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全文: "Origin of life"
384件中 1-20の結果を表示しています
  • 中嶋 悟, 伊藤 由紀, 塩田 大
    岩石鉱物科学
    2002年 31 巻 1 号 58-61
    発行日: 2002年
    公開日: 2008/05/08
    ジャーナル フリー
    At the earth's surface, divers organic-inorganic interactions are occurring and controlling the biogeochemical cycling. In this paper, we will review the experimental results on silica-organic interactions in aqueous solutions. The kinetics of dehydration-crystallization of hydrated amorphous silica into more crystalline forms during the diagenesis of siliceous marine sediments was studied and the influence of some biogenic organic compounds was evaluated. The transformation of amino acids on hydrous silica was also studied in order to test a new hypothesis on the origin of life: coupled dehydration-polymerization in silica-amino acid systems. The significance of organic-inorganic interactions in the fate of organic pollutants in the earth's surface will also be pointed out.
  • 丸山 茂徳
    日本地質学会学術大会講演要旨
    2012年 2012 巻 T6-O-11
    発行日: 2012年
    公開日: 2013/03/26
    会議録・要旨集 フリー
  • Genji MATSUDA
    Acta Medica Nagasakiensia
    2004年 49 巻 4 号 121-128
    発行日: 2004年
    公開日: 2005/04/28
    ジャーナル フリー
    A hypothesis of the dualistic chemical evolution to the stabilization of the energy-balance is proposed and explained in connection with the origin of life on the earth. From author's viewpoint, the existence of all things and all phenomena in the universe are closely related to the stabilization of the energy-balance and life is not an exceptional case in this matter. It is presumed that the first life on the earth was formed as the process towards the stabilization of the energy-balance by interactions between the earth and other heavenly body. A white dwarf was considered as this other heavenly body and the base-bonding polypeptide was assumed to be the origin of protein and nucleic acid.
  • 藤原 鎮男, 西本 右子
    日本地球化学会年会要旨集
    2002年 49 巻 3C08
    発行日: 2002年
    公開日: 2004/01/08
    会議録・要旨集 フリー
    地球化学・宇宙科学の現下の課題の一つは生命の起源が地球の内外何れであるかである。塩化ナトリウムと水が共晶体をつくることは古くから知られていたが、演者らはこの共晶が酸素と錯体を形成し、この酸素錯体がアミノ酸鏡像異性体と100%の効率で分別反応することを見いだした。さらに硫化水素が酸素と同様の分別能を持つことも明らかとした。ここで見いだされた知見は、生命の起源が地球にあることを示唆するであろう。
  • 小宮 剛
    日本地質学会学術大会講演要旨
    2015年 2015 巻 R24-O-1
    発行日: 2015年
    公開日: 2016/03/31
    会議録・要旨集 フリー
  • 古川 善博
    高圧力の科学と技術
    2009年 19 巻 3 号 195-200
    発行日: 2009年
    公開日: 2009/09/04
    ジャーナル フリー
      High-pressure and high-temperature reactions in meteorite impact events were subjected to extensive research in order to resolve origin of organic molecules on the early Earth. In this article, I introduce several researches of impact chemical reactions synthesizing ammonia and organic molecules on the early Earth. Atmosphere of the early Earth is thought to be slightly oxidized from which organic molecules are difficult to be synthesized. Several hypotheses related to impact synthesis of organic molecules have been proposed. Recently, ammonia and several organic molecules were synthesized demonstrating meteoritic impact reactions experimentally and numerically. Progress about the impact-induced chemical reactions will be able to reveal more clearly the origin of biomolecules on the early Earth.
  • 村井 拓朗, 奥野 正幸, 荒砂 茜, 奥寺 浩樹, 濵田 麻希, 水上 知行, 荒井 章司, 阿藤 敏行
    日本鉱物科学会年会講演要旨集
    2014年 2014 巻 R5-09
    発行日: 2014年
    公開日: 2019/03/20
    会議録・要旨集 フリー
    彗星のモデル物資として、シリカゲル―グリシン複合体を用いて、その衝撃圧縮による構造変化を、X線回折測定、赤外・ラマン分光測定法により分析した。得られた結果から、グリシン分子は18GPaの衝撃圧縮でも分解せずに残存することを明らかにした。この結果は、初期地球の生命起源物質が宇宙起源である可能性を示している。
  • Motoo KIMURA
    遺伝学雑誌
    1991年 66 巻 4 号 367-386
    発行日: 1991年
    公開日: 2006/06/10
    ジャーナル フリー
    In sharp contrast to the Darwinian theory of evolution by natural selection, the neutral theory claims that the overwhelming majority of evolutionary changes at the molecular level are caused by random fixation (due to random sampling drift in finite populations) of selectively neutral (i.e., selectively equivalent) mutants under continued inputs of mutations. The theory also asserts that most of the genetic variability within species at the molecular level (such as protein and DNA polymorphism) are selectively neutral or very nearly neutral and that they are maintained in the species by the balance between mutational input and random extinction. The neutral theory is based on simple