Biotechnology: Viral endgame

Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0705362104 (2007)

Viruses could be placed in a 'checkmate' position with a strategy that identifies and blocks off all escape routes for evading antiviral agents by mutation.

Richard Lerner, Sydney Brenner and their colleagues at the Scripps Research Institute in La Jolla, California, engineered bacteria-infecting phages to express the surface proteins of other viruses, such as a strain of influenza. They then exposed the phages to libraries of small molecules or antibodies to identify molecules that blocked the viral protein's interaction. Cycles of mutagenesis create phages in which the viral protein evades the blocker, whereupon new blockers can be found that stop that mutated form. In effect, the likely viral mutations in the wild are thus explored and counteracted in advance in vitro, so that the antidotes can be prepared in anticipation.

Evolutionary biology: Interaction over time

Curr. Biol. 17, 1225–1230 (2007)

Researchers have traced the evolution of a mechanism that controls the growth of more recently evolved plants.

The hormone gibberellin acts by promoting the interaction of two proteins. Nicholas Harberd and his colleagues at the John Innes Centre in Norwich, UK, looked for this interaction in plants that diverged at different points in time.

The proteins are present in the most ancient plant studied, a moss, but don't interact. In spikemosses, which evolved later, the hormone is present and the proteins interact, but they do not control growth. When they looked in the most recently evolved plant, the angiosperm Arabidopsis thaliana (or thale cress), they found that the system regulated plant growth.

This suggests that the gibberellin-response mechanism evolved in a step-by-step fashion between around 300 million and 400 million years ago.

Microbiology: Build-up in the brain

Credit: D. SCHARF/SCIENCE FACTION/GETTY

Mol. Microbiol. doi:10.1111/j.1365-2958.2007.05837.x (2007)

Certain variants of the malaria parasite Plasmodium falciparum preferentially accumulate in the brain, researchers have found.

P. falciparum manufactures proteins that make the red blood cells it infects (pictured right) stick to the lining of small blood vessels. In the brain, this can lead to blockages that may ultimately cause the infected person's death.

Jacqui Montgomery of the Malawi-Liverpool-Wel lcome Programme of Clinical Tropical Research in Blantyre, Malawi, and her colleagues compared the expression of var genes, which encode such proteins, in parasites taken from the brain, lung, heart and spleen of malaria patients. The team identified a couple of var genes that are specifically expressed in the brain and could represent targets for future therapies.

Neurobiology: Release from helplessness

Neuron 55, 289–300 (2007)

Researchers report that a protein called ΔFosB may help mice to cope with repeated stress.

When mice experience recurrent, inescapable stress, some simply stop trying to get away. This behaviour, called 'learned helplessness', is relieved by antidepressants and is used to model depression and post-traumatic stress disorder.

Now, Eric Nestler of the University of Texas Southwestern Medical Center in Dallas and his colleagues have found that ΔFosB is expressed by neurons that contain a pain-signalling peptide called substance P, in a brain region called the periaqueductal gray. Overexpressing ΔFosB in stressed mice diminishes stress-induced release of substance P, and reduces learned helplessness.

Materials science: Water pores

J. Am. Chem. Soc. doi:10.1021/ja073067w (2007)

Specially designed lipids can polymerize to create a three-dimensional network of pores perfectly tailored to filter salts out of water, researchers in the United States have found. The hope is that such 'nanofilters' could be used for desalination in regions where fresh water is scarce.

The nanofilter developed by Douglas Gin, Richard Noble and their colleagues at the University of Colorado in Boulder has uniform pores that have an effective size of just 0.75 nanometres — around three times as big as a water molecule. This means that water can flow through but larger ions get blocked.

Biotechnology: Pick up a prion

Nature Methods doi:10.1038/nmeth1066 (2007)

A new assay may prove quicker than existing techniques for detecting prions — the proteins responsible for brain diseases such as scrapie in livestock and Creutzfeldt–Jakob disease in people.

Currently, researchers monitor the ability of a sample of tissue or neural fluid to convert normally folded prion protein from brain tissue into the infectious, misfolded aggregates characteristic of disease. But the assay takes weeks to reach optimal sensitivity.

