过氧化物酶-辅酶NADH催化O_2/H_2O_2产生羟基自由基研究及其氯苯处理初探

利用光谱学和波谱学手段研究HRP-NADH-O2/H2O2体系中自由基生成机理及HRP状态的变化,并应用该酶体系对有机污染物氯苯进行初步处理研究。紫外可见光谱表明酶-辅酶体系在过氧化氢的氧化下,产生了强氧化性的化合物Ⅲ,说明可能产生羟基自由基。分别选用DMPO和POBN两种自由基捕获剂,通过电子自旋顺振(EPR)检测到HRP+NADH体系在O2和H2O2存在下产生超氧阴离子自由基(O2-·)和羟自由基(·OH)。在开始10min内过氧化物酶主要以化合物Ⅲ形式存在,随后转化为HRP,同时检测出较高浓度的·OH。O2存在条件下产生·OH浓度大约是单独H2O2存在条件下的4倍。超氧化物歧化酶(SODZn-Cu)在HRP+NADH+O2体系中能消除由NADH还原O2产生的O2-·从而抑制·OH生成。HRP+NADH体系相对于传统酶法处理能提高20%左右的酶活力,说明酶-辅酶体系能够提高酚类化合物的去除效率。实验条件下HRP+NADH+H2O2和HRP+NADH+H2O2+O2体系对于非酚类污染物氯苯的去除率分别到达了24.6%和48.2%,远高于传统酶法的1.42%,突破了传统酶处理只能处理酚类污染物的局限性。     

过氧化物酶-辅酶NADH催化O2/H2O2产生经基自由基研究及其氯苯处理初探

利用光谱学和波谱学手段研究HRP-NADH-O2/H2O2体系中自由基生成机理及HRP状态的变化,并应用该酶体系对有机污染物氯苯进行初步处理研究.紫外可见光谱表明酶辅酶体系在过氧化氢的氧化下,产生了强氧化性的化合物III,说明可能产生羟基自由基.分别选用DMPO和POBN两种自由基捕获剂,通过电子自旋顺振(EPR)检测到HRP+NADH体系在O2和H2O2存在下产生超氧阴离子自由基(O2-)和羟自由基(·OH).在开始10 min内过氧化物酶主要以化合物III形式存在,随后转化为HRP,同时检测出较高浓度的·OH.O2有存在条件下产生·OH浓度大约是单独H2O2存在条件下的4倍.超氧化物歧化酶(SOD Zn-Cu)在HRP+NADH+O2体系中能消除由NADH还原O2产生的(O2-.从而抑制·OH生成.HRP+NADH体系相对于传统酶法处理能提高20%左右的酶活力,说明酶-辅酶体系能够提高酚类化合物的去除效率.实验条件下HRP+NADH+ H2O2和HRP+NADH十H2O2+O2体系对于非酚类污染物氯苯的去除率分别到达了24.6%和48.20,,远高于传统酶法的1.42%,突破了传统酶处理只能处理酚类污染物的局限性.     

基于循环平稳信号相干统计量的脉冲星周期估计新方法

讨论了脉冲星的周期估计在脉冲星搜索中的重要性.将脉冲星观测信号建模为二阶循环平稳模型,仿真验证了其合理性.在此基础上,提出了一种基于双谱相干统计量的周期估计新方法,并给出了稳健有效的周期搜索策略以消除其对数据量的敏感性.分别对单脉冲脉冲星(PSR J0437-4715)的实测信号和双脉冲脉冲星(PSR B1821-24)的仿真信号进行了周期估计,实验表明,相比较于常用的傅里叶频谱法,该时域方法直观、有效,在低信噪比情况下仍具有很好的性能,且适用于非连续观测数据.尽管方法运算量较大,但仍然可为微弱脉冲星的周 关键词： 脉冲星 脉冲星搜索 周期估计 循环平稳信号     

