海带中生命元素的ICP－AES研究

应用ＩＣＰ－ＡＥＳ技术测定了Ｓｒ、Ｃａ、Ｍｇ、Ｐ、Ｆｅ、Ｃｕ、Ｍｎ和Ｚｎ等８种生命元素在海带中的分布，发现三种分布模式：（１）Ｆｅ、Ｃｕ、Ｍｎ、Ｚｎ在叶状体末端和边缘、固着器末端含量高．其余部位含量低；（２）Ｓｒ和Ｃａ的分布规律与第一类相似，但固着器基部高于固着器末端；（３）Ｍｇ和Ｐ均匀分布．Ｓｒ和Ｃａ分布上的相似性提示了它们生理功能上的相似性．这些数据为研究微量元素在海带中的生理功能提供了新资料。     

必需微量元素的发现简史及锗的必需性问题

概述了必需微量元素的发现简史和锗在生物微量元素周期表中的特殊地位，列出了锗可能也是必需微量元素的某些证据。     

儿童的铅中毒问题——Ⅰ.上海和苏州地区儿童发铅水平研究

用X射线荧光分析法测定了上海和苏州地区2402例正常人头发样品,探讨了儿童的发铅特征及正常值上限和慢性铅中毒界限。结果表明,人发铅的正常值上限为25.0×10~(-6),筛选慢性铅中毒的界限为42.5×10~(-6)。以苏州地区260例0～10岁儿童所作的统计,有38.8％的儿童发铅超过正常值上限,17％的儿童可能有慢性铅中毒的危险。其中0～4岁儿童超标分别占超标总数的88.1％和86.7％。     

海带细胞壁及细胞壁多糖中Sr,Ca,Mg,P分布

对海带细胞壁及细胞壁中的藻酸盐、褐藻糖胶、纤维素等多糖类物质中的Ｓｒ、Ｃａ、Ｍｇ、Ｐ含量作了ＩＣＰ－ＡＥＳ测定。结果显示，海带中的锶主要位于细胞壁，细胞壁中的锶主要位于揭藻糖胶。     

A concise total synthesis of (+/-)-alantrypinone by a novel hetero-Diels-Alder reaction

[reaction: see text] An efficient total synthesis of (+/-)-alantrypinone (1) and its 17-epi isomer (17) has been accomplished employing a novel aza-Diels-Alder reaction as the key step. The reaction sequence comprises 8 steps starting from anthranilic acid and proceeds in 13.5% overall yield. An interesting anionic equilibration between 1 and its epimer 17 has also been discovered.     

Calcium adsorption on MgO(100): energetics, structure, and role of defects

The adsorption of Ca on the MgO(100) surface at 300 K has been studied using microcalorimetry, in combination with LEED, AES, ISS, work function, sticking probability measurements, and density functional theory (DFT) calculations. The MgO(100) thin films (approximately 4 nm thick) were grown epitaxially on a 1 microm thick Mo(100) single-crystal. The sticking probability of Ca on MgO(100) at 300 K is unity. On the basis of AES and ISS measurements, it was determined that Ca grows mainly as 3D particles on the MgO(100) surface with a density of approximately 1 x 10(12) islands/cm2. Ca adsorbs initially at defect sites with a very high heat of adsorption (approximately 410 kJ/mol). DFT calculations attribute this high initial heat to Ca binding to kink sites (376 kJ/mol), step sites (205 kJ/mol), and lower concentrations of stronger binding sites. The heat of adsorption decreases rapidly with coverage, reaching a minimum of 162 kJ/mol at approximately 0.3 ML, where Ca is mainly adding to small 3D Ca clusters. Afterward, it increases to the value of bulk Ca heat of sublimation (178 kJ/mol) at approximately 1.2 ML, attributed to the increase in stability with increasing Ca particle size. A 1.0 eV decrease of the work function with Ca coverage from 0 to 0.3 ML indicates that Ca adsorbed at defects is cationic, in agreement with calculations showing that Ca donates electron density to the MgO. Light ion sputtering of the MgO(100) surface generates point defects, but these do not change the heat of adsorption versus coverage, implying that they do not nucleate Ca particles. Oxygen vacancies are a likely candidate; DFT calculations show that F and F+ center vacancies bind Ca more weakly than terrace sites. More extensive sputtering creates extended defects (such as steps and kinks) that adsorb Ca with heats of adsorption up to approximately 400 kJ/mol, similar to that at the intrinsic defect sites.     

Study of protein binding and micellar partition of highly hydrophobic molecules in a single system using capillary electrophoresis

The measurement of protein binding of highly hydrophobic molecules is challenging due to poor solubility and strong adsorption, and further complicated by the competition of lipophilic partition in biological systems. Here, an attempt is presented to simultaneously simulate protein binding and lipophilic partition of hydrophobic molecules in a single system using CE. In this system, the incorporated biocompatible micelles also facilitate the protein binding study of hydrophobic molecules by enhancing their solubility (27 to 10(4) times) and eliminating the problematic adsorption. An equation is derived to describe the competition of protein binding and lipophilic partition and to estimate the protein binding constants in nonmicellar aqueous solution. Five polycyclic aromatic hydrocarbons (PAHs) and HSA were used as model hydrophobic compounds and protein, respectively. The study of the competition between lipophilic partition and protein binding reveals that the binding of the PAHs to HSA is governed by hydrophobic interactions and such binding (except naphthalene) can be eliminated by the lipophilic partition in the nonionic surfactant Tween-20. The developed method may be extended to evaluate the interactions of various macromolecules (receptors, enzymes, proteins, and DNA/RNA) and hydrophobic molecules.     

科学补碘:消除碘缺乏病的成败关键

碘对甲状腺功能具有双向作用,在消除碘缺乏病的同时,切不可忽略全民食盐加碘后高碘甲状腺病的防治。分别从水碘和尿碘两个方面论述了碘与甲状腺病之间的双向关系,并根据流行病学调查数据和全国碘缺乏病监测数据确定了盐碘与尿碘之间的数学关系,计算了食盐碘含量的最适宜范围,提出了下调食盐碘含量、设计区域化碘盐和补碘个性化的科学补碘新策略。     

1953—2005年中国燃煤大气铅排放量估算

采用随时间变化的铅排放因子估算了中国1953—2005年燃煤大气铅排放量。在52年间,中国燃煤累计向大气排放19.1万t铅,平均每年以4.02%的速度增加,其中2001—2005年排铅38 688 t,平均增速达9.55%;工业用煤的铅排量占总量的87%,生活用煤铅排量占8%;2006年的燃煤铅排量超过了10 000 t。这表明,燃煤造成的铅污染已成为当前中国面临的重要环境问题。     

过渡金属催化醇氧化反应的研究进展

氧化醇为相应的羰基化合物在有机化学基础研究及其工业应用中占有非常重要的地位.在众多关于醇氧化反应的研究中,如何使用对环境友好的氧化剂替代传统的氧化剂,选择具有高性能、廉价、清洁、可回收的催化剂,一直是化学工作者研究的一个热点.综述了近年来该研究领域中的一些重要过渡金属催化体系,并简要介绍了各类催化氧化体系的催化效果.