A unique organic molecule that my pave the way toward the design of incredibly compact digital storage devices or computer memories has been developed by Weizmann Institute scientists.
The researchers -- a team or organic chemists including graduate student Lior Zelikovich, senior staff scientist Dr. Jacqueline Libman, and group leader Prof. Abraham Shanzer -- have synthesized novel, triple-stranded complexes of iron that my serve as the basis for switches the size of a small molecule.
Adapting these molecular-sized switches for use as ultracompact electronic devices -- whose digital circuitry would contain tens of million of "on"-"off" elements -- will require the solution of several inherent problems. There are no known methods for turning individual molecular switches "on" and "off" (the so-called "addressing" problem), or for detecting whether a particular molecular switch is "on" or "off" (the "reading" problem), or for "wiring" individual molecules to the external world. Improved switching complexes that operate much more rapidly will also be needed.
"There is no way to predict when molecular switches will become integrated into functional devices," says Shanzer. "But because of the importance of further miniaturization of electronic components, research into the ultimate level of miniaturization -- the use of molecular components -- is now attracting increasing scientific interest. When this technology comes of age, it could result in digital storage elements and memories millions of times more compact than now available, and in novel devices with capabilities far beyond anything possible today."
Building on their experience in synthesizing metal-binding organic compounds for medical, industrial and agricultural applications, the Shanzer-Libman team turned to the design of similar complexes with switch-like properties. In this work, they engineered an organic molecule with two sites, each of which binds iron in differently charged states. Using simple chemical techniques, the charge on the iron can be raised or lowered, causing it to jump between the two molecular sites. This jump causes the complex to change its color from yellow-brown to purple, a change that is easily seen in the test tube.
The Shanzer-Libman team is now working on other molecules that may have a potential to be "switched," as well as on molecular structures that may be applicable for use as conductors or diodes. They are also examining ways of turning their molecular switches "on" and "off" by electrochemical and photochemical means, approaches that are closer to real-life, solid-state conditions than reaction chemistry in a test tube.
This research, which was undertaken at the Institute's Department of Organic Chemistry, was supported by the Israel Science Foundation (which is administered by the Israel Academy of Sciences and Humanities) and by the Consortium of German Chemical Companies.
Prof. Shanzer is the incumbent of the Siegfried and Irma Ullmann Professorial Chair.
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Centers of Excellence: Gene Targeting
The Israel Science Foundation has recently initiated the establishment of Centers of Excellence at the country's leading academic institutions. The goal of this program -- to provide recognition and support for the work of outstanding groups of local scientists engaged in research at the highest international level. Ten Centers have been created to date, six of them headed by Weizmann Institute professors. Interface describes the activities of three Weizmann-led Centers of Excellence.
The Center takes advantage of the Weizmann Institute's expertise in the technique known as gene targeting, in which specific defects are introduced into genes in order to clarify their function. The method has been hailed as one of the most important advances in molecular genetics and is expected to have major implications for medical research.
Lonai, who played a leading role in introducing gene targeting to Israel, uses the technique to clarify embryonic development. The commonly held theory is that this process is entirely predetermined by a genetic code or DNA program. Lonai disagrees.
"A living organism does not take shape like a fighter plane, in which the instructions for every single component are programmed in advance. In living organisms, messages are constantly being sent back and forth between cells, with each cell helping to define what will happen to the others," says Lonai.
"We know a lot about embryonic development in flies and worms, but very little about how this process occurs in mammals. In fact, we don't usually give much thought to this crucial stage of life. It is only when we notice a mutation, like a little finger twice as long as it should be, that we start to appreciate how amazing it is that the body's countless components usually come out just right."
Gene targeting makes it possible to perform sophisticated studies in mammals that until now were possible only with much simpler organisms. "It will soon become the primary method for analyzing cloned genes," says Lonai.
Since breakdowns in intracellular signals controlling the growth of tissues are known to cause certain types of malignancies, this study also is expected markedly to advance cancer research.
The new Center of Excellence, which provides expertise in gene targeting to scientists throughout the country, includes four research groups -- three led by Weizmann Institute scientists and one by a Bar-Ilan University researcher. In addition to heading the new Center, Lonai, a member of the Immunology Department, is in charge of the three Institute teams. The other two are led by Profs. David Givol and Yosef Yarden of the Molecular Cell Biology Department.