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Possibility for polymerization of organic molecules in carbonates - Approach to research for origin of life

碳酸盐中有机分子聚合的可能性 - 生命起源研究方法

基本信息

批准号：
12640469
负责人：
KAI Ayako
金额：
$ 1.98万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640469/
关键词：
calcium carbonate calcite vaterite amino acid crystal growth hybridization radiation electron spin resonance ESR

项目摘要

Vaterite with a thermally unstable phase is crystallized dominantly under the coexistence of noncharged-polar and acidic amino acids. Basic amino acids slightly affected the vaterite formation, while nonpolar amino acids had no effect on it. SEM photographs indicated that vaterite was prevented from growing in the initial stage of precipitation. Among the factors investigated, it was determined that pH of the solution and the molecular weight of the amino acids did not affect the formation of vaterite but the incorporation of amino acids was necessary. The content of vaterite was correlated to the concentration of amino acids in CaCO_3.Differential scanning calorimetry showed an exothermic peak around 450℃ attributable to the phase transition from vaterite and an exothermic peak around 410℃ due to the phase transition from aragonite to calcite. The phase-transition temperature is related with the decomposition temperature of amino acid in the precipitates. The vaterite phase in amino-acid-doped CaCO_3 seemed to be stabilized at ambient temperature by the change of crystal energy.Semi-empirical quantum-mechanical techniques using ZINDO : INDO1 indicated the possibility that amino acids are covalently bonded to CaCO_3, and the assumption that the reactivity of the acidic amino acids is the highest, and that of the basic ones is the lowest of the four types of amino acids. This assumption is consistent with the experimental results.Radiation induced organic radicals in amino-acid -doped CaCO_3. However, the radicals have a -C(NH)CH_3 component which is absent from those in irradiated amino acid crystals. Thus, the radicals with amino group in amino-acid-doped CzCO_3 appear to play an important role in the synthesis of peptide with -CO-NH- bonds between two amino acid molecules. It is considered that the hybrid carbonate formed on the primitive earth might have provided a reaction field for the pre-biomolecule synthesis.

具有热不稳定相的钒矾主要在非带电极性和酸性氨基酸共存的条件下结晶。碱性氨基酸对水晶石的形成有轻微影响，非极性氨基酸对水晶石的形成没有影响。扫描电镜照片表明，在降水初期，水晶石被阻止生长。在研究的因素中，确定了溶液的pH值和氨基酸的分子量对水晶石的形成没有影响，但氨基酸的掺入是必要的。钙矾石的含量与CaCO_3中氨基酸的浓度相关。差示扫描量热法显示，在450℃左右有一个放热峰，这是由水晶石相变引起的；在410℃左右有一个放热峰，这是由文石向方解石相变引起的。相变温度与沉淀中氨基酸的分解温度有关。氨基酸掺杂CaCO_3的水晶石相似乎在室温下通过晶体能量的变化得到了稳定。利用ZINDO: INDO1的半经验量子力学技术表明，氨基酸与CaCO_3存在共价键的可能性，并假设酸性氨基酸的反应活性最高，碱性氨基酸的反应活性最低。这个假设与实验结果是一致的。辐射诱导氨基酸掺杂CaCO_3中的有机自由基。然而，自由基具有-C(NH)CH_3成分，这是辐照氨基酸晶体中不存在的。由此可见，氨基酸掺杂的CzCO_3中具有氨基的自由基在两个氨基酸分子间具有- co - nh -键的肽的合成中发挥了重要作用。认为原始地球上形成的杂化碳酸盐可能为前生物分子合成提供了反应场。