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Life-giving bonds caught on camera
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American Chemical Society
BY AFFECTING the way molecules bind to each other, hydrogen bonds are responsible for water’s high boiling point, ice’s propensity to float and DNA’s signature double helix. Now these life-enabling bonds – essentially the force of attraction between one molecule’s slightly positively charged hydrogen atoms, and negatively charged areas on a neighbouring molecule – seem to have been captured on camera. Individual atoms can be imaged using a scanning tunnelling microscope. As its sharp-tipped probe scans a surface, the extent to which electrons “tunnel” between the tip and surface indicates changes in height caused by the presence of atoms. In 2008, Stefan Tautz at the Jülich Research Centre in Germany and colleagues found that the resulting images became sharper if cold hydrogen is present between the tip and the surface. Now his team has shown that this allows hydrogen bonds to be imaged too. When the team applied the technique to a sample of the organic molecule PTCDA, not only did the molecules show up in intricate detail, an electrical signal was also detected between them (coloured green below), at exactly the locations where hydrogen bonds are present (Journal of the American Chemical Society, DOI: 10.1021/ja104332t).
Milky Way magnets explain heavy cosmic ray conundrum A PORTION of the high-energy cosmic rays raining down on Earth could have been swirling around the Milky Way for millions of years. The idea could help solve a conundrum that has puzzled physicists for the past year. Cosmic rays are protons and nuclei of varying energies that regularly strike Earth. Little is known about them, but it is assumed that those with higher energies should have lower masses, as they are thought more likely to break up en route to Earth. It was therefore a surprise when
the Pierre Auger Observatory in Argentina last year reported that the average mass of cosmic rays was increasing at high energies. Now a team led by Alexander Kusenko of the University of California, Los Angeles, have an explanation. The crux of their idea is the recent finding that the explosions in other galaxies believed to form cosmic rays can happen in the Milky Way too. To find out if this could explain the heavy cosmic rays, Kusenko’s team calculated the numbers of protons and nuclei that
such explosions would produce and whether the Milky Way’s magnetic field would be able to retain them. At low energies, both protons and nuclei were deflected by the magnetic field and therefore retained in the galaxy for millions of years. But at high energies, the protons tended to escape while the heavier, less mobile nuclei hung around. This could account for the increase in heavy cosmic rays seen at high energies by Auger, say the team. The work will appear in Physical Review Letters.
Why money can give you an itch NICKEL allergy is the most common contact allergy in the western world, with people affected reacting to costume jewellery, coins and even medical implants. Now we know why: it seems nickel imitates the action of bacteria. Matthias Goebeler at the University of Giessen in Germany and his colleagues looked at cells from the blood vessels of people with a nickel allergy. The team found that these cells react to nickel when a group of receptors known as Toll-like receptors (TLRs) are present. When the team “knocked out” the genes behind each of the 11 types of TLR, they identified TLR4 as nickel’s target – the same TLR that bacteria bind to, sparking the body’s immune response (Nature Immunology, DOI: 10.1038/ni.1919). “This receptor was thought to only be relevant for bacteria,” says Goebeler, who suspects that other allergens may act in the same way. Nickel and bacteria bind to different parts of the receptor, the team say, so blocking nickel’s binding site could prevent allergic responses to the metal without stopping the body’s inflammation response to infection.
gideon mendel/in pictures/corbis
Life-giving bonds caught on camera
You don’t need siblings to be social THE stigma attached to only children – that they have weaker social skills – is unwarranted. So say Doug Downey and Donna Bobbit-Zeher of Ohio State University, Columbus, who found that kids with siblings make no more friends than those without. Concerns about poor social skills among children raised alone stem in part from a paper Downey published in 2004, which asked kindergarten teachers in the US to rate the social skills of children, aged around 5, in their care. He found that children with siblings received higher ratings. But the difference appears to
disappear as children age. He and Bobbit-Zeher analysed a survey of 13,500 children from 100 schools around the US. One section required students to name up to 10 friends. Pupils were typically named by five other children, regardless of whether they had siblings or not. Bobbitt-Zeher presented the results this week at the annual meeting of the American Sociological Association in Georgia. “Only children move up quickly in their professions,” says Rebecca Hegar of the University of Texas at Arlington. “It’s unlikely they would do that if they didn’t interact well with peers.”
