Tuesday, November 29, 2011

Oil more easily converted into petrol thanks to a smart observational technique

NWO researcher Bert Weckhuysen and his team from Utrecht University in collaboration with the company Albemarle Catalysts, have now succeeded in imaging how well the particles do their work. As a result of this research better catalysts can now be found. This will enable the to continue producing qualitatively good fuels from the dwindling reserves of crude oil that are often of a poor quality. The research was published in the November issue of Nature Chemistry.

The catalysts used by are smart, minuscule full of pores and ‘acid sites’. The oil particles, long hydrocarbon chains, creep into the pores and are chopped into shorter chains at the acid sites. This is the so-called cracking of crude oil. These shorter hydrocarbon chains can then be combusted as petrol or diesel in a car engine.

‘Everyone had always thought that each cracking sphere had about the same activity and that active sites were spread equally over the grain. Yet the reality is very different,’ says Weckhuysen. ‘Under a fluorescence microscope we made a 3D map of the active sites in such spheres. We can detect those sites using thiophene. As soon as such a molecule is in the vicinity of the acid sites it emits green fluorescing light.’ Knowledge about these active acidic sites can be used to select the most effective catalysts. That will make it easier to convert oil into petrol. Furthermore, using this technique it can be seen when the particles become less active and therefore need replacing.

Provided by Netherlands Organisation for Scientific Research (NWO) (news : web)

Chemists reveal the force within you

"Now we're able to measure something that's never been measured before: The force that one molecule applies to another molecule across the entire surface of a living cell, and as this cell moves and goes about its normal processes," says Khalid Salaita, assistant professor of biomolecular chemistry at Emory University. "And we can visualize these forces in a time-lapsed movie."

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Salaita developed the florescent-sensor technique with chemistry graduate students Daniel Stabley and Carol Jurchenko, and undergraduate senior Stephen Marshall.

" are constantly tugging and pushing on their surroundings, and they can even communicate with one another using mechanics," Salaita says. "One way that cells use forces is evident from the characteristic architecture of tissue, like a lung or a heart. If we want to really understand cells and how they work, we have to understand cell mechanics at a molecular level. The first step is to measure the tension applied to specific receptors on the cell surface."

The researchers demonstrated their technique on the (EGFR), one of the most studied cellular signaling pathways. They mapped the exerted by EGFR during the early stages of endocytosis, when the of a cell takes in a , or binding molecule. The results showed that the cell does not passively absorb the ligand, but physically pulls it inside during the process. Their experiments provide the first direct evidence that force is exerted during .

Mapping such forces may help to diagnose and treat diseases related to cellular mechanics. , for instance, move differently from normal cells, and it is unclear whether that difference is a cause or an effect of the disease.

"It's known that if EGFR is over-active, that can lead to cancer," Salaita says. "And one of the ways that EGFR is activated is by binding its ligand and taking it in. So if we can understand how tugging on EGFR force changes the pathway, and whether it plays a role in cancer, it might be possible to design drugs that target this pulling process."

Several methods have been developed in recent years to try to study the mechanics of cellular forces, but they have major limitations.

One genetic engineering approach requires splitting open and modifying proteins of a cell. This invasive technique may change the behavior of the cell, skewing the results.

The technique developed at Emory is non-invasive, does not modify the cell, and can be done with a standard florescence microscope. A flexible polymer is chemically modified at both ends. One end gets a florescence-based turn-on sensor that will bind to a receptor on the cell surface. The other end is chemically anchored to a microscope slide and a molecule that quenches fluorescence.

"Once a force is applied to the polymer, it stretches out," Salaita explains. "And as it extends, the distance from the quencher increases and the fluorescent signal turns on and grows brighter. We can determine the force being exerted by measuring the amount of fluorescent light emitted."

The forces of any individual protein or molecule on the can be measured using the technique, at far higher spatial and temporal resolutions than was previously possible.

Many mysteries beyond the biology and chemistry of cells may be explained through measuring cellular forces. How does a cancer cell crawl when a tumor spreads? What are the forces involved in cell division and immune response? What are the mechanics that allow groups of cardiac cells to beat in unison?

"Our method can be applied to nearly any receptor, opening the door to rapidly studying chemical and mechanical interactions across the thousands of membrane-bound receptors on the surface of virtually any cell type," Salaita says. "We hope that measuring cellular forces could then become part of the standard repertoire of biochemical techniques that scientists use to study living systems."

