| POLYMERS Vol.63 No.6 |
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COVER STORY
Synthesizing “Life” with Macromolecules |
| COVER STORY: Highlight Reviews |
| Design and Construction of an Artificial Cell | Norikazu ICHIHASHI, Tetsuya YOMO |
| <Abstract> The construction of an artificial cell, in which cellular functions are reconstituted from purified molecules, is considered a promising way to understand the cell from another point of view and also provide new technology. In this article, we present several studies that attempted to reconsititute cellular functions and discuss what is lacking in our knowledge for the construction of an artificial cell that has the same function as the natural cell. Keywords: Design / Construction / Artificial Cell |
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| Cell-Free Protein Synthesis System | Hideaki MATSUBAYASHI, Takuya UEDA |
| <Abstract> Cell-free protein synthesis systems have originally been developed as a technology for the biochemical analysis of translation or the in vitro protein preparation. More recently, these systems have been applied to synthetic biology research such as the reconstruction of the artificial cell. We have developed a reconstituted cell-free protein synthesis system（PURE system; Protein synthesis Using Recombinant Elements system）, which is composed of individually purified ribosome and translational enzymes. This article summarizes the construction and application of the cell-free protein synthesis system, focusing on the PURE system. Keywords: Cell-Free System / Translation / PURE System / Protein Maturation / Unnatural Amino Acids / Ribosome Display |
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| Chemical Construction of Artificial-Cell | Tadashi SUGAWARA, Kentaro SUZUKI |
| <Abstract> A vesicle-based artificial cell, in which DNA was amplified by a polymerase chain reaction, was constructed. Giant vesicles containing amplified DNA grew and divided when a membrane precursor was added to the outer water phase. It was found that the complex composed of amplified DNA and cationic lipid including an amphiphilic catalyst plays a crucial role for the chemical linkage between DNA amplification and GV self-reproduction. We also discuss how the newly formed GV can be replenished with depleted nucleotides through the vesicular transport. Such constructive approach will reveal the mystery of the origin of life. Keywords: Giant Vesicle / Artificial Cell / DNA Amplification / Self-reproduction / Vesicular Transport |
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| COVER STORY: Topics and Products |
| Synthetic RNA Technologies to Control molecular Information and Structure | Hirohide SAITO |
| <Abstract> Research in the synthetic biology field, which attempts to bring about new technologies by understanding life through the process of “artificially creating” biomolecules and biological systems, is becoming established worldwide. Creating artificial biomolecules that freely control the functions of living cells and applying them to examinations and medical treatments is one of the research goals of this new field. We will use the unique synthetic RNA technologies to tackle these issues. For example, we have succeeded in developing “synthetic RNA switches” that can control translation of desired genes in target mammalian cells. We have also developed a method to control cell fate by using protein-responsive RNA translational ON/OFF switches. Moreover, for the first time we have succeeded in designing and constructing synthetic RNA-protein complexes （RNP）-based nanostructures, providing great potential for nanomedicine and biotechnology applications. Keywords: RNA / Synthetic Biology / Translation / RNP / Nanotechnology / Human Health Care |
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| Self-Organization in Cell-Scale Nonequilibrium Systems: Spontaneous Motions and Oscillatory Reactions | Masahiro TAKINOUE |
| <Abstract> In natural living systems, we find self-organized dynamic phenomena such as cellular tactic motion, cell division, pattern formation of animal body surface, beating of heart, circadian rhythm, etc. Amazingly, all the dynamic phenomena are realized by autonomous molecular reactions. In general, these phenomena are known to occur in nonequilibrium open systems, which have sustained influx and dissipation of matter and energy into/out of the systems. In recent years, autonomous and dynamic molecular systems such as artificial cells and molecular robots have been developed by learning from the nonequilibrium self-organized phenomena of living systems. Using these molecular systems, we can accelerate understanding of dynamic properties of living systems, and also achieve highly functionalized micro/nano-scaled molecular devices. In this topic, I describe two cell-sized nonequilibrium self-organized phenomena: （i） autonomous motion of cell-sized objects and （ii） spontaneous chemical oscillation in a cell-sized reaction system. We believe that these basic studies will be applied to more complex and highly functionalized molecular systems in the future. Keywords: Artificial cell / Nonequilibrium / Self-Organization / Molecular Robot / Water-in-Oil Microdroplet |
