Hydroxyapatite gels and nanocrystals prepared through a sol-gel process

We have investigated the effect of the Ca/P molar ratio on the structural and morphological properties of hydroxyapatite (HA) gels and nanocrystals. The sol-gel process was carried out in aqueous, and alternatively in alcoholic medium (50% water-50% ethanol), at 37°C. Gel samples were obtained by drying the sols at 37°C or at 80°C, whereas powder samples were obtained by filtering the sols. Heat treatment at temperatures as low as 300°C is enough to obtain pure HA from the gels with a Ca/P molar ratio of 1.00 and 1.67. At variance, heat treatment of the gels with a Ca/P of 2.55 always produces secondary phases. The degree of crystallinity of HA increases with the Ca/P molar ratio of the sols, and it is slightly affected by the presence of ethanol in the precipitation medium. Filtering of the sols provides powders constituted of nanocrystalline HA that exhibit degree of crystallinity, crystal morphology and thermal stability closely related to the sols composition.     

THE EFFECTS OF PERFUSION OF LATERAL VENTRICLE WITH CaCl_2 ON THE FEBRILE RESPONSE AND cAMP CONTENT IN PLASMA AND CEREBROSPINAL FLUID DURING LP-INDUCED FEVER

Artificial cerebrospinal fluid (c.s.f.) containing 40 mmol/L excess calcium was perfus-ed through the lateral ventricles of New Zealand white rabbits in order to reduce the Na~+/Ca~(++) ratio in the brain and the effects on both the febrile response and adenosine cyclic mo-nophosphate (cAMP) concentration in plasma and c.s.f, during leucocytic pyrogen (LP)-induced fever were observed. The results showed that cAMP concentration in c.s.f, increas-ed significantly during LP-induced fever while the cAMP level in Plasma remained unchang-ed, and the perfusion of artificial c.s,f, containing 40 mmol/L excess calcium can signif-icantly inhibit not only the febrile response but also the increase in c.s.f, cAMP level,while there appears no effect on plasma cAMP concentration, thus demonstrating that theincrease of Na~+/Ca~(++) ratio causing the increase of cAMP content in the brain may be anessential link in the pathogenesis of LP-induced fever.     

Structure-property modelling of complex formation of strontium with organic ligands in water

The method of substructural molecular fragments based on representation of the molecular graph by ensembles of fragments and involving calculations of those contributions to the given property is applied to the modelling of stability constants of the complexes of strontium(II) with organic ligands in water. Reliability of predictions of developed structure-property models was examined using three different test sets of structurally diverse ligands. The obtained models have been used for generation and screening of combinatorial library of virtual ligands. Some hypothetical efficient Sr(II) binders were suggested.     

桑蚕丝素蛋白初始结构对其矿化作用的影响

以碱金属离子诱导桑蚕丝素蛋白溶液发生构象转变, 研究了蛋白质初始结构对其矿化作用的影响. FT-IR, XRD和SEM等测试结果显示, 未经任何处理的桑蚕丝素蛋白溶液矿化后形成片状复合物, 其无机相以二水磷酸氢钙(DCPD)为主; 而经过K^＋和Na^＋金属离子处理后, 桑蚕丝素溶液的结构由无规线团/螺旋构象向β-折叠发生转变, 矿化后成纤维状, 并相互结合呈现纳米级的三维多孔结构, 其无机相以热力学稳定的羟基磷灰石(HA)为主. 可以认为, 丝素蛋白结构转化为较伸展的β-折叠后, 使得更多的亲水基团暴露在外面, 在丝素蛋白分子不断凝聚成纤过程中, HA结晶快速生长并附着在这些微纤上, 最终形成纤维状的丝素蛋白/HA复合物. 该结果为阐明蛋白质的生物矿化过程及其调控机理提供了理论依据, 同时可以从矿化复合物的形成来反映这些微量元素可能对骨组织形成的影响, 为临床骨组织的修复提供一定的参考.     

钙钛矿型复合氧化物Ca_xSr_（1－x）TiO_3催化剂上的甲烷氧化偶联反应

在固定床反应器上，评价了不同温度下钙钛矿型复合氧化物ＳｒＴｉＯ３和ＣａＴｉＯ３的组成变化对甲烷氧化偶联反应的影响．同时，利用ＸＰＳ和ＣＯ２－ＴＰＤ对催化剂的结构及其氧物种的反应特性进行了表征．结果表明：ＳｒＴｉＯ３和少量Ｃａ掺杂的ＣａｘＳｒｌ－ｘＴｉＯ３有利于在较低温度（９２３Ｋ）下催化反应的活性和选择性，而ＣａＴｉＯ３体系则在高温（１０７３Ｋ）下表现出较好的活性和选择性．钙钛矿型复合氧化物ＳｒＴｉＯ３和ＣａＴｉＯ３组成变化对不同温度下反应活性的影响与ＣＯ２－ＴＰＤ的脱附谱图有很好的平行关系．     

