Review, News & Views, Perspectives, Hypotheses and Analyses in 1999

To have new ideas, it helps to be small, hungry and female —at least, it does if you're a guppy. These are the distinguishing characteristics of the fish that were most likely to negotiate mazes to find a food source. This seems to be because they are the ones that need the food most. But, as well as being driven to cleverness, some guppies seem just to be better problem-solvers than others.

Not all lubricants are liquids, some, such as graphite and molybdenum sulphide, are solid. Under certain conditions molybdenum sulphide chemically reacts to absorb energy from the friction process. Daedalus seeks a lubricant that will react in a way that releases energy. Such a lubricant would decrease friction, and if the reaction was sufficiently forceful it might generate propulsive power, or negative friction.

Electrons confined in two dimensions, such as within ultra-thin semiconductor layers, lead to quantum-well states. Creating such states in metallic thin films, produces quantum wells that are spin-polarized or magnetic. This phenomenon may find applications in a new generation of magnetic recording media.

Creating asymmetric structures is useful for liquid crystal displays and optical switches, but it has not been easy. Now, subtle chemical interactions between block copolymers —which are themselves a blend of carefully selected polymers - are tailored to produce a self-assembling non-centrosymmetric nanostructure.

According to the exon-shuffling hypothesis, new genes are assembled from chunks of old ones. But how? A study of the L1 retrotransposon —which usually moves its own sequence from one genomic location to another —suggests a new mechanism. This retrotransposon can co-mobilize a 3' flanking segment of non-L1 DNA to new locations, allowing the juxtaposition of two previously unlinked DNAs.

Measurements of CO₂ concentrations in air bubbles enclosed in polar ice, provides many details about ancient climates, but there has been a gap in the records until now. New data for the Holocene (from 11,000-1,000 years ago) reveal that the global carbon cycle was never in equilibrium during the last 11,000 years, despite overall climate stability. This work may inform future estimates of CO₂levels.

To be broken down, p27^Kip1— a protein that regulates the cell cycle — must be exported from the nucleus. This unexpected step could turn out to be a general way to regulate the turnover of many nuclear proteins.

For many years we've know that there is an imbalance between the levels of carbon released by man's activities and measured concentrations in the atmosphere. The current theory is that this is due to uptake of carbon by terrestrial ecosystems in the northern hemisphere. But we now have evidence that the forests' contribution is far too small to account for all of the 'missing' carbon.

Little is known about the molecular basis of taste perception compared with, say, vision or touch. Now, not one, but two, potential mammalian taste receptors have been discovered. Both are guanine-nucleotide-binding (G) protein-coupled receptors, with sequence homology to other known chemosensory receptors.

A giant, multilayered carbon nanotube, one micrometre across and coated with slippery graphite fluoride, would be an ideal biological electrode, thinks Daedalus. In the brain, such a microdermic needle could work like a precise electroencephalograph. And a mass of needles distributed through the nervous system, and hooked up to a computer, could be used to create the very first cyborg robot.

Proteins inside cells that convey information from the outside often contain special signalling modules known as SH2 domains. These domains may have developed during the evolution of multicellular animals, and were typically identified by their amino-acid sequence. But now one has been discovered in a human protein called Cbl that has a quite different sequence, raising questions about the ancestral origin of these domains.

Supernova observations have indicated that the Universe is expanding faster than the theory of inflation predicts. Some theoretical cosmologists suggest that an exotic form of energy density called quintessence may be responsible. Quintessence began as Einstein's cosmological constant, but if it is not, in fact, constant it may explain why we appeared just when it had the same value as the density of ordinary matter.

Sapropels are layers of sediment on the sea floor that are rich in organic carbon. The way in which they were formed has been a matter of intense debate, with researchers usually invoking one of two alternative explanations. Work in the Mediterranean now allows those explanations to be reconciled.

Africa is splitting apart down the East African Rift. An analysis of the relative motion of the tectonic plates involved allows the rate of continental rifting to be estimated.

To flag themselves for destruction, virus-infected cells express viral peptides on their surface. It was always thought that these peptides were generated from viral peptide made inside the cell. Over the years, however, another theory has gained ground —namely that cells can also take up viral antigens. The first direct evidence to support this theory is now reported.

One way of switching on certain genes to express their encoded proteins is to increase the concentration of calcium ions inside the cell nucleus, which can happen in response to an instruction from outside the cell. A new mediator of this effect has been discovered: it is a protein called DREAM, which sits tightly on the gene, preventing its expression, until it has bound four calcium ions. It then detaches itself, leaving the gene exposed for transcription.

The modern hypodermic needle is not only feared by many patients, but it is an extremely wasteful way of administering drugs. Daedalus prefers the idea of a ‘microdermic needle’, which is so small it could pass harmlessly through tissues to a specific target in the body, requiring perhaps a millionth of the usual drug dose.