Chemistry News Archive January 2010

Older dental fillings contain form of mercury unlikely to be toxic

A new study on the surface chemistry of silver-colored, mercury-based dental fillings suggests that the surface forms of mercury may be less toxic than previously thought. It appears online in ACS' journal Chemical Research in Toxicology.

In the study, Graham George and colleagues note that mercury-based fillings, also called amalgams, have been used by dentists to repair teeth for well-over a century. In recent decades their use has become controversial because of concerns about exposure to potentially toxic mercury. However, mercury can potentially exist in several different chemical forms, each with a different toxicity. Prior to this report, little was known about how the chemical forms of mercury in dental amalgam might change over time.

Using a special X-ray technique, the scientists analyzed the surface of freshly prepared metal fillings and compared these with the surface of aged fillings (about 20 years old) from a dental clinic. Fresh fillings contained metallic mercury, which can be toxic. Aged fillings, however, typically contain a form of mercury, called beta-mercuric sulfide or metacinnabar, which is unlikely to be toxic in the body. The scientists found that the surfaces of metal fillings seem to lose up to 95 percent of their mercury over time. Loss of potentially toxic mercury from amalgam may be due to evaporation, exposure to some kinds of dental hygiene products, exposure to certain foods, or other factors. The scientists caution that "human exposure to mercury lost from fillings is still of concern."

Chemical Research in Toxicology: "The Chemical Forms of Mercury in Aged and Fresh Dental Amalgam Surfaces" [Chem. Res. Toxicol., 2009, 22 (11), pp 1761?1764; DOI: 10.1021/tx900309c].

Ginkgo herbal medicines may increase seizures in people with epilepsy

Restrictions should be placed on the use of Ginkgo biloba (G. biloba) - a top-selling herbal remedy - because of growing scientific evidence that Ginkgo may increase the risk of seizures in people with epilepsy and could reduce the effectiveness of anti-seizure drugs, a new report concludes. The article appears in ACS' monthly Journal of Natural Products. It also suggests that Ginkgo may have harmful effects in other people after eating raw or roasted Ginkgo seed or drinking tea prepared from Ginkgo leaves.

Eckhard Leistner and Christel Drewke note that consumers use pills, teas, and other products prepared from leaves of the Ginkgo tree to treat a wide array of health problems. Those include Alzheimer's disease and other memory loss, clinical depression, headache, irritable bladder, alcohol abuse, blockages in blood vessels, poor concentration, and dizziness. Scientific concern focuses mainly on one chemical compound in the herb. It is a potentially toxic material known as ginkgotoxin.

They reviewed scientific research on Ginkgo, and found 10 reports indicating that patients with epilepsy who take Ginkgo products face an increased risk of seizures. They note that laboratory studies explain how Ginkgo could have that unwanted effect. Ginkgotoxin seems to alter a chemical signaling pathway in ways that may trigger epileptic seizures. Further evidence showed that Ginkgo can interact with anti-seizure medications and reduce their effectiveness. "Contrary to our own previous assumption, we are now convinced, however, that G. biloba medications and other products can have a detrimental effect on a person's health condition," the report concludes. "It is therefore important that the large number of G. biloba product users and their health care providers be made aware of these risks, in order to enable them to make informed decisions about the use of these preparations."

Journal of Natural Products: "Ginkgo biloba and Ginkgotoxin" [J. Nat. Prod., 2010, 73 (1), pp 86?92; DOI: 10.1021/np9005019].

The secret life of smoke in fostering rebirth and renewal of burned landscape

The innermost secrets of fire's role in the rebirth and renewal of forests and grasslands are being revealed in research that has identified plant growth promoters and inhibitors in smoke. In the latest discovery about smoke's secret life, an international team of scientists are reporting discovery of a plant growth inhibitor in smoke. The study appears in ACS's Journal of Natural Products, a monthly publication.