Ryuichiro Atarashi and his team at the Rocky Mountain Laboratories in Hamilton, Montana, instead tested samples against prion proteins produced by bacteria. These proteins can be engineered to carry probes that make it easy to monitor the structural changes that occur in the protein when aggregates form. The assay, tested on samples from hamsters with scrapie, takes three days or less.

Cell biology: Quick change

Cell 130, 77–88 (2007)

Our cells may be poised to change fate, reports a team led by Richard Young of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts.

Young's team looked in embryonic stem cells and two types of adult cell for chemical signals usually found close to genes that are being actively transcribed. They found these signals near about three-quarters of protein-coding genes in all the cell types. This was a surprise, because less than half of these genes were turned into the complete mRNAs needed to make proteins.

Although the cellular machinery initiates transcription at many genes, it only finishes transcribing some. This may allow the cell to quickly change fate under certain conditions by extending to completion the transcription of key genes.

Genetics: Time waits for no fly

Credit: J. BURGESS/SPL

Genome Res. doi:10.1101/gr.6216607 (2007)

Whether you look at brain, gut, muscle or fat, ageing exacts its toll on an animal's body. Now a study of fruitflies (pictured right) has found that gene expression follows different ageing patterns in different body tissues, with little overlap.

Researchers led by Sige Zou at the National Institute on Aging in Baltimore, Maryland, did a genome-wide screen of fruitflies aged between 3 and 60 days old. They identified hundreds of genes that were turned up or down in seven different tissues as the flies aged. When they compared the gene expression patterns of any two tissues, fewer than 10% of the changes were in the same genes.

Palaeontology: When dinos hit puberty

Biol. Lett. doi: 10.1098/rsbl.2007.0254 (2007)

Many dinosaurs hit puberty before they reached adult size, according to a new study.

Gregory Erickson of Florida State University in Tallahassee and his colleagues studied seven fossilized dinosaurs that were brooding when they died. The specimens' body sizes indicate that they followed a growth and maturation pattern more akin to that of modern crocodilians than their other descendants, birds.

Birds reach their full size long before sexual maturation. The discovery hints that this life-history trait may have emerged relatively recently, and no earlier than the first true bird, Archaeopteryx.

Earth sciences: Carbon lost from lakes

Credit: T. JOHNSON

Global Biogeochem. Cycles 21, GB3002 (2007)

An assessment of the carbon cycles of 41 lakes on five continents has put new global numbers on lakes' contribution to carbon in the atmosphere. The lakes' net carbon emission, at around 86 million tonnes, is roughly equivalent to Spain's annual carbon emissions.

Simone Alin of the University of Washington in Seattle and Thomas Johnson of the University of Minnesota in Duluth compiled available data for primary production, carbon burial and lake–atmosphere gas exchange for lakes (including Lake Malawi, pictured) representing more than two-thirds of the world's total volume of freshwater and saline lakes.

Overall, the lakes lose an order of magnitude more carbon to the atmosphere than they remove through burial of sediments.

Journal club

Jon Kleinberg

Cornell University, Ithaca, New York

A computer scientist wonders how much information is really good for us.

I am interested in understanding how groups of people or computer systems work together to solve complex problems. This is relevant in real-life situations that demand collective problem-solving, ranging from scientific research to military operations, so we hope to learn about the underlying mechanisms through experiment.

Stanley Milgram's famous 'six degrees of separation' studies form one such set of experiments. In these, participants were asked to help send a letter to a far-away stranger by forwarding it to a friend they thought might know the target. That this strategy often succeeded hints at how people lacking a global picture of the social network they inhabit can still jointly solve a difficult search problem.

One of the interesting questions here is how a group's ability to solve a problem is affected by the amount of information available. I expected that if people had a global view of the system, rather than just a local one, their effectiveness at solving the problem would increase.

A fascinating experiment (M. Kearns et al. Science 313, 824–827; 2006) shows that this isn't always so. The researchers posed a task in which they deliberately varied how much information was revealed to participants about what others in their group were doing.

For certain settings of the problem, giving participants a global view significantly slowed down progress. People faced with too much information in a time-pressured setting became 'overloaded', and this impaired the group's function.

As we consider designing tools to help people work together effectively, we should remember that increasing everyone's situational awareness might not always lead to improved performance.

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