News Article | August 29, 2016
For a number of years now, an increasing number of synthetic nanoparticles have been manufactured and incorporated into various products, such as cosmetics. For the first time, a research project at the Technical University of Munich and the Bavarian Ministry of the Environment provides reliable findings on their presence in water bodies. Nanoparticles can improve the properties of materials and products. That is the reason why an increasing number of nanoparticles have been manufactured over the past several years. The worldwide consumption of silver nanoparticles is currently estimated at over 300 metric tons. These nanoparticles have the positive effect of killing bacteria and viruses. Products that are coated with these particles include refrigerators and surgical instruments. Silver nanoparticles can even be found in sportswear. This is because the silver particles can prevent the smell of sweat by killing the bacteria that cause it. Previously, it was unknown whether and in what concentration these nanoparticles enter the environment and e.g. enter bodies of water. If they do, this poses a problem. That is because the silver nanoparticles are toxic to numerous aquatic organisms, and can upset sensitive ecological balances. In the past, however, nanoparticles have not been easy to detect. That is because they measure only 1 to 100 nanometers across — a nanometer is a millionth of a millimeter. "In order to know if a toxicological hazard exists, we need to know how many of these particles enter the environment, and in particular bodies of water," explains Michael Schuster, Professor for Analytical Chemistry at the TU Munich. This was an analytical challenge for the researchers charged with solving the problem on behalf of the Bavarian Ministry of the Environment. In order to overcome this issue, they used a well-known principle that utilizes the effect of surfactants to separate and concentrate the particles. "Surfactants are also found in washing and cleaning detergents," explains Schuster. "Basically, what they do is envelop grease and dirt particles in what are called micelles, making it possible for them to float in water." One side of the surfactant is water-soluble, the other fat-soluble. The fat-soluble ends collect around non-polar, non-water soluble compounds such as grease or around particles, and "trap" them in a micelle. The water-soluble, polar ends of the surfactants, on the other hand, point towards the water molecules, allowing the microscopically small micelle to float in water. The researchers applied this principle to the nanoparticles. "When the micelles surrounding the particles are warmed slightly, they start to clump," explains Schuster. This turns the water cloudy. Using a centrifuge, the surfactants and the nanoparticles trapped in them can then be separated from the water. This procedure is called cloud point extraction. The researchers then use the surfactants that have been separated out in this manner — which contain the particles in an unmodified, but highly concentrated form — to measure how many silver nanoparticles are present. To do this, they use a highly sensitive atomic spectrometer configured to only detect silver. In this manner, concentrations in a range of less than one nanogram per liter can be detected. To put this in perspective, this would be like detecting a box of sugar cubes that had dissolved in the Walchensee lake. With the help of this analysis procedure, it is possible to gain new insight into the concentration of nanoparticles in drinking and waste water, sewage sludge, rivers, and lakes. In Bavaria, the measurements yielded good news: The concentrations measured in the water bodies were extremely low. In was only in four of the 13 Upper Bavarian lakes examined that the concentration even exceeded the minimum detection limit of 0.2 nanograms per liter. No measured value exceeded 1.3 nanograms per liter. So far, no permissible values have been established for silver nanoparticles. Representative for watercourses, the Isar river was examined from its source to its mouth at around 30 locations. The concentration of silver nanoparticles was also measured in the inflow and outflow of sewage treatment plants. The findings showed that at least 94 percent of silver nanoparticles are filtered out by the sewage treatment plants.
