YOSHIMURA PI-ELECTRON MATERIALS PROJECT: NEW HORIZON OF PI-ELECTRON MATERIALS Project Director: Susumu Yoshimura The plants, animals, and minerals of nature contain two kinds of electrons, sigma electrons and pi electrons. The sigma electrons hold nature together. They provide the strength that holds trees up and keeps mountains high. The pi electrons make nature work. They give us the bright greens and reds. They catch the light needed for photosynthesis. Organic chemistry has a long history of making new compounds that hold pi electrons. But the pi electrons in these compounds can only move in small areas; they cannot wander freely very far without running into walls. One compound of nature is different. In graphite, the pi electrons can wander far and wide. Recently, scientists have learned to make graphites that are large single crystals. They have also found pi electrons in inorganic materials, for example, on the surface of silicon that is used in transistors and in compounds of boron or nitrogen. The pi electrons in large single crystals of graphite are light and fast. They can be faster than the electrons in the gallium arsenide high electron mobility transistors (HEMTs) that are being developed for the newest generation of supercomputers. Under the right conditions, they may become superconducting. When placed in electric fields, pi electrons move to and fro over long distances, a phenomenon called "superpolarizability.” Up until now, our knowledge of pi electrons has come indirectly from research not aimed at pi electrons themselves. For example, pi electrons are important for photosynthesis so research on photosynthesis has taught us something about pi electrons. Little research has focused directly on pi electrons and the pi-electron materials that carry them. The Yoshimura Pi-Electron Materials Project will do this. The Yoshimura Pi-Electron Materials Project will assemble international teams of chemists, physicists, materials scientists, and biochemists to attack the secrets of pi electrons and pi-electron materials. These researchers will discover ways to make new pi-electron materials. What they learn about why pi electrons are so light and fast may lead to new high-speed electronic devices. What they learn about superpolarizability may lead to new nonlinear (red light in, blue light out) optical devices, which are essential for computers based on light. Their study of the biocompatibility of pi-electron materials may lead to new materials for use in medicine. By focusing the attention of researchers from a wide range of backgrounds on pi-electron materials, the Yoshimura Pi-Electron Materials Project hopes to generate a wide range of new knowledge, new materials, and new devices. "Pi electrons" are mobile electrons whose cloud extends normal to the bond axis between atoms. Since the delocalized pi electrons can move about throughout a crystal or molecule without distorting it, pi-electron materials out distorting it, pi-electron materials have many peculiar characteristics, such as extremely high electron mobility and superpolarization. The pi-electron cloud is also a fundamental reaction field for organic and biological materials. Examorganic and biological materials. Examples are photo-charge-transfer reaction and photosynthesis. Little is known, however, about the roles of pi electrons in solid surface state or quantum effects in two-dimensional conductors. Low-dimensional graphites, which are typical organic pi-electron materials, have been made in the forms of fibers and sheets that have physical properties almost identical to those of single crystals. Superaromatic carbon clusters such as C and C, can now be 60 70 obtained in quantity. As a result, the materials science of carbon is active again. Single crystals of inorganic materials that have a pi-electron system based on boron, nitrogen, or oxygen molecules have recently been synthesized. Scanning tunneling microscope observations have recently revealed that the reconstructed surface of a silicon single crystal contains pi-electron-like defect states. These new pi-electron materials prompt research on the solid state physics and on the control of their electronic behaviors. The Yoshimura Pi-Electron Materials Project will view the large space occupied by the freely moving pi electrons as domains of electron motion and materials transformation. The project will exploit and elucidate unique physical, chemical, and biochemical phenomena that result from these domains. For this, the project will develop synthetic methods and processes for new organic and inorganic materials with extended pi-electron systems and with high crystallinity. It will elucidate the mechanisms of superpolarization, high electron mobility, and nonlinear phenomena (Ref 67). The project may propose new electronic devices based on unique features of pi electrons. Other work will focus on biological or biochemical activities of pi electrons and reactions in two dimensions that take place in graphite