Strengthening metal alloys would provide energy, environment conservation benefit

The results of the work promise to help engineers and scientists better understand how to enhance the performance of new light-weight materials used in a wide variety of technological applications. The light-weight materials can be particularly effective in helping to improve the energy efficiency of motor vehicles and reduce their polluting emissions.

Solanki recently joined ASU as an assistant professor in the School for Engineering of Matter, Transport and Energy, one of the university’s Ira A. Fulton Schools of Engineering. He combines expertise in solid mechanics and material science to study the microstructural properties of materials and predict their behavior under various conditions.

The Minerals, Metals & Materials Society (TMS) has awarded Solanki and two co-authors its 2011 Light Metals Magnesium Best Paper award for the report detailing their research on light-weight metal alloys.

He has been aided by Mehul Bhatia, who is pursuing a doctoral degree in mechanical engineering at ASU, and Amitava Moitra, a former postdoctoral fellow at Mississippi State University who worked there with Solanki. Bhatia and Moitra are the winning paper’s other co-authors. 

Titled “Effect of Substituted Aluminum in Magnesium Tension Twin,” the paper addresses a major challenge in development of new alloys. It involves finding ideal concentrations of new solutes that can be added to base metals to optimize their performance. Solutes are substances that dissolve into another substance in solutions.

The solute additions are critical to enhance the deformation and failure modes of materials, which occurs both when alloys are manufactured and when they are subjected to complex loading such as in a crash impact, Solanki explains.

Understanding how the metal alloy will respond in such circumstances provides information needed to make effective adjustments in the ratio of the solute to the base metal in a solution. That ratio is important in affecting the mechanical properties of an alloy to produce an optimal performance.

In the award-winning paper, Solanki’s research team demonstrates use of a nanoscale simulation technique to reveal how an aluminum substitution in pure magnesium affects its deformation and its behavior when the material fails.

“Our research provides a fundamental understanding of the role of solutes on deformation and fracture modes of metal alloys,” Solanki says. “This will guide the science of designing structural materials with enhanced properties and performance capabilities.”

He is working with magnesium and magnesium alloys because they are particularly light-weight materials that also offer the advantage of being highly recyclable.

“With the world’s energy needs increasing, energy efficiency and conservation become more important. More effective light-weight structural materials that help reduce the energy consumption needed for transportation will contribute to meeting that goal,” Solanki says.

Prior to coming to ASU, Solanki was an associate director at the Center for Advanced Vehicular Systems at Mississippi State University, where he earned a doctorate degree in 2008.

He has published more than 50 peer-reviewed journal and conference papers and he serves on the editorial board of the Journal of Surfaces and Interfaces in Materials. His paper “Finite element analysis of plasticity-induced fatigue crack closure: an overview,” published in Engineering Fracture Mechanics, was one of the most highly cited papers from 2002-05.

Solanki won the 2008 Henry O. Fuch Award from the Society of Automotive Engineers International for outstanding achievements in fatigue and fracture mechanics.

Solanki and Bhatia will be presented their best paper award from the Minerals, Metals & Materials Society at the organization’s annual meeting in March in Orlando, Fla.

Provided by Arizona State University (news : web)

How soft corals defy their environment

Many marine organisms, including corals, build skeletons from calcium carbonate -- in the form of calcite or aragonite. The current composition of seawater favors the formation of aragonite -- but soft corals have a specific protein that allows them to form calcite skeletons instead.

Calcium carbonate is a salt for all seasons. It turns up not only in marble, but also in biogenic sediments such as limestone and coral reefs – and even in pearls. The compound exists in two major crystalline forms, as calcite or aragonite. However, it is not clear what determines which variant an organism will exploit under conditions in which both forms can precipitate.

A team of researchers led by LMU geobiologist Dr. Azizur Rahman, who is also a Research Fellow of the Alexander von Humboldt Foundation, has now answered this question, in collaboration with colleagues based at the University of the Ryukyu Islands in Japan. Together, the scientists have shown that, in the soft coral species Lobophytum crissum, a secreted, extracellular protein known as ECMP-67 is the decisive factor that results in the precipitation of calcite, irrespective of the chemical conditions prevailing in the surrounding seawater.

"Over the course of Earth's history, and most probably depending on the relative amounts of dissolved magnesium and calcium ions, either calcite or aragonite has dominated in the world's oceans," says Professor Gert Wörheide, one of the authors of the new study. Current conditions favor the formation of aragonite, and many stony corals build their skeletons exclusively from this material. However, thanks to ECMP-67, Lobophytum crassum can still produce calcite in an aragonite sea.

"We have also been able to show how the extracellular protein ECMP-67 contributes to the production of calcite at the molecular level," says Rahman. "These findings should also allow us to elucidate the crystal structure of calcite in natural environments." The study was funded by the Alexander von Humboldt Foundation and the Japanese Society for the Promotion of Sciences.

More information: Calcite formation in soft coral sclerites is determined by a single reactive extracellular protein, Azizur Rahman, Tamotsu Oomori and Gert Wörheide, Journal of Biological Chemistry 286: 31638-31649, 2. September 2011. Doi 10.1074/jbc.M109.070185

Provided by Ludwig-Maximilians-Universitat Munchen

Protein adaptation shows that life on early earth lived in a hot, acidic environment

A new study reveals that a group of ancient enzymes adapted to substantial changes in ocean temperature and acidity during the last four billion years, providing evidence that life on Early Earth evolved from a much hotter, more acidic environment to the cooler, less acidic global environment that exists today.

