Unusual Shape of Exploded Star Puzzles Scientists

Penn State astronomers have used NASA's Chandra X-ray Observatory to produce a new image of a ghostly exploded star with an unusual shape in a galaxy near the Milky Way. Astronomers think the object may be the remains of a white-dwarf star that disintegrated in a thermonuclear explosion, known as a Type Ia supernova, but it does not look like other likely Type Ia remnants found in our own Milky Way galaxy.

The research that led to the new image of this object was led by Penn State University astronomers Sangwook Park and Jae-Joon Lee, and was presented at the 214th meeting of the American Astronomical Society in Pasadena, California, on 9 June 2009. The strange object, known as SNR 0104-72.3 (SNR 0104 for short), is in the Small Magellanic Cloud galaxy, which is a neighbor of our Milky Way galaxy.

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Mobile DNA Elements in Woolly Mammoth Genome Give New Clues to Mammalian Evolution

The woolly mammoth died out several thousand years ago, but the genetic material they left behind is yielding new clues about the evolution of mammals. In a study published online in Genome Research, scientists at Penn State have analyzed the mammoth genome looking for mobile DNA elements, revealing new insights into how some of these elements arose in mammals and shaped the genome of an animal headed for extinction.

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Scientists Determine the Structure of Highly Efficient Light-Harvesting Molecules in Green Bacteria

An international team of scientists has determined the structure of the chlorophyll molecules in green bacteria that are responsible for harvesting light energy. The team's results one day could be used to build artificial photosynthetic systems, such as those that convert solar energy to electrical energy.

The scientists found that the chlorophylls are highly efficient at harvesting light energy. "We found that the orientation of the chlorophyll molecules make green bacteria extremely efficient at harvesting light," said Donald Bryant, Ernest C. Pollard Professor of Biotechnology at Penn State and one of the team's leaders. According to Bryant, green bacteria are a group of organisms that generally live in extremely low-light environments, such as in light-deprived regions of hot springs and at depths of 100 meters in the Black Sea. The bacteria contain structures called chlorosomes, which contain up to 250,000 chlorophylls. "The ability to capture light energy and rapidly deliver it to where it needs to go is essential to these bacteria, some of which see only a few photons of light per chlorophyll per day."

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Hundreds of Natural-Selection Studies Could Be Wrong, Study Demonstrates

Scientists at Penn State and the National Institute of Genetics in Japan have demonstrated that several statistical methods commonly used by biologists to detect natural selection at the molecular level tend to produce incorrect results. "Our finding means that hundreds of published studies on natural selection may have drawn incorrect conclusions," said Masatoshi Nei, Penn State Evan Pugh Professor of Biology and the team's leader.

The team examined the branch-site method and several types of site-prediction methods commonly used for statistical analyses of natural selection at the molecular level. The branch-site method enables scientists to determine whether or not natural selection has occurred within a particular gene, and the site-prediction method allows scientists to predict the exact location on a gene in which natural selection has occurred.

"Both of these methods are very popular among biologists because they appear to give valuable results about which genes have undergone natural selection," said Nei. "But neither of the methods seems to give an accurate picture of what's really going on."

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A New Family of Molecules for Self-Assembly: The Carboranes

To be useful in real-world applications, a self-assembled monolayer (SAM) of molecules on a surface must have a stable and controllable geometry. Researchers at Penn State and the Sigma-Aldrich company have found a way to control geometry and stability by making SAMs out of different carboranethiol isomers, which are cage-like molecules.

"Our results allow us to control the chemical and physical properties of the SAM without changing its structure," said team leader Penn State Distinguished Professor of Chemistry and Physics Paul Weiss. "The ability to control these types of properties enables us to create SAMs that, for example, selectively capture biomolecules from complex mixtures. These carboranethiol molecules give us exceptionally high-quality SAMs, largely because of their simplicity. This innovation opens up new capabilities in terms of patterning and control. We are trying to come up with simple and economical means to control the chemistry of a surface all the way from the wafer scale (several centimeters) down to the single-molecule scale (sub-nanometer)."