intercalation compounds (Ref 68). The project will study selective and/or anomalous reactions in which the pi-electron domains participate. This work may shed light on mechanisms of biocompatibility and proliferation on carbonaceous materials in relation to electronic structures of the pi-electron systems. This project hopes to establish a materials science based on pi electrons by reexamining and enriching our knowledge on optical, electronic, magnetic, chemical, and biochemical properties of pi-electron materials. NOYORI MOLECULAR CATALYSIS PROJECT: FROM READY-MADE TO TAILOR-MADE CATALYSTS Project Director: Ryoji Noyori The perfect chemical reaction produces only the desired product and no wastes. It starts with economical raw materials and wastes little energy. It allows the chemist to construct exactly the molecule desired in the shape desired. Until recently, perfect chemical reactions were found almost only in nature. The chemical reactions developed by man are still far from perfect. Many consume large amounts of energy and produce hazardous wastes that endanger the environment. Removing reaction wastes from pharmaceuticals is very expensive. The reactions of nature are brought about by catalysts called enzymes. These catalysts speed reactions by reducing the barriers to the reactions. They also direct the reactions along exactly the right pathways. They have long been the envy of chemists. Indeed, many chemists are trying to adapt the reactions of nature to make the chemicals needed for our modern everyday lives. The Noyori Molecular Catalysis Project, however, is taking a different approach. Rather than try to improve on nature, which is already close to perfect, researchers in this project will design and study molecules that approach perfection in catalyzing reactions that nature cannot perform. The researchers will start with metal atoms or ions. Metals can catalyze many reactions. However, a metal ion by itself is somewhat like a naked bit on a woodworker's tool. It cuts quickly but is very hard to control. It often cuts wrong and wastes the wood. The researchers of the Noyori Molecular Catalysis Project will mount these metal ions in special organic "jigs" called ligands. These ligands will make certain that the metal ion cuts only the desired bonds and joins only the desired molecules in the desired way, much as a woodworker's jig hold the wood pieces so that precisely the desired joint can be made quickly, efficiently, and with little waste. These metal-ligand catalysts are called "molecular catalysts." The Noyori Molecular Catalysis Project will focus mainly on reactions that can make either left-handed or right-handed molecules. Many reactions used for making drugs do this. Getting rid of the undesired molecule can be very expensive. Researchers in the project will design metal-ligand catalysts that cause the reaction to make only one of the two molecules. Researchers will also design and study molecular catalysts for making polymers. Many polymers come in left-handed and right-handed helices. By themselves, the left-handed helices may have special electrical or optical properties. However, if the right-handed helices are also present, they cancel out the special effects. Polymers that are purely left-handed or purely right-handed may provide new electronic or optical devices. The Noyori Molecular Catalysis Project will also research molecular catalysts for making polymers in which all the chains are the same length. Currently, most reactions for making polymers make the chains in many different lengths. If the chains are all the same length, the polymer may have special properties, much as a paintbrush with bristles of the same length spreads paint better than a brush having bristles of varying lengths. Intrinsic properties and functionalities in materials are strongly influenced not only by their molecular and/ or atomic composition but also by their purity. Particularly, chirality plays an important role in science and technologies related to molecular electronics and optics. The perfect chemical reaction producing only the desired substances and no wastes is crucially significant. In contrast to enzymatic reaction, which efficiently gives chiral substances, synthetic reaction remains far from perfect. Recently, synthetic chemists are meeting this challenge by developing highly selective reactions catalyzed by organometallic complexes, and the chemist's dream of achieving perfect reaction is now being converted into reality. Particularly, reality. Particularly, homogeneous asymmetric catalysis using chiral metal complexes provides a promising way and powerful tool to produce chiral substances, complementary to biological transformations, structural modification of naturally occurring chiral substances, classical resolution methods, etc. Asymmetric catalysis is capable of multiplying chirality, and the efficiency of the chiral multiplication, defined as [major enantiomer-minor enantiomer (in mole)]/chiral source (catalyst) in