脉冲电场对脂肪氧化酶及多酚氧化酶构象影响的光谱分析

以多酚氧化酶(Polyhenol oxidase, PPO)和脂肪氧化酶(Lipoxygenase, LOX)为研究材料, 利用圆二色谱(CD)和荧光光谱分析了脉冲电场(PEF)对此两种酶蛋白二级和三级构象的影响。PPO和LOX酶活在电场强度为20 kV·cm-1的同轴处理室内处理320 μs分别降低了60.3%和21.7%,并且,随着电场强度的增大, 脉冲处理时间的延长, PPO与LOX酶的活性进一步降低。通过CD光谱图发现, PEF处理后,PPO和LOX的α-螺旋含量显著降低, 而β-折叠含量则呈现增长, 表明PPO与LOX酶蛋白中的二级构象在PEF处理后发生了极大的改变, 酶活钝化和二级结构的破坏之间存在对应关系。PEF处理后LOX的荧光强度增加, 随电场强度增强荧光强度增加幅度显著增大,表明PEF破坏了LOX三级构象,酶活钝化和三级结构的破坏之间存在对应关系。     

高压脉冲电场对脂肪氧化酶二级和三级构象的影响效果

应用圆二色谱和荧光光谱研究了高压脉冲电场(PEF)对脂肪氧化酶(LOX)的二级和三级构象的影响效果。研究结果表明PEF破坏了LOX二级和三级结构。PEF处理后,LOX的CD光谱中两个特征负峰值显著降低,二级结构中α-螺旋含量显著降低(p<0.05),并且LOX中α-螺旋含量和电场强度之间存在良好线性关系。PEF处理后LOX发射光谱中特征峰(337和583 nm)的荧光强度显著增大(p<0.05),特征峰相对荧光强度和电场强度之间存在良好线性关系。结果表明PEF酶活钝化跟酶二级和三级结构的破坏有关,为PEF钝酶机理研究提供理论基础。     

脉冲电场防治水生生物附着

为探究脉冲电场对防治水生生物附着效果的影响因素,确定有效防治附着生物所需的最低电场条件,搭建了脉冲电场试验平台,通过人工脉冲形成线产生近似方波的脉冲,统计不同条件下大型溞死亡率和形态结构发生的变化,通过函数拟合得到了脉冲电场诱导死亡率与电场强度、总等效处理时间、脉冲注入能量密度之间的函数关系,并以某干渠工程为例介绍了脉冲电场防治大型溞的参数选取原则和平台搭建方法。结果表明,脉冲电场对大型溞的处理效果与电场强度、总等效处理时间和脉冲注入能量密度都呈正相关关系。电场强度介于0.5～1.5 kV/cm之间时,电场强度每增加0.5 kV/cm,诱导死亡率增加35%左右。电场强度高于2.0 kV/cm、总等效处理时间大于900μs或脉冲注入能量密度高于80 J/L时,脉冲电场都可以产生80%以上的诱导死亡率。     

LED诱导延迟荧光技术评价脉冲电场对玉米幼苗抗旱性的影响（英文）

脉冲电场(pulsed electric field,PEF)对作物抗旱性的影响是电场生物学效应研究的重要课题,作物叶片延迟荧光动力学参数可以从不同角度灵敏地反映叶片细胞光合系统发生的变化。为了从活体细胞角度揭示脉冲电场对作物幼苗抗旱性的影响及其机理,使用频率为1Hz、场强为200kV·m~(-1)、脉宽为80ms的PEF处理萌发玉米种子,再采用渗透势为-0.1MPa的PEG-6000溶液形成干旱胁迫,研究了玉米幼苗生长过程中叶片干质量和LED诱导的叶片延迟荧光动力学参数的变化。结果发现,在-0.1 MPa的PEG-6000溶液形成的干旱胁迫下,玉米幼苗叶片干质量逐渐增加,经过PEF处理的玉米幼苗叶片干质量大于对照,相对增长率在5.8%~18.7%之间(p0.05)。叶片延迟荧光动力学分析显示,干旱胁迫下玉米幼苗叶片延迟荧光动力学参数初始光子数I0、相干时间τ、衰减参数β和延迟荧光积分强度I(T)都发生了波动性的变化,这些变化是叶片细胞对干旱胁迫的适应性反应,PEF处理使玉米幼苗叶片延迟荧光各动力学参数和延迟荧光积分强度均明显大于对照组,表明PEF处理使玉米幼苗叶片细胞的光合潜力、组织序性和功能分子之间的相互作用都有所加强,叶片综合光合能力提高了。研究结果为阐明PEF对作物幼苗抗旱性的影响及其机理提供参考。     

