Researchers discover a new class of magic atomic clusters called superhalogens

 

An international team of researchers has discovered a new class of magnetic superhalogens – a class of atomic clusters able to exhibit unusual stability at a specific size and composition, which may be used to advance materials science by allowing scientists to create a new class of salts with magnetic and super-oxidizing properties not previously found.

The discovery, which was published Feb. 10 in the Early View issue of the international chemistry journal Angewandte Chemie International Edition, was based on theoretical work by researchers from Virginia Commonwealth University, McNeese State University, and Peking University in China, and experimental work at Johns Hopkins University.

Unlike conventional superhalogens that are composed of a metal atom at the core and surrounded by halogen atoms, the magnetic superhalogens discovered by this team are composed of stoichiometric metal-halogen moieties at the core to which an additional halogen is attached.

The new chemical species known as magnetic superhalogens mimic the chemistry of halogens which are a class of elements from the periodic table, namely, iodine, astatine, bromine, fluorine and chlorine. The word halogen means "salt-former," and when one of the elements above combines with sodium, they can form a salt.

Specifically, the cluster is MnxCl2x+1, where x = 1, 2, 3, and so on, have manganese and chlorine atoms as a core to which only one chlorine atom is attached. The manganese atoms carry a large magnetic moment and therefore make these superhalogens magnetic.

"One can now design and synthesize yet unknown magnetic superhalogens by changing the metal atom from manganese to other transition metal atoms and changing chlorine to other halogen atoms. In addition to their use as oxidizing agents, being magnetic opens the door to the synthesis a new class of salts," said lead investigator Puru Jena, Ph.D., distinguished professor of physics at VCU.

According to Jena, superhalogens are like halogens, in the sense they form negative ions, but their affinity to attract electrons is far greater than those of any halogen atoms. Negative ions are useful as oxidizing agents, for purification of air and in serotonin release for uplifting mood.

"Superhalogens can do the same thing as halogens can do, only better," said Jena. "The ability of superhalogens to carry large quantities of fluorine and chlorine can be used for combating biological agents as well."

"In addition, superhalogens, due to their large electron affinity, can involve inner core electrons of metal atoms in chemical reaction, thus fundamentally giving rise to new chemistry," said Jena.

In October, Jena and his colleagues reported the discovery of a new class of highly electronegative chemical species called hyperhalogens, which use superhalogens as building blocks around a metal atom. The chemical species may have application in many industries.

Provided by Virginia Commonwealth University (news : web)

One step closer to chemotherapy with reduced side-effects

Researchers have created a tiny device that triggers reactions in cells.

The technology could enable cancer drugs to be activated at the site of a tumor.

Targeting drug treatment where it is needed could safeguard the rest of the patient’s body.

This approach could help curb side-effects associated with chemotherapy such as hair loss, sickness and weakened immunity.

The device delivers tiny quantities of palladium.

This metal is not naturally found in human cells, but helps to trigger reactions in the cell.

The palladium works without altering everyday cell functions, such as producing proteins and metabolizing energy.

Researchers encased tiny particles of palladium in a harmless coating that is able to enter live cells.

They found that, in the lab, the metal was able to trigger specific reactions in the cell without having any effect elsewhere.

Although the research is at an early stage, scientists believe the technique will allow the therapeutic use of palladium to manipulate cell activity.

This could produce substances, such as drugs, without affecting the rest of the body.

The discovery could pave the way for delivering therapies to where they are needed in the body, scientists say, and could also be used to deliver dyes to organs for diagnostic tests

More information: The study, published in Nature Chemistry, was carried out in collaboration with the Universiti Kebangsaan Malaysia.

Provided by University of Edinburgh

Firefly glow: Scientists develop a safe hydrogen peroxide probe based on firefly luciferin

by Lynn Yarris

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Bioluminescent signal from firefly luciferase lights up mouse 30 minutes after injection with PCL-1, a probe that can be used to monitor hydrogen peroxide levels without harming the animal. (Photo from Christopher Chang group)

(PhysOrg.com) -- A unique new probe based on luciferase, the enzyme that gives fireflies their glow, enables researchers to monitor  hydrogen peroxide levels in mice and thereby track the progression of infectious diseases or cancerous tumors without harming the animals or even having to shave their fur. Developed by researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley, this new bioluminescent probe has already provided the first direct experimental evidence that hydrogen peroxide is continuously made even in a healthy animal.

“We are reporting the design, synthesis, and in vivo applications of Peroxy Caged Luciferin-1 (PCL-1), a chemoselective bioluminescent probe for the real-time detection of hydrogen peroxide within living animals,” says Christopher Chang, a chemist who holds appointments with Berkeley Lab’s Chemical Sciences Division and UC Berkeley’s Chemistry Department, as well as the Howard Hughes Medical Institute.