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Geriatric Pulsar Discovered and Found Still Kicking

The oldest isolated pulsar ever detected in X-rays has been found with NASA's Chandra X-ray Observatory by a team of Penn State astronomers led by George Pavlov, professor of astronomy and astrophysics. This very old and exotic object turns out to be surprisingly active. The pulsar, PSR J0108-1431 (J0108) is about 200 million years old. Among isolated pulsars -- those whose spin has not been accelerated within a binary system -- and among pulsars detected with X-rays, it is over 10 times older than the previous record holder. At a distance of 770 light years, it is one of the nearest pulsars known. The surprise came when a team of astronomers led by Pavlov observed J0108 in X-rays with the orbiting Chandra X-ray observatory. They found that this pulsar glows much brighter in X-rays than was expected for a pulsar of such advanced years. "This pulsar is pumping out high-energy radiation much more efficiently than its younger cousins," said Pavlov.
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Researchers Discover Biomarker Linked to Prostate Cancer

Researchers from Penn State University and the University of Michigan have identified a group of small molecules, called metabolites, whose presence in urine indicates that a patient has prostate cancer. According to the American Cancer Society, over 186,000 Americans will be diagnosed with prostate cancer this year and nearly 29,000 will die from the disease. The team's findings could lead to a simple test that would help doctors determine which prostate cancers are slow-growing and which require immediate, aggressive treatment. Results of the study will appear in the 12 February 2009 issue of the journal Nature.

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Scientists Find New Way to Produce Hydrogen

Scientists at Penn State University and the Virginia Commonwealth University have discovered a way to produce hydrogen by exposing selected clusters of aluminum atoms to water. The findings are important because they demonstrate that it is the geometries of these aluminum clusters, rather than solely their electronic properties, that govern the proximity of the clusters' exposed active sites. The proximity of the clusters' exposed sites plays an important role in affecting the clusters' reactions with water. The results could open up a new area of research, not only related to splitting water, but also to breaking the bonds of other molecules as well. The team investigated the reactions of water with individual aluminum clusters by combining them under controlled conditions in a custom-designed flow-reactor. They found that a water molecule will bind between two aluminum sites in a cluster as long as one of the sites behaves like a Lewis acid, a positively charged center that wants to accept an electron, and the other behaves like a Lewis base, a negatively charged center that wants to give away an electron. The Lewis-acid aluminum binds to the oxygen in the water and the Lewis-base aluminum dissociates a hydrogen atom. If this process happens a second time with another set of two aluminum sites and a water molecule, then two hydrogen atoms are available, which then can join to become hydrogen gas (H₂).

Native Lizards Evolve to Escape Invasive Fire Ants

Penn State biologist Tracy Langkilde has shown that native fence lizards in the southeastern United States are adapting to potentially fatal invasive fire-ant attacks by developing behaviors that enable them to escape from the ants, as well as by developing longer hind legs, which can increase the effectiveness of this behavior. Not only does this finding provide biologists with an example of evolution in action, but it also provides wildlife managers with knowledge that they can use to develop plans for managing invasive species. Langkilde conducted an experiment in which she compared the responses to fire ant attacks of lizards that were collected from four different sites: one that had not yet been invaded by fire ants and ones that were invaded by fire ants 23, 54, and 68 years ago. Her goal was to determine whether the amount of time since invasion influences the ways in which lizards respond to attacks. She found that the lizards from sites that have been invaded the longest were more likely than the lizards from sites that have not yet been invaded to twitch vigorously to remove ants and then to run away from the mound. She also found that the lizards with the longest hind legs were the most successful at getting away from ants.

Hair of Tasmanian Tiger Yields Genes of Extinct Species

Scientists at Penn State and their international team of colleagues have revealed all the genes that the exotic Tasmanian Tiger inherited only from its mother. The research marks the first successful sequencing of genes from this carnivorous marsupial, which looked like a large tiger-striped dog and became extinct in 1936. The research also opens the door to the widespread, nondestructive use of museum specimens to learn why mammals become extinct and how extinctions might be prevented. The team extracted and sequenced DNA from the hair of two specimens, not from bone, which has been used in previous studies of extinct species. The new gene sequences permitted the team to accurately determine how the Tasmanian Tiger is related to other marsupials.