酶循环荧光法定量检测人血红细胞NADH浓度

用酶循环荧光测定法,多功能微孔板检测系统检测人血清还原型烟酰胺腺嘌呤二核苷酸(NADH)的浓度。通过底物和酶的循环反应将待测物质NADH的量扩大至荧光可检测范围。该方法的荧光强度与NADH的质量在0.00—0.80pmol范围内呈良好的线性关系,建立的线性方程式为:y=99.377x+13.481,r=0.9941,加标回收率为95.5%—100.0%,批内RSD为1.0%—2.7%,批间RSD为1.9%—12.6%。该方法准确度、灵敏度高、稳定性好,可用于NADH的定量检测。     

噪声交叉关联强度的时间周期调制对线性过阻尼系统的随机共振的影响

针对由加性、乘性噪声和周期信号共同作用的线性过阻尼系统, 在噪声交叉关联强度受到时间周期调制的情况下,利用随机平均法推导了系统响应的信噪比的解析表达式. 研究发现这类系统比噪声间互不相关或噪声交叉关联强度为常数的线性系统具有更丰富的动力学特性, 系统响应的信噪比随交叉关联调制频率的变化出现周期振荡型随机共振, 噪声的交叉关联参数导致随机共振现象的多样化.噪声交叉关联强度的时间周期调制的引入有利于提高对微弱周期信号检测的灵敏度和实现对周期信号的频率估计. 关键词： 随机共振 周期振荡型共振 噪声交叉关联强度 信噪比     

基于注入半导体激光器的微波副载波相位调制信号产生

光载无线技术是解决终端超宽带无线通信的重要方法,光信号与微波/毫米波信号的融合处理技术在光-无线的数据格式转换中至关重要.提出了一种基于相位调制信号光注入Fabry-Perot型半导体激光器实现微波副载波相位调制信号产生的方法.光学注入半导体激光器的输出光场会产生一周期(P1)振荡效应, P1振荡产生的边带实现了相位调制信号光的调制分量的放大,被放大的调制分量与注入光载波在激光器腔内拍频形成微波副载波.注入光相位的变化导致新产生的微波副载波相位变化, 实现了注入信号光相位信息转化为微波副载波相位信息.本系统完成1.3 Gb/s, 2.7 Gb/s, 2 Gb/s光相位调制信号到微波副载波相位调制信号的转换,并测量了微波的单边带相位噪声. 通过光电转换和电域混频将还原出的光基带信号与原信号进行逻辑对比,证明了数据信息转换的正确性.     

3种中草药的振荡指纹图谱

采用H2SO4-BrO3-Mn2+-丙酮为振荡器,其一,通过添加不同浓度的中草药泽兰为底物,探讨振荡体系中底物、H2SO4、KBrO3以及Mn2+浓度对振荡体系的周期、振幅及寿命的影响,明晰了各种物质在振荡反应中扮演的角色;其二,保持H2SO4、KBrO3以及Mn2+浓度不变,通过改变泽泻及鱼腥草的浓度,得到这两种草药的特征振荡图谱和其体系底物的振荡浓度范围,而且对其特征参数(周期振幅以及振荡寿命)进行研究.通过这些振荡指纹图谱可用于辨识中草药.     

基于次谐波调制光注入半导体激光器获取窄线宽微波信号的实验研究

实验研究了处于单周期振荡的光注入半导体激光器在频率等于单周期振荡频率一半的1/2次谐波调制下所产生的微波信号的特性.实验结果显示:在合适的注入条件下,处于单周期(P1)振荡的光注入半导体激光器可输出频率可达26.5 GHz、光谱具有单边带结构的光生微波信号,但微波信号的线宽比较宽(MHz量级);通过采用频率为单周期振荡频率一半的次谐波信号调制光注入半导体激光器,可将微波线宽从十几MHz压缩到几十k Hz.进一步分析了次谐波调制信号的功率以及频率对微波信号的相位噪声的影响,并在由次谐波调制信号的功率和频率构成的参数空间绘制出了能实现次谐波频率锁定的分布区域.     

