Taming the molecule's Dr. Jekyll and Mr. Hyde

Many organic molecules are non-superimposable with their mirror image. The two forms of such a molecule are called enantiomers and can have different properties in biological systems. The problem is to control which enantiomer you want to produce – a problem that has proved to be important in the pharmaceutical industry. Researchers at the University of Gothenburg have now come up with a new method to control the process.

"Organic chemists think that it's impossible to create only one of the enantiomers without introducing some kind of optical activity into the reaction, but I've succeeded," says Theonitsa Kokoli at the University of Gothenburg's Department of Chemistry. "My method will allow the industry to produce the version they want without the use of a catalyst."

The phenomenon of non-superimposable mirror-image molecular structures is known as chirality. The two enantiomers can be compared to a pair of hands; they are non-superimposable mirror images of each other. A consequence of the different properties in biological systems is that a molecule can behave either as Dr Jekyll or Mr Hyde. The different characteristics in the enantiomers can be harmless, like in the limonene molecule. One enantiomer smells like orange and the other like lemon.

 

"Organic chemists think that it's impossible to create only one of the enantiomers without introducing some kind of optical activity into the reaction, but I've succeeded," says Theonitsa Kokoli at the University of Gothenburg's Department of Chemistry. Credit: University of Gothenburg

Thalidomide is a good example of how different forms of the same molecule can have disastrous consequences. One of the enantiomers was calming and eased nausea in pregnant women, while the other caused serious damage to the foetus. The thalidomide catastrophe is one of the reasons that a lot of research is devoted to chirality, as it is absolutely vital to be able to control which form of the molecule that is produced. Research on chirality has resulted in several Nobel Prizes over the years.

In biomolecules like DNA and proteins only one of the enantiomers exists in nature. In contrast to biomolecules, the same does not apply when chiral compounds are created synthetically in the lab. Generally an equal amount of both enantiomers is produced. One way of creating an excess of one enantiomer is to use a chiral catalyst, but this only transfers the properties that are already present in the catalyst.

"I've been working with absolute asymmetric synthesis instead, where optical activity is created," says Kokoli. "This is considered impossible by many organic chemists. I've used crystals in my reactions, where the two forms have crystallised as separate crystals, which in itself is fairly unusual. The product that was formed after the reactions comprised just one enantiomer."

While the results of Kokoli's research are particularly significant for the pharmaceuticals industry, they can also be used in the production of flavourings and aromas.

Provided by University of Gothenburg (news : web)

How to choose a catalyst: Predicting which materials will perform best in fuel cells and metal air batteries

MIT researchers have found a new way to predict which materials will perform best as catalysts for oxygen reduction, a core process in metal air batteries and fuel cells, opening up the possibility of faster and more effective development of new high-efficiency, low-cost energy-storage technologies.

Such catalysts are the crucial materials that govern the performance of fuel cells, as well as air-breathing batteries and other energy storage systems that are becoming increasingly important for everything from portable electronic devices to cars to the electric grid — where inexpensive storage is seen as key to increasing use of renewable but intermittent energy sources, such as solar or wind. But so far, selecting and testing such materials has essentially been a matter of trial and error, and most of the high-performing materials found have been rare and expensive, such as palladium and platinum.

The new principle, by contrast, should allow rapid assessment of a range of alternative catalysts made of metal-oxide materials, many of which are made of inexpensive and abundant elements.

The MIT researchers’ analysis found that the effectiveness of different materials could be determined by the arrangement of electrons in the outer shells of their atoms, and the way surface metal ions bond to oxygen. The research — led by Yang Shao-Horn, an associate professor of mechanical engineering and materials science and engineering at MIT, and Hubert A. Gasteiger, a visiting professor at MIT and a chemistry professor at the Technische Universität München in Garching, Germany — was published June 13 in the journal Nature Chemistry. Graduate student Jin Suntivich of MIT’s Department of Materials Science and Engineering is the lead author, and John B. Goodenough of the University of Texas at Austin is a co-author.

Shao-Horn explains that until now, there has not been any systematic approach to looking for new, inexpensive and high-performance oxides to use as electrodes in fuel cells or metal-air batteries. Typically, good catalysts for oxygen reduction will bind neither too strongly nor too weakly with oxygen. “For some time, we knew that platinum was good” as a catalyst, she says, but it was unclear whether the explanation could be applied to other materials such as metal oxides.

Research pioneered by Jens Norskov and colleagues at Stanford University and Denmark Technical University established a simple parameter: average energy of the outermost electron, which correlates with the binding energy of oxygen to metal surfaces. This principle explains why certain metals perform better than others, and it turns out that platinum just has the right electronic structure to provide optimum binding of oxygen — and thus high catalytic activity.

Now, “we have a theoretical framework and experimental evidence that explains why” certain metal oxides perform better than others, Shao-Horn says. When plotted on a chart comparing the electronic configuration of oxides’ surface metal ions and their catalytic activity, the result is a “volcano” shape: a sharp peak at the center, with steeply sloping sides indicating poorer performance. By simply changing the electronic configuration, materials can vary in their activity by a factor of at least 10,000 from the base of the volcano to the peak, Shao-Horn says.

Graduate student Jin Suntivich, lead author of the Nature Chemistry paper, holds up an electrochemical cell used for catalyst testing. Photo: Melanie Gonick

The new work now makes it possible to screen thousands of candidate metal-oxide materials without the time-consuming tests needed to prove their exact performance. A material’s behavior can now be predicted from a single parameter: how its electrons are distributed in the orbitals responsible for the bonding of metal to oxygen.

