Research highlights

Circadian biology: Periodic regulation

Mol. Cell 22, 375–382 (2006)

The circadian feedback loop known as the biological clock has recently been indirectly implicated in cancer development.

Researchers have now provided more direct evidence, by showing that a gene called Per1, a key component of the circadian clock, regulates growth and DNA damage in human cancer cells.

A team led by Sigal Gery at the University of California, Los Angeles, reports that overexpression of Per1 interferes with the cell's complex molecular defences against the cancer-inducing effects of ionizing radiation. What's more, the group found reduced levels of Per1 in human cancer patient samples.

Physical chemistry: Goldenballs

Proc. Natl Acad. Sci. doi:10.1073/pnas.0600637103 (2006)

Credit: T. NÜCHTER

Forming football-shaped molecules is no longer the sole preserve of carbon atoms, say researchers. Now gold has joined the game.

Theory predicted that a few dozen gold atoms could naturally order themselves into a structure similar to carbon-60 ‘buckyballs’, but early experiments showed that groupings of 32 or more atoms resembled little more than a tangled gold nugget.

Now Lai-Sheng Wang of Washington State University, Richland, Xiao Cheng Zeng of the University of Nebraska, Lincoln, and their team have examined clusters of 20 gold atoms or less and found a wide range of naturally occurring arrangements — from pyramids to gold cages (pictured below).

The authors believe the cages could be used to hold single atoms of various types, potentially useful in nanotechnology applications.

Cell biology: Well sorted

Nature Struct. Mol. Biol. doi:10.1038/nsmb1098 (2006)

Newly made proteins need to find their way to the right places in the cell. To do this, they carry a molecular address label spelling out where they should go. Now, a team in the United States has discovered a molecular courier that reads labels and helps to deliver proteins to an exclusive location in the cell's nucleus.

Sharon Braunagel of Texas A&M University and her colleagues studied proteins destined for the inner of the two membranes bounding the nucleus. They discovered another protein, called importin-α-16, that identifies these molecules and delivers them, possibly by hitching a lift on one of the cell's motor proteins.

Planetary science: Magnetic sunscreen

Astron. Astrophys. 451, L43–L46 (2006)

An asteroid's colour may reveal whether it has a magnetic field to shield it from the ageing effects of the solar wind.

Space rocks are darkened and reddened by the stream of ions from the Sun. But the surface of Vesta, the second-largest asteroid known in our Solar System, is surprisingly pristine.

Simulating this process in the lab, Pierre Vernazza of the Paris Observatory, France, and colleagues exposed a meteorite, thought to originate from Vesta, to ions in the lab to show that its parent should indeed be substantially more weathered than it appears. They suggest that the asteroid must have a magnetic field of at least 0.2 microtesla at its surface, a few hundred times smaller than Earth's own field, which diverts the damaging ions.

Animal biology: Good shot

Curr. Biol. 16, R316–R318 (2006)

Jellyfish stings can puncture their targets with the power of rifle bullets, say researchers in Germany. The study reveals intriguing insight into how these tiny structures, known as cnidae, penetrate the tough skins of prey.

Thomas Holstein of the University of Heidelberg and his colleagues used an ultra-high-speed ballistics camera to watch stinging cells from the jellyfish-like animal Hydra (pictured right) discharge. They calculated that the sharply pointed stings were released at speeds of up to 40 metres per second (140 kph), with an acceleration of 5.4 × 10⁶ g, resulting in a pressure on impact of 7 gigapascals.

This movement, one of nature's fastest, owes its force to powerful spring-like proteins that contract when the pressure in the cnidae drops as they discharge.

Neurobiology: Same but different

Credit: NASA/SPL

Neuron 50, 589–601; 603–616 (2006)

GABA (γ-aminobutyric acid), the main inhibitory chemical in the vertebrate nervous system, has many different modes of action. This is partly thanks to the precise location and activity of one of its receptor components, two new studies reveal.

The GABA_B receptor is made of two pieces, and one piece known as GABA_B1 comes in two versions: GABA_B1a and GABA_B1b. Teams in Switzerland led by Bernhard Bettler of the University of Basel and Matthew Larkum of the University of Bern studied mice in which the different GABA_B1 versions were inactivated one at a time.

They found that GABA_B1a localizes to one side of the neuronal synapse and helps to inhibit the release of neurotransmitters, whereas GABA_B1b localizes to the opposite side, where it helps to dampen neuronal firing of post-synaptic cells.