The study found that a group of ancient enzymes known as thioredoxin were chemically stable at temperatures up to 32 degrees Celsius (58 degrees Fahrenheit) higher than their modern counterparts. The enzymes, which were several billion years old, also showed increased activity at lower pH levels -- which correspond to greater acidity.

"This study shows that a group of ubiquitous proteins operated in a hot, acidic environment during early life, which supports the view that the environment progressively cooled and became more alkaline between four billion and 500 million years ago," said Eric Gaucher, an associate professor in the School of Biology at the Georgia Institute of Technology.

The study, which was published April 3 in the advance online edition of the journal Nature Structural & Molecular Biology, was conducted by an international team of researchers from Georgia Tech, Columbia University and the Universidad de Granada in Spain.

Major funding for this study was provided by two grants from the National Aeronautics and Space Administration to Georgia Tech, a grant from the National Institutes of Health to Columbia University, and a grant from the Spanish Ministry of Science and Innovation to the Universidad de Granada.

Using a technique called ancestral sequence reconstruction, Gaucher and Georgia Tech biology graduate student Zi-Ming Zhao reconstructed seven ancient thioredoxin enzymes from the three domains of life -- archaea, bacteria and eukaryote -- that date back between one and four billion years old.

To resurrect these enzymes, which are found in nearly all known modern organisms and are essential for life in mammals, the researchers first constructed a family tree of the more than 200 thioredoxin sequences available from the three domains of life. Then they reconstructed the sequences of the ancestral thioredoxin enzymes using statistical methods based on maximum likelihood. Finally, they synthesized the genes that encoded these sequences, expressed the ancient proteins in the cells of modern Escherichia coli bacteria and then purified the proteins.

"By resurrecting proteins, we are able to gather valuable information about the adaptation of extinct forms of life to climatic, ecological and physiological alterations that cannot be uncovered through fossil record examinations," said Gaucher.

The reconstructed enzymes from the Precambrian period -- which ended about 542 million years ago -- were used to examine how environmental conditions, including pH and temperature, affected the evolution of the enzymes and their chemical mechanisms.

"Given the ancient origin of the reconstructed thioredoxin enzymes, with some of them predating the buildup of atmospheric oxygen, we thought their catalytic chemistry would be simple, but we found that thioredoxin enzymes use a complex mixture of chemical mechanisms that increases their efficiency over the simpler compounds that were available in early geochemistry," said Julio Fernández, a professor in the Department of Biological Sciences professor at Columbia University.

Fernández led a team that included Columbia University postdoctoral researchers Raul Perez-Jimenez, Jorge Alegre-Cebollada and Sergi Garcia-Manyes, and graduate student Pallav Kosuri in using an assay based on single molecule force spectroscopy to measure the activity level of the thioredoxin enzymes under different pH levels.

For their experiments, the researchers used an atomic force microscope to pick up and stretch an engineered protein in a solution containing thioredoxin. They first applied a constant force to the protein, causing it to rapidly unfold and expose its disulfide bonds to the thioredoxin enzymes. The rate at which a thioredoxin enzyme snipped the disulfide bonds determined the enzyme's level of efficiency.

The study results showed that the three oldest thioredoxin enzymes -- those thought to have inhabited Earth 4.2 to 3.5 billion years ago -- were able to operate in lower pH environments than the modern thioredoxin enzymes.

"Our analysis indicates that ancient thioredoxin enzymes were well adapted to function under acidic conditions and that they maintained their high level of activity as they evolved in more alkaline environments," said Fernández.

To measure the temperature range in which the enzymes operated, professor Jose Sanchez-Ruiz and graduate student Alvaro Inglés-Prieto from the Departamento de Química-Física at the Universidad de Granada in Spain used a technique called differential scanning calorimetry. This method measures the stability of enzymes by heating the enzymes at a constant rate and measuring the heat change associated with their unfolding.

The researchers found that the ancient proteins were stable at temperatures up to 32 degrees Celsius higher than the modern thioredoxins. The experiments showed that the enzymes exhibited higher temperature stability the older they were. The results provide evidence that ancestral thioredoxins adapted to the cooling trend of ancient oceans, as inferred from geological records.

"Our results confirm that life has the remarkable ability to adapt to a wide range of historical environmental conditions; and by extension, life will undoubtedly adapt to future environmental changes, albeit at some cost to many species," said Gaucher.

This study also showed that the experimental resurrection of ancient proteins together with the sensitivity of single-molecule techniques can be a powerful tool for understanding the origin and evolution of life on Earth.

The researchers are currently using this strategy to assess other enzymes to get a clearer picture of what life was like on Early Earth. They are also applying these tools to the field of biotechnology, where enzymes play important roles in many industrial processes.

"The functions and characteristics we observed in the ancestral enzymes show that our techniques can be implemented to generate improved enzymes for a wide range of applications," added Perez-Jimenez.

Provided by Georgia Institute of Technology (news : web)