铝离子对辅酶NADH分子荧光增强和构象变化的影响

烟酰胺腺嘌呤二核苷酸(NADH)是生物体内重要的辅酶分子,在细胞能量代谢中发挥着关键作用。金属离子可以影响NADH所参与的酶促反应,其中铝离子（Al3+）对神经系统具有毒性,可以引发神经退行性疾病。因此,Al3+和NADH分子间相互作用的研究有助于了解Al3+对生物体内TCA循环和酶促反应的影响,具有重要的生物学意义。本文采用紫外-可见吸收和稳态荧光光谱,结合时间相关单光子计数技术(TCSPC),研究了Al3+对水溶液中NADH的本征荧光光谱和分子构象变化的影响。紫外-可见吸收光谱显示,NADH与Al3+的结合不会改变NADH分子腺嘌呤和烟酰胺两个本征发色团的吸收特性。为避免NADH分子内两个本征发色团之间的荧光共振能量转移效应的影响,采用340 nm作为激发波长,比较了NADH与Al3+作用前后的荧光特性。实验结果证实,Al3+可以与NADH焦磷酸盐桥上的两个氧原子相结合,使NADH分子的结构变得相对更加刚性,从而抑制NADH分子在溶液中的转动等非辐射过程,导致NADH分子平均荧光寿命增加,最终引起NADH分子荧光强度随Al3+浓度的增加而线性增强。进一步,采用NADH本征荧光寿命振幅比的研究方法表征了NADH分子在溶液中的两种主要构象形式：腺嘌呤和烟酰胺相互堆积的折叠构象以及腺嘌呤和烟酰胺相互分离的展开构象。研究发现,Al3+会打破溶液中NADH分子展开构象和折叠构象的平衡状态,促使辅酶NADH分子的展开构象转变为折叠构象,最终达到新的动态平衡,并且当NADH和Al3+以不大于1∶2的浓度比结合时,NADH分子两种构象的振幅比与铝离子浓度的对数间存在线性关系,在Al3+浓度检测等领域具有良好的应用前景。     

铂族金属氧化过程中的簇发振荡及其诱发机理

铂族金属表面氧化过程是典型的多相催化反应之一, 具有广泛的应用背景及丰富的振荡行为, 因此深入研究铂族金属的氧化中的物理及化学过程具有重要的理论意义及工程应用前景. 通过对铂族金属CO的氧化过程中实测数据的回归分析, 建立了不同尺度耦合解析动力学理论模型. 通过对平衡态的稳定性分析, 指出在一定条件下稳态解会由鞍-结同宿轨道分岔导致周期振荡. 当快子系统产生Hopf分岔时, 该周期振荡会进一步演化为两尺度耦合的周期簇发振荡, 即N^k振荡, 并由加周期分岔使得系统处于激发态的时间显著增加.在此基础上, 利用分岔理论进一步分析了周期簇发及加周期分岔的产生机理, 揭示了周期簇发中沉寂态和激发态相互转化时的不同分岔模式.     

Application of polyaniline as enzyme based biosensor

The PANI films have been synthesized electrochemically and are used as matrix for immobilization of glucose oxidase (GOD) and lactate dehydrogenase (LDH) enzymes. The temporal aspects of anion self-exchange in PANI films have been investigated. The exchange of bulkier tosylate–ferricyanide ion with Cl⁻ ion has been monitored by photometry and electrochemical techniques. The relative changes in porosity brought about by self-exchange have been experimentally determined to be 323 and 2125/k in tosylate-exchanged and ferricyanide-exchanged polyaniline films, respectively. It is seen that the polyaniline films exhibit enhanced loading of glucose oxidase after a self-ion exchange, and, hence they can be used for the fabrication of a third generation glucose biosensor.Lactate is determined by the photometric detection of NADH formed in the reaction catalysed by LDH. Studies have been carried out with PANI as a matrix for the immobilization of LDH and its feasibility as a biosensor. The results of the photometric and amperometric measurements conducted on such LDH/PANI electrodes show a response to pyruvate concentration upto 0.45 mM, a response time of 90 s and a shelf life of about two weeks.     

