Chemistry News Archive October 2009

Next-generation microcapsules deliver 'chemicals on demand'

Scientists in California are reporting development of a new generation of the microcapsules used in carbon-free copy paper, in which capsules burst and release ink with pressure from a pen. The new microcapsules burst when exposed to light, releasing their contents in ways that could have wide-ranging commercial uses from home and personal care to medicine.

Jean Fr?het, Alex Zettl and colleagues note that liquid-filled microcapsules have many other uses, including self-healing plastics. Those plastics contain one group of microscapsules filled with monomer and another with a catalyst. When scratches rip open the capsules, the contents flow, mix, and form a seal. Microcapsules that burst open when exposed to light would have great advantages, the scientists say. Light could be focused to a pinpoint to kill cancer cells, for instance, or shined over an large area to print a pattern.

The new microcapsules consist of nylon spheres about the size of a grain of sand. They enclose a liquid chemical sprinkled with carbon nanotubes. The nanotubes convert laser light to heat that bursts the nylon capsule, releasing the chemical. Using such a system, doctors, for example, might inject microcapsules containing anti-cancer drugs to specific cells and make the capsules burst upon exposure to laser light, delivering their contents precisely where and when they are needed in the body.

Journal of the American Chemical Society: "Chemicals On Demand with Phototriggerable Microcapsules" [J. Am. Chem. Soc., 2009, 131 (38), pp 13586?13587, DOI: 10.1021/ja905378v].

Pumpkin skin may scare away germs

The skin of that pumpkin you carve into a Jack-o'-Lantern to scare away ghosts and goblins on Halloween contains a substance that could put a scare into microbes that cause millions of cases of yeast infections in adults and infants each year. That's the conclusion of a new study in the current issue of ACS' Journal of Agricultural and Food Chemistry, a bi-weekly publication.

In the study, Kyung-Soo Hahm, Yoonkyung Park and colleagues note that some disease-causing microbes are becoming resistant to existing antibiotics. As a result, scientists worldwide are searching for new antibiotics. Past studies hinted that pumpkin, long used as folk medicine in some countries, might have antibiotic effects.

The scientists extracted proteins from pumpkin rinds to see if the proteins inhibit the growth of microbes, including Candida albicans (C. albicans). That fungus causes vaginal yeast infections, diaper rash in infants, and other health problems. One protein had powerful effects in inhibiting the growth of C. albicans, in cell culture experiments, with no obvious toxic effects. The pumpkin protein could be developed into a natural medicine for fighting yeast infections in humans, the report suggests. The protein also blocked the growth of several fungi that attack important plant crops and could be useful as an agricultural fungicide, they add.

Journal of Agricultural and Food Chemistry: "Antifungal Mechanism of a Novel Antifungal Protein from Pumpkin Rinds against Various Fungal Pathogens" [J. Agric. Food Chem., 2009, 57 (19), pp 9299?9304, DOI: 10.1021/jf902005g].

Knocking nanoparticles off the socks

Scientists in Switzerland are reporting results of one of the first studies on the release of silver nanoparticles from laundering those anti-odor, anti-bacterial socks now on the market. Their findings may suggest ways that manufacturers and consumers can minimize the release of these particles to the environment, where they could harm fish and other wildlife.

In the study, Bernd Nowack and colleagues note that widespread use of silver nanoparticles in consumer products, especially textiles, likely results in the distribution of nanoparticles in lakes and streams. Manufacturers favor silver nanoparticles because of their antibacterial action, which slows the growth of odor-causing bacteria. The scientists studied release of nanoparticles in laundry water from nine different textiles, including different brands of commercially available anti-odor socks. Previous studies laundered socks, but in pure distilled water.

They found that most of the released particles were relatively large and that most came out of the fabrics during the first wash. The total released varied from 1.3 to 35 percent of the total nanosilver in the fabric. Bleach generally did not affect the amount released. "These results have important implications for the risk assessment of silver textiles and also for environmental fate studies of nanosilver, because they show that under certain conditions relevant to washing, primarily coarse silver-containing particles are released," the paper says.

Environmental Science & Technology: "The Behavior of Silver Nanotextiles During Washing" [Environ. Sci. Technol., 2009, 43 (21), pp 8113?8118, DOI: 10.1021/es9018332].

Answering that age-old lament: Where does all this dust come from?

Where does it come from? Scientists in Arizona are reporting a surprising answer to that question, which has puzzled and perplexed generations of men and women confronted with layers of dust on furniture and floors. Most of indoor dust comes from outdoors.

