Friday, November 18, 2011

New tool developed for the study of spatial patterns in living cells

 Football has often been called "a game of inches," but biology is a game of nanometers, where spatial differences of only a few nanometers can determine the fate of a cell -- whether it lives or dies, remains normal or turns cancerous. Scientists with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a new and better way to study the impact of spatial patterns on living cells.

Berkeley Lab chemist Jay Groves led a study in which artificial membranes made up of a fluid bilayer of lipid molecules were embedded with fixed arrays of gold nanoparticles to control the spacing of proteins and other cellular molecules placed on the membranes. This provided the researchers with an unprecedented opportunity to study how the spatial patterns of chemical and physical properties on membrane surfaces influence the behavior of cells.

"The gold nanoparticles are similar to the size of a single protein molecule, which gets us to a scale we couldn't really access before," says Groves. "As the first example of a biological membrane platform that combines fixed nanopatterning with the mobility of fluid lipid bilayers, our technique represents an important improvement over previous patterning methods."

Groves holds joint appointments with Berkeley Lab's Physical Biosciences Division and the University of California (UC) Berkeley's Chemistry Department, and is a Howard Hughes Medical Institute (HHMI) investigator. He is the corresponding author of a paper that reports these results in the journal Nano Letters.

Spatial patterning of chemical and physical properties on artificial membranes of lipid bilayers is a time-tested way to study the behavior of cultured biological cells. Natural lipid bilayer membranes surround virtually all living cells as well as many of the structures inside the cell including the nucleus. These membranes provide a barrier that restrains the movement of proteins and other cellular molecules, penning them into their proper locations and preventing them from moving into areas where they do not belong. Past spatial patterning efforts on artificial membranes have been done on an all-or-nothing basis -- proteins placed on a membrane either had complete mobility or were fixed in a static position.

"Immobile patterning intrinsically defeats any cellular process that naturally involves movement," Groves says. "On the other hand we need to be able to impose some fixed barriers in order to manipulate membranes in really novel ways."

Groves is a recognized leader in the development of unique "supported" synthetic membranes that are constructed out of lipids and assembled onto a substrate of solid silica. He and his group have used these supported membranes to demonstrate that living cells not only interact with their environment through chemical signals but also through physical force.

"We call our approach the spatial mutation strategy because molecules in a cell can be spatially re-arranged without altering the cell in any other way," he says.

However, until now Groves and his group were unable to get to the tens of nanometers length-scales that they can now reach by embedding their supported membranes with gold nanoparticles.

"Our new membranes provide a hybrid interface consisting of mobile and immobile components with controlled geometry," Groves says. "Proteins or other cellular molecules can be associated with the fluid lipid component, the fixed nanoparticle component, or both."

The gold nanoparticle arrays were patterned through a self-assembly process that provides controllable spacing between particles in the array in the important range of 50 to 150 nanometers. The gold nanoparticles themselves measure about five to seven nanometers in diameter.

Groves and his team successfully tested their hybrid membranes on a line of breast cancer cells known as MDA-MB-231 that is highly invasive. With their hybrid membranes, the team demonstrated that in the absence of cell adhesion molecules, the membrane remained essentially free of the cancer cells, but when both the nanoparticles and the lipid were functionalized with molecules that promote cell adhesion, the cancer cells were found all over the surface.

Groves and his research group are now using their gold nanoparticle membranes to study both cancer metastasis and T cell immunology. They expect to report their results soon.

Co-authoring the Nano Letters paper with Groves were Theobald Lohmuller, Sara Triffo, Geoff O'Donoghue, Qian Xu and Michael Coyle. This research was supported by the DOE Office of Science.

Story Source:

The above story is reprinted from materials provided by DOE/Lawrence Berkeley National Laboratory.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Theobald Lohmüller, Sara Triffo, Geoff P. O’Donoghue, Qian Xu, Michael P. Coyle, Jay T. Groves. Supported Membranes Embedded with Fixed Arrays of Gold Nanoparticles. Nano Letters, 2011 DOI: 10.1021/nl202847t

Advance toward a breath test to diagnose multiple sclerosis

Hossam Haick and colleagues report that doctors now diagnose MS based on its characteristic symptoms, which include muscle spasms, numbness, coordination problems and slurred speech. One common tool for confirming the diagnosis and making informed decisions on treatment is (MRI) of the brain. Another tool is a or "spinal tap" to analyze the fluid that bathes the brain and spinal cord. But are costly, and lumbar punctures are invasive.

