Rapid determination of underivatized pyroglutamic acid, glutamic acid, glutamine and other relevant amino acids in fermentation media by LC-MS-MS

Determination of amino acids in a complex matrix without derivatization is advantageous, however, difficulties are found in both the detection and the separation of those compounds. In this study, a rapid and reliable LC-MS-MS method for the quantitation of underivatized amino acids in exocellular media was established. Injections were made directly after centrifugation of the samples, without further preparation. The separation of seven underivatized amino acids was achieved on a reversed-phase C18 column with pentadecafluorooctanoic acid as a volatile ion-pair reagent, and the specific detection of most amino acids was achieved by MS-MS of the specific transitions [M + H]+-->[M + H - 46]+. The calibration curves of all analytes were linear over the range of 1.0-1000 microg ml(-1) and the detection limits ranged from 0.1 to 5 ng ml(-1), with an injection volume of 20 microl. The inter-day and intra-day precisions ranged from 2.6 to 5.7% and 4.8 to 8.2%, respectively; the mean recoveries of the seven analytes were 81-104%, 91-107% and 93-101% respectively at the spiked level of 10, 40 and 200 microg ml(-1). A large number of fermentation samples were analysed using this method. The technique is simple, rapid, selective and sensitive, and shows potential for the high-throughput quantitation of amino acids from other biological matrices.     

Swallowtail porphyrins: synthesis, characterization and incorporation into porphyrin dyads

The incorporation of symmetrically branched tridecyl ("swallowtail") substituents at the meso positions of porphyrins results in highly soluble building blocks. Synthetic routes have been investigated to obtain porphyrin building blocks bearing 1-4 swallowtail groups. Porphyrin dyads have been synthesized in which the zinc or free base (Fb) porphyrins are joined by a 4,4'-diphenylethyne linker and bear swallowtail (or n-pentyl) groups at the nonlinking meso positions. The swallowtail-substituted Zn(2)- and ZnFb-dyads are readily soluble in common organic solvents. Static absorption and fluorescence spectra and electrochemical data show that the presence of the swallowtail groups slightly raises the energy level of the filled a(2u)(pi) HOMO. EPR studies of the pi-cation radicals of the swallowtail porphyrins indicate that the torsional angle between the proton on the alkyl carbon and p-orbital on the meso carbon of the porphyrin is different from that of a porphyrin bearing linear pentyl groups. Regardless, the swallowtail substituents do not significantly affect the photophysical properties of the porphyrins or the electronic interactions between the porphyrins in the dyads. In particular, time-resolved spectroscopic studies indicate that facile excited-state energy transfer occurs in the ZnFb dyad, and EPR studies of the monocation radical of the Zn(2)-dyad show that interporphyrin ground-state hole transfer is rapid.     

Synthesis, Structure and Characterization of [Cu(2,2'-bpy)2][{Cu(2,2'-bpy)2}2W12O40(H2)]·4H2O

An organic-inorganic compound [Cu(2,2'-bpy)2][{Cu(2,2'-bpy)2}2W12O4o(H2)]·4H2O (Mr = 4048.00) was prepared from the hydrothermal reaction of Na2WO4·2H2O, CuCl2·2H2O,2,2'-bipyridine (2,2'-bpy) and H2O at 160 ℃ for 4 days. The compound crystallizes in the monoclinic system, space group P21/n with a = 18.9196(8), b = 20.4212(8), c = 21.8129(9)(A), β=96.992(3)°, V= 8365.0(6) (A)3, Dc= 3.214 g/cm3, Z = 4,μ(MoKα) = 17.269 mm-1 and F(000) = 7324.Of the 119837 total reflections, 17315 were unique (Rint = 0.0489). The final R = 0.0385 and wR =0.0770 for 11142 observed reflections with I ＞ 2σ(I). Single-crystal X-ray diffraction reveals that the structure is composed of [{Cu(2,2'-bpy)2}2W12O40(H2)]2- anions, discrete [Cu(2,2'-bpy)2]2 cations and lattice water molecules, and the anion is made up of a {W12O40(H2)}6- α-Keggin core decorated with two {Cu(2,2'-bpy)2}2 groups through bridging oxygen atoms.     

