Preparative separation of a multicomponent peptide mixture by mass spectrometry

We report on the first multiplex preparative separation by mass spectrometry of bio-organic molecules in the 200-350 Da mass range that is typical for synthetic drugs. A five-component mixture consisting of two di- and three tripeptides has been separated by mass using a specially designed mass spectrometer. The instrument for preparative separations consists of an electrospray ionization (ESI) source, ion transfer optics, an electrostatic sector, and an inhomogeneous-field magnetic mass analyzer that achieves linear mass dispersion of ion beams. Protonated peptides produced by electrospray were separated, nondestructively landed on a 16-channel array of dry collector plates, and reconstituted in solution. The preparation procedures and the instrumental conditions have been optimized to maximize the ion currents. The significant features of the special mass spectrometer are high ion currents and simultaneous separation and collection of mixture components.     

Triterpenoid saponins from Lysimachia davurica

Three new saponins were isolated from the whole plants of Lysimachia davurica. On the basis of 1D and 2D NMR ((1)H-(1)HCOSY, HMBC, HMQC, and TOCSY) techniques, MS, and hydrolysis, their structures were found to be 3-O-beta-D-glucopyranosyl-(1-->2)-[beta-D-glucopyranosyl-(1-->4)]-alpha-L-arabinopyranosyl-13,28-epoxy-3beta-hydroxy-16-oleanaone (1), 3-O-beta-D-glucopyranosyloxyuronic acid-(1-->2)-beta-D-xylopyranosyl-cyclamiretin A (2), and 3-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-cyclamiretin A (3), respectively. Compounds 2 and 3 showed significant cytotoxicities against human A-2780 cells.     

Simultaneous determination of cefepime and vancomycin in plasma and cerebrospinal fluid by MEKC with direct sample injection and application for bacterial meningitis

A simple MEKC with UV detection at 214 nm for simultaneous analysis of cefepime and vancomycin in plasma and in cerebrospinal fluid (CSF) by direct injection without any sample pretreatment is described. The separation of cefepime and vancomycin from biological matrices was performed at 25 degrees C using a BGE consisting of a Tris buffer with SDS and methanol as the electrolyte solution. Under optimal MEKC conditions for biological samples, good separations with high efficiency and short analysis time are achieved. Several parameters affecting the separation of the drugs from biological matrices were studied, including methanol, pH, and concentrations of the Tris buffer and SDS. The linear ranges of the method for the determination of cefepime and vancomycin in plasma and in CSF using imidazole or cefazolin as an internal standard, respectively, were all over the range of 1-30 microg/mL; the detection limits of cefepime and vancomycin in biological matrices (injection 10 kV, 15 s) were 0.3 and 0.5 microg/mL, respectively. The applicability of the proposed method for the determination of cefepime and vancomycin in plasma and CSF collected after intravenous administration of the drugs in patients with meningitis was demonstrated.     

A simple molecular mechanics potential for μm scale graphene simulations from the adaptive force matching method

A simple molecular mechanics force field for graphene (PPBE-G) was created by force matching the density functional theory Perdew-Burke-Ernzerhof forces using the adaptive force matching method recently developed in our group. The PPBE-G potential was found to provide significantly more accurate forces than other existing force fields. Several properties of graphene, such as Young's modulus, bending rigidity, and thermal conductivity, have been studied with our potential. The calculated properties are in good agreement with corresponding density functional theory and experimental values. The thermal conductivity calculated with reverse non-equilibrium molecular dynamics depends sensitively on graphene size thus requiring the simulation of large sheets for convergence. Since the PPBE-G potential only contains simple additive energy expressions, it is very computationally efficient and is capable of modeling large graphene sheets in the μm length scale.     

过氧化氢与N—甲基苯胺盐酸盐引发体系的研究

在水介质中,研究了新型的过氧化氢/N-甲基苯胺盐酸盐引发体系对 AM 与 PVA 的接枝共聚。产物经紫外光谱、红外光谱和 ~1H-核磁共振进行表征,并提出了引发机理。     

Immunosuppressive ent‐Kaurene Diterpenoids from Isodon serra

Three new enmein‐type ent‐kaurenoids, i.e., the two pairs 1 and 2 of 20‐epimers and the (20R)‐isomer 3 , besides the seven known diterpenoids 4 – 10 , were isolated from the aerial parts of Isodon serra. Their structures were elucidated by spectroscopic techniques and X‐ray diffraction. The immunosuppressive effect for T‐lymphocytes proliferation induced by Con A in BALB/c mouse was evaluated for the isolates 1 – 10 . They all displayed a remarkable inhibitory effect, with multi‐glycosides of Tripterygium wilfordii as positive reference substance (Table 3).     

非自伴非紧的抽象边值问题

在Ｈｉｌｂｅｒｔ空间研究了一类非自伴非紧的抽象边值问题,利用Ｗｉｅｎｅｒ－Ｈｏｐｆ方法构造了空间Ｘ的分裂投影,进而得出了方程解的适定性．     

On extending real functions to finite dimensional algebras

In a finite dimensional real algebra, we define functional calculus for real functions. The analytic hypothesis is replaced by a differentiable hypothesis. High order differentibility is essentially necessary and sufficient to our discussions. Moreover, we give some examples. Partially supported by NSF of China The authors gratefully acknowledge the support of K. C. Wong Education Foundation, Hong Kong     

Self-Consistent Nonlinear Theory of Inner-Slotted High Harmonic Gyrotron

The self-consistent nonlinear theory is employed to analyze the inner-slotted high harmonic gyrotron, it is found that the structure of advantiageus to the interactin, the efficiency of interaction is above 30%.     

实用化双折射式光纤温度传感器系统最佳设计

利用双折射效应和偏振调制原理,设计了一种实用化的反射式光纤温度传感器,分析了精度、灵敏度等的主要指标与光源、双折射晶体及传输光纤之间的相互关系,并进行了相应的实验,给出了系统参数选择的最佳设计方案。