21 August 2010 | NewScientist | 17
American Chemical Society
BY AFFECTING the way molecules bind to each other, hydrogen bonds are responsible for water’s high boiling point, ice’s propensity to float and DNA’s signature double helix. Now these life-enabling bonds – essentially the force of attraction between one molecule’s slightly positively charged hydrogen atoms, and negatively charged areas on a neighbouring molecule – seem to have been captured on camera. Individual atoms can be imaged using a scanning tunnelling microscope. As its sharp-tipped probe scans a surface, the extent to which electrons “tunnel” between the tip and surface indicates changes in height caused by the presence of atoms. In 2008, Stefan Tautz at the Jülich Research Centre in Germany and colleagues found that the resulting images became sharper if cold hydrogen is present between the tip and the surface. Now his team has shown that this allows hydrogen bonds to be imaged too. When the team applied the technique to a sample of the organic molecule PTCDA, not only did the molecules show up in intricate detail, an electrical signal was also detected between them (coloured green below), at exactly the locations where hydrogen bonds are present (Journal of the American Chemical Society, DOI: 10.1021/ja104332t).
Milky Way magnets explain heavy cosmic ray conundrum A PORTION of the high-energy cosmic rays raining down on Earth could have been swirling around the Milky Way for millions of years. The idea could help solve a conundrum that has puzzled physicists for the past year. Cosmic rays are protons and nuclei of varying energies that regularly strike Earth. Little is known about them, but it is assumed that those with higher energies should have lower masses, as they are thought more likely to break up en route to Earth. It was therefore a surprise when
the Pierre Auger Observatory in Argentina last year reported that the average mass of cosmic rays was increasing at high energies. Now a team led by Alexander Kusenko of the University of California, Los Angeles, have an explanation. The crux of their idea is the recent finding that the explosions in other galaxies believed to form cosmic rays can happen in the Milky Way too. To find out if this could explain the heavy cosmic rays, Kusenko’s team calculated the numbers of protons and nuclei that
such explosions would produce and whether the Milky Way’s magnetic field would be able to retain them. At low energies, both protons and nuclei were deflected by the magnetic field and therefore retained in the galaxy for millions of years. But at high energies, the protons tended to escape while the heavier, less mobile nuclei hung around. This could account for the increase in heavy cosmic rays seen at high energies by Auger, say the team. The work will appear in Physical Review Letters.
Why money can give you an itch NICKEL allergy is the most common contact allergy in the western world, with people affected reacting to costume jewellery, coins and even medical implants. Now we know why: it seems nickel imitates the action of bacteria. Matthias Goebeler at the University of Giessen in Germany and his colleagues looked at cells from the blood vessels of people with a nickel allergy. The team found that these cells react to nickel when a group of receptors known as Toll-like receptors (TLRs) are present. When the team “knocked out” the genes behind each of the 11 types of TLR, they identified TLR4 as nickel’s target – the same TLR that bacteria bind to, sparking the body’s immune response (Nature Immunology, DOI: 10.1038/ni.1919). “This receptor was thought to only be relevant for bacteria,” says Goebeler, who suspects that other allergens may act in the same way. Nickel and bacteria bind to different parts of the receptor, the team say, so blocking nickel’s binding site could prevent allergic responses to the metal without stopping the body’s inflammation response to infection.
gideon mendel/in pictures/corbis
Life-giving bonds caught on camera
You don’t need siblings to be social THE stigma attached to only children – that they have weaker social skills – is unwarranted. So say Doug Downey and Donna Bobbit-Zeher of Ohio State University, Columbus, who found that kids with siblings make no more friends than those without. Concerns about poor social skills among children raised alone stem in part from a paper Downey published in 2004, which asked kindergarten teachers in the US to rate the social skills of children, aged around 5, in their care. He found that children with siblings received higher ratings. But the difference appears to
disappear as children age. He and Bobbit-Zeher analysed a survey of 13,500 children from 100 schools around the US. One section required students to name up to 10 friends. Pupils were typically named by five other children, regardless of whether they had siblings or not. Bobbitt-Zeher presented the results this week at the annual meeting of the American Sociological Association in Georgia. “Only children move up quickly in their professions,” says Rebecca Hegar of the University of Texas at Arlington. “It’s unlikely they would do that if they didn’t interact well with peers.”
21 August 2010 | NewScientist | 17