"Smoke plays an intriguing role in promoting the germination of seeds of many species following a fire," Johannes Van Staden and colleagues point out in the report. They previously discovered a chemical compound in smoke from burning plants that promotes seed germination. Such seeds, which remain in the undercover on forest and meadow floors after fires have been extinguished, are responsible for the surprisingly rapid regrowth of fire-devastated landscapes.

In their new research, the scientists report discovery of an inhibitor compound that may block the action of the stimulator, preventing germination of seeds. They suspect that the compounds may be part of a carefully crafted natural regulatory system for repopulating fire-ravaged landscapes. Interaction of these and other compounds may ensure that seeds remain dormant until environmental conditions are best for germination. The inhibitor thus may delay germination of seeds until moisture and temperature are right, and then take a back seat to the germination promoter in smoke.

Journal of Natural Products: "Butenolides from Plant-Derived Smoke: Natural Plant-Growth Regulators with Antagonistic Actions on Seed Germination" [J. Nat. Prod., Article ASAP; DOI: 10.1021/np900630w].

The fungus among us: An eco-friendly way of decomposing BPA-containing plastic

Just as cooking helps people digest food, pretreating polycarbonate plastic - source of a huge environmental headache because of its bisphenol A (BPA) content - may be the key to disposing of the waste in an eco-friendly way, scientists have found. Their new study is in ACS' Biomacromolecules, a monthly journal.

Mukesh Doble and Trishul Artham note that manufacturers produce about 2.7 million tons of plastic containing BPA each year. Polycarbonate is an extremely recalcitrant plastic, used in everything from screwdriver handles to eyeglass lenses, DVDs, and CDs. Some studies have suggested that the BPA may have a range of adverse health effects, sparking the search for an environmentally safe way of disposing of waste plastic to avoid release of BPA.

The scientists pretreated polycarbonate with ultraviolet light and heat and exposed it to three kinds of fungi - including the fabled white-rot fungus, used commercially for environmental remediation of the toughest pollutants. The scientists found that fungi grew better on pretreated plastic, using its BPA and other ingredients as a source of energy and breaking down the plastic. After 12 months, there was almost no decomposition of the untreated plastic, compared to substantial decomposition of the pretreated plastic, with no release of BPA.

Biomacromolecules: "Biodegradation of Physiochemically Treated Polycarbonate by Fungi" [2010, 11 (1), pp 20?28; DOI: 10.1021/bm9008099].

Consumers over age 50 should consider steps to cut copper and iron intake

With scientific evidence linking high levels of copper and iron to Alzheimer's disease, heart disease, and other age-related disorders, a new report in ACS' Chemical Research in Toxicology suggests specific steps that older consumers can take to avoid build up of unhealthy amounts of these metals in their bodies. "This story of copper and iron toxicity, which I think is reaching the level of public health significance, is virtually unknown to the general medical community, to say nothing of complete unawareness of the public," George Brewer states in the report.

The article points out that copper and iron are essential nutrients for life, with high levels actually beneficial to the reproductive health of younger people. After age 50, however, high levels of these metals can damage cells in ways that may contribute to a range of age-related diseases.

"It seems clear that large segments of the population are at risk for toxicities from free copper and free iron, and to me, it seems clear that preventive steps should begin now." The article details those steps for people over age 50, including avoiding vitamin and mineral pills that contain cooper and iron; lowering meat intake: avoiding drinking water from copper pipes; donating blood regularly to reduce iron levels; and taking zinc supplements to lower copper levels.

Chemical Research in Toxicology: "Risks of Copper and Iron Toxicity during Aging in Humans" [Chem. Res. Toxicol., Article ASAP; December 7, 2009; DOI: 10.1021/tx900338d].