荧光偏振法研究脉冲电场对酿酒酵母细胞膜流动性影响

以DPH(1,6-二苯基-1,3,5-己三烯)为荧光探剂,采用荧光偏振法探讨了脉冲电场(0～25 kV·cm-1,0～266 ms)对酿酒酵母细胞膜流动性影响。经5 kV·cm-1电场处理后,酿酒酵母细胞膜的流动性显著减小,并且随电场强度和处理时间的增加而减小;通过平板计数法和紫外分光光度计法分别检测了脉冲电场对酿酒酵母细胞存活对数及膜通透性影响。结果显示,5 kV·cm-1虽然只能使少量的酵母致死,却能使酵母细胞膜的通透性显著增加,膜流动性显著降低。并且细胞的存活率随电场强度增大而减小,细胞膜的通透性随电场强度增大而增大。这表明细胞膜的流动性降低与细胞膜的通透性升高成正相关,与细胞的存活率成负相关。由此推测脉冲电场在对酿酒酵母灭菌过程中,细胞膜是其作用的一个关键位点,膜流动性减小,细胞膜通透性增强,是细胞死亡的主要原因。     

LED诱导延迟荧光技术评价脉冲电场对玉米幼苗抗旱性的影响

脉冲电场(pulsed electric field,PEF)对作物抗旱性的影响是电场生物学效应研究的重要课题,作物叶片延迟荧光动力学参数可以从不同角度灵敏地反映叶片细胞光合系统发生的变化。为了从活体细胞角度揭示脉冲电场对作物幼苗抗旱性的影响及其机理,使用频率为1 Hz、场强为200 kV·m-1、脉宽为80 ms的PEF处理萌发玉米种子,再采用渗透势为-0.1 MPa的PEG-6000溶液形成干旱胁迫,研究了玉米幼苗生长过程中叶片干质量和LED诱导的叶片延迟荧光动力学参数的变化。结果发现,在-0.1 MPa的PEG-6000溶液形成的干旱胁迫下,玉米幼苗叶片干质量逐渐增加,经过PEF处理的玉米幼苗叶片干质量大于对照,相对增长率在5.8%～18.7%之间(p＜0.05)。叶片延迟荧光动力学分析显示,干旱胁迫下玉米幼苗叶片延迟荧光动力学参数初始光子数I₀、相干时间τ、衰减参数β和延迟荧光积分强度I(T)都发生了波动性的变化,这些变化是叶片细胞对干旱胁迫的适应性反应,PEF处理使玉米幼苗叶片延迟荧光各动力学参数和延迟荧光积分强度均明显大于对照组,表明PEF处理使玉米幼苗叶片细胞的光合潜力、组织序性和功能分子之间的相互作用都有所加强,叶片综合光合能力提高了。研究结果为阐明PEF对作物幼苗抗旱性的影响及其机理提供参考。     

500 fs超短脉冲激光对CCD探测器的破坏效应

 采用脉宽500 fs,脉冲能量250 μJ的超短脉冲激光辐照线阵CCD探测器,观察到了CCD从线性响应到像元饱和、饱和串音直至硬损伤的整个过程,并着重对两种辐照能量密度下的硬损伤机理进行了理论分析。结果表明：激光能量密度为0.45 μJ/cm²时,达到像元饱和;能量密度为0.14 J/cm²时,辐照6个脉冲后实现了CCD器件的硬损伤,硬损伤源于晶格被加热并汽化形成等离子体;能量密度为1.41 J/cm²时,单个脉冲就使CCD器件的输出波形无法辨认,2个脉冲后CCD器件没有任何信号输出,硬破坏源于电荷分离形成的电场库仑力。     

