Synthesis and anion binding properties of 2,5-diamidothiophene polypyrrole Schiff base macrocycles

[reaction: see text] Two easy-to-synthesize polypyrrolic 2,5-diamidothiophene Schiff base macrocycles are reported, along with their anion binding properties as determined via UV-vis spectroscopic titrations carried out in dichloroethane. There is a striking difference between the interactions with anions of the two macrocycles, a finding ascribed to differences in their rigidity. For example, the more flexible dipyrromethane-derived macrocycle displays a 1.2:1 hydrogen sulfate versus nitrate selectivity, while its more rigid bipyrrole-derived congener shows a 7.4:1 selectivity in favor to hydrogen sulfate.     

Thermal expansion properties of organic crystals: a CSD study

The thermal expansion properties of crystalline organic compounds are investigated by data mining of the Cambridge Structural Database (CSD). The mean volumetric thermal expansion coefficient is 168.8 × 10⁻⁶ K⁻¹ and the mean uniaxial thermal expansion coefficient is 71.4 × 10⁻⁶ K⁻¹, based on 745 and 1129 different observations, respectively. Normal and anomalous coefficients can be identified using these values and the associated standard deviations. The anisotropy of the thermal expansion is also evaluated and found to have a very broad distribution. 4719 different structures, comprising 4093 different molecular compounds and 626 additional polymorphs have been analyzed on their thermal expansion properties. Approximately 34% of these structures may have at least one orthogonal axis with negative thermal expansion, much more than generally believed. Moreover 127 structures have been identified which could have negative volumetric thermal expansion. Experimental validation using a robust protocol with data collected at more than 2 different temperatures is required to validate these cases.

The thermal expansion properties of crystalline organic compounds are investigated by data mining of the Cambridge Structural Database (CSD). Negative uniaxial thermal expansion is much more common than generally believed.     

Hydrogen peroxide-generating nanomedicine for enhanced chemodynamic therapy

Chemodynamic therapy(CDT) is an emerging endogenous stimulation activated tumor treatment approach that exploiting iron-containing nanomedicine as catalyst to convert hydrogen peroxide(H_2O_2)into toxic hydroxyl radical(·OH) through Fenton reaction.Due to the unique characteristics(weak acidity and the high H_2O_2 level) of the tumor microenvironment,CDT has advantages of high selectivity and low side effect.However,as an important substrate of Fenton reaction,the endogenous H_2O_2 in tumor is still insufficient,which may be an important factor limiting the efficacy of CDT.In order to optimize CDT,various H_2O_2-generating nanomedicines that can promote the production of H_2O_2 in tumor have been designed and developed for enhanced CDT.In this review,we summarize recently developed nanomedicines based on catalytic enzymes,nanozymes,drugs,metal peroxides and bacteria.Finally,the challenges and possible development directions for further enhancing CDT are prospected.     

Mechanism of OH formation from ozonolysis of isoprene: a quantum-chemical study

The formation and unimolecular reactions of primary ozonides and carbonyl oxides arising from the O(3)-initiated reactions of isoprene have been investigated using density functional theory and ab initio molecular orbital calculations. The activation energies of O(3) cycloaddition to the two double bonds of isoprene are found to be comparable (3.3-3.4 kcal mol(-1)), implying that the initial two O(3) addition pathways are nearly equally accessible. The reaction energies of O(3) addition to isoprene are between -47 and -48 kcal mol(-1). Cleavage of primary ozonides to form carbonyl oxides occurs with a barrier of 11-16 kcal mol(-1) above the ground state of the primary ozonide, and the decomposition energies range from -5 to -13 kcal mol(-1). OH formation is shown to occur primarily via decomposition of the carbonyl oxides with the syn-positioned methyl (alkyl) group, which is more favorable than isomerization to form dioxirane (by 1.1-3.3 kcal mol(-1)). Using the transition-state theory and master equation formalism, we determine an OH yield of 0.25 from prompt and thermal decomposition of the carbonyl oxides.     