Robert Savinell, the George S. Dively Professor of Chemical Engineering at Case Western Reserve University, says this work is “of very high quality in rigor and innovation.” He adds that it “allows for optimizing chemical compositions for other important catalyst characteristics such as ease of synthesis, durability,” and other qualities. He says the research results will have an impact on searches for catalyst materials “for alkaline fuel cells, metal-air batteries, and even for electrolysis cells [that] … will be important for converting renewable energy sources such as wind and solar to hydrogen for energy storage or for use in fuel cells for transportation.”

The research was sponsored by and done in collaboration with Toyota Motor Company, because of its potential to lead to better materials for electric car batteries. It also received support from the U.S. Department of Energy’s Hydrogen Initiative, the National Science Foundation, the Chesonis Family Foundation, the Robert A. Welch Foundation and the Office of Naval Research.
This story is republished courtesy of MIT News (http://web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.

Provided by Massachusetts Institute of Technology (news : web)

Scientists develop algorithm to understand certain human diseases

 Patricia Clark, the Rev. John Cardinal O’Hara, C.S.C. Associate Professor of Chemistry and Biochemistry at the University of Notre Dame, and Bonnie Berger, professor of applied mathematics at the Massachusetts Institute of Technology, have published a paper on the development of a computer algorithm that can accurately predict which parts of protein sequences help prevent the proteins from aggregating.

Their article, the second published by the interdisciplinary research team, was submitted to the journal Proceedings of the National Academy of Sciences. The experimental work was completed at Notre Dame in Clark’s laboratory with Berger testing the computational predictions in her lab.

Protein aggregation occurs when the long linear sequence of a protein misfolds and begins to interact with copies of itself, thus preventing it from performing its essential functions in the cell.

Clark and Berger found that aggregation-resistant proteins tend to possess “capping” structures at either end of their correctly folded structure. However, if a “cap” is removed, the remaining protein aggregates quickly.

Proteins known to be highly prone to aggregation do not contain said capping structures, a finding that could help predict which proteins along with which genetic mutations will likely lead to aggregation.

Misfolding and aggregation can lead to numerous diseases ranging from juvenile cataracts to cystic fibrosis and cancer. Aggregated proteins can also form toxic structures known as amyloid fibers, which are linked to Alzheimer’s, Huntington’s, Lou Gehrig’s and other neurodegenerative diseases.

The two hope that by studying the mechanisms that can lead to aggregation as well as the structural features that some proteins possess that help avoid aggregation, strategies can be discovered to help treat aggregation diseases.

Provided by University of Notre Dame (news : web)

Chemists developing materials to detect, repel E. coli

A University of Houston (UH) chemist who is developing materials for detecting and repelling E. coli has published papers in two high-impact journals this month.

Rigoberto "Gobet" Advincula, a polymer chemist, says he and his colleagues have developed two different materials that are both equally effective against E. coli. He discusses the findings in the June issues of Chemical Communications (ChemComm) and Chemistry of Materials.

The ChemComm paper, Advincula says, describes a graphene material that is proving to be an effective antimicrobial, while the research appearing in the journal Chemistry of Materials uses a conducting polymer that can repel E. coli. He says his team has created a smart film that not only can be used to turn bacterial adhesion on and off, but also may be used for detecting bacteria. The work was done in collaboration with Debora Rodrigues and her group from UH's department of civil and environmental engineering.

Prolific in inventing new and smart materials such as these, Advincula has compiled an impressive record as a leading polymer, thin films and nanomaterials researcher. In addition to these most recent publications, three other papers were cover stories in top journals in April. In May, he released a new book with Wolfgang Knoll of the Austrian Institute of Technology titled "Functional Polymer Films" that Advincula considers to be akin to an encyclopedia on polymer thin films.

Additionally, Advincula was recently inducted as a fellow of the American Chemical Society (ACS), as well as being named a fellow in two of its technical divisions – the Polymer Chemistry Division and the Polymer Materials Science and Engineering Division. The ACS is the world's largest scientific society and one of the world's leading sources of authoritative scientific information. Achieving fellow status is a competitive process, based on research, contribution and service accomplishments to science and society.

"It is a rare distinction to become a triple fellow with the ACS, which has more than 163,000 members," Advincula said. "With only one out of every 1,000 members qualifying for selection as a fellow, I am extremely honored to achieve this trifecta for my work in advancing polymer and nanomaterial research and applications."

He asserts that much of this is really a tribute to his research group at UH, saying that his discovery-driven laboratory provides an environment that allows for readily filing patents, authoring publications and mentoring future scholars and inventors. He says the joy of working with students and budding scientists and engineers is reflected in his record of mentoring, with nearly 20 Ph.D. students, 50 undergraduates and dozens of high school students coming through his lab over the years.

"It is an extraordinary achievement to be named a fellow of the ACS and two ACS divisions," said David Hoffman, professor and chair of the chemistry department in the College of Natural Sciences and Mathematics at UH. "The honors are a reflection of the respect Gobet's colleagues have for him personally and for his scientific work."

In addition to his lab research, Advincula has been active in ACS, giving hundreds of presentations, organizing symposia and serving on the editorial advisory board of several scientific journals. He has nine U.S. patents and has authored more than 300 papers. Advincula, who is both a professor of chemistry and chemical engineering, has been continuously funded by the National Science Foundation, Robert A. Welch Foundation and several companies interested in the applications of his work.

Provided by University of Houston (news : web)