First evidence that blueberry juice improves memory in older adults

Scientists are reporting the first evidence from human research that blueberries - one of the richest sources of healthful antioxidants and other so-called phytochemicals - improve memory. They said the study establishes a basis for comprehensive human clinical trials to determine whether blueberries really deserve their growing reputation as a memory enhancer. A report on the study appears in ACS' Journal of Agricultural and Food Chemistry, a bi-weekly publication.

Robert Krikorian and colleagues point out that previous studies in laboratory animals suggest that eating blueberries may help boost memory in the aged. Until now, however, there had been little scientific work aimed at testing the effect of blueberry supplementation on memory in people.

In the study, one group of volunteers in their 70s with early memory decline drank the equivalent of 2-2 l/2 cups of a commercially available blueberry juice every day for two months. A control group drank a beverage without blueberry juice. The blueberry juice group showed significant improvement on learning and memory tests, the scientists say. "These preliminary memory findings are encouraging and suggest that consistent supplementation with blueberries may offer an approach to forestall or mitigate neurodegeneration," said the report. The research involved scientists from the University of Cincinnati, the U.S. Department of Agriculture, and the Canadian department of agriculture.

Journal of Agricultural and Food Chemistry: "Blueberry Supplementation Improves Memory in Older Adults" [J. Agric. Food Chem., Article ASAP, January 4, 2010; DOI: 10.1021/jf9029332].

An electrifying advance toward tomorrow's power suits

Could powering an iPod or cell phone become as easy as plugging it into your tee shirt or jeans, and then recharging the clothing overnight? Scientists in California are reporting an advance in that direction with an easier way of changing ordinary cotton and polyester into "conductive energy textiles" - e-Textiles that double as a rechargeable battery. Their report on the research appears in ACS' Nano Letters, a monthly journal.

"Wearable electronics represent a developing new class of materials with an array of novel functionalities, such as flexibility, stretchability, and lightweight, which allow for many applications and designs previously impossible with traditional electronics technology," Yi Cui and colleagues note. "High-performance sportswear, wearable displays, new classes of portable power, and embedded health monitoring systems are examples of these novel applications."

The report describes a new process for making E-textiles that uses "ink" made from single-walled carbon nanotubes - electrically conductive carbon fibers barely 1/50,000 the width of a human hair. When applied to cotton and polyester fabrics, the ink produced e-Textiles with an excellent ability to store electricity. The fabrics retained flexibility and stretchability of regular cotton and polyester, and kept their new e-properties under conditions that simulated repeated laundering.

Nano Letters: "Stretchable, Porous, and Conductive Energy Textiles" [Nano Lett., Article ASAP; January 5, 2010; DOI: 10.1021/nl903949m].

School classroom air may be more polluted with ultrafine particles than outdoor air

The air in some school classrooms may contain higher levels of extremely small particles of pollutants - easily inhaled deep into the lungs - than polluted outdoor air, scientists in Australia and Germany are reporting in an article in ACS' semi-monthly journal Environmental Science & Technology.

Lidia Morawska and colleagues note increasing concern in recent years over the health effects of airborne ultrafine particles. Evidence suggests that they can be toxic when inhaled into the lungs. Much of the scientific research, however, has focused on outdoor sources of these invisible particles, particularly vehicle emissions. Little research has been done, however, on indoor sources, and even less on ultrafine particles in school classrooms.

In an effort to fill those gaps in knowledge, the scientists studied levels of ultrafine particles in 3 elementary school classrooms in Brisbane, Australia. They found that on numerous occasions ultrafine particle levels in the classrooms were significantly higher than outdoors. The highest levels occurred during art activities such as gluing, painting and drawing when indoor levels were several times higher than outdoor levels. There also were significant increases in ultrafine particle levels when detergents were used for cleaning.

Environmental Science & Technology: "Ultrafine Particles in Indoor Air of a School: Possible Role of Secondary Organic Aerosols" [Environ. Sci. Technol., 2009, 43 (24), pp 9103?9109; DOI: 10.1021/es902471a].