The production of hydroxyl radical in HRP-NADH-H2O/O2 systems and its application in chlorobenzene removal

The mechanism of radical generation in HRP-NADH-O2/H2O2 systems and state-change of horseradish peroxidase (HRP) was investigated by using ESR and UV measurements, and the novel enzyme-coenzymatic systems were performed to degrade chlorobenzene as a non-phenolic persistent organic pollutants. The UV results showed that compound III was produced from HRP oxidized by hydrogen peroxide with the catalysis of NADH, which would generate hydroxyl radical. The ESR results demonstrated the production of *OH and O2-. in enzyme-coenzymatic system in the presence of O2 or H2O2 with DMPO and POBN as spin-trappers, respectively. In HRP-NADH-H2O2 system, compound III was the main state of HRP in the initial 10 min, and then converted to HRP with generating hydroxyl radical; and after the addition of oxygen, the production of hydroxyl radical was promoted rapidly, as 4 times as that of the system in absence of oxygen. The addition of SOD(Zn-Cu) decreased the production of hydroxyl radical significantly, resulting from that SOD eliminated O2 reduction to O2-. by NADH and then inhibited *OH formation. The results showed that NADH could improve by about 20% enzyme activity of HRP for phenol removal. The removal of chlorobenzene with HRP-NADH-H2O2 and HRP-NADH-H2O2-O2 systems reached 24.6% and 48.2%, respectively, which was much higher than that with traditional enzymatic system (1.42%), showing a promising prospect in proposal     

Spectroscopic studies of lanthanide(III) ion complexes with diethyl(phthalimidomethyl) phosphonate

Complexation and photophysical properties of complexes of lanthanide ions, Ln(III), with diethyl(phthalimidomethyl)phosphonate ligand, DPIP, were studied. Interactions between Ln(III) and DPIP were investigated using Nd(III) absorption and Eu(III) and Tb(III) luminescence (emission and excitation) spectra, recorded in acetonitrile solution containing different counter ions (NO₃^-, Cl^- and ClO₄^-). Results of the absorption spectroscopy have shown that counter ions play a significant role in the complexation of Ln(III)/DPIP complexes. Studies of luminescence spectra of Eu(III) and Tb(III) ions proved that the formation of Ln(III)/DPIP complexes of stoichiometry Ln:L=1:3 is preferred in solution. Based on the results of elemental analysis, Nd(III) absorption spectra and IR and NMR data, it was shown that the DPIP ligand binds Ln(III) ions via oxygen from phosphoryl group, forming complexes of a general formula Ln(DPIP)₃(NO₃)₃·H₂O, in which the NO₃^- ions are coordinated with the metal ion as bidentate ligands. Luminescent properties and energy transfer, from the ligand to Ln(III) ions in the complexes formed, were studied based on the emission and excitation spectra of Eu(III) and Tb(III). Their luminescent lifetimes and emission quantum yields were also measured.     

酶荧光毛细分析法测定血清中微量丙酮酸

提出了一种用于血清微量丙酮酸（PA）测定的酶荧光毛细分析法（P-LE-FCA）。优选的测定条件为：乳酸脱氢酶和还原型辅酶Ⅰ的浓度分别为100U/L和60μmol/L,反应时间5min。测定PA的线性范围4—80μmol/L,检出限0.73μmol/L,RSD〈1.3%。血清共存物质对PA测定无明显干扰。使用该方法对血清PA进行测定,其回收率在93.0%—106.5%之间;结果与常规紫外分光光度法一致。本方法的样品预处理过程简单、省时,省试剂,灵敏度高,重现性好。     

Quantitative evaluation of the lactate signal loss and its spatial dependence in press localized (1)H NMR spectroscopy