甲烷在SrO-La2O3/CaO催化剂上的氧化偶联Ⅱ.反应动力学的研究

在２０％Ｌａ２Ｏ３／ＣａＯ（ＬＣ）催化剂中添加ＳｒＯ（添加ＳｒＯ的ＬＣ以ＳＬＣ表示）明显地提高了反应活性和Ｃ２选择性。反应动力学研究表明，ＬＣ和ＳＬＣ催化剂在甲烷氧化偶联反应中，在表观活化能和表观反应级数上存在很大的差异。ＬＣ催化剂在ＣＨ４转化以及Ｃ２和ＣＯｘ形成过程中，表观活化能大于ＳＬＣ催化剂，而ＳＬＣ催化剂的指前因子小于ＬＣ体系，两者存在着补偿形象。ＳＬＣ催化剂的反应速率常数比ｋｃ２／ｋＣＨ     

Measurement of acid-catalyzed isomerization of unsaturated aldehyde-2,4-dinitrophenylhydrazone derivatives by high-performance liquid chromatography analysis

Aldehyde-2,4-dinitrophenylhydrazones exist as (E)- and (Z)-geometrical isomers, and adventitious isomerization during sample preparation can cause analytical errors. Purified alkenal-2,4-dinitrophenylhydrazone derivatives comprise only the (E)-isomer. However, partial isomerization to the (Z)-isomer occurs upon addition of acid to attain an equilibrium isomer ratio. The UV-visible spectral properties of the isomers differ; the (Z)-isomer exhibiting a 6-10 nm lower absorption maximum compared to the (E)-isomer. Alkenal-2,4-dinitrophenylhydrazones having a CC double bond at the 2- or 3-position of the alkenal exhibited similar absorption maxima with an equilibrium isomer ratio (0.035) that was much lower than those of other alkenals. The CC double bond at the 3-position migrates to a position of conjugation with the CN double bond during hydrazone synthesis to form a stabilized molecular structure. Alkenal-2,4-dinitrophenylhydrazones having a double bond at the 4-position or greater exhibited a similar absorption maxima equilibrium isomer ratio (0.14) to alkanal-2,4-dinitrophenylhydrazones. The quantitative analysis of carbonyl compounds in air or water using DNPH is usually conducted in the presence of an acid catalyst. Consequently, the solution of the direct extract prepared for HPLC or GC analysis contains both (E)- and (Z)-isomers.     

反相液相色谱中固定相和流动相对柱相比的贡献

依据柱相比的热力学定义和反相液相色谱中溶质的计量置换保留理论(the stoichiometric dispheement heory of solute for retention，SDT-R)，对反相液相色谱中固定相和流动相性质、温度对柱相比的影响进行了研究。结果表明：固定相的种类和配基的疏水性对柱相比影响较大，而流动相中有机溶剂的种类，特别是脂肪酸作为置换剂时，对柱相比的影响更大，而柱相比受温度的影响较小。此外，通过用27种小分子溶质对柱相比的测定，其logI和Z良好的线性关系，进一步证明柱相比是一个与溶质性质无关的常数。     

1,3-二烯基-1,1,3,3-四甲基二硅氧烷/苯乙烯共聚合的环化率与竞聚率

对１３０℃下１，３ 二烯基 １，１，３，３ 四甲基二硅氧烷（ＤＶＤＳ）／苯乙烯（Ｓｔ）的溶液环化共聚合动力学进行了研究．根据低转化率（＜１０％）的共聚物组成及环状结构比例，通过参数估计方法，求得环化率与竞聚率，分别为ｒ１＝０１０２、ｒ２＝３４８、ｒｃ＝００２１０、Ｋｃ＝３８１ｍｏｌ／Ｌ、Ｋ′ｃ＝０３８９ｍｏｌ／Ｌ，同时得到它们９５％置信概率的联合置信区间及其交互影响的联合置信区间．表明ＤＶＤＳ的反应活性较Ｓｔ低，其非环状结构自由基具有较强的分子内环化反应能力；环的位阻效应使环状结构ＤＶＤＳ自由基的活性低于其非环状结构自由基．     

Selective Oxidation of Methane to Methanol Using Molecular Oxygen on MoOx／（LaCoO3＋Co3O4） Catalysts

Comparatively high CH3OH selectivity (60.0%) and yield (6.7%) were obtained on MoOx/(LaCoO3 Co3O4) catalysts in selective oxidation of methane to methanol using molecular oxygen as oxidant. The interaction between MoOx and La-Co-oxide modified the molecular structure of molybdenum oxide and the ratio of O^-/O^2- on the catalyst surface, which controlled the catalytic performance of MoOx/(LaCoO3 Co3O4) catalysts.