing through them changes, creating a detectable electrical signal.

The crystalline and indigestible form of cellulose, the most abundant biomass material on earth, can now be broken down into a gelatinous and amorphous form using pressurized superheated hot water. This novel form of cellulose becomes open to enzymic action and so could be a useful new feedstock for a wide range of products. Shigeru Deguchi of the Japan Agency for Marine-Earth Science and Technology and colleagues at Hokkaido University reasoned that the fact that the common polysaccharide starch can be gelatinized at 60-70 Celsius might suggest that cellulose could be converted similarly under more extreme conditions. They were successful at 320 Celsius and 25 MPa, by following loss of birefringence using polarized optical microscopy. As with starch, the gelatinization process was not reversible.