Engineered DNA and electronics: Researchers including engineering and physics professor Jimmy Xu are exploring ways to engineer DNA to alter its conductivity, which might make the molecule useful in electronics someday. A paper reporting their first success is scheduled for publication in the Physical Review Letters on April 16.
"We're hoping we now have a new set of building blocks for future electronics, and so we could assemble some of the engineered DNA into some kind of networked architecture or electronic circuit, to make them function like an electronic signal processor," Xu said. "Perhaps in the future we could have some new technologies that are developed from the basis of biomolecules."
A nearer-term possibility is that the researchers may have the ability to use the engineered DNA as a biosensor that could measure the change in electrical current in the detection, for example, of a single signature molecule of a cancer.
The team of researchers includes students and research associates of Xu's lab — Andrei Rakitin, Chris Papadopoulos, Yuri Kobzar and Alex Vedeneev — and biochemists from the University of Saskatchwan. Their work demonstrated that the conductivity of DNA molecules can be altered and made hundreds of times higher by substituting the imino proton of each base pair of a DNA molecule with a metal ion. Their work was supported by the Canadian Institute of Advanced Research, the National Science Foundation, the Defense Advanced Research Projects Agency and the Office of Naval Research. — Janet Kerlin
Visual control of human locomotion: Which visual cues humans rely upon to make their way toward a target depends on the nature of the environment, according to a new study by Brown researchers that used virtual reality to manipulate the laws of optics.
The findings, published in the journal Nature Neuroscience in February, add new information to a discussion that began 50 years ago on how human locomotion is visually controlled.
In theory, navigation could be guided by several types of information. It’s possible that a person moving toward a target aligns it within the rush of visual stimuli known as optic flow that bombards the eyes. It is also possible that people gauge the direction of a target relative to their own bodies by centering it in their line of sight and then moving forward, known as the egocentric direction hypothesis.
The findings indicate that the human visual system can control navigation under a variety of conditions, and that — contrary to previous claims — optic flow cues are used to control human walking when they are available, according to William H. Warren, professor of cognitive and linguistic sciences.
Researchers used virtual reality to allow study participants to walk through four virtual worlds. Participants were asked to walk to a goal nine meters away with a head-mounted device that varied the available optic flow. In each trial, the subject turned to face a marker and began walking when the virtual environment appeared.
When little optic flow information was available, the behavior of participants was consistent with the egocentric direction hypothesis. But when the environment was made more complex, by adding information such as textured floors and ceilings, optic flow information was increasingly used.
In other words, when optic flow is reduced or distorted, such as on a grassy lawn or in the darkness of night, behavior tends to be governed by egocentric direction. In a more complex environment, such as a forest, optic flow dominates behavior, according to Warren.
Warren conducted the research with Brown colleagues Bruce A. Kay, assistant professor of research in cognitive and linguistic sciences; Wendy D. Zosh, grant fellow in cognitive and linguistic sciences; Andrew P. Duchon, postdoctoral fellow in cognitive and linguistic sciences; and Stephanie Sahuc, an engineering student. The research was supported by the National Eye Institute, National Institute of Mental Health and the National Science Foundation. — Kristen Cole
Space weathering on minerals: Planetary geology senior research associate Takahiro "Taki" Hiroi was part of a group of scientists who are the first to have duplicated space weathering on minerals here on Earth. Their research is more proof that many meteorites which have fallen to Earth probably came from the "S" asteroids orbiting in the part of the asteroid belt closest to Earth.
Space-weathered rocks have been bombarded by tiny micrometeorites and buffeted by solar winds. Hiroi and colleagues ground the minerals olivine and pyroxene into powders and pressed them into pellets. The pellets were bombarded with a laser pulse, which mimicked the effects of the heating and vaporization on the surface of a meteorite. The laser-pulsed minerals turned out to have thin deposits of vapor containing tiny iron particles just as the "S" do. The minerals and the asteroids also had similar optical properties (reflectance spectra), Hiroi said.
The research was published in Nature on March 29. His co-authors are Sho Sasaki et al of the University of Tokyo and Keiko Nakamura of Kobe University. — Janet Kerlin