Spectrophotometric Studies of Cerium(III) and Thorium(IV) Chelates of Diethylenetriaminepentaacetic Acid (DTPA)

The interaction between diethylenetriaminepentaacetic acid (DTPA or H_sZ) and Ce(III) and Th(IV) ions has been investigated spectrophotometrically in aqueous solution at an ionic strength of 0.1 and for various temperatures. It has been found that the Ce(III)-DTPA chelate (1:1) exhibited a characteristic absorption maximum at 297 nm, and the optimum pH range is between 3.4 to 4.4. The absorption of Ce(III)-DTPA chelate is considerably diminished by adding small amounts of Th(IV) ions. This phenomenon was used to evaluate the formation constant of Th(IV)-DTPA chelate (1:1). The formation constants and the thermodynamic properties characterizing the formation of the chelates have been calculated at 25°. The results are as follows:      

电爆炸箔断路开关的理论和实验研究

 采用金属箔电爆炸过程的二维数值计算模型，对含电爆炸金属箔断路开关的电感储能脉冲功率调节系统进行了数值计算。以此为基础，研制出了一种低电感型的电爆炸箔断路开关，并以4μF/75kV脉冲电容器组作为初级能源，13Ω电阻作为负载进行实验研究。研究结果表明：在负载上可获得约250kV，脉宽大于400ns的脉冲电压。     

基于快速扫描光学延迟线谐振扫描的相位调制方法

提出利用快速扫描光学延迟线(Rapid Scanning Optical Delay Line,RSOD)作为光学相干层析成像(Optical Coherence Tomography,OCT)系统的相位调制器,并采用正弦驱动方式(谐振扫描)来提高扫描频率,进而实现高频相位调制的方法.介绍了基于RSOD相位调制器的干涉信号包络解调方法,分析了大振镜低频率线性驱动、小振镜高频线性驱动和大振镜高速正弦驱动三种实施方案对OCT性能的影响,并针对谐振扫描方案中轴向扫描的非线性提出了图像畸变定量校正的方法.结果表明:RSOD大振镜谐振扫描的模式能够兼顾系统成像速度、成像范围以及系统信噪比的要求,是一种行之有效的相位调制方法.     

一维对称光量子阱结构多通道滤波特性研究

利用传输矩阵法研究了一维对称光量子阱结构的多通道滤波特性,发现该结构的多透射峰具有分布对称、近似等间距和高透射率等特点,且峰值位置能利用等效理论近似解析求出.透射峰的数目可通过阱区结构参量确定和进行调整,结构的光子禁带范围可通过材料参量的选择获得极大的展宽.该结构只采用两种材料,结构简单,易于制作,具有较大的材料选择性.     

反馈调节的局部正则化鲁棒光流估计

提出了一种引入反馈调节机制的新局部鲁棒光流场计算思想.该思想结合局部法和全局法的特点,首先划分整场为有公共边界的子块,定义距离来判断每个点的子块归属,然后在每个子块内进行光流约束和平滑约束正则化的优化计算.将光流约束中的光强残差作为控制参量,衡量光流准确度的峰值信噪比作为输出,经反馈处理,调节控制参量使光流估计准确度趋向最优.实验结果表明,这种新的结合反馈调节机制局部光流场计算法能使光流准确度获得提升.     

一种基于纠缠态的量子中继通信系统

提出了一种基于纠缠态的量子中继通信系统,该系统应用纠缠为基本资源.纠缠为量子隐形传态和绝对安全的量子通信提供了保证.量子中继器用来延长高纠缠度的纠缠光子对的纠缠距离,利用纠缠交换和纠缠纯化在系统的发信者与受信者之间建立光子对的纠缠.应用量子隐形传态的原理传输量子信息.系统分析表明,量子通信系统的吞吐率随着通信双方成功建立纠缠的概率增大而显著增加,量子信号的传输距离取决于量子中继节点的级数.     

全自动高温水解-离子色谱法测定氧化镧铈中氟、氯

为探究稀土氧化物中氟(F)和氯(Cl)元素含量的快速检测方法,通过全自动高温水解仪对氧化镧铈样品进行前处理,并利用氢氧根体系离子色谱仪检测吸收液中F-、Cl-离子的含量,建立了基于全自动高温水解-离子色谱法测定氧化镧铈中的F、Cl元素含量的快速检测方法,该方法有效避免了传统前处理方法过程复杂、分析时间慢、极易受人为干扰的问题。称取0.3g氧化镧铈样品,在氧气流量为300 mL/min,1100 ℃高温下水解燃烧20 min,吸收定容为体积20mL的吸收液,以NAOH(15mmol/L)作为淋洗液,经色谱柱分离,测得F-与Cl-在质量浓度为1.00 mg/L-15.00 mg/L范围内,质量浓度与离子色谱峰面积呈线性关系,相关系数均为0.9999。检出限分别为0.003mg/L和0.12mg/L。全自动高温水解仪联用离子色谱仪检测系统对氧化镧铈中F-的平均加标回收率测定结果为98.4%,标准偏差RSD为0.94%;对Cl-的加标回收率测定结果为97.8%,RSD为2.86%。说明该方法较高准确度及精密度,测试结果准确可靠满足企业和检测机构的测试需求,为稀土氧化中氟、氯元素含量的研究及相关产品的开发提供了理论基础。