To overcome these obstacles, the researchers have identified that can be associated with MS from exhaled breath. Based on these findings, the researchers developed a new that can diagnose MS by analyzing the determined chemical compounds that appear in the breath of MS patients. Using the developed sensors, the researchers carried out a proof-of-concept clinical study on 34 MS patients and 17 healthy volunteers and found that the developed sensors are just as accurate as a spinal tap but without the pain or the risk of side effects.

"The results presented here open new frontiers in the development of fast, noninvasive and inexpensive medical diagnosis tools for detection of chronic neurological diseases," the scientists stated. "The results could serve as a launching pad for the discrimination between different subphases of stages of multiple sclerosis as well as for the identification of multiple sclerosis patients who would respond well to immunotherapy." A large clinical study with the reported sensors is underway and will be reported in the future.

More information: Detection of Multiple Sclerosis from Exhaled Breath Using Bilayers of Polycyclic Aromatic Hydrocarbons and Single-Wall Carbon Nanotubes, ACS Chem. Neurosci., Article ASAP. DOI: 10.1021/cn2000603

A cross-reactive array of polycyclic aromatic hydrocarbons and single wall carbon nanotube bilayers was designed for the detection of volatile organic compounds (tentatively, hexanal and 5-methyl-undecane) that identify the presence of disease in the exhaled breath of patients with multiple sclerosis. The sensors showed excellent discrimination between hexanal, 5-methyl-undecane, and other confounding volatile organic compounds. Results obtained from a clinical study consisting of 51 volunteers showed that the sensors could discriminate between multiple sclerosis and healthy states from exhaled breath samples with 85.3% sensitivity, 70.6% specificity, and 80.4% accuracy. These results open new frontiers in the development of a fast, noninvasive, and inexpensive medical diagnostic tool for the detection and identification of multiple sclerosis. The results could serve also as a launching pad for the discrimination between different subphases or stages of multiple sclerosis as well as for the identification of multiple sclerosis patients who would respond well to immunotherapy.

Provided by American Chemical Society (news : web)

'Magnetic tongue' ready to help produce tastier processed foods

Antonio Randazzo, Anders Malmendal, Ettore Novellino and colleagues explain that sensing the odor and flavor of food is a very complex process. It depends not only on the combination of ingredients in the food, but also on the taster's emotional state. Trained taste testers eliminate some of the variation, but food processors need more objective ways to measure the sensory descriptor of their products. That's where electronic sensing technologies, like E-noses, come into play.

However, current instruments can only analyze certain food components and require very specific sample preparation. To overcome these shortcomings, Randazzo and Malmendal's team turned to (NMR) to test its abilities as "a magnetic tongue."

The researchers analyzed 18 canned tomato products from various markets with NMR and found that the instrument could estimate most of the tastes assessed by the human taste testers. But the NMR instrument went even farther. By determining the , it showed which compound is related to which sensory descriptor. The researchers say that the "magnetic tongue" has good potential as a rapid, sensitive and relatively inexpensive approach for food processing companies to use.

More information: NMR Spectrometers as “Magnetic Tongues”: Prediction of Sensory Descriptors in Canned Tomatoes, J. Agric. Food Chem., 2011, 59 (20), pp 10831–10838. DOI: 10.1021/jf203803q

The perception of odor and flavor of food is a complicated physiological and psychological process that cannot be explained by simple models. Quantitative descriptive analysis is a technique used to describe sensory features. Nevertheless, the availability of a number of instrumental techniques has opened up the possibility to calibrate the sensory perception. In this frame, we have tested the potentiality of nuclear magnetic resonance spectroscopy as a predictive tool to measure sensory descriptors. In particular, we have used an NMR metabolomic approach that allowed us to differentiate the analyzed samples based on their chemical composition. We were able to correlate the NMR metabolomic fingerprints recorded for canned tomato samples to the sensory descriptors bitterness, sweetness, sourness, saltiness, tomato and metal taste, redness, and density, suggesting that NMR might be a very useful tool for the characterization of sensory features of tomatoes.