In the study, David Layton and Paloma Beamer point out that household dust consists of a potpourri that includes dead skin shed by people, fibers from carpets and upholstered furniture, and tracked-in soil and airborne particles blown in from outdoors. It can include lead, arsenic and other potentially harmful substances that migrate indoors from outside air and soil. That can be a special concern for children, who consume those substances by putting dust-contaminated toys and other objects into their mouths.

The scientists describe development and use on homes in the Midwest of a computer model that can track distribution of contaminated soil and airborne particulates into residences from outdoors. They found that over 60 percent of house dust originates outdoors. They estimated that nearly 60 percent of the arsenic in floor dust could come from arsenic in the surrounding air, with the remainder derived from tracked-in soil. The researchers point out the model could be used to evaluate methods for reducing contaminants in dust and associated human exposures.

Environmental Science & Technology: "Migration of Contaminated Soil and Airborne Particulates to Indoor Dust" [Environ. Sci. Technol., 2009, 43 (21), pp 8199?8205, DOI: 10.1021/es9003735].

Spider web glue spins society toward new biobased adhesives

With would-be goblins and ghosts set to drape those huge fake spider webs over doorways and trees for Halloween, scientists in Wyoming are reporting on a long-standing mystery about real spider webs: It is the secret of spider web glue. The findings are an advance toward a new generation of biobased adhesives and glues - "green" glues that replace existing petroleum-based products for a range of uses.

Omer Choresh and colleagues note that much research has been done on spider web silk, which rivals steel in its strength. However, scientists know comparatively little about web glue, which coats the silk threads and is among the world's strongest biological glues. Past studies revealed that spiders make web glue from glycoproteins, or proteins bits of sugar attached.

The scientists analyzed web glue from the golden orb weaving spider, noted for spinning intricate webs. They identified two new glycoproteins in the glue and showed that domains of these proteins were produced from opposite strands of the same DNA. "Once the cloned genes are over expressed in systems such as insect or bacterial cell cultures, large-scale production of the glycoprotein can be used to develop a new biobased glue for a variety of purposes," the report notes.

Biomacromolecules: "Spider Web Glue: Two Proteins Expressed from Opposite Strands of the Same DNA Sequence" [Biomacromolecules, 2009, 10 (10), pp 2852?2856 DOI: 10.1021/bm900681w].

A scientific basis the 'golden rule' of pairing wines and foods

Scientists in Japan are reporting the first scientific explanation for one of the most widely known rules of thumb for pairing wine with food: "Red wine with red meat, white wine with fish." The scientists are reporting that the unpleasant, fishy aftertaste noticeable when consuming red wine with fish results from naturally occurring iron in red wine.

Takayuki Tamura and colleagues note that wine connoisseurs established the rule of thumb because of the flavor clash between red wine and fish. They point out, however, that there are exceptions to the rule, with some red wines actually going well with seafood. Until now, nobody could consistently predict which wines might trigger a fishy aftertaste because of the lack of knowledge about its cause.

The scientists asked wine tasters to sample 38 red wines and 26 white wines while dining on scallops. Some of the wines contained small amounts of iron, which varied by country of origin, variety, and vintage. They found that wines with high amounts of iron had a more intensely fishy aftertaste. This fishy taste diminished, on the other hand, when the researchers added a substance that binds up iron. The findings indicate that iron is the key factor in the fishy aftertaste of wine-seafood pairings, the researchers say, suggesting that low-iron red wines might be a good match with seafood.

Journal of Agricultural and Food Chemistry: "Iron Is an Essential Cause of Fishy Aftertaste Formation in Wine and Seafood Pairing" [J. Agric. Food Chem., 2009, 57 (18), pp 8550?8556, DOI: 10.1021/jf901656k].

Advance in 'nano-agriculture': Tiny stuff has huge effect on plant growth

With potential adverse health and environmental effects often in the news about nanotechnology, scientists in Arkansas are reporting that carbon nanotubes (CNTs) could have beneficial effects in agriculture. Their study found that tomato seeds exposed to CNTs germinated faster and grew into larger, heavier seedlings than other seeds. That growth-enhancing effect could be a boon for biomass production for plant-based biofuels and other agricultural products, they suggest.

Mariya Khodakovskaya, Alexandru Biris, and colleagues note that considerable scientific research is underway to use nanoparticles - wisps 1/50,000th the width of a human hair - in agriculture. The goals of "nano-agriculture" include improving the productivity of plants for food, fuel, and other uses.

The scientists report the first evidence that CNTs penetrate the hard outer coating of seeds, and have beneficial effects. Nanotube-exposed seeds sprouted up to two times faster than control seeds and the seedlings weighed more than twice as much as the untreated plants. Those effects may occur because nanotubes penetrate the seed coat and boost water uptake, the researchers state. "This observed positive effect of CNTs on the seed germination could have significant economic importance for agriculture, horticulture, and the energy sector, such as for production of biofuels," they add.