News Article | May 6, 2009
The prepaid cell phone market has finally hit the U.S. in a big way as economically strapped consumers flock to inexpensive pay-as-you-go services. The result will likely mean that big cell phone providers may be forced to slash prices on contract service plans to keep consumers from defecting. This is good news for consumers, who could see lower prices on both prepaid and post-paid service plans. But it is very bad news for cell phone operators, which make more money from their post-paid customers than they do from prepaid customers. Prepaid cell phone plans, which have been very popular in Europe and other parts of the world for several years, allow consumers to buy a phone at full retail price, without committing to a contract, and pay for service in advance. By contrast, post-paid services require consumers to sign a one- to two-year service contract, and their usage is billed on a monthly basis. In exchange for signing a contract, wireless operators often subsidize the cost of the phone. For years, the post-paid business model has dominated the U.S. cell phone market, providing strong growth for U.S. wireless operators. Meanwhile, the prepaid market in the U.S. has been largely left to consumers who are young, price-sensitive, or considered credit risks. While all of the major cell phone operators offer prepaid services, smaller operators, such as Leap Wireless, MetroPCS, and Virgin Mobile USA, have largely dominated this market. Now, it looks like the tide is turning. First-quarter earnings from all of the major cell phone operators indicate that consumers are flocking to new all-you-can-eat prepaid plans instead of the contract-bound post-paid plans. "Post-paid (wireless service) growth is arguably over," Craig Moffett, a Sanford Bernstein equities analyst, said in a research note published this week. Post-paid subscriber growth came to a "virtual halt" in the first quarter of 2009, Moffett noted. He estimates that net additions of post-paid customers across all major carriers fell 58 percent from the first quarter of 2008 to the first quarter of 2009. Meanwhile, prepaid customers are on the rise. A year ago about 50 percent of new cell phone users signed up for prepaid cell phone service, Moffett said in his note. But in the first quarter of 2009, about 80 percent of cell phone subscriber growth came from prepaid plans. Sprint Nextel, which reported results on Monday, is the most obvious example of how things appear to be shaking out in the wireless industry. Sprint added about 674,000 new prepaid subscriptions in the first quarter, according to Moffett's estimates. But the company lost nearly 1.25 million post-paid subscribers. Driven by bad economy The boom in prepaid cell phone service is likely being driven by the sour economy, and by the fact that providers, such as Sprint and Virgin Mobile USA, have recently introduced $50 unlimited voice services. Sprint's Boost Unlimited service also includes unlimited text messaging and unlimited wireless Web access. Leap Wireless and MetroPCS also offer similar all-you-can-eat plans. Sprint's service, offered through its subsidiary Boost Mobile, uses excess capacity on the former Nextel iDEN network. So the low-cost service didn't require an expensive network upgrade. The service launched in January, and it was deemed a huge success. Sprint executives said Monday the initial uptake of the service was more than the company had expected. It seems the $50 price tag could be too good for some consumers to pass up. Comparable post-paid service plans offered by AT&T and Verizon Wireless cost $99.99 a month. And Sprint's own "Simply Everything" plan, which includes unlimited Web surfing and e-mail in addition to unlimited voice and messaging service, costs $99.99 a month. Sprint's CEO Dan Hesse said during the conference call with analysts and investors that there "is no question that there is a movement toward prepaid." But he was careful to point out that he doesn't see the prepaid market cannibalizing the more lucrative post-paid business model. In fact, he said that the prepaid market is actually expanding the entire wireless market. "Some of these prepaid customers are people using cell phones for the first time," he said. "So I think overall, as an industry, we will see more revenue growth than we would have seen without prepaid services." But with more than 80 percent of the U.S. population already using a cell phone service, it's getting harder to sell wireless service to people who don't already own a cell phone. That means that wireless operators are already trying to steal each other's existing customers. The problem for wireless carriers is that not all cell phone customers are equal. Moffett's analysis indicates that prepaid customers typically generate less than half the value of post-paid subscribers over time. And the reason is simple. On average, prepaid customers generate less revenue per month than post-paid customers. They are more likely to switch back and forth between service providers. And they typically use more network resources, averaging around 2,000 voice minutes per month compared to about 1,000 minutes per month, than post-paid customers. As a result, carriers, such as Sprint, that are growing their prepaid subscriber base at the expense of their post-paid customers, will, over time, make less money, Moffett reasons. But regardless of whether carriers want to offer more prepaid services, the troubled economy is likely accelerating the trend. As more Americans lose their jobs and household budgets get tighter, some cell phone subscribers are starting to opt for cheaper prepaid cell phone plans when their current post-paid contracts run out. A recent study conducted by Opinion Research Corporation (ORC) for the New Millennium Research Council (NMRC) suggests that many people are already canceling their cell phone plans and getting prepaid cell phones as a reaction to the financial crisis. It is clear that the current trend is probably bad for wireless operators. But if more wireless operators match Boost with their own $50 all-you-can-eat prepaid service plans, a pricing war could emerge, which will likely benefit consumers. And it's very likely the price drops won't stop at the prepaid plans. If carriers start losing even more post-paid customers, they may also be forced to reduce the price of their contract-based all-you-can-eat plans. But because most prepaid services only offer basic phones, the price war may not immediately affect more advanced smartphone sales and service plans. Still, as the cell phone market reaches saturation, wireless operators can't afford to lose any subscribers.