Provided by American Chemical Society (news : web)

Highly efficient oxygen catalyst found

The new compound, composed of cobalt, iron and oxygen with other metals, splits oxygen from water (called the Oxygen Evolution Reaction, or OER) at a rate at least an order of magnitude higher than the compound currently considered the gold standard for such reactions, the team says. The compound’s high level of activity was predicted from a systematic experimental study that looked at the catalytic activity of 10 known compounds.

The team, which includes materials science and engineering graduate student Jin Suntivich, mechanical engineering graduate student Kevin J. May and professor Yang Shao-Horn, published their results in Science on Oct. 28.

The scientists found that reactivity depended on a specific characteristic: the configuration of the outermost electron of transition metal ions. They were able to use this information to predict the high reactivity of the new compound — which they then confirmed in lab tests.

“We not only identified a fundamental principle” that governs the OER activity of different compounds, “but also we actually found this new compound” based on that principle, says Shao-Horn, the Gail E. Kendall (1978) Associate Professor of Mechanical Engineering and Materials Science and Engineering.

Many other groups have been searching for more efficient catalysts to speed the splitting of water into hydrogen and oxygen. This reaction is key to the production of hydrogen as a fuel to be used in cars; the operation of some rechargeable batteries, including zinc-air batteries; and to generate electricity in devices called fuel cells. Two catalysts are needed for such a reaction — one that liberates the hydrogen atoms, and another for the — but the oxygen reaction has been the limiting factor in such systems.

Other groups, including one led by MIT’s Daniel Nocera, have focused on similar catalysts that can operate — in a so-called “artificial leaf” — at low cost in ordinary water. But such reactions can occur with higher efficiency in alkaline solutions, which are required for the best previously known catalyst, iridium oxide, as well as for this new compound.

Shao-Horn and her collaborators are now working with Nocera, integrating their catalyst with his artificial leaf to produce a self-contained system to generate hydrogen and when placed in an alkaline solution. They will also be exploring different configurations of the catalyst material to better understand the mechanisms involved. Their initial tests used a powder form of the catalyst; now they plan to try thin films to better understand the reactions.

In addition, even though they have already found the highest rate of activity yet seen, they plan to continue searching for even more efficient materials. “It’s our belief that there may be others with even higher activity,” Shao-Horn says.

Jens Norskov, a professor of chemical engineering at Stanford University and director of the Suncat Center for Interface Science and Catalysis there, who was not involved in this work, says, “I find this an extremely interesting ‘rational design’ approach to finding new catalysts for a very important and demanding problem.”

The research, which was done in collaboration with visiting professor Hubert A. Gasteiger (currently a professor at the Technische Universität München in Germany) and professor John B. Goodenough from the University of Texas at Austin, was supported by the U.S. Department of Energy’s Hydrogen Initiative, the National Science Foundation, the Toyota Motor Corporation and the Chesonis Foundation.
This story is republished courtesy of MIT News (, a popular site that covers news about MIT research, innovation and teaching.

Provided by Massachusetts Institute of Technology (news : web)

A better target for B-cell lymphomas: From a library of MAG antagonists to nanomolar CD22 ligands

This therapy is not a cure, however, and new treatments that kill B-cells through different mechanisms are required, especially for patients with indolent lymphoid malignancies. An alternative clinical target for B-cell is CD22, a B-cell-specific member of the sialic acid binding Ig-like lectin (Siglec) family that recognizes ?2,6-linked sialylated glycans as ligands. When it was demonstrated that B-cell activation can be down-regulated with sialosides, an intensive search for low-molecular-weight high-affinity was initiated.

A collaborative research effort led by Beat Ernst and colleagues at the University of Basel in Switzerland has identified selective and high-affinity CD22 antagonists, and their results are reported in ChemMedChem.

Using surface plasmon resonance, the team screened an existing library of antagonists (which were initially designed for another member of the Siglec family) for binding affinity toward CD22. The initial hit was then optimized to yield a series of CD22 antagonists with nanomolar binding affinity. Ernst's research group will next examine the potential application of these CD22 in cell depletion therapy.

More information: Beat Ernst, From a Library of MAG Antagonists to Nanomolar CD22 Ligands, ChemMedChem, Permalink to the article: … dc.201100407

Provided by Wiley (news : web)