Month: November 2012

This is a significant scientific breakthrough that represents an effective solution to a major problem in organic synthesis that has, yet, never been resolved, and which could lead to large-scale reductions in pharmaceutical industry processes

Technion researchers found a novel solution to a major problem in organic synthesis that has to date never been resolved, despite worldwide intensive efforts. The Technion team successfully prepared a new molecular framework possessing a challenging asymmetric center in a single chemical step from easily available starting materials. Until now, by lack of available efficient strategies, very few attempts were made and they were all based on long and tedious approaches. This is a significant scientific breakthrough in synthesis, which could lead to a considerable reduction in the production of pharmaceuticals. This groundbreaking discovery is reported by the popular scientific journal “Nature.”

“Synthetic organic synthesis is a science that deals with the building of complex organic molecules from simpler elements,” explains Professor Ilan Marek from the Schulich Faculty of Chemistry at Technion, whose team of researchers were responsible for this major breakthrough. “One of the greatest applications of this new approach is a quick and efficient synthesis of complex natural materials that may be used in pharmaceutical industry. It must be the goal of the 21st century to accomplish more with less. In today’s society, no one can afford to follow the inefficient route of long and tedious synthesis. We should think organic synthesis differently and I am sure that new transformations that were not possible to perform by conventional methods will soon appear” continues Professor Marek.

Although, there are still molecular frameworks that are extremely challenging to prepare, the real question of the 21st century is no longer “can we synthesize this molecule”, but rather “how can we synthesize it efficiently, using the fewest number of steps, with optimum convergence, with as little as possible functional group transformations, little or no by-products and maximum atom-efficiency and at minimal cost.” Over the years, Professor Marek’s research team developed several innovative new synthetic methods that not only fulfilled these requirements, but also gave solutions to challenging problems in organic synthesis.

One of these critical challenges is the formation of chiral all-carbon quaternary stereogenic centers in acyclic systems. A chiral molecule is a type of molecule that has a non-superposable mirror image. Human hands are perhaps the most universally recognized example of chirality: the left hand is a non-superposable mirror image of the right hand; no matter how the two hands are oriented, it is impossible for all the major features of both hands to coincide. This difference in symmetry becomes obvious if someone attempts to shake the right hand of a person using his left hand, or if a left-handed glove is placed on a right hand. This characteristic is also present in organic molecules and two mirror images of a chiral molecule are called enantiomers.

Many biologically active molecules are chiral, including the naturally occurring amino acids (the building blocks of proteins) and sugars. In biological systems, most of these compounds are of the same chirality and understanding the origin of chirality may shed some light on the origin of life. In many cases, both enantiomers of a specific material can affect the human body in completely different ways, and therefore understanding these chiral molecular characteristics is of great importance for the pharmaceutical and food industries. The most infamous case of medical disaster was caused by a misunderstanding of the different pharmacological characteristics of two enantiomers of the same material, known as Thalidomide which caused severe birth defects. Many infants were born without limbs because the drug Thalidomide, which was administered to their mothers, could in-vivo interconvert the two enantiomers.

In the context of building molecules, the aldol reaction is one of the most versatile carbon-carbon bond formation processes available to synthetic chemists but also a critical biological reaction in the context of metabolism. However, coming back to efficiency, the aldol reaction combines only two components with the creation of only one new carbon-carbon bond per chemical step. As discussed previously, better efficiency is now necessary in organic synthesis in which several new carbon-carbon bonds should be formed. Moreover, the construction of chiral all-quaternary carbon centers could not be achieved in the previously aldol-based methodologies. In the most recent report published in Nature by Professor Marek and his colleagues, a very efficient solution to this problem has been reported through a completely different approach. In a single-pot operation, starting from classical hydrocarbons, the formation of aldol products containing the desired all-carbon quaternary stereocenter have been prepared through the concomitant formation of three new bonds. This groundbreaking discovery represents an innovative solution to a challenging synthetic problem.

For the development of original synthetic approaches, Professor Ilan Marek received the prestigious Royal Society Chemistry Organometallic Award (2011) and in 2012 the Janssen Pharmaceutica Prize for Creativity in Organic Synthesis.

Scientists from Technion and the University of Colorado, Boulder have taken a closer look at how stars systems and their planets grow old together.

The influence of stellar aging on systems composed of three stars in orbit about each other is particularly intriguing. Binary stars systems where one of the stars is orbited by a planet, react similarly to stellar maturation. Stars and planets in these systems can change orbital partners. In some cases, they may even collide or be expelled from the star system all together. This wild and turbulent scenario may have produced of the brightest star system in the sky, Sirius A and B. These findings raise the possibility that collisions between stars are more common (at least 30 times over) than conventional wisdom has shown.

Most stars either live a solitary existence, or pair up with one other star to make a binary system. However 15 percent of all stars orbit at least two other stars, forming a triple star system. Similarly, planets can be “hosted” by a binary system, which then behave much like a triple star system except that one object is vastly smaller than the other two. The evolution of stars in these systems can generate dramatic outcomes. The aging process of stars involves many major changes: a star can expand to a circumference greater than hundreds of times its original size, and then lose most of its mass in intense winds. At the end of this process the stellar core, a white dwarf, is all that is left behind.  While much work has been devoted to understanding the evolution of single and binary star systems, studies on the evolution of triple stars are novel As is evident in the most recent research of Prof. Hagai Perets from the Faculty of Physics at Technion University, and Dr. Kaitlin Kratter from CU-Boulder, triple-star systems and their evolution are deserving of more interest. “Binary stars are systems that are generally stable,” says Perets. “The triple-star systems, on the other hand, are much more fragile,” and thus susceptible to disruption.

