Nature: Rhodopsin is a light-sensing pigment in the photoreceptor cells of human retinas. It consists of proteins called opsins surrounding a chromophore molecule called retinal. Rhodopsin’s peak absorbance ranges in wavelength from 420 nm (blue) to 560 nm (green). When retinal absorbs a photon, the molecule changes shape and triggers the transmission of an electrical signal to the brain. Babak Borhan from Michigan State University and his research team genetically engineered a variation of rhodopsin that was able to absorb wavelengths up to 644 nm (red). Borhan’s work sheds light on how pigment molecules absorb the ranges of light that they do. By altering the amino acids in the pigment, the researchers caused the electrical charge of the molecule to be more evenly distributed instead of localizing at a particular spot. That change alone was responsible for the redshift in absorption. Because of the simplicity of the change, it appears that the ability to engineer other pigments is not far away.
Daily Archives: December 7, 2012
Maori ovens yield data on Earth’s magnetic field
BBC: A researcher in New Zealand is searching for abandoned Maori steam ovens, called hangi, in order to gather data on Earth’s magnetic field. Gillian Turner of Victoria University in Wellington spoke at the annual meeting of the American Geophysical Union, held this week in San Francisco. The ovens, which date back to about AD 1200, were pits in the ground filled with stones that were heated to very high temperatures for cooking food. The stones the Maori used tended to have a high concentration of magnetite, which became demagnetized as they were heated past their Curie temperature. As they cooled, they became remagnetized in the direction of the local field, writes Jonathan Amos for the BBC. Using radiocarbon analysis of the charcoal left by the firewood burned, Turner and her team are working to gather data on Earth’s magnetic field in the South Pacific from the past 800 years. Her ultimate goal is to gather data that covers the past 10 000 years, but to go deeper in time, she will need to find other sources, such as volcanic rocks and lake sediments.
Gravity map reveals lunar secrets
Science News: The first full lunar gravity map from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) has revealed the Moon’s violent history. The new GRAIL map is the most detailed gravity map ever created, and is 1000 times as precise as previous maps of the Moon. One of the most significant findings is that the lunar crust is 10–20 km thinner than expected, averaging just 34–43 km in thickness. The map has also revealed buried formations several hundred kilometers long that were created by molten rock. Jeffrey Andrews-Hanna from the Colorado School of Mines says that these were caused by cracks in the crust during the early part of the Moon’s existence. At that time, the surface was hotter than the interior, which caused the crust to expand and the cracks to form, with molten rock from below filling the space. GRAIL‘s primary mission is now over. The twin probes are orbiting lower and lower for additional readings in specific areas; they will then crash into the Moon’s surface.
ARPA–E grants focus on energy storage
MIT Technology Review: The US Department of Energy’s Advanced Research Projects Agency–Energy (ARPA–E) announced the award of 66 new grants totaling $130 million. The grants show a notable shift in investment toward companies working with US natural gas deposits, but they are even more heavily focused on advancements in energy storage technology. The 20 grants for energy storage include projects developing advanced aqueous rechargeable lithium-sulfur batteries, sodium-ion batteries, fuel cells, and thermal storage devices. ARPA–E grants are for potential “transformational” technologies. The high-risk investments are intended to help the companies prototype their products within two to three years, with the hope that the products will be commercialized.