ACS Nano "Carbon Nanotubes Are Able To Penetrate Plant Seed Coat and Dramatically Affect Seed Germination and Plant Growth" [ACS Nano, Article ASAP, DOI: 10.1021/nn900887m].

Glacial melting may release pollutants in the environment

Those pristine-looking Alpine glaciers now melting as global warming sets in may explain the mysterious increase in persistent organic pollutants in sediment from certain lakes since the 1990s, despite decreased use of those compounds in pesticides, electric equipment, paints and other products. That's the conclusion of a new study, scheduled for the Nov. 1 issue of ACS' Environmental Science & Technology, a semi-monthly journal.

In the study, Christian Bogdal and colleagues focused on organic pollutants in sediment from a model body of water ? glacier-fed Lake Oberaar in the Bernese Alps, Switzerland ? testing for the persistent organic pollutants, including dioxins, PCBs, organochlorine pesticides and synthetic musk fragrances. They found that while contamination decreased to low levels in the 1980s and 1990s due to tougher regulations and improvements in products, since the late 1990s flow of all of these pollutants into the lake has increased sharply. Currently, the flow of organochlorines into the lake is similar to or even higher than in the 1960s and 1970s, the report states.

The study attributed the most recent spike in the flow of pollutants into Lake Oberaar to the accelerated release of organic chemicals from melting Alpine glaciers, where contaminants were deposited earlier and preserved over decades. "Considering ongoing global warming and accelerated massive glacial melting predicted for the future, our study indicates the potential for environmental impacts due to pollutants delivered into pristine mountainous areas," Bogdal said.

Environmental Science & Technology: "Blast from the Past: Melting Glaciers as a Relevant Source for Persistent Organic Pollutants" [Environ. Sci. Technol., Article ASAP, DOI: 10.1021/es901628x].

Fabled 'vegetable lamb' plant contains potential treatment for osteoporosis

The "vegetable lamb" plant - once believed to bear fruit that ripened into a living baby sheep - produces substances that show promise in laboratory experiments as new treatments for osteoporosis, the bone-thinning disease. That's the conclusion of a new study in ACS' monthly Journal of Natural Products.

Young Ho Kim and colleagues point out that osteoporosis is a global health problem, affecting up to 6 million women and 2 million men in the United States alone. Doctors know that the secret to strong bones involves a delicate balance between two types of bone cells: Osteoblasts, which build up bone, and osteoclasts, which break down bone.

Seeking potential medications that might tip the balance in favor of bone building, the researchers turned to the "vegetable lamb" plant as part of a larger study plants used in folk medicine in Vietnam. In the 16th and 17th centuries, some of the world's most celebrated scientists believed the plant (Cibotium barmoetz) fruited into a newly born lamb, which then grazed on nearby grass and weeds. Kim's group isolated compounds from C. barmoetz and showed that they blocked formation of bone-destroying osteoclasts formation in up to 97 percent of the cells in laboratory cultures without harmful effects on other cells. The substances "could be used in the development of therapeutic targets for osteoporosis," the article notes.

Journal of Natural Products: "Inhibitors of Osteoclast Formation from Rhizomes of Cibotium barometz" [J. Nat. Prod., 2009, 72 (9), pp 1673?1677; DOI: 10.1021/np9004097].

Heat forms potentially harmful substance in high-fructose corn syrup

Researchers have established the conditions that foster formation of potentially dangerous levels of a toxic substance in the high-fructose corn syrup (HFCS) often fed to honey bees. Their study, which appears in ACS' bi-weekly Journal of Agricultural and Food Chemistry, could also help keep the substance out of soft drinks and dozens of other human foods that contain HFCS. The substance, hydroxymethylfurfural (HMF), forms mainly from heating fructose.

In the new study, Blaise LeBlanc and Gillian Eggleston and colleagues note HFCS's ubiquitous usage as a sweetener in beverages and processed foods. Some commercial beekeepers also feed it to bees to increase reproduction and honey production. When exposed to warm temperatures, HFCS can form HMF and kill honeybees. Some researchers believe that HMF may be a factor in Colony Collapse Disorder, a mysterious disease that has killed at least one-third of the honeybee population in the United States.

