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Putting the squeeze on milk may be a long-sought solution to the search for improved ways of killing harmful bacteria in milk and increasing its shelf life without introducing off-flavors into the beverage, researchers report.
Michael C. Qian and colleagues at Oregon State University point out that ultrahigh-temperature pasteurization (UHT) does produce milk that stays fresh at room temperature for six months. They add, however, that UHT leaves a “cooked” flavor in milk that has limited the popularity of UHT milk in the United States.
In experiments scheduled for publication in the Nov. 29 issue of the ACS biweekly Journal of Agricultural and Food Chemistry, they describe how a new food processing technology affects the taste of milk. Called high hydrostatic pressure processing (HPP), it involves putting foods under pressures that crush and kill bacteria while leaving food with a fresh, uncooked taste.
"Milk processed at a pressure of about 85,000 pounds per square inch for five minutes, and lower temperatures than used in commercial pasteurization, causes minimal production of chemical compounds responsible for the cooked flavor. HPP gives milk a shelf life at refrigerated temperature of at least 45 days,” they note.
Why would anyone want to shrink carbon nanotubes (CNTs), those cylinders of pure carbon with properties ideal for a new generation of sensors, transistors, super-strong fabrics, and nanoscale devices? CNTs already are about 50,000 times narrower than the finest human hair.
There are good reasons for doing so, according to Alex Zettl and colleagues at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory. They report development of a method for controllably altering the diameter of individual CNTs in the Dec. 13 issue of the ACS’s Nano Letters. Zettl explains that CNTs’ ability to conduct electricity and other electrical and mechanical properties depend heavily on their size. However, current methods for making CNTs cannot reliably control nanotube diameter, making it more difficult to fabricate devices from nanotubes.
“We have developed a method to shrink individual nanotubes to any desired diameter,” the researchers report. “The process can be repeated in a highly controlled fashion, yielding a high-quality CNT of any preselected and precise diameter.” The method involves a high-temperature that shrinks regular-sized CNTs and reforms them into high-quality tubes of a smaller diameter.
Scientists in California report a major advance in the technology for cleaning up oil spills on oceans, lakes and other waterways. Victoria Broje and Arturo A. Keller describe construction and field tests of an improved version of the mechanical skimmer, the mainstay device for recovering oil spilled on water.
Relatively unchanged for decades, the typical skimmer consists of a revolving steamroller-like drum that picks up a film of oil on the drum’s surface. A scraper then removes the oil, which drops into a collector. Broje and Keller note that traditional skimmers are inefficient, work poorly with thin oils like light crude or diesel and can be expensive to use in cleaning up large spills.
The new mechanical skimmer, described in a report scheduled for the Dec. 15 issue of the semi-monthly ACS journal Environmental Science & Technology uses a grooved surface. With a larger surface area, the grooves scoop up more oil than the smooth-surfaced traditional skimmer. The scraper is machined to precisely match the groove geometry, removing almost 100 percent of the adhered oil with each rotation. The grooves also are coated with an improved oil-adhering polymer. Field tests show that the new skimmer is up to three times more efficient than traditional skimmers, the scientists report.
James Watson and Francis Crick deciphered the structure of regular DNA 53 years ago. Now, scientists from Stanford University have determined the structure of xDNA. That’s “expanded DNA,” a strange double helix molecule that is 20 percent wider and more heat-resistant than natural DNA. Inherently fluorescent, expanded DNA glows in ways that may make xDNA useful as a medical and scientific probe.
Eric T. Kool and colleagues developed xDNA in 2003 by adding a benzene ring to the chemical bases that form natural DNA. Natural DNA, which is 20 angstroms wide, and benzene, with a girth of 2.4 angstroms, produced the wholly new wider double helix. The researchers now have combined all four expanded DNA bases with the four natural DNA bases to produce a complete eight-base molecule. They then used nuclear magnetic resonance to reveal the structure of xDNA and study the molecule.
In an article scheduled for publication Nov. 22 in the weekly Journal of the American Chemical Society, they describe the features needed for DNA that encodes and transfers genetic information. They report: “The present work shows that the eight-base xDNA system may have most if not all of these features, which suggests the future possibility of a functioning, replicable genetic system using xDNA as the genetic material.”
Journal: American Chemical Society
Journal Article: “Toward a Designed, Functioning Genetic System With Expanded-Size Base Pairs: Solution Structure of the Eight-Base xDNA Double Helix”
The gene silencing technology showcased in the 2006 Nobel Prize in Physiology or Medicine is on an amazingly fast track toward use in treating a variety of serious diseases, according to an article scheduled for the Nov. 13 issue of the ACS’s weekly newsmagazine, Chemical & Engineering News.
Much has happened to RNA interference (RNAi) technology in the eight years since discovery of this natural method for blocking the expression of specific genes, writes C&EN senior editor Celia Henry Arnaud. In addition to the Nobel Prize, RNAi-based treatments have gone into clinical trials for a common eye disease (age-related macular degeneration) and a viral infection of the lungs. Big pharma is confident that RNAi will find other uses, as evidenced by Merck’s move in October to spend $1.1 billion in acquiring a company specializing in RNAi therapeutics.
The article explains that expanding the medical uses of RNAi depends on development of new systems for delivering so-called small interfering RNAs (siRNAs) to other parts of the body. Researchers are making progress on those delivery systems, with the first clinical trials of RNAi-packaged in delivery systems — for cancer and hepatitis C — possible in 2007.
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