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| In vitro Microvasculature Models: Designing Living Tissue Structures | Yukiko T. MATSUNAGA |
| <Abstract> Conventional preclinical drug evaluation models include a lack of similarity between two-dimensionally cultured systems and in vivo systems, and a discrepancy between animal models and human models. Microtechnologies is a powerful tool to mimic the microenvironment （i.e. chemical and mechanical properties） of the tissues. Therefore, the concept of organ-on-chips was recently proposed to establish in vitro models that precisely recapitulate in vivo characteristics as well as drug response. Here we explain a importance of in vitro tissue models and organ-on-chips, and emphasize need for the in vitro microvasculature models that are deeply involved in various organ/tissue events such as inflammation, metabolism and regeneration. Keywords: Tissue Engineering / Microfabrication / Microvasculature / Collagen Gel |
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| Why 20 Amino Acids? | Kazuaki AMIKURA, Daisuke KIGA |
| <Abstract> It is generally accepted that primitive genetic codes employed fewer than 20 amino acids. In other words, biochemistry in a primitive cell was realized by using simplified proteins including only the amino acids that were considered to be used in primitive genetic codes. We wonder whether it is possible to construct such biochemical systems using simplified proteins. In this paper, we will describe previous studies about the number of amino acids in genetic codes and introduce our research in order to answer the question. In our recent study for construction of simplified genetic code, codons for amino acids are reassigned to alanine or serine to reduce a number of amino acids in the engineered code. Simplified genetic codes will provide an effective tool for construction of simplified proteins （A. Kawahara-Kobayashi, et al., Nucl. Acids Res, （2012）, K. Amikura, et al., RSC advances, （2013））. Keywords: Amino Acids / Genetic Code / tRNA / Protein / Evolution / Engineering / Origin of Life |
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| Genetic Alphabet Expansion and its Application | Ichiro HIRAO, Michiko KIMOTO, Ken-ichiro MATSUNAGA |
| <Abstract> Expansion of the genetic alphabet by an unnatural base pair system could provide a powerful platform for new biotechnology. Recently, we developed unnatural base pairs that exhibit high fidelity in replication as a third base pair, and applied them to an evolutionaly engeneering method. Through the application, we succeeded in the generation of high affinity DNA aptamers containing unnatural bases and proved that unnatural bases significantly augment nucleic acid functionalities. Keywords: Unnatural Base Pair / Genetic Alphabet Expansion / PCR / DNA Aptamer |
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| Polymer Science and I: A Personal Account |
| To Make Own Skill | Sunnam KIM |
| <Abstract> With new idea and own skill, we can develop a new technology. New idea comes up for advanced life with solving inconvenience. To make own skill, we need to make an effort with special training and knowledge. Also, communication with nearby professionals is very helpful. |
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| Front-Line Polymer Science |
| Ultrasmall Metal Clusters with Unusual Structures and Properties | Katsuaki KONISHI |
| <Abstract> Subnanometer-sized noble metal clusters with defined nuclearity have recently attracted special attention in relation to their unique optical（electronic absorption / luminescence）properties arising from their molecular-like characters. In this article, recent progresses in structure determination of ultrasmall gold and silver clusters by X-ray crystallography is summarized. An example is provided by the crystal structure of thiolate-capped Ag44 cluster, which has a Keplerate-type double-structured silver core and is markedly different from those of the related gold clusters with similar nuclearity. Examples of several diphosphine-coordinated non-spherical gold clusters with core＋exo type geometries and their unique optical properties are also presented. Unlike conventional spherical clusters, they exhibit isolated visible absorption bands, indicating that the attachment of metal atoms drastically alters the electronic structures of the cluster moiety. Keywords: Metal Cluster / Gold / Silver / Crystal Structure / Optical Properties / Geometry |
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