Phase transition of calcium carbonates induced by amino acids

氨基酸诱导碳酸钙的相变

• 批准号: 10640466
• 负责人: KAI Ayako
• 金额: $ 2.11万
• 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: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640466/
• 关键词: phase transition; calcite; vaterite; aragonite; amino acid; transition temperature; method of molecular orbitals; enthalpy; 転移エンタルピー; 炭酸カルシウム

Vaterite of unstable phase yielded dominantly under the coexistence of Asp with an acidic side-chain, Gly, Asn, Ser and Thr with a noncharged-polar side chain. Basic amino acids affected slightly on the vaterite formation, while nonpolar amino acids had no effect on it. Among the factors investigated, pH of the solution and the molecular weight of the amino acids were independent of the formation of vaterite but incorporation of amino acids was effective. Since the yield of vaterite correlated with the concentration of amino acids in the sample, the amino acids seem to stabilize the structure of vaterite and consequently inhibited to recrystallize to calcite of the thermally stable phase. SEM photographs also indicated that vaterite was prevented from growing in the initial stage of precipitation.Frontier orbitals and electrostatic potential computed by ZINDO : INDO1 leaded to two models for covalent bonds between amino acids and CaCOィイD23ィエD2. One, which is common for nonpolar, noncharged-polar and acidic amino acids, is a bond between the nitrogen of α-amino group and an oxygen of the surface COィイD23ィエD2ィイD12-ィエD1 ion in CaCOィイD23ィエD2. Another for basic amino acids is a bond between an oxygen of α-carboxyl group and a carbon of the surface COィイD23ィエD2ィイD12-ィエD1 ion. Taking the Coulomb interaction into consideration, it is presumed that the reactivity is higher for the amino acids, and lower for the basic amino acids than the others. The presumption is consistent with the experimental results.DSU curves of hybrid crystals containing vaterite revealed an exothermic reaction peak at about 450℃ corresponding to the transition from vaterite to calcite, while aragonitic samples showed an exothermic reaction peak at about 410℃, to the transition to calcite. The temperatures depended on the species of amino acids, and the correlation was found between the temperature of the transition of the transition from vaterite to calcite and the melting point of amino acids.

在酸性侧链的Asp和极性侧链的Gly、Asn、Ser、Thr共存时，不稳定相球文石的生成占主导地位。碱性氨基酸对球文石的形成影响不大，非极性氨基酸对球文石的形成影响不大，溶液pH值和氨基酸分子量对球文石的形成没有影响，但加入氨基酸对球文石的形成有促进作用。由于球文石的产率与样品中氨基酸的浓度相关，氨基酸似乎稳定了球文石的结构，因此抑制重结晶为热稳定相的方解石。用ZINDO：INDO 1计算的前线轨道和静电势，得到了氨基酸与CaCO_（23）D_2形成共价键的两种模型。一种是非极性、非带电极性和酸性氨基酸常见的键，是α-氨基的氮和CaCO_（23）D_2中表面CO_（23）D_2 D_2 D_12-D_1离子的氧之间的键。碱性氨基酸的另一个键是α-羧基的氧与表面CO键D23键D2键D12-键D1离子的碳之间的键。考虑到库仑相互作用，推测氨基酸的反应活性较高，碱性氨基酸的反应活性较低。含球文石和文石的混合晶体在DSU曲线上分别在450℃和410℃出现一个放热反应峰，对应于球文石向方解石的转变。温度依赖于氨基酸的种类，并且发现从球文石到方解石的转变的转变温度与氨基酸的熔点之间存在相关性。