Toward a less expensive version of the anti-flu drug Tamiflu

Scientists have developed an alternative method for producing the active ingredient in Tamiflu?, the mainstay for fighting H1N1 and other forms of influenza. The new process could expand availability of the drug by reducing its cost, which now retails for as about $8 per dose. Their study is in ACS' Organic Letters, a bi-weekly journal.

Anqi Chen, Christina Chai and colleagues note that the global pandemic of H1N1 has resulted in millions of infected cases worldwide and nearly 10,000 deaths to date. Tamiflu?, also known as oseltamivir phosphate, remains the most widely used antiviral drug for the prevention and treatment of H1N1 infections as well as bird flu and seasonal influenzas. But growing demand for the drug has put pressure on the supply of shikimic acid, the raw material now used in making the drug. "As a result, chemists worldwide including ourselves have explored the possibility of using other alternative raw materials for the synthesis of the drug" said Chen and Chai, who led the research.

The scientists describe a new process for making the drug that does not use shikimic acid. They found that D-ribose, a naturally-occurring sugar produced by fermentation in large scales, potentially provides an inexpensive and abundant source of starting material for making the drug. D-ribose costs only about one-sixth as much as shikimic acid. In lab studies, the scientists demonstrated the potential use of D-ribose as an alternative source for the synthesis of Tamiflu?.

Organic Letters: "Efficient Formal Synthesis of Oseltamivir Phosphate (Tamiflu) with Inexpensive D-Ribose as the Starting Material" [Org. Lett., 2010, 12 (1), pp 60?63; DOI: 10.1021/ol9024716].

Unlocking the mystery of the duck-billed platypus' venom

Abandon any notion that the duck-billed platypus is a soft and cuddly creature - maybe like Perry the Platypus in the Phineas and Ferb cartoon. This platypus, renowned as one of the few mammals that lay eggs, also is one of only a few venomous mammals. The males can deliver a mega-sting that causes immediate, excruciating pain, like hundreds of hornet stings, leaving victims incapacitated for weeks. Now scientists are reporting an advance toward deciphering the chemical composition of the venom, with the first identification of a dozen protein building blocks. Their study is in the Journal of the American Chemical Society, a weekly publication.

Masaki Kita, Daisuke Uemura, and colleagues note that spurs in the hind limb of the male platypus can deliver the venom, a cocktail of substances that cause excruciating pain. The scientists previously showed that the venom triggers certain chemical changes in cultured human nerve cells that can lead to the sensation of pain. Until now, however, scientists did not know the exact components of the venom responsible for this effect.

To unlock its secrets, the scientists collected samples of platypus venom and used high-tech analytical instruments to separate and characterize its components. They identified 11 new peptides, or protein subunits, in the venom. Studies using nerve cells suggest that one of these substances, called Heptapeptide 1, is the main agent responsible for triggering pain. The substance appears to work by interacting with certain receptors in the nerve cells, they suggest.

Journal of the American Chemical Society: "Duck-Billed Platypus Venom Peptides Induce Ca²⁺ Influx in Neuroblastoma Cells" [J. Am. Chem. Soc., 2009, 131 (50), pp 18038?18039; DOI: 10.1021/ja908148z].

New biomarkers for predicting the spread of colon cancer

Scientists in China are reporting discovery of two proteins present in the blood, of people with colon cancer that may serve as the potential biomarkers for accurately predicting whether the disease will spread. Their study is in ACS' Journal of Proteome Research, a monthly publication.

Maode Lai and colleagues note that in 2008, 150,000 new cases of colon cancer and over 50,000 deaths from the disease occurred in the United States alone. Surgery is the main method of treating the disease. However, half of colon cancer patients undergoing surgery develop a recurrence of the disease within 5 years due to its spread, or metastasis, to other parts of the body. The spread of colon cancer can be difficult to detect and there are currently no reliable chemical markers in the body for predicting its spread, the scientists say.