assumptions, enabling us to develop mathematical theories based on population genetics to treat molecular evolution and variation in quantitative terms. The theory can be tested against actual observations. Neo-Darwinians continue to criticize the neutral theory, but evidence for it has accumulated over the last two decades. The recent outpouring of DNA sequence data has greatly strengthened the theory. In this paper, I review some recent observations that strongly support the neutral theory. They include such topics as pseudoglobin genes of the mouse, αA-crystallin genes of the blind mole rat, genes of influenza A virus and nuclear vs. mitochondrial genes of fruit flies. I also discuss such topics as the evolution of deviant coding systems in Mycoplasma, the origin of life and the unified understanding of molecular and phenotypic evolution. I conclude that since the origin of life on Earth, neutral evolutionary changes have predominated over Darwinian evolutionary changes, at least in number.
  • Yutaka Toyozawa
    Journal of the Physical Society of Japan
    2000年 69 巻 6 号 1907-1916
    発行日: 2000/06/01
    公開日: 2000/07/28
    ジャーナル 認証あり
    Considering the estimated chemical energy per atom of typical biomolecules and the continuance of living activities for billions of years, we present a scenario of the origin of life according to which the solar radiation caused successive photochemical reactions in aqueous solution of simple molecules and brought them up to the biomolecules through virtual molecules as intermediate states.The result is a severe competition for the acquisiton of chemical energy among different channels of successive photoexcitations, which built in the mechanism of natural selection into chemical evolution at its very beginning. Peculiar structure of biomolecules is ascribed to the natural selection with maximal path probability. Photoionization of solute molecules assisted by the strong hydration effect plays an important role in promoting chemical reactions in the solution, sometimes as photocatalyst.
  • SORIN KIHARA, MITSUO SANADA, SHINJI KUWADA, YOSHIKI SOHRIN, OSAMU SHIRAI, HISAO KOKUSEN, MITSUKO SUZUKI, MASAKAZU MATSUI
    Analytical Sciences
    1991年 7 巻 Supple 号 663-666
    発行日: 1991年
    公開日: 2007/07/27
    ジャーナル フリー
    It has been demonstrated that amino acids and nucleic acid bases can be synthesized by UV irradiation even in such rather oxidizing atmosphere as aqueous solutions containing CO2, HCO3- and/or CO32- in the absence of CH4 or H2. For the production of amino acids and nucleic acid bases from ammonium carbonate solution or water to which CO2 and NH3 gases had been dissolved, UV shorter than 250nn, temperature higher than 80°C and the coexistence of Mg2+ were found to be effective. On the basis of some experimental evidences, oxalic acid and/or oxamic acid are assumed to be the possible intermediates for the synthesis.
  • Kunio KAWAMURA
    Analytical Sciences
    2011年 27 巻 7 号 675
    発行日: 2011/07/10
    公開日: 2011/07/10
    ジャーナル フリー
    Continuous extensive studies on thermophilic organisms have suggested that life emerged on hydrothermal systems on primitive Earth. Thus, it is well known that hydrothermal reactions are, therefore, very important to study fields deeply related to the origin-of-life study. Furthermore, the importance of hydrothermal and solvothermal systems is now realized in both fundamental and practical areas. Here, our recent investigations are described for the development of real-time and in situ monitoring systems for hydrothermal reactions. The systems were primarily developed for the origin-of-life study, but it was also applicable to fundamental and practical areas. The present techniques are based on the concept that a sample solution is injected to a narrow tubing flow reactor at high temperatures, where the sample is rapidly heated up in a very short time by exposure at to a high-temperature narrow tubing flow reactor with a very short time scale. This enables millisecond to second time-scale monitoring in real time and/or in situ at temperatures of up to 400°C. By using these techniques, a series of studies on the hydrothermal origin-of-life have been successfully carried out.
  • ROBERT F. WHITTIER, MACHIKO HATSUDA
    順天堂醫事雑誌
    2018年 64 巻 2 号 96-97
    発行日: 2018年
    公開日: 2018/06/19
    ジャーナル フリー

