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珍珠、贝壳和甲壳是生物矿化的产物,具有高强度、高韧性。人们已对它们的组成、结构等进行了大量的研究犤1~4犦。结果表明,它们的主要成分是碳酸钙,但由于含有少量的蛋白质等有机基质,使其结构具有特殊的组装方式,从而显示出与纯碳酸钙迥然不同的优良物理性质和重要的生物功能。另一些研究表明胆结石、尿结石等异常生物矿化产物中也含有一定量的碳酸钙犤5犦。然而生物矿化过程非常复杂,其机理至今尚无统一说法。因此模拟生物矿化过程,了解有机基质在矿化过程中的作用,已成为化学、生物、医学和材料等多学科相互渗透和相互交叉的… 相似文献
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N3- is a kind of ligand with very strong power for coordination, and is able to bind with many kinds of metal ions or metalloproteins. The metal ions in metalloproteins usually locate at the active site of them, and the combination of other chemical compound(s) to them will cause great influence on the structure and function of them. In addition, the combination can also provide information of the structure of the active site of the enzymes, and that of the higher-order structure of the enzyme. In this paper, we studied the interaction between N3- and PPOⅡ from Nicotina Tobacco by the determination of changes in enzymatic activity, UV-Vis, fluorescence spectra and FT-IR. The results showed that N3- can activate PPOⅡ with a near linear increase in enzymatic activity to the concentration of N3- when the [N3-]/[PPOⅡ](molar/molar) is less than or equal to 1.0, and that the enzymatic activity begins to decrease from 1.0 to 4.0; N3- didn’t coordinate directly with Cu2+ in the active site, but may interact with the side chain groups with positive charges, and further resulted in the increase in α-helix and the slightly decrease in β-turn, random coil and extended chain; the Cu2+ may locate deeply in the inner part of PPOⅡ, and coordinates strongly with nitrogen atoms in imidazole of histidine; N3- can quench the fluorescence of PPOⅡ, and make the microenvironments of Trp residues more polar after the interaction between N3- PPOⅡ. 相似文献
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用FT-IR、XRD、SEM和TGA等研究了4种不同模拟体系中胆红素钙晶体的成核与生长情况,考察了生物大分子和CO2对胆红素钙的成核与结晶等的影响。结果表明,水溶液中胆红素钙很难结晶形成晶体结构,但在暴露大气中的葡聚糖水溶液模拟体系中则形成了含质量分数为12%碳酸钙的胆红素钙/碳酸钙复合晶体。在此过程中,CO2气体促进了碳酸钙晶体的形成,碳酸钙晶体不同晶面的选择吸附性能和葡聚糖分子的含O功能团为胆红素钙的成核提供了有效位点和定向调控作用,共同模板作用诱导调控了在2θ为19.8°、21.8°有强衍射峰的胆红素钙晶体的形成。晶态胆红素钙具有明显的热分解温度,而处于非晶态时则无此种现象。 相似文献
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The Thermal Decomposition of Calcium Carbonate 总被引:1,自引:0,他引:1
Yu Ting ZHAO* Tong Shan SUN Bing SUN Department of Chemistry Shandong University Jinan 《中国化学快报》2001,(8)
The thermal decomposition reaction of calcium carbonate is a typical thermal decompo- sition reaction of the solid state. A great deal of studies on this reaction have been performed by previous investigators. This paper reports a procedure for estimating the non-isothermal kinetic parameters and the reaction mechanism of calcium carbonate.TG-DTG experiments were carried out on a LCT-1 model thermobalance and a WF-1 model differentiator with a TG-DTA-DTG simultaneous device. The size of… 相似文献
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Calcium carbonate was synthesized in a CaCl2/NaCO3 mixed solution by using ethylenedi-aminetetraacetic acid (EDTA) as an additive. The thermodynamics and kinetics analyses indicate that although the driving force of amorphous calcium carbonate (ACC) precipi-tation is always less than that of calcite and vaterite precipitation, the nucleation rate of ACC is greater than that of calcite and vaterite at the initial stage of the precipitation reaction. With the increasing incubation time, vaterite and calcite particles nucleate het-erogeneously by using the as-formed particles as active sites. Scanning electron microscopyimages indicate that the transformation mechanism of ACC and vaterite to calcite is the dissolution-recrystallisation reaction. The presence of EDTA not only improves the stabil-ities of ACC and vaterite, but also leads to forming enlongated, connected rhombohedralcalcite crystals after incubation 7 days in solutions. The ACC and vaterite are stabler in air than in solutions at room temperature, although the dissolution-recrystallisation reaction occurs on the surface. 相似文献
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以葡聚糖为模板控制合成文石型碳酸钙 总被引:9,自引:0,他引:9
