Monday, February 13, 2012

Chemists reveal how algae delete unwanted 'competitors'

Like a 'molecular toothbrush', which removes other thoroughly, every morning this chemical mace 'disinfects' the ground on which these diatoms grow. "Thus they can ideally grow and keep direct competitors for light and free space in check," Professor Dr. Georg Pohnert of the Friedrich Schiller University Jena (Germany) states. The director of the Institute of Inorganic and revealed together with his team and colleagues of the University Ghent (Belgium) the chemical devastating blow of the diatoms. Their findings were published in the new edition of the well known science magazine .

Cyanogen bromide is a highly poisonous metabolic toxin and is – amongst other things – being used for the lixiviating of gold ores. During the First World War it was also used as a chemical weapon. "Until now it wasn't even known that this poison occurs in the living nature at all," says Professor Pohnert. For "Nitzschia cf pellucida" the production of cyanogen bromide seems to be easy though. As soon as the first rays of sunlight find their way into the water, the cellular 'devil's workshop' starts to work. "From two up to four hours after day break the concentration of the released cyanogen bromide is at its highest, later on it decreases," Professor Pohnert explains one of the results of his new study.

The scientists can still only speculate about the fact that the poison doesn't harm the diatoms themselves. One thing is for sure: While the 'competing' algae give up after two hours at most, subsequent to being attacked by cyanogen bromide the poison at the same time doesn't harm Nitzschia cf pellucida. To find the reasons for this is one of the next research objectives of the Jena scientists and their Belgian partners.

But according to chemist Pohnert this would be pure basic research. Cyanogen bromide is completely inapplicable to practical use – for instance as a means against unwanted algae growth. Because it is certain that in this case it is not only the that would be damaged.

More information: Vanelslander B et al.: Daily bursts of biogenic cyanogen bromide (BrCN) control biofilm formation around a marine benthic diatom. PNAS 2012, doi:10.1073/pnas.1108062109

Provided by Friedrich-Schiller-Universitaet Jena

MSU technology spin-out company to market portable biohazard detection

Food contamination and other biohazards present a growing public health concern, but consumes precious time. The company, nanoRETE, will develop and commercialize an inexpensive test for handheld to detect a broad range of threats such as E.coli, Salmonella, and tuberculosis.

A significant leap forward in detection and diagnostic technology, it utilizes novel with magnetic, polymeric and developed by Evangelyn Alocilja, MSU professor of biosystems and agricultural engineering and chief scientific officer of nanoRETE.

“Our unique preparation, extraction and detection protocol enables the entire process to be conducted in the field, without significant training,” Alocilja said. “Results are generated in about an hour from receipt of sample to final readout, quickly identifying contaminants so that proper and prompt actions can be taken.”

The mobile technology comes at only a fraction of the cost of the closest currently available competing technology, company officials said.

“Although the technology originates from research for biodefense applications, its potential reaches far beyond the initial scope,” said Fred Beyerlein, CEO of nanoRETE. “Our X-MARK platform-based technology has the ability to detect multiple or toxins at one time, in a rapid, point-of-use, cost-effective manner. Imagine the potential applications for food growers, packagers or sellers. Contaminated food or water could be quickly identified, isolated and resolved before reaching the ultimate consumer – you or me.”

nanoRETE is backed by Michigan Accelerator Fund I, a Grand Rapids, Mich., investment partnership focused on Michigan-based early stage life science and technology companies.

“Our task was to find promising technologies, identify strong management and support with investment dollars,” MAF-1 managing director Dale Grogan said. “We reviewed literally hundreds of technologies developed within MSU and determined that this particular technology best fit our investment model. We are excited about nanoRETE’s future and hope this is the first of many companies we help develop with MSU.”

“We have had great faith that Dr. Alocilja’s work in nano-scale detection would be a very successful platform on which to start a new company,” said Charles Hasemann, executive director of MSU Technologies. “MAF-1 has been a great partner in building nanoRETE. With its partnership and investment, we expect to move rapidly to a marketable product.”

Provided by Michigan State University (news : web)

Of microchemistry and molecules: Electronic microfluidic device synthesizes biocompatible probes

The research team, led by Professors R. Michael van Dam and Pei Yuin Keng in UCLA’s Crump Institute for Molecular Imaging and Professor CJ Kim in the Mechanical and Aerospace Engineering Department, faced a particularly challenging issue in developing their digital microfluidic device and applying it to microscale chemical synthesis. “When working with organic solvents at small volume scales – especially those that are volatile – evaporation is a significant problem in the relatively open configuration of EWOD chips,” van Dam tells “Unwanted evaporation can change concentrations, dry the sample, and so on, leading to imprecise control over the chemical process and low reproducibility of the chemistry. Our main challenge was in overcoming this effect.”