In an effort to identify useful biomarkers for tracking the spread of colon cancer, the scientists compared proteins produced by primary, or original, tumor cells to those of metastasized cells came from a single individual with colon cancer. They identified two proteins that occurred at significantly higher levels in the metastatic cells than in the primary cancer cells. The two proteins could serve as potential biomarkers in a blood test for predicting the spread of colon cancer, allowing earlier intervention and treatment, the scientists say.

Journal of Proteome Research: "Identification of serum biomarkers for colorectal cancer metastasis using a differential secretome approach" [J. Proteome Res., 2010, 9 (1), pp 545?555; DOI: 10.1021/pr9008817].

China stakes claim as global center for scientific research

Contrary to popular belief, China is doing much more than exporting clothing, toys, electronics, and other popular consumer goods. The country is on a scientific roll, to the point where it could conceivably be regarded as the emerging global center for scientific research, a new report indicates. It describes an amazing growth in chemical patenting and publishing that could bring new and innovative products to the world market ranging from pharmaceuticals to microchips, according to an article in the current issue of Chemical & Engineering News, (C&EN) ACS' weekly newsmagazine.

C&EN Senior Editor Sophie L. Rovner reports that China in 2009 became the world leader in the number of chemistry patent applications published annually. China published 67,000 patent applications in 2009, compared to 52,000 for Japan and 41,000 for the United States. Publication of scientific papers originating in China increased faster than any other nation during the last 10 years. The output of papers with Chinese authors more than quadrupled - from 20,000 papers in 1998 to more than 112,000 in 2008. The publication of U.S. scientific papers rose by barely 30 percent during that period.

In achieving this growth, scientists in China are embracing collaborators in the U.S. and other countries. It is becoming increasingly clear that the country is changing the "world map of research," with China conceivably at its center, the article suggests.

Chemical & Engineering News: "China Ascendant" [Volume 88, Number 2pp. 35-37].

'Nanodragster' races toward the future of molecular machines

Scientists in Texas are reporting the development of a "nanodragster" that may speed the course toward development of a new generation of futuristic molecular machines. The vehicle - only 1/50,000th the width of a human hair - resembles a hot-rod in shape and can outperform previous nano-sized vehicles. Their report is in ACS' Organic Letters, a bi-weekly journal.

James Tour, Kevin Kelly and colleagues note that the ability to control the motion of small molecules is essential for building much-anticipated molecular machines. Some of these machines may find use in manufacturing computer circuits and other electronic components in the future. Scientists have already made strides by designing nano-sized vehicles, including a "nanocar" with wheels made of buckyballs - spheres of carbon containing 60 atoms apiece. The car can scoot around a gold surface when exposed to heat or an electric field gradient. But control of its movement is limited. These drawbacks prevent its widespread use. But the most limiting factor is the nanoscopic resolution tools available for studying their range of motions and capabilities.

The new vehicle addresses some of these problems. The front end has a smaller axle and wheels made of special materials that roll easier. The rear wheels sport a longer axle but are still made of buckyballs, which provide strong surface grip. These changes result in a "nanodragster" that can operate at lower temperatures than a regular nanocar and possibly has has better agility, paving the way for better molecular machines, the scientists say.

Organic Letters: "Molecular Machinery: Synthesis of a Nanodragster" [Org. Lett., 2009, 11 (24), pp 5602?5605; DOI: 10.1021/ol902312m].

Nitric oxide-releasing wrap for donor organs and cloth for therapeutic socks

Scientists in Texas are reporting development of a first-of-its-kind cloth that releases nitric oxide gas - an advance toward making therapeutic socks for people with diabetes and a wrap to help preserve organs harvested for transplantation. The study is in ACS' Chemistry of Materials, a bi-weekly journal.