依据生物矿化的基本原理,在动态条件下以葡聚糖为模板,采用仿生的方法控制合成了具有独特形貌并含有少量葡聚糖的碳酸钙复合材料.用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外吸收光谱(FTIR)和电导率测定等手段对所得的复合碳酸钙进行了形貌与结构表征.结果表明,所得CaCO3为文石晶型,外貌类似菜叶.进一步的研究发现,在CaCO3结晶过程中葡聚糖与CaCO3之间存在超分子相互作用,并讨论了这种作用的可能机理. 相似文献
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聚合物基底上碳酸钙生物矿化的研究进展 总被引:1,自引:0,他引:1
生物矿化作用是自然界广泛存在的一种现象。它是在生物体的严格控制下进行的,生物体从周围的环境中有选择地吸收各种元素用于构建生物体内具有特殊功能的无机结构。本文系统综述了聚合物膜上碳酸钙生物矿化的研究进展。详细介绍和比较了"直接合成法"和"通过无定性碳酸钙转化法"两种不同的矿化模式,并讨论了各矿化因素包括:酸性大分子、温度和聚合物基底种类等不同的影响。直接合成法:即通过酸性大分子的调节直接在大分子表面生成稳定晶型的碳酸钙。无定性碳酸钙转化法既在高度饱和的碳酸钙溶液中,在大分子表面生成一层无定性碳酸钙膜,然后将其在一定湿度下转化成一种或几种结晶形式的碳酸钙。前一种模式是一种常规的方法,研究得也最多。后一种模式相对较新,它简单快捷,而且影响因素少。 相似文献
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Dr. John K. Berg Dr. Andreas Kempter Prof. Dr. Julian D. Gale Dr. Denis Gebauer 《Chemphyschem》2016,17(21):3535-3541
The understanding of the molecular mechanisms underlying the early stages of crystallisation is still incomplete. In the case of calcium carbonate, experimental and computational evidence suggests that phase separation relies on so‐called pre‐nucleation clusters (PNCs). A thorough thermodynamic analysis of the enthalpic and entropic contributions to the overall free energy of PNC formation derived from three independent methods demonstrates that solute clustering is driven by entropy. This can be quantitatively rationalised by the release of water molecules from ion hydration layers, explaining why ion association is not limited to simple ion pairing. The key role of water release in this process suggests that PNC formation should be a common phenomenon in aqueous solutions. 相似文献
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碳酸钙的原位合成及表面改性 总被引:3,自引:0,他引:3
利用碳化法, 选用几种常见的改性剂(硬脂酸钠、十八碳醇磷酸酯和油酸)对碳酸钙进行了原位合成及表面改性. 通过活化度、白度、接触角的测定, 对比了其改性效果, 同时通过傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)、透射电镜(TEM)等测试手段对产品进行表征. FT-IR结果表明, 改性剂与碳酸钙表面是以化学键合和物理吸附方式相结合. 碳酸钙改性后, 其红外υ3特征吸收峰出现约44 cm-1的蓝移现象. 对反应机理进行了初步探讨. 实验结果表明, 当十八碳醇磷酸酯用量达到2%(以碳酸钙的质量分数计)时, 产品活化度达到99.9%, 白度值达到97.3%, 接触角达到了122.25°, 从而为新型无机填料的制备提供了理论依据和合成手段. 相似文献
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采用慢气体扩散法, 以十八烯酸为软模板, 在天然木浆-聚酯纤维复合膜(Jetspun ClothTM膜)上仿生矿化原位合成碳酸钙. 衰减全反射傅里叶变换红外光谱表征和扫描电镜结果表明, 溶液中的部分十八烯酸会富集到Jetspun ClothTM膜上, 同时, 由于十八烯酸的羧酸根对钙离子的结合作用, 钙离子也被富集到Jetspun ClothTM膜上. 碳酸钙在Jetspun ClothTM膜的纤维上生长, 并最终形成碳酸钙薄膜-高分子纤维膜复合结构. 相似文献
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近年来国内外对以CaCO3为主的无机刚性粒子增强、增韧聚烯烃的基础和应用研究取得重大进展,填充的主要目的已从降低成本转向提高材料性能,展现出钙塑材料新的更广阔的应用前景。本文用人工光老化方法和红外光谱分析手段,对涉及材料使用寿命的光老化性能进行了研究,以期为这类钙材料的进一步推广应用提供更全面的理论和实际依据。 相似文献
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Effects of Calcium Ions on Thermodynamic Properties of Mixed Bilirubin/Cholesterol Monolayers 下载免费PDF全文
Qiong Wu Yu-feng Tang Ye-min Li An-jian Xie Yu-hua Shen Jin-miao Zhu Chuan-hao Li 《化学物理学报(中文版)》2008,21(2):156-162
The mixed monolayer behavior of bilirubin/cholesterol was studied through surface pressure-area (?-A) isotherms on aqueous solutions containing various concentrations of calcium ions. Based on the data of ?-A isotherms, the mean area per molecule, collapse pressure, surface compressibility modulus, excess molecular areas, free energy of mixing, and excess free energy of mixing of the monolayers on different subphases were calculated. The results show an expansion in the structure of the mixed monolayer with Ca2+ in subphase, and non-ideal mixing of the components at the air/water interface is observed with positive deviation from the additivity rule in the excess molecular areas. The miscibility between the components is weakened with the increase of concentration of Ca2+ in subphase. The facts indicate the presence of coordination between Ca2+ and the two components. The mixed monolayer, in which the molar ratio of bilirubin to cholesterol is 3:2, is more stable from a thermodynamic point of view on pure water. But the stable 3:2 stoichiometry complex is destroyed with the increase of the concentration of Ca2+ in subphase. Otherwise, the mixed monolayers have more thermodynamic stability at lower surface pressure on Ca2+ subphase. 相似文献