Controlling liquids via electrowetting is very attractive due to the absence of moving parts, as well as the ease of integrating droplet actuation with heating and sensing. “It had been shown a few years ago that organic solvents can be manipulated on the same chips as water droplets, although not exactly by pure electrowetting,” van Dam continues. “Indeed, we didn’t have any problems moving droplets. Rather, the main operational challenges we encountered were related to on-chip mixing of liquids with solid residues, and the well-controlled evaporation of solvents at temperatures above the solvent boiling point.” This is due to the fact that under such superheated conditions, liquids can undergo bumping – the bursting of droplets and loss of reagents out of the chip.

The team explored a number of ideas to address the issue of undesired evaporation during reaction steps. “Altering the chip and droplet geometry to limit evaporation was somewhat effective, but also adversely impacted the ability to evaporate solvents during steps where evaporation was actually desired,” van Dam explains. Replenishing the solvent by loading additional droplets is a promising approach – but other technical challenges would then need to be addressed, such as how to avoid a drop in reaction temperature when a new droplet is added, and how to effectively mix the incoming droplet with the existing reaction mixture.

“The real breakthrough in the application we presented was realizing that we could alter the solvent without encountering the same difficulties associated with doing so at the macroscale. Since our reaction volume is so small, we could effectively evaporate dimethyl sulfoxide (DMSO) – a very non-volatile solvent – at a modest temperature.” At the macroscale, DMSO is typically avoided because it is very difficult to remove quickly – a concern in certain applications where synthesis time is critical, such as synthesis of positron emission tomography (PET) probes – and more volatile solvents are selected instead. However, van Dam points out, for some applications, the length of time would be less critical – for example, chemical and pharmaceutical production processes can take days, weeks or months.

Moreover, adds van Dam, the team is developing several additional innovations to enhance the current experimental design. “One area we’re working on is increasing the level of automation,” van Dam illustrates. “Once the droplets of chemicals are on-chip, they’re manipulated electronically, so sophisticated sequences of operations can readily be automated. In contrast,” he continues, “in our proof-of-concept synthesis chip, the necessary steps of adding reagents to the chip and extracting the final product are performed by pipetting or other manually-operated techniques. Increased overall automation is therefore critical to making the platform user-friendly and safe.

Another area of investigation is in situ sensing of liquid droplets. “With a very simple modification of the EWOD voltage driving circuit, it’s possible to monitor the AC current through the droplet, says van Dam. “This small current gives information about impedance, which in turn is related to droplet volume and composition. Other groups have shown how verifying that droplets have actually moved as instructed can increase the fidelity of on-chip assays and we’re planning to extend this principle to verify that the correct liquid is in the correct location and to perform real-time monitoring of chemical process variables.” This could be used, for example, to increase the reliability of on-chip microchemical production or provide an integrated readout for a chemical assay.

Van Dam also notes that microscale will eventually transition to nanoscale. “There are research efforts underway to shrink the size of electrodes and droplets handled by EWOD microfluidic devices to subnanoliter volumes. The microchemistry principles we presented could likely be scaled down to operate on these devices.”

On the other hand, van Dam points out that an in silico simulation model would be difficult to derive, given the current general lack of understanding of microscale chemistry in droplets. “For example,” he relates to PhysOrg, “one surprising result we observed was the need to use somewhat higher reagent concentrations in droplets compared to what is normally used at the macroscale to achieve comparable reaction yields. Our microchemistry platform could perhaps be used to study microscale chemistry and gather data that could lead to development of a simulation.”

One of the next steps in the group’s work is to increase the level of automation as mentioned above. “We envision a compact, benchtop system that, if loaded with the right reagents, could produce a variety of compounds on demand at the push of a button. We’re also pursuing applications of this device – in particular for the production of PET probes. Unlike most chemicals which can be produced in large batches and stored, these compounds are short-lived and require production just prior to use for medical imaging.” Currently, the production of PET probes requires expensive, complicated, and bulky equipment and infrastructure.

“Commercial networks of radiopharmacies have invested in this equipment and produce and ship the probes daily to supply hospitals, imaging centers, and research labs,” van Dam adds. “Making large batches that are divided among numerous customers provides economy of scale that makes these probes affordable, but at a cost – these radiopharmacies provide only a small number of different probes. But as we move into an era of personalized medicine, it will become increasingly important to have a diversity of diagnostic probes available so that patients can be matched to the correct drugs.” Compact, inexpensive, benchtop chemistry systems could be transformative, in that clinicians and researchers could afford to produce exactly the probes they want, when they want.

 Van Dam also points out that although these techniques have been demonstrated in the context of medical diagnostics, many different areas could also be served by performing microchemistry on EWOD. “Small scale could be useful to chemists doing natural products synthesis, where reagents and intermediates can be very costly due to the large number of reaction steps, and time, needed to produce them,” he adds. “It’s also likely that the ability to handle chemicals and organic solvents on-chip could lead to new assays in a variety of areas such as contaminant detection, environmental monitoring, and quality control in chemical production.” The techniques might also be useful for optofluidics due to the use of organic and high-index liquids in such devices.

“EWOD chips enable programmable control of liquids and thus a single chip design may be capable of supporting a wide range of reactions and assays with only software changes,” van Dam concludes. “By not having to produce a different chip for each application, cost could be substantially reduced.”

