News & Views in 1999

The Sm proteins are a conserved family that form the core of the small nuclear ribonucleoprotein particles (snRNPs), which are involved in RNA splicing. There are seven Sm proteins in all, and they can form three stable sub-complexes. The crystal structures of two of these sub-complexes have now been solved, giving an insight into organization of the Sm core domain, and how it might bind RNA.

What social and environmental consequences will result from altered climate in the future? A modelling study, in which the authors examined projected river flow and wheat yields in Europe up to the middle of the next century, emphasizes the need to take natural climate variability into account in assessing the impacts to be expected from human-induced climate change through increased levels of atmospheric CO₂.

Physicists are investigating phenomena at ever smaller scales. One example comes from work on the ‘Aharonov-Bohm effect’, the quantum mechanical influence of a magnetic field on electron motion — the effect has now been shown to occur in a carbon nanotube, illustrating the potential for doing basic physics with single molecules.

Vacant crystal lattice sites, or vacancies, allow atoms to migrate in a crystalline solid. A new way of measuring such vacancies using laser interferometry shows how vacancy concentration changes with a sudden increase in temperature. This technique could be used to study the mechanical strength of certain alloys.

Do nestling birds signal their food needs honestly to their parents? A study of begging reed warblers shows that they do, but that parental sensitivites to vocal and visual cues can be exploited by an invading cuckoo chick.

Hox proteins are transcription factors that operate during the development of different tissues. The structure has now been determined of a complex between DNA, a Hox protein and its cofactor. The homeodomains of the two proteins bind to opposite sides of the DNA but make contact through a short length of the Hox protein that reaches round the DNA to insert itself into a pocket on the cofactor, thereby strengthening the complex.

It has long been thought that the energetic costs of running are higher than for flying, and that swimming is cheaper than both. But recent estimates for mammals indicate that, weight for weight, these are about the same. Swimming is expensive for semi-aquatic mammals, so they tend to move slowly as a result: over a distance of 50 metres, dolphins swim five times faster than human world-record holders.

To propel itself forward, any spacecraft needs to fire something in the opposite direction. But Daedalus likes the idea of a motor that acts on the tenuous gas in space itself. So, he proposes to build a device based on the Crookes radiometer — the little ‘light mill’ in a glass bulb, which spins in sunlight.

An experiment with atoms at nanokelvin temperatures has produced the remarkable observation of light pulses travelling at velocities of only 17 m s⁻¹. The large optical nonlinearities seen in this system may open up new opportunities in quantum optics.

The hippocampus is thought to be essential for learning and memory, but is it a highly specialized memory store for spatial memories, or does it deal with more general memory? A study using rats that learn to associate particular smells with foraging for food indicates that hippocampal neurons fire when the rat detects certain odours, indicating that the hippocampus may have a much broader function than previously thought.

Explanations for the nature of excess protons in liquid water, including their extraordinarily high mobility, have long eluded researchers. New quantum molecular dynamics simulations suggest that the hydrated proton is of an inherently fluxional character, with two favoured theoretical views featuring only as limiting structures.

Chemists have just achieved the total synthesis of the antibiotic vancomycin. The structure was 99% complete last year, but two sugar groups had to be added to produce totally synthetic vancomycin. The selective addition of these sugars may suggest ways of modifying antibiotics to produce drugs that are effective against multidrug-resistant bacteria.

Stem cells have the remarkable ability to become one of any number of different cell types. Take neural stem cells, for example, which can develop into neurons or different types of glial cell. Two studies indicate that these cells are not only much more widespread in the central nervous system than previously thought, but that they can somehow cross from the brain and develop into blood cells.

Spectacular images from the Mars Orbiter Camera — an instrument on the Mars Global Surveyor spacecraft — are providing new views of that planet. These images, and what can be inferred from them, add to knowledge of the processes that shaped the Martian surface; together with other data, they offer the hope that a self-consistent view of the planet's early climate can be pieced together.

The bony fishes gave rise to two living subgroups, the ray-finned fishes, and the lobe-fins and tetrapods (or land vertebrates, including ourselves). An analysis of the evolutionary position of a 400-million-year-old fossil both adds to the current picture of bony-fish origins and complicates it — the fossil has such a mix of characteristics that large parts of the vertebrate family tree come into question.

DNA methylation is important for repressing gene expression, and much is known about how methyl groups are added to DNA. But little has been done to work out how they're taken off again. Now, a hitherto unknown gene has been cloned, which encodes a protein that seems to catalyse demethylation by directly removing the methyl groups from 5-methyl-cytosine.

Plants contain many useful substances — sugar, nicotine and steroids, for example — that are often tricky to extract, so Daedalus is developing supercritical cell culture. Because supercritical fluids are wonderful solvents, product molecules will diffuse out through the plant cell walls at an incredible rate. The technique could have applications in herbal medicine and even in genetic engineering.

The question of whether DNA is like a wire or an insulator is a controversial one, with some experiments finding DNA is conducting and some not. A new experiment suggests that it may all depend on the DNA sequence — electron transfer in DNA only occurs with high efficiency between guanine bases. This mechanism may help explain previous disparate results.

Many transplant patients are given the drug cyclosporine to suppress their immune systems and prevent rejection. But cyclosporine also increases the risk of cancer, always thought to be a side effect of the depressed immune system. A new study shows that cyclosporine directly affects tumour growth and may be the culprit.