FTIR分析脉冲电场和热处理后的大豆分离蛋白结构变化

采用自行研制的脉冲电场设备,利用傅里叶变换红外光谱(FTIR)比较研究了脉冲电场(PEF)和热处理对大豆分离蛋白(SPI)分子结构的影响.结果表明:50 kV·cn-1的脉冲场强处理引起SPI分子内和分子间氢键增强,分子中C-O-O糖苷键伸缩振动和P=O,P-O-C伸缩振动增强,且其增加值与PEF处理时间呈正相关.研究发现较短时间(1 600 μs)PEF处理导致了SPI分子结构中α-螺旋和β-折叠分别减少了5.9%和0.7%,β-转角和侧链结构分别增加了7.5%和9.6%;处理时间延长至2 400 μs,其α-螺旋和β-折叠减少量增至6.0%和5.6%.对比而言,热处理对SPI分子结构中C-O-O糖精苷键伸缩振动和P=O,P-O-C伸缩振动的影响程度较大,而对蛋白质二级结构影响程度较小:90℃热处理30 min,α-螺旋和β-折叠分别减小5.1%和6.6%,β-转角结构增加19.1%.由此可以认为PEF和热处理对SPI的影响机理是不一样的.     

超高压和热杀菌对草莓浊汁及清汁品质的影响

研究超高压(常温下,550MPa,处理5min)、热处理(中心温度90℃,处理1min)及高温短时杀菌(110℃,处理8.6s)对草莓浊汁和清汁品质的影响。结果表明:(1)经超高压处理后,草莓浊汁的黏度、果胶含量和浊度无显著变化,悬浮稳定性显著增加;而热处理和高温短时杀菌处理后,浊汁的黏度和果胶含量显著减小,浊度增大,悬浮稳定性降低,但高温短时杀菌组好于热处理组;(2)草莓浊汁和清汁经超高压处理后Vc分别损失11.09%和13.59%,而热烫结合超高压处理后分别损失7.75%和10.73%;热处理和高温短时杀菌组浊汁和清汁中Vc的损失率高于超高压组,分别为28.86%~38.89%和20.38%~29.02%;(3)超高压处理对草莓浊汁和清汁的单体花色苷、聚合色度及总酚含量、DPPH和FRAP抗氧化活性没有显著影响;热处理和高温短时杀菌处理后草莓浊汁中的花色苷总量分别损失了3.89%~4.63%和7.46%~8.02%,而清汁中分别损失了5.97%~6.02%和8.09%~9.20%;聚合色度和聚合色度百分比增加,总酚含量无显著变化,抗氧化活性显著降低;(4)超高压处理对草莓浊汁和清汁的亮度L*、红值a*、黄值b*、彩度C*及色调角hab均没有显著影响;而热处理和高温短时杀菌处理使L*值和a*值均显著减小。     

土壤中机油激光诱导荧光信号随激发光能量变化的特性研究

石油的勘探开发遍布我国各地区,其产品的应用与工农业生产和人民日常生活密不可分。石油及石油制品在使用过程中泄漏到土壤中不断累积,会破坏生态环境。激光诱导荧光(LIF)是检测土壤中石油烃类有机污染物的重要方法。激光脉冲能量是LIF的重要实验参数,对检测灵敏度,稳定性有显著影响。为探究土壤中石油烃的激光诱导荧光信号随激发光脉冲能量变化的特性,以机油为例,在实验室制备了机油浓度为0.5%～6%的土壤样品,使用Nd∶YAG激光器作为激发光源,通过改变266 nm激光的脉冲能量,获取不同能量密度下油污土壤的荧光光谱。实验结果表明,土壤和土壤中机油的荧光光谱强度随激光脉冲能量的增加而增加,但增加到一定程度后增幅明显减小。原因是虽然激光能量密度逐渐增强荧光强度也在增强,土壤中单位面积的有机物含量有限,部分有机质已经被光解,有机物被激发的荧光趋于饱和。在适当的能量密度下,土壤中机油的荧光强度与其浓度有良好线性关系。实验发现,随着激光能量密度的减小, LIF系统测量机油的平均相对误差先减小后增大,其原因是,当激光能量密度小于一定范围时,信号的信噪比随之减小,因此测量的平均相对误差逐渐增大;当激光能量密度大于一定范围时,虽然信号的信噪比随之增大,但已经逐渐超出系统最佳的测量范围,所以测量的平均相对误差逐渐增大。当激光能量密度在2.4～4.0 mJ·cm~(-2)时,土壤中机油的荧光强度随激光脉冲能量密度线性增强,且对机油浓度的测量误差均小于2.5%,检测限在200～300 mg·kg~(-1)之间。当能量密度大于4.0mJ·cm~(-2)时,机油的荧光强度增幅显著降低,测量误差也随之增大。因此,兼顾LIF测量土壤中机油的平均相对误差和测量检测限,激光脉冲能量选择2.4～4.0 mJ·cm~(-2)较优。所述方法也可扩展其他土壤中石油烃荧光信号检测。     