More information: Micro-chemical synthesis of molecular probes on an electronic microfluidic device. PNAS January 17, 2012 vol. 109 no. 3 690-695, doi: 10.1073/pnas.1117566109

Copyright 2012
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Grafted watermelon plants take in more pesticides

Mehmet Isleyen and colleagues explain that farmers watermelon and other fruits onto the roots of gourd plants because it makes the fruit more resistant to diseases. In Turkey, where the group did the study, more than 95 percent of watermelons grow from grafted seedlings. Although the gourds are hardier, previous research has shown they accumulate pesticides called organochlorines. Organochlorines have been widely banned because of concerns about their effects on and wildlife. Despite the fact that their remnants can linger in the soil for decades, some organochlorines remain in use. While traditional watermelon plants do not take up these compounds, the researchers wanted to resolve uncertainty about watermelon grown on the roots of plants in the squash family.

The group grew common Turkish watermelon-squash graft in soil taken from a farming region there. They tested the roots, stems, leaves and fruit of the plants and found that organochlorine levels were as much as 140 times higher in the stems of squash-grafted watermelons than in intact watermelons. However, while still urging caution, the group notes that these levels are 6-12 times lower than accepted limits of the pesticides in produce in the U.S. and Turkey.

More information: Accumulation of Weathered p,p'-DDTs in Grafted Watermelon, J. Agric. Food Chem., Article ASAP. DOI:10.1021/jf204150s

The grafting of melon plants onto cucurbit rootstocks is a common commercial practice in many parts of the world. However, certain cucurbits have been shown to accumulate large quantities of weathered persistent organic pollutants from the soil, and the potential contamination of grafted produce has not been thoroughly evaluated. Large pot and field experiments were conducted to assess the effect of grafting on accumulation of weathered DDX (the sum of p,p'-DDT, p,p'-DDD, and p,p'-DDE) from soils. Intact squash (Cucurbita maxima × moschata) and watermelon (Citrullus lanatus), their homografts, and compatible heterografts were grown in pots containing soil with weathered DDX at 1480–1760 ng/g soil or under field conditions in soil at 150–300 ng/g DDX. Movement of DDX through the soil–plant system was investigated by determining contaminant levels in the bulk soil and in the xylem sap, roots, stems, leaves, and fruit of the grafted and nongrafted plants. In all plants, the highest DDX concentrations were detected in the roots, followed by decreasing amounts in the stems, leaves, and fruit. Dry weight concentrations of DDX in the roots ranged from 7900 ng/g (intact watermelon) to 30100 ng/g (heterografted watermelon) in the pot study and from 650 ng/g (intact watermelon) to 2430 ng/g (homografted squash) in the field experiment. Grafting watermelon onto squash rootstock significantly increased contaminant uptake into the melon shoot system. In the pot and field studies, the highest stem DDX content was measured in heterografted watermelon at 1220 and 244 ng/g, respectively; these values are 140 and 19 times greater than contaminant concentrations in the intact watermelon, respectively. The xylem sap DDX concentrations of pot-grown plants were greatest in the heterografted watermelon (6.10 µg/L). The DDX contents of the leaves and fruit of watermelon heterografts were 3–12 and 0.53–8.25 ng/g, respectively, indicating that although the heterografted watermelon accumulated greater pollutant levels, the resulting contamination is not likely a food safety concern.

Provided by American Chemical Society (news : web)

How seawater could corrode nuclear fuel

But Navrotsky and others have since discovered a new way in which seawater can corrode nuclear fuel, forming uranium compounds that could potentially travel long distances, either in solution or as very small particles. The research team published its work Jan. 23 in the journal .

"This is a phenomenon that has not been considered before," said Alexandra Navrotsky, distinguished professor of ceramic, earth and environmental . "We don't know how much this will increase the rate of corrosion, but it is something that will have to be considered in future."

Japan used seawater to avoid a much more serious accident at the Fukushima-Daiichi plant, and Navrotsky said, to her knowledge, there is no evidence of long-distance from the plant.

Uranium in nuclear fuel rods is in a chemical form that is "pretty insoluble" in water, Navrotsky said, unless the uranium is oxidized to uranium-VI — a process that can be facilitated when radiation converts water into peroxide, a powerful oxidizing agent.

Peter Burns, professor of civil engineering and geological sciences at the University of Notre Dame and a co-author of the new paper, had previously made spherical uranium peroxide clusters, rather like carbon "buckyballs," that can dissolve or exist as solids.

In the new paper, the researchers show that in the presence of alkali metal ions such as sodium — for example, in seawater — these clusters are stable enough to persist in solution or as small particles even when the oxidizing agent is removed.

In other words, these clusters could form on the surface of a fuel rod exposed to and then be transported away, surviving in the environment for months or years before reverting to more common forms of uranium, without peroxide, and settling to the bottom of the ocean. There is no data yet on how fast these uranium peroxide clusters will break down in the environment, Navrotsky said.

Provided by University of California - Davis