Kenneth Balkus and Harvey Liu note in the new study that nitric oxide (NO) helps increase blood flow and regulates a range of other body functions. Scientists have tried for years to find practical ways to store and deliver NO for use in medicine. However, they have had difficulty finding a suitable material that allows controlled delivery of NO. Recent studies suggested that zeolites could work. These porous materials soak up and store large amounts of gases like NO.

The scientists describe development of a new bandage composed of nitric oxide-absorbing zeolites embedded in a special water-repellant polymer. In experiments with laboratory rats, the bandage slowly released nitric oxide and increased blood flow. "The bandage could be used to wrap a donor organ ensuring intimate contact and direct delivery of nitric oxide," the report states. "Additionally, these interwoven fabrics could also find applications in smart textiles such as NO-releasing socks for diabetic patients, who have been shown to produce less nitric oxide than healthy patients."

Chemistry of Materials: "Novel Delivery System for the Bioregulatory Agent Nitric Oxide" [Chem. Mater., 2009, 21 (21), pp 5032?5041; DOI: 10.1021/cm901358z].

Coal from mass extinction era linked to lung cancer mystery

The volcanic eruptions thought responsible for Earth's largest mass extinction - which killed more than 70 percent of plants and animals 250 million years ago - is still taking lives today. That's the conclusion of a new study showing, for the first time, that the high silica content of coal in one region of China may be interacting with volatile substances in the coal to cause unusually high rates of lung cancer. The study, which helps solve this cancer mystery, appears in ACS' Environmental Science & Technology, a semi-monthly publication.

David Large and colleagues note that parts of China's Xuan Wei County in Yunnan Province have the world's highest incidence of lung cancer in nonsmoking women - 20 times higher than the rest of China. Women in the region heat their homes and cook on open coal-burning stoves that are not vented to the outside. Scientists believe that indoor emissions from burning coal cause cancer, but are unclear why the lung cancer rates in this region are so much higher than other areas. Earlier studies show a strong link between certain volatile substances, called PAHs, in coal smoke and lung cancer in the region.

The scientists found that coal used in parts of Xuan Wei County had about 10 times more silica, a suspected carcinogen, than U.S. coal. Silica may work in conjunction with PAHs to make the coal more carcinogenic, they indicate. The scientists also found that this high-silica coal was formed 250 million years ago, at a time when massive volcanic eruptions worked to deposit silica in the peat that formed Xuan Wei's coal.

Environmental Science & Technology: "Silica-Volatile Interaction and the Geological Cause of the Xuan Wei Lung Cancer Epidemic" [Environ. Sci. Technol., 2009, 43 (23), pp 9016?9021; DOI: 10.1021/es902033j].

More evidence on benefits of high blood pressure drugs in diabetic eye disease

Scientists in Massachusetts are reporting new evidence that certain high blood pressure drugs may be useful in preventing and treating diabetic retinopathy, the leading cause of vision loss in people with diabetes. The study, the largest to date on proteins in the retina, could lead to new ways to prevent or treat the sight-threatening disease, they say. The findings are in ACS' Journal of Proteome Research, a monthly publication.

Edward Feener and colleagues point out that diabetic retinopathy is a common complication of diabetes, which affects millions of people worldwide. It involves damage to blood vessels in the retina, the light sensitive tissue in the back of the eye. Previous studies suggested that drugs used to treat high blood pressure, including ACE inhibitors and angiotensin receptor blockers (ARBs), may help prevent the condition.

The scientists analyzed proteins from the retinas laboratory mice with normal blood pressure and diabetes and compared them to those of non-diabetic mice. They identified 65 abnormal proteins in the diabetic mice out of more than 1,700 proteins in the study. Treatment with the ARB medication, candesartan, prevented the abnormal changes in more than 70 percent of the proteins.

Journal of Proteome Research: "Angiotensin AT1 receptor antagonism ameliorates murine retinal proteome changes induced by diabetes" [J. Proteome Res., 2009, 8 (12), pp 5541?5549; DOI: 10.1021/pr9006415].