A new paradigm for the development of photo-bioelectrochemical cells has been reported in the journal Nature Energy by researchers from The Hebrew University of Jerusalem and the University of Bochum. The design of photo-bioelectrochemical cells based on native photosynthetic reaction is attracting substantial recent interest as a means for the conversion of solar light energy into electrical power. In the natural photosynthetic apparatus, photosynthetic reaction is coupled to biocatalytic transformations leading to CO fixation and O evolution. Although significant progress has been achieved in the integration of native photosystems with electrodes for light-to-electrical energy conversion, the conjugation of the photosystems to enzymes to yield photo-bioelectrocatalytic solar cells remains a challenge. Now, researchers report on the construction of photo-bioelectrochemical cells using the native photosynthetic reaction and the enzymes glucose oxidase or glucose dehydrogenase. The system consists of modified integrated electrodes that include the natural photosynthetic reaction center, known as photosystem I, conjugated to the enzymes glucose oxidase or glucose dehydrogenase. The native proteins are electrically wired by means of chemical electron transfer mediators. Photoirradiation of the electrodes leads to the generation of electrical power, while oxidizing the glucose substrate acting as a fuel. The system provides a model to harness the native photosynthetic apparatus for the conversion of solar light energy into electrical power, using biomass substrates as fuels. In contrast to numerous bioelectrochemical systems using electrical power to oxidize glucose, the present study introduces the implementation of the native photosystem to produce electrical power using light as the energy source. The novel photo-bioelectrochemical cells point to a new method to photonically drive biocatalytic fuel cells while generating electrical power from solar energy. Professor Itamar Willner, at the Hebrew University’s Institute of Chemistry, says, “The study results provide a general approach to assemble photo-bioelectrochemical solar cells with wide implications for solar energy conversion, bioelectrocatalysis, and sensing.” The research was headed at the Hebrew University by Willner, Institute of Chemistry and Minerva Center for Biohybrid Complex Systems, in collaboration with Professor Rachel Nechushtai, Alexander Silberman Institute of Life Sciences and Minerva Center for Biohybrid Complex Systems; and at Ruhr-Universität Bochum, by Professor Wolfgang Schuhmann, Analytical Chemistry, Center for Electrochemical Sciences (CES). Release Date: January 19, 2016 Source: The Hebrew University of Jerusalem
News Article | August 24, 2016
It takes a lot of packaging to squeeze DNA into the nucleus of a cell. The DNA in our chromosomes is packaged into nucleosomes, which consist of about 150 DNA base pairs wrapped around eight-protein spools called histones. “The level of gene packaging in a human nucleus is extreme,” according to Tae-Hee Lee, a chemistry professor at Pennsylvania State University. “Two meters of DNA is packaged into a 10-µm nucleus. That’s the equivalent of about 30 miles of string compacted in a basketball.” Copying or reading the DNA requires getting through all that packaging. Researchers have hypothesized that a path to the DNA opens up during thermally activated spontaneous motions of the histones and DNA. In a session sponsored by the Division of Analytical Chemistry at the ACS national meeting in Philadelphia, Lee described work demonstrating that such motions really do happen. The work also was published earlier this month (J. Phys. Chem. B 2016, DOI:10.1021/acs.jpcb.6b06235). Lee’s group immobilized nucleosomes on a microscope slide and monitored the complexes using a method based on fluorescence resonance energy transfer (FRET). Through a combination of two techniques, the team analyzed the FRET signals to quantify the motions of the histone proteins in the nucleosomes. They found that a protein dimer dissociates from the histone core every three milliseconds and moves back into place within two milliseconds. Modifications of the histone, including acetylation at a particular amino acid, affect these dynamics without significantly altering the histone structure. “It is quite exciting to see these more extensive single-molecule studies on nucleosome dynamics,” said Peter G. Wolynes, a chemistry professor at Rice University, who uses computational methods to study nucleosomes. “The system is central to understanding gene regulation, and its large number of components have made ensemble studies complex. The single-molecule approach allows much greater clarity.” Vasily M. Studitsky, an expert on epigenetics and gene regulation at Fox Chase Cancer Center in Philadelphia, told C&EN: “Although the majority of past studies in the field of epigenetics were focused on nucleosome structure, it seems very likely that future analysis of chromatin dynamics will help to reveal new fascinating mechanisms that simply cannot be detected by current, mostly structure-oriented, technologies.”
News Article | January 31, 2016
Engineered liver tissue could have a range of important uses, from transplants in patients suffering from the organ's failure to pharmaceutical testing. Now scientists report in ACS' journal Analytical Chemistry the development of such a tissue, which closely mimics the liver's complicated microstructure and function more effectively than existing models.