When mass is lost from one star during the ageing process, all of the orbits in the system change. These changes can induce dynamical instability, driving the system into a wild dynamic ‘dance,’ whereby the stars exchange partners until one of them gets expelled from the system altogether. Because the mass losing star begins to swell as it ages, it becomes a large target, significantly increasing its chances of crashing into another star in the midst of its wild ‘dance.’

Ordinarily, stars only collide in dense star clusters (systems with millions of stars packed into a volume of only a few cubic light years; for comparison, within the same volume in the neighbourhood of the Solar system there is only one star – the sun). Even in these dense clusters, the probability of a collision is very low.

“We discovered that when it comes to triple star systems, there is a different picture all together. Star collisions outside of dense star clusters can occur at a rate of 30 times higher in comparison to those coincidental collisions that occur within star clusters,” says Perets.

An answer to a Sirius mystery

According to Perets and Kratter, this type of chaotic evolution may be relevant to one of the best known stars, Sirius – the brightest star in the sky.  Sirius is accompanied by a white dwarf in a binary system, but on a very eccentric orbit. This configuration is unusual for a star in a close orbit to a white dwarf; astronomers normally expect such orbits to be nearly circular, due to the exchange of mass between the stars as they age. The most recent findings show that this strange configuration may be explained if the Sirius binary system is the remnant of a triple system that became unstable and lost a star. “This surprising revelation that the triple evolution scenario we studied could solve the decades old mystery related to our brightest night-time star, Sirius, is very exciting; it appears that Sirius had a much wilder history than we could have ever imagined,” adds Perets.

Planetary “star-hoppers”

What would you do if your neighbourhood started to deteriorate? Would you consider moving to a better neighbourhood? It seems as if planets might make the same decision. Kratter and Perets also investigated systems where one of the three elements is not a star but a planet. Much like the case with three stars, mass loss by the planet-host can drive the planet into an unstable, chaotic orbit. The outcome, says Kratter, is surprising. “A planet can actually change which star it orbits, bouncing back and forth between the two.” Sometimes, such a star-hopper will settle down into a new, stable orbit around the companion star.  More often, this story has an unhappy ending. It is more likely that the planet will collide with one of the two stars during its voyages between the two. Such a collision would obliterate the planet.

Will serve researches from all universities, as well as the high-tech industry

The microscope has sophisticated detectors that not only provide extremely high resolution, but also provide direct information about the material composition and local defects. It has a heating system with temperatures of up to 1100 degrees Celsius, which allows researchers to carry out manufacturing processes in-situ in the microscope, and to directly characterize changes to a material during a specific manufacturing process. Thus, for example, one can directly see solidification of a molten alloy inside the microscope, or track the mechanism by which thin films break-up or agglomerate into individual particles during thermal treatments. “With this innovative microscope, we can follow the process and discover how to prevent agglomeration, or utilize it”, emphasizes Prof. Kaplan. “Thus we developed, together with Prof. Gadi Eisenstein of the Department of Electrical Engineering, new flash memories with a stability and working range that are not currently available, and that are based on tiny platinum particles 4-5 nanometers in size. We produced these particles at the desired size and form, by following the agglomeration process of a continuous layer inside the microscope. This provides us with engineering criteria that we have not had to date”.

Dr. Alex Berner and Michael Kalina are responsible for the operation of the advanced microscope, which is part of the Technion’s advanced Electron Microscopy Center, and for related training.

Above: Inaugurating the innovative microscope. From right to left: Nobel Laureate in Chemistry Prof. Dan Shechtman, Technion Executive Vice President for Research Prof. Oded Shmueli,  and Prof. Wayne D. Kaplan. Photo: Yoav Becher, Technion Spokesman

Using the power of the sun and ultrathin films of iron oxide (commonly known as rust), Technion-Israel Institute of Technology researchers have found a novel way to split water molecules to hydrogen and oxygen.  The breakthrough, published this week in Nature Materials, could lead to less expensive, more efficient ways to store solar energy in the form of hydrogen-based fuels.  This could be a major step forward in the development of viable replacements for fossil fuels.

            “Our approach is the first of its kind,” says lead researcher Associate Prof. Avner Rothschild, of the Department of Materials Science and Engineering. “We have found a way to trap light in ultrathin films of iron oxide that are 5,000 thinner than an office paper. This enables achieving high solar energy conversion efficiency and low materials and production costs. ”

Iron oxide is a common semiconductor material, inexpensive to produce, stable in water, and – unlike other semiconductors such as silicon – can oxidize water without itself being oxidated, corroded, or decomposed.  But it also presents challenges, the greatest of which was finding a way to overcome its poor electrical transport properties. “For many years researchers have struggled with the tradeoff between light absorption and the separation and collection of the photogenerated charge carriers before they die out by recombination,” says Prof. Rothschild. “Our light-trapping scheme overcomes this tradeoff, enabling efficient absorption in ultrathin films wherein the photogenerated charge carriers are collected efficiently. The light is trapped in quarter-wave or even deeper sub-wavelength films on mirror-like back reflector substrates. Interference between forward- and backward-propagating waves enhances the light absorption close to the surface wherein the photogenerated charge carriers are collected before recombination takes place.”

The breakthrough could make possible the design of inexpensive solar cells that combine ultrathin iron oxide photoelectrodes with conventional photovoltaic cells based on silicon or other materials to produce electricity and hydrogen.  According to Prof. Rothschild, “these cells could store solar energy for on demand use, 24 hours per day.”  This is in strong contrast to conventional photovoltaic cells, which provide power only when the sun is shining (and not at night or when it is cloudy).

The findings could also be used to reduce the amount of rare elements that the solar panel industry uses to create the semiconductor material in their second-generation photovoltaic cells.  The Technion team’s light trapping method could save 90% or more of rare elements like Tellurium and Indium, with no compromise in performance.