A fast pulsed power source applied to treatment of conductingliquids and air

Two pilot pulsed power sources were developed for fundamental investigations and industrial demonstrations of treatment of conducting liquids. The developed heavy-duty power sources have an output voltage of 100 kV (rise time 10 ns, pulse duration 150 ns, pulse repetition rate maximum 1000 pps). A pulse energy of 0.5-3 J/pulse and an average pulse power of 1.5 kW have been achieved with an efficiency of about 80%. In addition, adequate electromagnetic compatibility is achieved between the high-voltage pulse sources and the surrounding equipment. Various applications, such as the use of pulsed electric fields (PEFs) or pulsed corona discharges for inactivation of microorganisms in liquids or air, have been tested in the laboratory. For PEF treatment, homogeneous electric fields in the liquid of up to 70 kV/cm at a pulse repetition rate of 10-400 pps could be achieved. The inactivation is found to be 85 kJ/L per log reduction for Pseudomonas fluorescens and 500 kJ/L per log reduction for spores of Bacillus cereus. Corona directly applied to the liquid is found to be more efficient than PEF. With direct corona we achieve 25 kJ/L per log reduction for both Gram positive and Gram negative bacteria. For air disinfection using our corona pulse source, the measured efficiencies are excellent: 2 J/L per log reduction     

Electropermeabilization responses in Gram-positive and Gram-negative bacteria

Effects of 3-kJ kg^?1 nanosecond pulsed electric fields (PEFs) on cellular permeabilization of Salmonella enterica and Staphylococcus aureus were observed. It was seen that bacterial responses depend on both the electrical pulse attribute and the cell plasma membrane structure. For traditional permeabilization, the responses involved the thickness of the peptidoglycan layer where a maximum of 2.5 log reduction in S. enterica population was achieved. Meanwhile, in the area of selective permeabilization, it showed insignificant reduction in both pathogens. Such inactivation mechanisms were described through the behavior of potential across plasma membrane and intracellular organelles by PSPICE simulations incorporating PEF-cell interaction model.     

荧光光谱法研究低频脉冲电场对胰岛素分子的作用

胰岛素作为一种胞间信号分子,对于生命信息的传递起着极为重要的作用。探讨低频脉冲电场对胰岛素分子的作用,对于从细胞信号系统的角度来解释生物电磁效应有着十分重要的意义。在实验中,对照组和场暴露组之间荧光峰值强度的差别表明了低频脉冲电场改变了胰岛素分子的构象,低频脉冲电场可能通过破坏胰岛素分子氢键和重新形成某些氢键来改变它的构象。本文结果表明胞间信号分子也是低频电磁场作用的一个重要靶体。     

Inactivation of pathogenic and spoilage microorganisms in a testliquid using pulsed electric fields

Experiments have been carried out to investigate the effect of pulsed electric fields (PEFs) on the inactivation of microbial populations suspended in liquids using nonflowing and continuous flowing test chambers. Electric fields of ~30 kV/cm, and a pulse duration of 500 ns, were generated from a coaxial table Blumlein pulse forming network (PFN) and applied to a parallel plate, circular electrode test configuration. Sample microorganisms were grown under standardized conditions and were introduced into test liquids in order to produce known population densities within the treatment celt. The organisms investigated include the mold Aspergillus niger, the yeast Sacckaromyeces cerevisiae, and the bacterial pathogens Bacillus cereus, Staphylococcus aureus, and Pseudomonas aeruginosa. The PEF studies were undertaken at a sample temperature range of 25°C-30°C, and the effect of the number of pulses on the test microbial population was studied. The results of this investigation showed that the greater the number of pulses applied, the larger the corresponding reduction in microbial cells/spores obtained. With the exception of dormant fungal spores, all of the test organisms were reduced by -3 to 4 log orders after 3000 pulses. The number of B. Cerus cells was reduced by -7.5 log orders after 15 000 pulses, of which 10 000 pulses were applied in a flowing system followed by 5000 pulses in a static system     

