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Imaging HIV in infected cells reveals viral tactics
IN BRIEF
NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI
HELEN of Troy was the face that launched 1000 ships. Meet Rheasilvia and Veneneia, the asteroid craters that launched 1000 meteorites. Meteoroids form when one asteroid or planet hits another, turfing out rocks that become known as meteorites if they ever land on Earth. Astronomers had suspected for decades that Vesta, the solar system’s second-biggest asteroid, was the source of the HED meteorites – about 1000 of which have been found on Earth. Now new images from NASA’s Dawn spacecraft, which has been orbiting Vesta since July last year and has mapped nearly 80 per cent of its surface, are filling in the details. The images, analysed by Paul Schenk of the Lunar and Planetary Institute in Houston, Texas, and colleagues, reveal two vast craters in Vesta’s southern hemisphere. The team calculates that the objects that created these craters – one of which was bigger than the Chicxulub impact thought to have wiped out the dinosaurs – could have scooped out enough material from Vesta to account for all known HED meteorites (Science, DOI: 10.1126/science.1223272). Rheasilvia is 500 kilometres wide, 20 kilometres deep and sits on top of Veneneia, which is almost as big.
16 | NewScientist | 19 May 2012
HIV’s plan of attack put under the microscope THE tactics that HIV uses to infect cells have been visualised in greater detail than ever before, thanks to a microscopy technique that allows even structures within viruses to be seen. Conventional light microscopes cannot resolve structures that are smaller than about 200 nanometres because they are limited by the wavelength of visible light. Viruses, which typically measure 25 to 300 nm, are just too small to see. One way around this has been to tag proteins with fluorescent
markers, activate them one at a time, and then map the locations of all these markers into a composite image. Markers can interfere with protein function, though, making it difficult to study proteins in action. Nathalie Arhel at the Pasteur Institute in Paris and her colleagues have modified this technique and inserted a six-amino-acid motif into the enzyme that HIV uses to integrate its DNA into its host’s genome. The motif is too short to affect the enzyme’s function, but long enough to bind to a
fluorescent marker molecule. They used the technique to take a closer look at HIV. Previously, it was unclear whether the virus’s genetic material is released into the cytoplasm of the host cell, or whether it remains in a container called a capsid until reaching the cell’s nucleus. The technique has revealed that it remains in the capsid – information that may provide opportunities for targeting the virus before it integrates its DNA (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1013267109). Tyrone Turner © 2012 National Geographic
Meteorites born of two young craters
For new stories every day, visit newscientist.com/news
Turn up the heat in obesity battle TURNING the body’s brown fat into a furnace fuelled by unwanted flab might provide a new way to lose weight. Brown fat helps to burn just enough fuel to keep body temperature constant, suggesting it could be manipulated to burn slightly more and combat obesity. Key to that manipulation may be a protein called bone morphogenetic protein 8B, or bmp8B. Mice kept at a chilly 5 °C make about 140 times more bmp8B than warm mice. Now Andrew Whittle of the University of Cambridge and colleagues have found that mice unable to make the protein become obese even when fed a normal diet. They also found that the protein is made both in the brain and inside the brown fat itself. It seems to increase nerve signals from the brain to brown fat cells. This makes them more attentive to the signals so they burn more energy than normal. Normal mice given extra bmp8B through infusions into the brain lost weight (Cell, DOI: 10.1016/j.cell.2012.02.066). The study could lead to a drug that steps up brown fat’s energy consumption, says Whittle.
The Mayan writing’s on the wall HERE’S one Mayan 2012 story that might not inspire a disaster movie: archaeologists have uncovered the earliest evidence of the Mayan astronomical calendar, painted on the wall of a 9th-century house. Until now, our main evidence of Mayan astronomical knowledge has come from books, such as the Dresden Codex, produced centuries after their society declined. In 2010, William Saturno of Boston University and colleagues were excavating Mayan ruins at Xultún in Guatemala. In one house they found a mural covered with pictures of
Mayan people (see above). In the gaps between the drawings were glyphs: Mayan writing that contained astronomical information (Science, DOI: 10.1126/science.1221444). “It seems obvious that the Maya were making Dresden Codex-like astronomical tables for over 1000 years,” says Joyce Marcus, an anthropologist at the University of Michigan in Ann Arbor. The house probably belonged to a senior public figure. That suggests astronomical information was broadly available, says Gary Feinman of the Field Museum in Chicago.
NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI
HELEN of Troy was the face that launched 1000 ships. Meet Rheasilvia and Veneneia, the asteroid craters that launched 1000 meteorites. Meteoroids form when one asteroid or planet hits another, turfing out rocks that become known as meteorites if they ever land on Earth. Astronomers had suspected for decades that Vesta, the solar system’s second-biggest asteroid, was the source of the HED meteorites – about 1000 of which have been found on Earth. Now new images from NASA’s Dawn spacecraft, which has been orbiting Vesta since July last year and has mapped nearly 80 per cent of its surface, are filling in the details. The images, analysed by Paul Schenk of the Lunar and Planetary Institute in Houston, Texas, and colleagues, reveal two vast craters in Vesta’s southern hemisphere. The team calculates that the objects that created these craters – one of which was bigger than the Chicxulub impact thought to have wiped out the dinosaurs – could have scooped out enough material from Vesta to account for all known HED meteorites (Science, DOI: 10.1126/science.1223272). Rheasilvia is 500 kilometres wide, 20 kilometres deep and sits on top of Veneneia, which is almost as big.
16 | NewScientist | 19 May 2012
HIV’s plan of attack put under the microscope THE tactics that HIV uses to infect cells have been visualised in greater detail than ever before, thanks to a microscopy technique that allows even structures within viruses to be seen. Conventional light microscopes cannot resolve structures that are smaller than about 200 nanometres because they are limited by the wavelength of visible light. Viruses, which typically measure 25 to 300 nm, are just too small to see. One way around this has been to tag proteins with fluorescent
markers, activate them one at a time, and then map the locations of all these markers into a composite image. Markers can interfere with protein function, though, making it difficult to study proteins in action. Nathalie Arhel at the Pasteur Institute in Paris and her colleagues have modified this technique and inserted a six-amino-acid motif into the enzyme that HIV uses to integrate its DNA into its host’s genome. The motif is too short to affect the enzyme’s function, but long enough to bind to a
fluorescent marker molecule. They used the technique to take a closer look at HIV. Previously, it was unclear whether the virus’s genetic material is released into the cytoplasm of the host cell, or whether it remains in a container called a capsid until reaching the cell’s nucleus. The technique has revealed that it remains in the capsid – information that may provide opportunities for targeting the virus before it integrates its DNA (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1013267109). Tyrone Turner © 2012 National Geographic
Meteorites born of two young craters
For new stories every day, visit newscientist.com/news
Turn up the heat in obesity battle TURNING the body’s brown fat into a furnace fuelled by unwanted flab might provide a new way to lose weight. Brown fat helps to burn just enough fuel to keep body temperature constant, suggesting it could be manipulated to burn slightly more and combat obesity. Key to that manipulation may be a protein called bone morphogenetic protein 8B, or bmp8B. Mice kept at a chilly 5 °C make about 140 times more bmp8B than warm mice. Now Andrew Whittle of the University of Cambridge and colleagues have found that mice unable to make the protein become obese even when fed a normal diet. They also found that the protein is made both in the brain and inside the brown fat itself. It seems to increase nerve signals from the brain to brown fat cells. This makes them more attentive to the signals so they burn more energy than normal. Normal mice given extra bmp8B through infusions into the brain lost weight (Cell, DOI: 10.1016/j.cell.2012.02.066). The study could lead to a drug that steps up brown fat’s energy consumption, says Whittle.
The Mayan writing’s on the wall HERE’S one Mayan 2012 story that might not inspire a disaster movie: archaeologists have uncovered the earliest evidence of the Mayan astronomical calendar, painted on the wall of a 9th-century house. Until now, our main evidence of Mayan astronomical knowledge has come from books, such as the Dresden Codex, produced centuries after their society declined. In 2010, William Saturno of Boston University and colleagues were excavating Mayan ruins at Xultún in Guatemala. In one house they found a mural covered with pictures of
Mayan people (see above). In the gaps between the drawings were glyphs: Mayan writing that contained astronomical information (Science, DOI: 10.1126/science.1221444). “It seems obvious that the Maya were making Dresden Codex-like astronomical tables for over 1000 years,” says Joyce Marcus, an anthropologist at the University of Michigan in Ann Arbor. The house probably belonged to a senior public figure. That suggests astronomical information was broadly available, says Gary Feinman of the Field Museum in Chicago.