mole, can be increased to infinite depending on catalyst designing. The selection of central metals and molecular designing of chiral ligands are particularly significant to attain perfect reaction. Such a molecular catalyst consisting of reactive metal center and auxiliaries (chiral source) not only promotes reactions of associated substrates but also controls the stereochemical outcome in an absolute sense. To our knowledge, the first catalytic asymmetric reaction of prochiral compounds promoted by homogeneous transition metal complexes was reported in 1966. Ever since this discovery spectacular progress has been made in this field, and with synthetic chiral metal complex catalysts optical yields over 80%, or even close to 100%, are frequently obtained. In certain cases, the efficiency of artificial complexes rivals that of natural enzymes and we can produce large amounts of chiral compounds having natural and unnatural configurations with the use of only a very small amount of a chiral source. Some of them are applied to commercial production of chiral products of extremely high enantiomeric purity. The Noyori Molecular Catalysis Project will focus mainly on perfectly controlled reactions leading to only desired small or large molecules. For this purpose we will design new, welldefined organometallic complexes as molecular catalysts. The concept for "molecular catalysis" will generate a new type of chiral materials having potent biological functions and unique physical properties. Our basic principle, “molecular catalysis,❞ relies on "four-dimensional chemistry," in which high efficiency is only attainable through a combination of both an ideal three-dimensional structure (x,y,z) and appropriate kinetics (t). This chemical methodology will certainly contribute to industrial production and molecular science and industry in the emerging generation. FUSETANI BIOFOULING Project Director: Nobuhiro Fusetani A barnacle larva hatches from its egg and embarks on its search for a place to settle and grow into an adult. Carried by ocean currents, it floats and swims, bumping into plants, fish, and rocks until, maybe days later, it touches the right place. In minutes, the larva bonds tightly to its new home and begins making its shell and growing. This settling process is repeated by countless sea animals: sponges, corals, mussels, barnacles, and tunicates. How does a larva know what surface is right and what surfaces are not? There must be some kind of chemical signal. Scientists have learned, for example, that if ocean sand contains certain odors (chemicals) that result from other adults of the same species, these odors will cause the larvae to attach to the sand OKAYAMA CELL-SWITCHING Once a larva touches the right place The Fusetani Biofouling Project will gather international teams of marine biologists, organic chemists, biochemists, and electrophysiologists to research how these marine larvae know when to stop, attach, and grow. They will pay special attention to barnacles, mussels, and bryozoans. The biggest challenge for the Fusetani Biofouling Project will be to learn how to test chemical signals and settling in the laboratory. Once this is achieved the researchers will be able to proceed rapidly to learn what kinds of chemical signals trigger settling and transformation of the larvae. They will be able to decipher the changes that occur inside the larvae after they receive the chemical signal and how the signal is transmitted inside the larvae. Even before the Fusetani Biofouling Project develops the tests for the chemical signals, the researchers will be isolating and characterizing possible signal chemicals. They will also be researching the basic physiology of the larvae to learn what pathways are there for the signals to follow. From this research we may learn better ways for controlling these marine organisms and thus help solve problems that have plagued man for millennia, such as barnacle growth on ships, and more recent problems such as beach erosion, the fouling of underwater pipes by clams, and the disruption of coral reefs. We may also learn better ways to cultivate clams, mussels, and other marine organisms for food. Cells in higher life forms such as yeasts, plants, and animals grow and divide in a four-step cycle. They divide, then grow some, then make a copy of their genes, grow some more, then divide again. This simple cycle is crucially important. Evolution has left it almost untouched. Genes controlling growth in human cells also work when they are put into yeasts. Among the four steps, the growth right after division (called G1) is a most critical time. Will the cell divide? Will it produce sperm and egg cells? Will it change form such as into a muscle cell or into a blood vessel cell? Or will it lose control and become cancer? The cell's fate is determined by events that occur during G1. The Okayama Cell-Switching Project will use an amazing array of recently developed tools to unravel the secrets of G1 and how genes