The scientists measured levels of HMF in HFCS products from different manufacturers over a period of 35 days at different temperatures. As temperatures rose, levels of HMF increased steadily. Levels jumped dramatically at about 120 degrees Fahrenheit. "The data are important for commercial beekeepers, for manufacturers of HFCS, and for purposes of food storage. Because HFCS is incorporated as a sweetener in many processed foods, the data from this study are important for human health as well," the report states. It adds that studies have linked HMF to DNA damage in humans. In addition, HMF breaks down in the body to other substances potentially more harmful than HMF.

Journal of Agricultural and Food Chemistry: "Formation of Hydroxymethylfurfural in Domestic High-Fructose Corn Syrup and Its Toxicity to the Honey Bee (Apis mellifera)" [J. Agric. Food Chem., 2009, 57 (16), pp 7369?7376; DOI: 10.1021/jf9014526].

Improving China's acid rain control strategy

Scientists are reporting the first evidence that China's sharp focus on reducing widespread damage to soil by acid rain by restricting sulfur dioxide air pollution may have an unexpected consequence: Gains from that pollution control program will be largely offset by increases in nitrogen emissions, which the country's current policy largely overlooks. The study, which suggests that government officials adapt a more comprehensive pollution control strategy that includes a new emphasis on cutting nitrogen emissions, is scheduled for the Nov. 1 issue of ACS' Environmental Science & Technology, a semi-monthly journal.

Lei Duan and colleagues explain that China is trying to stop soil acidification by reducing sulfur dioxide pollution from electric power plant smokestacks. Those emissions cause acid rain, which in turn has made vast areas of farmland more acid and less productive. China's is striving for a 10 percent reduction in sulfur dioxide emissions by 2010, a policy that seems have had only a limited impact so far, the researchers say. However, China has paid little attention to pollution from nitrogen oxides, which also contribute to acid rain and soil contamination.

The scientists' analysis found that the benefits of sulfur dioxide reductions will almost be offset by increased nitrogen emissions. To control this problem, "China needs a multipollutant control strategy that integrates measures to reduce sulfur, nitrogen, and particulate matter," the article notes.

Environmental Science & Technology "Soil Acidification in China: Is Controlling SO₂ Emissions Enough?" [Environ. Sci. Technol., Article ASAP, September 21, 2009].

Some color shades offer better protection against sun?s ultraviolet rays

Economy-minded consumers who want protection from the sun's harmful ultraviolet (UV) rays - but rather not pay premium prices for sun-protective clothing - should think blue and red, rather than yellow. Scientists in Spain are reporting that the same cotton fabric dyed deep blue or red provide greater UV protection than shades of yellow. Their study, which could lead to fabrics with better sun protection, is scheduled for the Nov. 4 issue of ACS' Industrial & Engineering Chemistry Research, a bi-weekly journal.

Ascensi? Riva and colleagues explain that the color of a fabric is one of the most important factors in determining how well clothing protects against UV radiation. Gaps, however, exist in scientific knowledge about exactly how color interacts with other factors to influence a fabric's ability to block ultraviolet protection factor (UPF).

The scientists describe use of computer models that relate the level of UV protection achieved with three fabric dyes to their effects in changing the UPF of fabrics and other factors. In doing so, they dyed cotton fabrics in a wide range of red, blue, and yellow shades and measured the ability of each colored sample to absorb UV light. Fabrics with darker or more intense colors tended to have better UV absorption. Deep blue shades offered the highest absorption, while yellow shades offered the least. Clothing manufacturers could use information from this study to better design sun-protective clothing, the scientists indicate.

Industrial & Engineering Chemistry Research: "Modeling the Effects of Color on the UV Protection Provided by Cotton Woven Fabrics Dyed with Azo Dyestuffs" [Ind. Eng. Chem. Res., Article ASAP; DOI: 10.1021/ie9006694].

Tracking down the human 'odorprint'

Each of the 6.7 billion people on Earth has a signature body odor - the chemical counterpart to fingerprints - and scientists are tracking down those odiferous arches, loops, and whorls in the "human odorprint" for purposes ranging from disease diagnosis to crime prevention.

C&EN Senior Correspondent Ivan Amato points out that police long have used trained dogs to sniff out these uniquely personal scents in pursuing criminals. Scientists now are trying to decipher the chemistry of human odor to develop technology that can detect and classify smells. That's a difficult task, the article says, noting that each person's odorprint is a complex mixture impacted by multiple environmental factors, including diet and cosmetics.

The article describes progress in that direction, explaining that scientists already have identified odors in human breath and skin associated with diabetes, cancer, and other diseases. Scientists are even trying to detect the "smell of deception," or chemical changes that occur with heightened stress that may help screen and identify, for example, terrorists planning to blow up an airplane and criminals intending to rob a bank.

Chemical & Engineering News: "You Smell. All of us have our very own odorprint, and scientists are hot on its trail."