    Here we present a brief anthology of selected reports produced in a problem-based learning (PBL) course required of medical students in their first year of studies at Juntendo University. None of the reports selected for this anthology deal with medical issues per se, but rather reflect the abilities of students in their first attempts to delve into a new subject and engage in teamwork with fellow students to explore an unfamiliar subject and produce a coherent report on their findings.

    Why would this be a useful exercise? After all, there is such a huge body of knowledge and clinical procedures that medical students are expected to absorb over just a few short years. How can we justify time spent on subjects not directly relevant to the practice of medicine or its scientific foundations?

    The answer is that we must prepare students for lifelong careers that will involve teamwork and continuous learning. Some of our international readers also need to know that in Japan, students enter medical school straight out of high school. Almost none have experience with self-driven research, as would be required to write an undergraduate term paper in the US. Moreover, while the students often bring valuable teamwork experiences from their club activities in high school (such as in sports or music), teamwork experience in more serious pursuits is frequently lacking. Yet, they will soon be tasked with teamwork aimed at ensuring high quality care for their patients. While the knowledge and skills they are taught during their six years of medical school are important, over the course of their careers their abilities will depend even more on their own active efforts to remain current with medical advances and to improve their skills. Equally important, their patients’ outcomes will depend on their abilities as doctors to cooperate and communicate effectively with other caregivers and administrators.

    After 12 years spent passively learning materials selected by their teachers, and with a few more years of similar studies yet ahead of them, it is time for the students to take their first steps in setting their own tasks and learning goals.

    In 2015, 14 PBL themes were offered, and within each theme, the students divided themselves into groups of two to four students centered around specific topics, often in the form of a question, chosen or even proposed by the students themselves. The PBLs themselves were conducted over the course of 5 days in early September before the start of the regular fall semester. While the fourteen themes offered included a number centered around the natural sciences, mathematics and medical issues as detailed in the table, the reports included here were all selected from the PBLs tutored by faculty members of the General Education English section, and hence written originally by the students in English. We were quite encouraged by the efforts the students put into their reports, and particularly proud of the four reports below.