Localized (1)H NMR spectroscopy using the 90 degrees -t(1)-180 degrees -t(1)+t(2)-180 degrees -t(2)-Acq. PRESS sequence can lead to a signal loss for the lactate doublet compared with signals from uncoupled nuclei which is dependent on the choice of t(1) and t(2). The most striking signal loss of up to 78% of the total signal occurs with the symmetrical PRESS sequence (t(1)=t(2)) at an echo time of 2/J (approximately 290 ms). Calculations have shown that this signal loss is related to the pulse angle distributions produced by the two refocusing pulses which leads to the creation of single quantum polarization transfer (PT) as well as to not directly observable states (NDOS) of the lactate AX(3) spin system: zero- and multiple-quantum coherences, and longitudinal spin orders. In addition, the chemical shift dependent voxel displacement (VOD) leads to further signal loss. By calculating the density operator for various of the echo times TE=n/J, n=1, 2, 3,..., we calculated quantitatively the contributions of these effects to the signal loss as well as their spatial distribution. A maximum signal loss of 75% can be expected from theory for the symmetrical PRESS sequence and TE=2/J for Hamming filtered sinc pulses, whereby 47% are due to the creation of NDOS and up to 28% arise from PT. Taking also the VOD effect into account (2 mT/m slice selection gradients, 20-mm slices) leads to 54% signal loss from NDOS and up to 24% from PT, leading to a maximum signal loss of 78%. Using RE-BURP pulses with their more rectangular pulse angle distributions reduces the maximum signal loss to 44%. Experiments at 1.5 T using a lactate solution demonstrated a maximum lactate signal loss for sinc pulses of 82% (52% NDOS, 30% PT) at TE=290 ms using the symmetrical PRESS sequence. The great signal loss and its spatial distribution is of importance for investigations using a symmetrical PRESS sequence at TE=2/J.     

应用荧光光谱法研究植物LEA3蛋白11-氨基酸基序的保护功能

胚胎晚期富集蛋白(late embryogenesis abundant,LEA)是增强生物抵抗干旱、低温和盐渍等多种胁迫的重要功能蛋白,但其保护机理仍不清楚.本文利用紫外光谱法证实,含多拷贝11-氨基酸基序的多肽(如PM2D和PM2E)可较好的保护经冻融的乳酸脱氢酶(LDH)活性.进一步通过荧光光谱法证实,含多拷贝11-氨基酸基序的多肽可通过多位点协同结合模式,稳定LDH酶的结构.而含低拷贝11-氨基酸基序的多肽(如PM2F和PM2G)与LDH酶只有一种结合位点,二者的结合强度较弱,因而不能表现出对LDH酶活性的保护作用.此外,含多拷贝11-氨基酸的多肽与海藻糖在保护LDH酶活性上存在协同作用,且二者有着不同的保护机理.     

Tuned CuCr layered double hydroxide/carbon-based nanocomposites inducing sonophotocatalytic degradation of dimethyl phthalate

This study is the first to explore the possibility of utilizing CuCr LDH decorated on reduced graphene oxide (rGO) and graphene oxide (GO) as sonophotocatalysts for the degradation of dimethyl phthalate (DMP). CuCr LDH and its nanocomposites were successfully fabricated and characterized. Scanning electron microscopy (SEM) along with high-resolution transmission electron microscope (HRTEM) both evidenced the formation of randomly oriented nanosheet structures of CuCr LDH coupled with thin and folded sheets of GO and rGO. The impact of diverse processes on the degradation efficiency of DMP in the presence of the so-prepared catalysts was compared. Benefiting from the low bandgap and high specific surface area, the as-obtained CuCr LDH/rGO represented outstanding catalytic activity (100 %) toward 15 mg L⁻¹ of DMP within 30 min when subjected to light and ultrasonic irradiations simultaneously. Radical quenching experiments and visual spectrophotometry using an O-phenylenediamine revealed the crucial role of hydroxyl radicals compared to holes and superoxide radicals. Overall, outcomes disclosed that CuCr LDH/rGO is a stable and proper sonophotocatalyst for environmental remediation.     