Microbiology: Stripped bare

PLoS Pathogens 2, e35 (2006)

Researchers in the United States have uncovered a network of genes that shields a fungus' cell wall from immune-system attack.

In disease-causing fungi, an outer coat protects an inner layer of a sugary protein called β-glucan. Robert Wheeler and Gerald Fink of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, screened a library of 4,800 mutant yeast strains to find genes that, when disabled, expose the β-glucan. They showed that disabling nearly 50 of these genes makes fungi more vulnerable to attack by mouse immune cells.

Targeting the proteins made by the masking genes might yield much-needed medicines to fight insidious pathogenic fungi such as Candida albicans.

Materials: Graphite unzipped

Phys. Rev. Lett. 96, 176101 (2006)

Graphene — a single graphite-like carbon sheet — has unusual and potentially useful electronic behaviour. But it is hard to make. One promising approach involves oxidizing graphite to form graphite oxide, which separates layer by layer into thin flakes.

These flakes are generally much smaller than the original layers, and now Je-Luen Li and colleagues at Princeton University, New Jersey, think they know why.

The team identified bright lines in microscopic images of graphite oxide as fault lines where the layers have cracked. Their quantum-chemical calculations showed that these cracks are created by an ‘unzipping’ process in which the cooperative bonding of oxygen atoms next to one another on the surface creates a row of broken carbon–carbon bonds.

Chemistry: Clean sweep

Science 312, 1024–1026 (2006)

Hydrogen atoms can now be stripped from a silicon surface using laser light in a process that generates virtually no heat. Hydrogen desorption is an important part of computer-chip manufacture that normally requires temperatures of around 800 °C, which can introduce defects into the chips.

The technique, developed by Philip Cohen from the University of Minnesota, Minneapolis, and his colleagues, is highly selective, picking off hydrogen but leaving atoms of its heavier isotope deuterium behind. This shows that there is no transfer of heat across the silicon surface, as this would cause both hydrogen isotopes to desorb.

A bigger bang

Geochem. Geophys. Geosyst. doi:10.1029/2005GC001086 (2006)

Credit: PNNL

Mauna Loa (pictured), the world's largest volcano, is even more enormous than thought, a recent study suggests.

Submersible dives and seafloor mapping studies yielded a new underwater map of Mauna Loa's western flank, including ten submarine vents where only one was known before. The data suggest that its 1877 underwater eruption, which made the surface of a nearby bay boil, was much larger than thought.

If so, the volume of Mauna Loa's historical eruptions is 10% greater than previously believed, contradicting the theory that this Hawaiian volcano is dying, say Dorsey Wanless of the University of Hawaii in Honolulu and colleagues. The volcano last erupted in 1984.

Journal club

Catherine L. Drennan

Massachusetts Institute of Technology, USA

A biochemist considers cool inorganic chemistry that is relevant to our energy crisis.

There is a class of enzymes, found in certain microorganisms, that are the envy of synthetic chemists. They catalyse the reversible conversion of carbon dioxide (CO₂) to carbon monoxide (CO) — a difficult feat in the lab because the carbon–oxygen double bond in CO₂ is very strong.

In striving to match nature's success, chemists seek twofold environmental benefits: making CO — a useful feedstock for synthesizing carbon compounds — without using precious fossil fuels while, at the same time, consuming the greenhouse gas CO₂.

After my group solved the crystal structure for two of these enzymes, known as carbon monoxide dehydrogenase/acetyl-CoA synthase, I sought out the company of Joseph Sadighi, an assistant professor in my department, to discuss possible mechanisms involving the use of the enzymes' nickel–iron–sulphur clusters as catalysts. Sadighi was searching for other first-row transition metals that could catalyse the same reaction.

As my research took me in new directions, our long conversations about CO₂ came to an end. I heard occasional updates on his progress, but it wasn't until last October that I learnt the full story. I received a preprint of a paper from Sadighi and his co-workers announcing their new catalyst for CO₂ reduction (D. S. Laitar, P. Müller & J. P. Sadighi J. Am. Chem. Soc. 127, 17196–17197; 2005). Instead of nature's choice of iron and nickel, they had prepared copper(I) boryl complexes. These catalysts convert an impressive 100 molecules of CO₂ per hour at room temperature.

This is not only an exciting development in catalysis, it also shows the potential of inorganic chemistry in tackling our environmental problems.