Provided by Emory University (news : web)

Glass sponges inspire: Hybrid material made of collagen fibers and silica as possible substrate for bone tissue culture

Biomineralization is a very complicated process that is not so easy to mimic. The silicate precursors required for the synthesis of the cell walls of diatoms are in a stabilized form, which prevents their uncontrolled polymerization. Special proteins then control the polymerization to make the highly complex structures of the resulting scaffold. Researchers would also like to control biomineralization processes to repair damaged teeth or to make synthetic cartilage and tissue. In order to culture bones, scientists would like to seed osteoblasts (bone building cells) from the patient’s own body onto a substrate, where they would attach and multiply. This scaffolding would be implanted to help damaged bone, in cases of osteoporosis-induced or highly complicated fractures for example, to regenerate. Osteoblasts release collagen, calcium phosphate, and calcium carbonate as the basis for new bone material.

would be an ideal substrate, but they are not solid enough for bone repair. The researchers once again turned to nature for inspiration: in glass sponges, a collagen matrix is one component of the silica scaffolding. Would it thus be possible to strengthen a collagen structure with silica (silicon dioxide)? Although many teams have previously failed in their attempts, the team led by Tay and Chen has now been successful.

They used collagen fibers as both a “mold” and a catalyst for the polymerization of the liquid phase of a silica precursor compound to make solid silica. The silica precursor is stabilized with choline to prevent an uncontrolled polymerization. This leaves enough time for the liquid precursor to fully infiltrate the space between the microfibrils of the collagen fibers before it polymerizes to form silica—one secret to the success of this new approach. After the polymerization the solid reflects the architecture determined by the collagen fibers. After drying, the original sponge-like, porous structure of the collagen fibers is maintained. In contrast to pure collagen, the scaffold of the hybrid compound is stable and could, the researchers hope, be used to repair bones.

More information: Franklin R. Tay, Infiltration of Silica Inside Fibrillar Collagen, Angewandte Chemie International Edition, http://dx.doi.org/ … ie.201105114

Provided by Wiley (news : web)

Iodate refuses to intimidate

Whether they are creating a catalyst for petroleum-free fuel or designing better drug therapies, scientists need to control ions' actions in . To control the ions, they must accurately characterize their behavior. This study answers a fundamental question about the behavior of large, negatively charged ions with multiple atoms, called polyoxyanions.

"To our knowledge, this is the first time anyone has microscopic insight into the solvation of a polyoxyanion," said Dr. Chris Mundy, a physical chemist at PNNL who co-authored the study.

When examining the behavior of large ions in water, the is that large anions, negatively charged ions, such as iodate (IO3-) should disrupt the ordered structure of water. For example, (I-) creates cavities within the water and is eventually expelled to the surface.

However, studies assigned iodate as strongly hydrating, meaning it resided in the liquid, not at the surface.

"The puzzle was why iodate did not behave like its slightly smaller cousin, iodide," said Mundy.

The research team took on that puzzle by integrating and experimental studies with iodate. The simulations determined that the central iodine atom is positively charged, even though the ion has a negative charge. The simulations were density-functional theory-based run on a powerful computing system known as NWIce at EMSL.

The iodine's cationic behavior strongly attracts the negative on three nearby . By tightly surrounding itself with water, the iodate is able to blend into the water.

"I would usually expect every water molecule to point a hydrogen at the anion," said Dr. Marcel Baer, a Linus Pauling Postdoctoral Fellow at PNNL who worked on the study. "The structure was surprising to me . . .very unexpected."

The simulations were confirmed by X-ray absorption fine structure spectroscopy studies. Using the light source at the Advanced Photon Source, the team was able to examine the structure of the ion in water.

"This one is not the same as the pure hydration that would normally be seen with a cation. It has its own structure," said Dr. Van-Thai Pham, a postdoctoral researcher at PNNL who worked on the spectroscopy investigations at the light source.

The research team's results appear in The Journal of Physical Chemistry Letters.

The researchers are further delving into the mysteries of iodate. The team is looking into the water surface to see if iodate is absorbed or the water shell that forms rejects the ion at the surface. In addition, team members are studying how other ions behave in water. They are focusing on ions based on positively charged cesium, bromide, and rubidium. Understanding these and others has implications from alternative energy sources to new drug therapies.

More information: MD Baer, et al. 2011. "Is Iodate a Strongly Hydrated Cation?" The Journal of Physical Chemistry Letters 2, 2650-2654. DOI: 10.1021/jz2011435.

Provided by Pacific Northwest National Laboratory (news : web)