  • 小林 潤平, 薮田 ひかる
    日本地球化学会年会要旨集
    2013年 60 巻 3P24
    発行日: 2013年
    公開日: 2013/08/31
    会議録・要旨集 フリー
    酵素がまだ存在しなかった初期地球では、簡単な物質が原始的な代謝すなわち酸化還元反応を担い、生命機能に類似した役割を果たしていたと考えられる。その一例として硫化鉄膜表面での自己触媒反応が挙げられる(Wachtershauser, 1988)。しかしこの仮説では自己複製が説明されない問題点も残る。プルシアンブルー(PB)は、水溶液中でコロイド状に分散し、広い表面積を有することで分子の吸着・化学反応の場を提供する。現在よりもFe2+が豊富に存在したであろう初期地球の海洋でPBは普遍的に生成したと考えられ(Orgel, 1974)、特にCold Origin of Life仮説(Bada et al. 1994)との繋がりが期待される。そこで本研究では、PBの代謝機能性を検証するため、室温水溶液中での有機分子との相互作用を調べた。
  • Dai Shiota, Satoru Nakashima
    Chemistry Letters
    2005年 34 巻 2 号 158-159
    発行日: 2005年
    公開日: 2004/12/25
    ジャーナル 認証あり
    In order to revisit the kinetics of amino acid transformation in the chemical evolution, a series of hydrothermal experiments has been conducted for threonine (Thr) solution. Thr transformed into glycine (Gly) and other products including peptides and polymers at 121 to 160 °C. The Thr → Gly decomposition rate (k1) is different from apparent Thr decreasing rate (k), because of the presence of other side reactions.
  • Y. Miura, S. Fukuyama
    高圧力の科学と技術
    1998年 7 巻 1306-1308
    発行日: 1998/03/03
    公開日: 2010/02/05
    ジャーナル フリー
    Shock wave energy plays an important role in formation of pseudo-life precursors (PLP), recycling of carbon-bearing compounds in primitive Earth and Mars. Strong candidates for the PLP is carbohydrate SO3 which shows duplicating reaction (polymerization), enzyme-like activity (supramolecules), recycling system between monomer-polymer, between inorganic-organic molecules) and easy formation in anoxic condition. The PLP can be formed widely if there are hot sea-water and carbon dioxide atmosphere on primitive Earth and Mars. Formation of primitive life evolution (mainly on the Earth) is caused by prolonged heavy and slow impacts from Earth's ring fragments (not from asteroids) produced by giant impact. Primitive sea-water is formed after multiple impacts.
  • Takuji Sasaki
    Breeding Science
    2011年 61 巻 3 号 223
    発行日: 2011年
    公開日: 2011/09/08
    ジャーナル フリー
  • へるまん べるぐ
    Review of Polarography
    2004年 50 巻 1 号 54-59
    発行日: 2004/05/28
    公開日: 2011/10/21
    ジャーナル フリー
  • Hironari Kurihara, Hikaru Yabuta, Takeo Kaneko, Yumiko Obayashi, Yoshinori Takano, Kensei Kobayashi
    Chemistry Letters
    2012年 41 巻 4 号 441-443
    発行日: 2012/04/05
    公開日: 2012/04/04
    ジャーナル オープンアクセス
    We observed formation of organic aggregates from a solution of complex organics which were abiotically synthesized from a simulated primitive earth atmosphere with high-energy protons. The structure of the complex organics was partly altered under hydrothermal conditions to form organic aggregates. The aggregates possessed properties of combined amino acids, which had high tolerance against heating. Formation of this kind of organic aggregates might have been an important step in the chemical evolution leading to the origin of life.
  • M. F. GLAESSNER
    地学雑誌
    1966年 75 巻 6 号 307-315
    発行日: 1966/12/25
    公開日: 2009/11/12
    ジャーナル フリー
  • Hideo Hashizume, Kazuko Fujii
    Clay Science
    2016年 20 巻 2 号 21-25
    発行日: 2016年
    公開日: 2017/12/05
    ジャーナル フリー

    Clay minerals are believed to play an important role in the origin of life. Bio-molecules initially formed in the shallow ocean could be adsorbed by clay minerals (e.g. montmorillonite) and/or intercalated between their interlayers, thereby protected from damage by cosmic ray and UV irradiation. The mineral particles could sink to the ocean floor and release bio-molecules under basic pH condition, such as near a highly basic hydrothermal vent. The mineral particles also serve as the location and catalyst for the polymerization of these bio-molecules, which is a crucial step in chemical evolution. As a model system, we experimentally investigated the adsorption and desorption of adenine on montmorillonite. Adsorption at pH 2.5 was found to be much larger than at pH 8.5. Since adenine is positively charged in the acidic condition, it is readily adsorbed by montmorillonite and/or intercalated into its interlayers. It was difficult to remove adenine from the interlayer, as it does not desorb in neutral or acidic (HCl) solutions. In a basic solution adenine is charge neutral, and the amount of its adsorption by montmorillonite at pH 8.5 is very small. Meanwhile, at pH 8.5, adenine in the montmorillonite interlayers is readily replaced by Na+ in the solution, and therefore desorbs easily. pH value clearly affects the adsorption/desorption behavior of adenine on/from montmorillonite.

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