Pharmacokinetics and metabolism study of veratramine in mice after oral administration using LC‐MS/MS

A simple and sensitive high‐performance liquid chromatography coupled with hybrid triple quadrupole–linear ion trap mass spectrometry (Q‐trap‐MS) method was developed and validated for the determination of veratramine, the major bioactive and neurotoxic component in Veratrum nigrum L. Veratramine and the internal standard (IS) were separated with a Waters Symmetry C₁₈ column and eluted with a gradient mobile phase system containing acetonitrile and 0.1% aqueous formic acid. The analysis was performed by using positive electrospray ionization mode with multiple reaction monitoring (MRM). Transition ions of m/z 410.2 → 295.2 for veratramine and m/z 426.1 → 113.8 for the IS were monitored. The method was validated with a good linearity in the range of 1–1000 ng/mL and lower limit of quantification of 1 ng/mL. The precision (CV) of intra‐ and inter‐day ranged from 3.92 to 7.29%, while the accuracy (bias) intra‐ and inter‐day were between ?4.78 and 1.65%. The recovery, stability and matrix effect were within the acceptable ranges. Five metabolites of veratramine, including four hydroxylated and one sulfated metabolites, were tentatively identified using predictive MRM–information dependent acquisition–enhanced product ion mode (predictive MRM‐IDA‐EPI). The developed method was successfully applied to the pharmacokinetic and metabolic study of veratramine in mice after oral administration of veratramine. Copyright © 2016 John Wiley & Sons, Ltd.     

Reduction and pH dual‐responsive block copolymers containing pendent p‐nitrobenzyl carbamate functionalities: Synthesis and self‐assembly behavior

We report on the preparation of reduction‐responsive amphiphilic block copolymers containing pendent p‐nitrobenzyl carbamate (pNBC)‐caged primary amine moieties by reversible addition–fragmentation chain transfer (RAFT) radical polymerization using a poly(ethylene glycol)‐based macro‐RAFT agent. The block copolymers self‐assembled to form micelles or vesicles in water, depending on the length of hydrophobic block. Triggered by a chemical reductant, sodium dithionite, the pNBC moieties decomposed through a cascade 1,6‐elimination and decarboxylation reactions to liberate primary amine groups of the linkages, resulting in the disruption of the assemblies. The reduction sensitivity of assemblies was affected by the length of hydrophobic block and the structure of amino acid‐derived linkers. Using hydrophobic dye Nile red (NR) as a model drug, the polymeric assemblies were used as nanocarriers to evaluate the potential for drug delivery. The NR‐loaded nanoparticles demonstrated a reduction‐triggered release profile. Moreover, the liberation of amine groups converted the reduction‐responsive polymer into a pH‐sensitive polymer with which an accelerated release of NR was observed by simultaneous application of reduction and pH triggers. It is expected that these reduction‐responsive block copolymers can offer a new platform for intracellular drug delivery. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1333–1343     

含分布时滞的时滞微分系统多步龙格-库塔方法的时滞相关稳定性

本文研究了一类含分布时滞的时滞微分系统的多步龙格-库塔方法的稳定性.基于辐角原理，本文给出了多步龙格-库塔方法弱时滞相关稳定性的充分条件，并通过数值算例验证了理论结果的有效性.     

锶原子互组跃迁荧光探测系统的研制

锶原子单态和三重态间的互组跃迁(5s2)1S0-(5s5p)3P1辐射率远小于一般的电偶极跃迁,共振跃迁荧光信号微弱。介绍了一种应用于探测该互组跃迁荧光谱的直流偏置探测器。该探测器选用极低输入偏置电流运算放大器作为前置放大,具有信噪比高、增益高、偏置可调等优点。此探测器探测增益为106 V/W量级,-3dB带宽为1MHz。实验中利用该探测器对锶原子互组跃迁(5s2)1S0-(5s5p)3P1微弱共振荧光进行探测,获得信噪比很好的共振荧光谱,且无直流偏置,并由此获得高信噪比的鉴频曲线。应用该探测器观测到了饱和荧光谱线以及对应的鉴频曲线,可用于689nm激光锁频,应用于锶光钟系统。     

High performance of N,P co-doped metal-free carbon catalyst derived from ionic liquid for oxygen reduction reaction

Journal of Solid State Electrochemistry - One-pot strategy to fabricate N, P co-doping carbon was developed based on the functional ionic liquid (IL) as the N, P, and C precursors. The IL featuring...     

Highly efficient AgNO3‐catalyzed approach to 2‐(benzo[d]azol‐2‐yl)phenols from salicylaldehydes with 2‐aminothiophenol, 2‐aminophenol and benzene‐1,2‐diamine

A new, convenient and efficient AgNO₃‐catalyzed strategy for the preparation of 2‐(benzo[d]azol‐2‐yl)phenol derivatives in good to excellent yields (63–98%) is described. The reaction proceeds via condensation/intramolecular nucleophilic addition/oxidation process between substituted salicylaldehydes and 2‐aminothiophenol, 2‐aminophenol or benzene‐1,2‐diamine under mild reaction conditions. Notably, this reaction utilizes cheap AgNO₃ as a readily available and low‐cost benign oxidant at low catalyst loadings with excellent functional group tolerance.