Inactivation of Bucillus Stearothermophilus by pulsed electricfield

B. Stearothermophilus remains alive even under intense electric field, since spores formed are highly resistant to damage from electric field effects. This paper describes the effects of pulsed electric field on B. Stearothermophilus (ATCC no, 12980). An aqueous suspension of B. Stearothermophilus spores was placed between parallel planar electrodes and subjected to pulsed electric fields of up to 189 kV/cm, which are obtained from a high-voltage pulsed voltage generator. Either a Blumlein generator or a magnetic compression circuit with a semiconductor opening switch was used as the pulsed voltage generator. The spores that survived the treatment were detected by a colony counting method. The growth activities were measured using a microbial calorimetry technique. The temperature and pH of the spore suspension remained unchanged during the treatment. It was found that the growth activity of B. Stearothermophilus was affected by the pulsed electric field. while no remarkable lethal effect was observed in the range of up to 40 kV/cm     

Comparative study of magnetic and electric field induced insulator-metal-transitions in Pr1-xCaxMnO3 films

The insulator-metal (IM)-transition in Pr_1-xCa_xMnO₃ (PCMO) is of particular interest because it can be induced by a variety of external forces, such as magnetic and electric fields, photon exposure and hydrostatic pressure. In this paper, we present a comparative study of the IM-transition in magnetic and electric fields for epitaxial thin films prepared by pulsed laser deposition. The transport data as a function of applied field or temperature give strong evidence for the presence of electronic phase separation. However, the observed different IM-transitions in magnetic and electric fields indicate that two different areas of spatially inhomogeneous electronic ground states in the phase diagram of PCMO are involved.     

The non-linear response of NbSe3 to pulsed electric fields

The non-linear response of NbSe₃ to pulsed electric fields has been measured using a bridge circuit which subtracts the ohmic contribution to the voltage from the total signal. The current-induced metastable states of the charge-density wave (CDW) reported by Gill are confirmed. The periodic voltage induced by dc electric fields is clearly resolved and in some cases may be synchronized with the applied pulses. The periodic voltage comprises a large fraction of the non-linear response, growing to 100% near threshold.     

The influence of the drift shift of electrons undergoing thermalization on the kinetic characteristics of geminate conductivity and recombination

A program for numerically solving the Smoluchowski equation with a modified initial condition taking into account the drift shift of electrons that experience thermalization in an external electric field was developed. The probability of survival and the polarization current of isolated ion pairs were calculated. Shift effects were shown to be especially strong in the region of medium electric fields on the order of 10⁷ V/m and noticeably weaker in both low and high fields. This was related to the proportional relation between the drift shift and electric field applied. The program was used to critically analyze the available experimental data on pulsed photoconductivity of polyacenes.     

A new type of magnetoplastic effects in linear amorphous polymers

A new type of magnetoplastic effects in polymers is revealed. This effect cannot be explained by the reorientation of macromolecular units that possess a magnetic susceptibility anisotropy. It is shown that the joint action of magnetic and electric fields and the rotational mobility of side groups in macromolecules are factors of crucial importance in changing the plasticity of polymers in pulsed magnetic fields.     

Measurement of spin-flip raman gain,effectiveg-value and absorption of radiation under transient electric field conditions in insb

We studied the change in Spin-flip Raman (SFR) gain and behaviour of the effectiveg-value as a function of pulsed electric fields inn-type InSb. The samples were held at 1.8 K in magnetic fields up to 1.4 T. Varying the strength of a pulsed electric field applied to the samples parallel to the magnetic field we found a direct correlation between the increase in electron temperature and the decrease of the Raman gain. Measurements of the Raman gain and spontaneous line width at different times after the starting of the electric pulse and during its fall time with a time resolution of 10 ns give no indication of a motional narrowing of the SFR line and of an increase of the gain during the decrease of the electric field pulse. These two predictions were made by Mooradian et al. (1972) to explain the observed transient increase of the intensity of the stimulated SFR Stokes radiation after an electric field across the sample was switched off. With our direct measurement of the Raman gain we could establish that at any time during and after the electric field pulse, the gain is less or equal to the value without electric field. In the electric field region from 0.3 V/cm up to 0.6 V/cm the Raman gain shows several maxima, originating from SFR scattering between different spin splitted conduction band levels. The electron distribution under pulsed electric field conditions give rise to a dynamically varying absorption mechanism of transmitted radiation. Time resolved transmission measurements explain the observed increase of stimulated SFR Stokes radiation during the switch-off time of electric field pulses by a lower absorption of radiation and not by a larger gain.