亚临床肝性脑病患者的血清锌,铜含量的测定及临床意义

检测了３０例慢性活动性肝炎患者、３０例肝硬化患者、３０例亚临床肝性脑病患者血清中的铜、锌含量，并与正常对照组进行比较分析，探讨了微量元素铜、锌的血清含量改变及其影响因素，分析其临床意义。结果表明体内的铜锌含量与肝脏功能有密切的关系。在慢性活动性肝炎时，虽然肝脏功能有一定的损害，但由于肝脏的代偿能力强，铜，锌含量仍可保持在正常水平，而在肝硬化、亚临床肝性脑病时，铜锌明显降低，而铜锌含量的降低又导致机     

Kinetic isotope effects implicate the iron-oxene as the sole oxidant in P450-catalyzed N-dealkylation

Multiple oxidants have been implicated as playing a role in cytochrome P450-mediated oxidations. Herein, we report results on N-dealkylation, one of the most facile reactions mediated by P450 enzymes. We have employed the N-oxides of a series of para-substituted 13C2H2-labeled N,N-dimethylanilines to function as both substrates and surrogate oxygen atom donors for P450cam and P4502E1. Kinetic isotope effect profiles obtained using the N-oxide system were found to closely match the profiles produced using the complete NAD(P)H/NAD(P)-P450 reductase/O2 system. The results are consistent with oxidation occurring solely through an iron-oxene species.     

超分子结构二氟尼柳插层镁铝水滑石的合成与表征

采用离子交换和共沉淀两种不同方法将二氟尼柳插入镁铝水滑石层间，得到一种新型的有机-无机层状复合材料。通过X射线粉末衍射、红外光谱、元素分析和热重-差热等手段对材料进行了表征。结果表明，离子交换法和共沉淀法成功地将二氟尼柳插入水滑石，得到的材料层状结构完整、晶相单一，且层间距均大于二氟尼柳分子尺寸，扩大为1.81～2.14 nm；二氟尼柳插入后，复合水滑石材料的热稳定性大幅度提高。客体二氟尼柳与主体层板之间存在超分子作用力，二氟尼柳分子的羧基与水滑石层板之间相互作用，以双层倾斜交替地排列于层板之间。此外，根据其超分子作用力建立了二氟尼柳插层镁铝水滑石的超分子结构模型。     

Effect of pressure on the proton transfer rate from a photoacid to a solvent. 4. Photoacids in methanol

The pressure dependence of the excited-state proton dissociation rate constant of four photoacids, 2-naphthol-6,8-disulfonate (2N68DS), 10-hydroxycamptothecin (10-CPT), 5-cyano-2-naphthol (5CN2), and 5,8-dicyano-2-naphthol (DCN2), are studied in methanol. The results are compared with the results of the pressure dependence study we recently conducted for several photoacids in water, ethanol, and propanol. The pressure dependence is explained using an approximate stepwise two-coordinate proton transfer model. The increase in rate, as a function of pressure, manifests a strong dependence of proton tunneling on the distance which decreases with an increase of pressure between the two oxygen atoms involved in the process. The decrease in the proton transfer rate with increasing pressure reflects the dependence of the reaction on the solvent relaxation rate. We found that, for the relatively weak photoacids 2N68DS, 10-CPT, and 5CN2, the proton transfer rate constant increases by a factor of about 5-8 at a pressure of about 1.5 GPa. For a strong photoacid like DCN2, the rate increase was only by a factor of 2.     

纳米TiO_2改性蚕丝丝素蛋白膜的研究

用溶胶凝胶法制备纳米TiO2改性再生蚕丝丝素蛋白膜.该丝素膜机械强度提高,在水中溶失率下降.UV、AFM、SEM测试的结果表明,丝素中纳米TiO2粒径约为80 nm,纳米粒子在丝素膜中分布均匀;XRD、FTIR测试结果表明,纳米TiO2的加入,可使改性丝素膜的结晶结构从SilkⅠ向SilkⅡ转化,其结晶度也随之提高;TGA测试表明改性丝素膜的热转变温度比纯丝素膜有所改变.     

5-溴水杨基荧光酮-溴化十六烷基三甲基铵吸光光度法测定微量锗

研究了在表面活性剂CTMAB存在下锗与5-溴水杨基荧光酮形成配合物的显色反应,在2mol·L~(-1)H_2SO_4介质中测得配合物的表观摩尔吸光系数为1.62×10~5.锗量在0～8μg/25ml范围内符合比耳定律.该体系反应酸度高,选择性好.方法稳定、决速.已用于水相直接测定人参、当归、灵芝、枸杞子和竹沥汁等中药材中微量锗,结果满意