control it. One tool is a specially designed gene library. This is not a library of books but a library containing DNA cloned from cells, for example, human muscle cells. There are millions of volumes in a gene library. There may be many duplicates and some may be missing pages or chapters. This library, however, is not a mere collection of cloned genes. It consists of genes engineered so as to work in a wide variety of cells from human to yeast. The Okayama Cell-Switching Project will search these libraries for genes that control G1. One search will be done with fission yeast mutants that have defects in G1. Using such a mutant, the researchers can find the human gene that fixes the defect. They can then decode the gene, that is, find out the structure of the protein that is made from it. From the protein's structure they can get clues to its role in G1. A different search will be done with a special kind of rat-kidney cell. These cells become cancerous if they are exposed to growth factors. If the growth factors are taken away, the cancer stops and the cells return to normal. In other words, the cancer can be turned on and off. Scientists have made several mutants of this rat-kidney cell and know that there are switches in G1. The Okayama Cell-Switching Project will search the human gene library for genes that correct the defects in the mutants. From these genes, the researchers hope to learn about switches that turn on cancer in humans and, perhaps, clues as to how to turn it off. Proliferation is a unique attribute of living organisms. Multicellular organisms proliferate through the process called development, which involves concerted replication and/or differentiation of each cell composing the organisms. However, cell differentiation is not unique to multicellular organisms, as yeast undergoes sexual differentiation and forms spores when it encounters poor nutrition, thereby surviving hostile environments. G1 until it receives the next growth This project will use one of the most Unraveling the mechanism controlling cell growth and differentiation will provide a clue to understanding the molecular mechanism of malignant transformation and cell aging. We also hope to find a basis for the next generation of biotechnology, which would allow us to manipulate the development of organisms. Eukaryotic cells replicate in a fourstep cycle called the cell cycle. Most cells in organisms are in a G1 phase, and they can stay there for quite a long period of time. When a cell receives growth stimuli, its enter the S phase, in which DNA synthesis occurs and its genetic information is duplicated. After DNA is synthesized, the cell proceeds CONCLUSIONS to the G2 phase, in which the timing of mitosis is determined, based on nutrition, cell organelle synthesis, and the completion of DNA synthesis. Finally, in mitosis, the cell divides into two identical cells. After division, the cell may enter another cell cycle or stay in The ERATO program is certainly unique in several aspects. Although clearly aimed at increasing Japan's technology base in wide areas of science, project managers are given encouragement to follow their scientific and technological intuition, even if it leads away from the stated objectives of the project. Basic scientific objectives are served as well as societal needs and objectives, with a focus on the distant future. Within the Japanese scientific and technical community, ERATO is given wide publicity and has earned great respect over its first decade of operation. The nation's best young scientists are attracted to work on ERATO projects, even though they have a limited 5-year lifetime (see Tables 1 and 2). Younger scientists are employed for the bulk of the research, and their experience prepares them well for greater responsibilities in the future. Even with the 5-year cutoff, mid-career scientists are not reluctant to accept such a limited 5-year appointment because they are confident that the experience and the contacts developed during the ERATO adventure will ensure them a satisfactory follow-on appointment. Assessing the overall success of ERATO is hardly necessary. A brief glance at the project reports above is enough to convince all but the most skeptical of the value of ERATO's technical achievements to date. In addition, the opportunity for younger and mid-career scientists to devote 5 years of their career to innovative, team-type, project research is of great value in their professional development. Many of the projects involve crossdisciplinary research teams and some involve international teams, thereby presenting a broadening of scope for most younger scientists. As Japanese scientists struggle to find the meaning and value of their role in global scientific leadership, ERATO's international component, while not large, contributes significantly to the international interaction, in both science and technology, that seems destined to grow in the next few years. Some data on this latter point are given in Table 3. |