Ultrasonic-assisted reduction for facile synthesis of ultrafine supported Pd nanocatalysts by hydroxyl groups on the surfaces of layered double hydroxides and their catalytic properties

Layered double hydroxide (LDH)-supported Pd nanocatalysts (Pd/LDH-OH) were prepared by ultrasonic-assisted reduction at 30 °C using an ultrasonic bath at a frequency of 25 kHz and an input power of 400 W for 30 min without the addition of any stabilizing reagent or chemical reductant, using LDH with a layered structure and interparticle mesoporosity as the reductant and carrier. This kind of pore structure allows ultrasound waves to spread inside the pore and make ultrasound directly act on the surface hydroxyl groups of LDH, producing highly reductive free radicals (H). The reductive free radicals rapidly reduced Pd²⁺ to Pd⁰, forming ultrafine Pd nanoparticles (PdNPs) with a particle size distribution of 1.85 nm–3.45 nm and an average particle size of 2.52 nm. The surface hydroxyl groups were converted to exposed oxygen groups after dissociation of hydrogen radicals, which is beneficial for anchoring and dispersing the resultant PdNPs. The resultant PdNPs were uniformly dispersed on the surface of the LDH carrier. The yield of the Suzuki coupling reaction between 4-bromotoluene and phenylboronic acid catalyzed by Pd/LDH-OH at 60 °C was 95.49% for 5 min and the TOF was 190.98 min⁻¹. After repeated for 5 times, the yield was maintained at 84.59%. The prepared Pd/LDH-OH nanocatalyst and the catalytic system are useful for Suzuki-Miyaura coupling reactions of N- and S-heterocyclic substrates. This provides an efficient and green approach for the preparation of supported nanopalladium catalysts.     

Comparison of Various Solvents for Poly(Phenylene Sulfide) Microporous Membrane Preparation via Thermally Induced Phase Separation

Six different solvents, i.e., diphenyl sulfone (DPS), diphenyl isophthalate (DPIP), benzoin (BZ), epsilon-caprolactam (CPL), hydrogenated terphenyl (HTP), and cyclohexyl pyrrolidinone (CHPN), were selected as diluents for poly(phenylene sulfide) (PPS) microporous membranes development via the thermally induced phase separation (TIPS) method. Phase separation behaviors for the various solvents were first identified through thermal analysis of their PPS solutions. Liquid-liquid separation behavior was identified for a group of solvents including DPS, DPIP, and BZ, whereas systems with the solvents CPL, HTP, and CHPN underwent solid-liquid separation during the cooling process. A newly designed casting device, which well simulated the industrial film casting process, was then used to produce films; it consisted of a side-by-side high-temperature plate and room-temperature plate. The different cooling conditions able to be produced by this casting device were found to greatly affect the TIPS process and the properties of the final membranes. The properties of PPS membranes prepared on this device from 30 wt.% binary solutions with the six solvents were investigated. The morphology of PPS membranes was also observed on the samples prepared under different cooling processes for the six solvents.     

Computational (MP2 and DFT) modeling of the substrate/inhibitor interaction with the LDH active pocket in the gas phase and aqueous solution: bimolecular charged (pyruvate/oxamate–guanidinium cation) and neutral adducts (pyruvic/oxamic acids–guanidine)

Two types of bimolecular adducts were studied for the substrate and inhibitor of lactate dehydrogenase (LDH), one type of adducts between ionic species, α‐keto‐carboxylates (pyruvate and oxamate) and the guanidinium cation, and the other type of adducts between neutral species, α‐ketocarboxylic (pyruvic and oxamic) acids and guanidine. Calculations were performed in the gas phase and aqueous solution using the MP2 and PCM methods and the 6‐31++G** basis set. Application of the DFT(B3LYP) and PCM methods led to similar results. A change of the adducts' preference was observed when proceeding from the gas phase to aqueous solution. This change is in good agreement with the acidity–basicity scales in both phases. Formation constant (K_HB) for adduct between neutral species is greater for pyruvic than for oxamic acid in the gas phase, whereas a reverse situation takes place in aqueous solution, where the K_HB value for adduct between ionic species is smaller for pyruvate than for oxamate. The water molecules favor interactions of more polar oxamate with the guanidinium cation. Stronger interaction with this cation, a model of the arginine fragment of the LDH pocket, suggests that oxamate (inhibitor of LDH) has stronger binding properties in aqueous solution than pyruvate (substrate of LDH). Copyright © 2008 John Wiley & Sons, Ltd.