Accelerated reactions of amines with carbon dioxide driven by superacid at the microdroplet interface

Microdroplets display distinctive interfacial chemistry, manifested as accelerated reactions relative to those observed for the same reagents in bulk. Carbon dioxide undergoes C–N bond formation reactions with amines at the interface of droplets to form carbamic acids. Electrospray ionization mass spectrometry displays the reaction products in the form of the protonated and deprotonated carbamic acid. Electrosonic spray ionization (ESSI) utilizing carbon dioxide as nebulization gas, confines reaction to the gas–liquid interface where it proceeds much faster than in the bulk. Intriguingly, trace amounts of water accelerate the reaction, presumably by formation of superacid or superbase at the water interface. The suggested mechanism of protonation of CO₂ followed by nucleophilic attack by the amine is analogous to that previously advanced for imidazole formation from carboxylic acids and diamines.

Microdroplets display distinctive interfacial chemistry, manifested as accelerated reactions relative to those observed for the same reagents in bulk.     

Disulfide bond cleavage induced by a platinum(II) methionine complex

The cleavage of a disulfide bond and the redox equilibrium of thiol/disulfide are strongly related to the levels of glutathione (GSH)/oxidized glutathione (GSSG) or mixed disulfides in vivo. In this work, the cleavage of a disulfide bond in GSSG induced by a platinum(II) complex [Pt(Met)Cl2] (where Met = methionine) was studied and the cleavage fragments or their platinated adducts were identified by means of electrospray mass spectrometry, high-performance liquid chromatography, and ultraviolet techniques. The second-order rate constant for the reaction between [Pt(Met)Cl2] and GSSG was determined to be 0.4 M(-1) s(-1) at 310 K and pH 7.4, which is 100- and 12-fold faster than those of cisplatin and its monoaqua species, respectively. Different complexes were formed in the reaction of [Pt(Met)Cl2] with GSSG, mainly mono- and dinuclear platinum complexes with the cleavage fragments of GSSG. This study demonstrated that [Pt(Met)Cl2] can promote the cleavage of disulfide bonds. The mechanistic insight obtained from this study may provide a deeper understanding on the potential involvement of platinum complexes in the intracellular GSH/GSSG systems.     

Adenanthusone,a New Ursane Type Nortriterpenoid from Isodon adenanthus

A new ursane‐type nortriterpenoid, adenanthusone (=(11α,12α)‐4‐demethyl‐11,12‐epoxy‐3,13‐dihydroxy‐2‐oxoursa‐3,20(30)‐diene‐28‐oic acid γ‐lactone; 1 ) was isolated from Isodon adenanthus. Its structure was determined by NMR spectra and X‐ray crystallographic diffraction analysis. The biogenetic implication of the nortriterpene is discussed.     

CH4, CO2和H2O在非金属原子修饰石墨烯表面的吸附

煤层气(矿井瓦斯)是一种有望替代传统化石燃料，如煤、石油和天然气的非常规气体. 作为可得的清洁能源，它的利用被认为是节能和经济的选择. 在本工作中，非金属原子X(X=H，O，N，S，P，Si，F，Cl)修饰的石墨烯(Gr)被用来代表具有结构异性的煤表面模型. 通过密度泛函理论系统地研究了煤层气组分Y(Y=CH₄，CO₂，H₂O)在非金属原子修饰石墨烯上的吸附作用. 结果表明Y在非金属原子修饰石墨烯上的吸附均为物理吸附. 态密度和差分电荷密度共同表明了这种弱的相互作用.其中，H和Cl对CH₄的作用较大； N、O、F、Cl对CO₂的作用较强； N，Cl对H₂O的影响不容忽视. 总的来说，吸附能大小依次为：H₂O>CO₂>CH₄. 因此，在CH₄富集的煤层里注入H₂O或CO₂可以与CH₄形成竞争吸附，进而提高煤层气采收率. 本工作提供了在分子水平下煤层气与非金属原子修饰石墨烯之间的相互作用的详情，并为煤层瓦斯的开采与分离提供了有用的信息.     

不同孔径硅胶聚合物键合相对蛋白质分离的影响

介绍了不同孔径的硅胶聚合物键合相的合成，比较了其对蛋白质的分离特性。结果表明，大孔径的硅胶聚合物键合相比表面积小，易于获得生物大了分子的快速分离。     

A note on differentiability of the cluster density for independent percolation in high dimensions

The cluster density function of independent percolation in ad-dimensional lattice is considered. For eachn, it is shown that(p) has finitenth leftderivative at critical probabilityp _c ifd is sufficiently large. This result agrees with the Bethe lattice approximation, where thenth one-sided derivative of(p) is bounded atp _c for alln.     

基于三维静电势参数研究C60溶解性的构效关系

在量子化学从头算基础上,对一系列溶剂化合物分子进行了结构优化和三维静电势参数计算,运用多元线性回归分析和神经网络方法对C60在121种不同溶剂的溶解性与计算的结构参数进行了构效关系研究.用建立起来的QSPR 关系式对15种不同结构类型溶剂进行了预测,并阐述了C60溶质与不同溶剂之间的相互作用,获得了满意的结果.