Chang is the corresponding author of a paper in the Proceedings of the National Academy of Science (PNAS) that describes this research. The paper is titled “In vivo imaging of hydrogen peroxide production in a murine tumor model with a chemoselective bioluminescent reporter.” Co-authoring with Chang were Genevieve Van de Bittner, Elena Dubikovskaya and Carolyn Bertozzi.

The PCL-1 probe consists of a light-emitting luciferin molecule enclosed inside a molecular cage of boronic acid. The boronic acid selectively reacts with hydrogen peroxide molecules to release the luciferin, triggering a bioluminescent response in the presence of firefly luciferase. For their studies, Chang and his co-authors worked with transgenic mice that carried the firefly luciferase gene.

“The high sensitivity and selectivity of the PCL-1 probe for hydrogen peroxide, combined with the favorable properties of bioluminescence for in vivo imaging, afford a unique technology for monitoring physiological fluctuations in hydrogen peroxide levels in real-time,” Chang says. “This offers opportunities to dissect the  disparate contributions of hydrogen peroxide to health, aging and disease.”

Hydrogen peroxide is nature’s disinfectant. Cells produce this small but highly reactive molecule to kill invading pathogens. It also plays a critical role in cellular signaling that is essential to the growth, development and physical well-being of humans and other organisms. However, over-production of hydrogen peroxide in cells is the mark of oxidative stress and inflammation, and has been linked to the onset and advancement of cancer and diabetes, and numerous cardiovascular and neurodegenerative diseases.

Chang and his group have shown that hydrogen peroxide can serve as a highly effective signaling agent for in vivo imaging. To this end, they’ve developed a series of hydrogen peroxide fluorescent tags for tracking small-molecule oxygen metabolites in living cells, tissue and organisms. With their new PCL-1 probe, they were able to study mice with prostate cancers and monitor fluctuations in the hydrogen peroxide generated by cancerous cells based on the amount of light emitted by the probe.

“The PCL-1 probe enables us to study the chemistry in living animals as cancers and other diseases progress,” Chang says. “We can use the probe to look at the same mouse over time to see how see how therapeutics and other treatments affect its physiology, without having to do biopsies or sacrifice the animal. This is a significant advance over previous hydrogen peroxide probes.”

In addition to doing no harm to the animal, Chang and his group wanted a probe that could simultaneously detect hydrogen peroxide signals from multiple regions or the entire organism. They also wanted a probe that could detect intracellular signals, and preferred not having to remove fur or skin to detect a signal from a specific tissue of interest. They elected to pursue bioluminescence because of its favorable properties for in vivo imaging.

“The fact that in nature fireflies use the luciferin enzyme to communicate by light inspired us to adapt this same strategy for pre-clinical diagnostics,” Chang says. “Bioluminescence from the catalytic transformation of firefly luciferin by the firefly luciferase enzyme exhibits a high efficiency for photon production and a 612 nanometer emission frequency that provides a detectable bioluminescent signal in all organs of a mouse. The PCL-1 probe is small enough to travel through a mouse’s body andits red-shifted luminescent reaction with luciferase allows for deep tissue signal penetration with an optical readout.”

Chang and his colleagues are now working to improve the sensitivity of the PCL-1 probe. They would also like to refine their methodology to be able to simultaneously examine multiple biomarkers.

Provided by Lawrence Berkeley National Laboratory (news : web)

Food scientist develops 'rechargeable' anti-microbial surfaces to improve food-handling safety

(Using nano-scale materials, a University of Massachusetts Amherst food scientist is developing a way to improve food safety by adding a thin anti-microbial layer to food-handling surfaces. Only tens of nanometers thick, it chemically "re-charges" its germ-killing powers every time it’s rinsed with common household bleach.

Food scientist Julie Goddard recently received a four-year, $488,000 grant from the United States Department of Agriculture’s Agriculture and Food Research Initiative to lead the development of the new method for modifying polymer and stainless steel processing surfaces by adding a nano-scale layer of antimicrobial compound to gaskets, conveyor belts and work tables, for example.

As she explains, "This layer replenishes its anti-microbial qualities with each repeated bleach rinse. So at the end of the day in a meat-packing plant, for example, when employees clean their equipment, the regular bleach rinse will re-charge the surface’s anti-microbial activity. They will not need to add any more steps." The chemical action comes from a halamine structure that holds chlorine in an applied layer only nanometers thick. The treatment does not affect the strength of tables or trays.

Food production is increasingly automated and as the number of surfaces contacted by food increases, there is greater potential for contamination. Goddard and colleagues’ new method will cost industry less than incorporating anti-microbials into an entire conveyor belt construction, for example. The technique is effective at the square-inch scale in the laboratory now, the food scientist adds, and a major goal will be to show that it can be effective at larger scales in commercial food processing.

Goddard, who did the preliminary work to show that this nanotech method is effective against organisms relevant to food safety and others relevant to food spoilage, such as E. coli and Listeria, says the technology is already being applied in hospital textiles whose anti-microbial properties are replenished each time they’re laundered in bleach.

"It’s not meant to replace thorough cleaning, which should always be in place, but it’s meant to add power to the process and a further layer of low-cost protection against contamination." Goddard’s collaborators on this project include UMass Amherst food scientist Lynne McLandsborough and Joe Hotchkiss, director of the Michigan State University School of Packaging.

Provided by University of Massachusetts Amherst (news : web)

Small molecule may deactivate enemy of cancer-fighting p53

Scientists are conducting a pioneering clinical trial to test the effectiveness in leukemia of a small molecule that shuts down MDM2, a protein that can disable the well-known tumor suppressor p53.

The clinical trial is under way at MD Anderson and five other sites in the United States and United Kingdom.

The first-in-class drug has shown clinical activity in some patients and been well-tolerated, Michael Andreeff, at The University of Texas MD Anderson Cancer Center said.

“P53 can be activated by chemotherapy or radiation, but both of these therapies carry risks of causing secondary tumors,” Andreeff said.

“If we can activate this tumor-suppressor with a method that is non-genotoxic and does not cause damage to a patient”s DNA, we may be able to help avoid secondary tumors caused by other treatments,” he added.

Normally, p53 halts the division of defective cells and forces them to commit suicide or lose the ability to reproduce. However, the tumor suppressor is disabled in many types of cancer, often because of gene mutations or defective signaling.

While mutations of the TP53 gene are rare in cancers of the blood, the p53 protein may be degraded by other factors, including high levels of MDM2, which binds to p53 and orchestrates its degradation.

In preclinical studies, small-molecule MDM2 antagonists called Nutlins were found to be effective in solid tumors, leukemia and lymphoma.

The drug used in this study, RG7112, a novel small molecule being developed by Roche, is a member of the Nutlin family.

Patients with relapsed or refractory acute or chronic leukemia were given RG7112 orally each day for 10 days, followed by 18 days of rest. Forty-seven patients, including 27 with acute myeloid leukemia (AML), have been treated to date.

There has been evidence of clinical activity, and one patient with AML has been leukemia-free for nine months. Reductions in lymph node and spleen size, as well as in circulating leukemia cells, were seen in chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL).

The preliminary results of this ongoing Phase I study were presented at the 52nd Annual Meeting of the American Society of Hematology. (ANI)

Disclaimer: Bioscholar is not intended to provide medical advice, diagnosis or treatment. The articles are based on peer reviewed research, and discoveries/products mentioned in the articles may not be approved by the regulatory bodies.

Green chemistry offers route towards zero-waste production

Novel green chemical technologies will play a key role helping society move towards the elimination of waste while offering a wider range of products from biorefineries, according to a University of York scientist.

Professor James Clark, Director of the University's Green Chemistry Centre of Excellence, will tell a symposium at the Annual meeting of the American Association for the Advancement of Science (AAAS) that the use of low environmental impact green chemical technologies will help ensure that products are genuinely and verifiably green and sustainable.

He says the extraction of valuable chemicals from biomass could form the initial processing step of many future biorefineries.

"We have shown that wax products with numerous applications, can be extracted from crop and other by-products including wheat and barley straws, timber residues and grasses, using supercritical carbon dioxide – a green chemical technology that allows the production of products with no solvent residues," he says.

"The extracted residues can be used in applications including construction as well as in bioprocessing."

Low-temperature microwaves can also be used to pyrolyse biomass, allowing greater control over the heating process. The process results in significant energy savings and produces high quality oils, and oils and solids with useful chemical properties.

Professor Clark says that combining continuous extraction with microwave irradiation, it is possible separate an aqueous phase leaving the oils cleaner, less acidic and with lower quantities of other contaminants such as alkali metals. The oils have significant potential as feedstocks for making chemical products as well as for blending into transport fuels.

"Our microwave technology can also be tuned to produce bio-chars with calorific values and physical properties that make them suitable for co-firing with coal in power-stations," he adds.

More information: Professor Clark will be among the speakers the session 'Biorefinery: Toward an Industrial Metabolism' at the Annual Meeting of the AAAS, Washington, D.C. on Friday, 18 February, 2011.

Provided by University of York