Stabilization of hydrated electrons in irradiated frozen sugar solutions

Yields of free radicals in irradiated aqueous solutions of saccharides at 77 degrees K are larger and qualitatively different from those observed in the components alone. In addition, a blue color results only with the solution. The mechanism proposed to explain the observations is the stabilization of hydrated electrons by the solute.     

Reduction of ferricytochrome c by some free radical agents

Fast pulse radiolysis and kinetic spectroscopy were used to rapidly generate a variety of free radicals in situ and study their reactions with ferricytochrome c in the time range 10(-6) to 1 second. The radicals included t-butanol, which is inert to ferricytochrome c; malate, lactate, and ethanol, which react with it relatively slowly but are completely utilized in reducing it to ferrocytochrome c; and hydrated electrons and hydrogen atoms, which react with it very rapidly but yield ferrocytochrome c only in part, showing intramolecular consecutive reactions and further attack on the ferrocytochrome c protein. From a detailed comparison between malate and hydrogen atoms it is argued that malate reacts directly and selectively with a specific part of the ferricytochrome c surface while hydrogen atoms react with other parts of the protein too, yielding radicals which in part transfer intramolecularly to yield ferrocytochrome c.     

Mobility of the hydrated electron

The transient change in conductivity in diluted barium hydroxide solutions during and immediately after irradiation with single pulses of electrons from a 15-million-electron-volt linear accelerator was measured. Ionic mobility of the radiation-produced hydrated electrons was 1.84 x 10(-3)cm(-2) volt(-1) sec(-1) +/- 10 percent. This value corresponds to a diffusion constant of 4.75 x 10(-5) cm(2) sec(-1).     

Hanbury brown and twiss-type experiment with electrons

Fermion anti-bunching was directly observed by measuring the cross-covariance of the current fluctuations of partitioned electrons. A quantum point contact was used to inject single-mode electrons into a mesoscopic electron beam splitter device. The beam splitter output currents showed negative cross-covariance, indicating that the electrons arrived individually at the beam splitter and were randomly partitioned into two output channels. As the relative time delay between the outputs was changed, the observed ringing in the cross-covariance was consistent with the bandwidths used to monitor the fluctuations. The result demonstrates a fermion complement to the Hanbury Brown and Twiss experiment for photons.     

Electrochemical reduction of horse heart ferricytochrome c at chemically derivatized electrodes

Platinum or gold electrodes derivatized with an N,N'-dialkyl-4,4'-bipyridinium reagent can be used to reduce horse heart ferricytochrome c, whereas reduction doses does not occur at the "naked" electrodes. From 3 to 17.7 millimoles per liter, the reduction of ferricytochrome c is mass transport-limited at electrode potentials more negative than about -0.6 volt against a saturated calomel reference electrode. Data for the photoreduction of ferricytochrome c at derivatized p-type silicon photocathodes show directly that the rate of reduction is mass transport-limited. Use of derivatized electrodes may allow convenient manipulation and analysis of biological molecules that do not ordinarily respond at conventional electrodes.     

Observation of large water-cluster anions with surface-bound excess electrons

Anionic water clusters have long been studied to infer properties of the bulk hydrated electron. We used photoelectron imaging to characterize a class of (H2O)n- and (D2O)n- cluster anions (n 相似文献   

OH自由基与C2H5Br反应的密度泛函理论研究

用量子化学密度泛函理论（DFT）方法,对OH与C2H5Br的反应进行了理论研究．在UB3LYP／6-31G＊,UB3LYP／6-311＋G（2df,2pd）计算水平上,优化了反应势能面上各驻点（反应物、产物、中间体和过渡态）的几何构型,在UB3LYP／6-31G＊水平上通过内禀反应坐标（IRC）计算和振动分析,对过渡态进行了确认．在UCCSD（T）／6-311＋G（2d,2p）水平上进行了单点能量计算,并确定了反应机理．研究结果表明,反应主要产物为CH2CH2Br和H2O     

OH自由基与C2H5Br反应的密度泛函理论研究

用量子化学密度泛函理论(DFT)方法,对OH与C2H5Br的反应进行了理论研究.在UB3LYP/6-31G*,UB3LYP/6-311+G(2df,2pd)计算水平上,优化了反应势能面上各驻点(反应物、产物、中间体和过渡态)的几何构型,在UB3LYP/6-31G*水平上通过内禀反应坐标(IRC)计算和振动分析,对过渡态进行了确认.在UCCSD(T)/6-311+G(2d,2p)水平上进行了单点能量计算,并确定了反应机理.研究结果表明,反应主要产物为CH2CH2Br和H2O.     

Electrides: ionic salts with electrons as the anions

Electrides are ionic compounds that have alkali metal cations complexed by a crown ether or cryptand, with trapped electrons as counterions. The crystal structures and properties of two electrides illustrate the diversity that is encountered. One Cs(+) (18-crown-6)(z)e(-), has relatively isolated, trapped electrons apparently centered at each anionic site. It has a low conductivity consistent with electron localization, with an activation energy for conductivity of at least 0.45 electron volt. The other, K(+) (cryptand[2.2.2])e(-), has electron pairs trapped in an elongated cavity in a singlet ground state, but there is also a thermally accessible paramagnetic state available. This electride is much more conducting, with an activation energy of only 0.02 electron volt.     

Electron diffraction of frozen, hydrated protein crystals

High-resolution electron diffraction patterns have been obtained from frozen, hydrated catalase crystals to demonstrate the feasibility of using a frozen specimen hydration technique. The use of frozen specimens to maintain the hydration of complex biological structures has certain advantages over previously developed liquid hydration techniques.     

Bidirectional counting of single electrons

A bidirectional single-electron counting device is demonstrated. Individual electrons flowing in forward and reverse directions through a double quantum dot are detected with a quantum point contact acting as a charge sensor. A comprehensive statistical analysis in the frequency and time domains and of higher order moments of noise reveals antibunching correlation in single-electron transport through the device itself. The device can also be used to investigate current flow in the attoampere range, which cannot be measured by existing current meters.     

Generation of light from free electrons

Experiments with the interaction of a rectangular cross- section beam of electrons which is brought into contact with a metallic diffraction grat e ng produce light variable in wavelength throughout the visible spectrum. Con tinuous variation of the beam thickness shows that light is produced by electrons hundreds of wavelengths from the grating, if the side of the beam near the grating is in contact with it. The results can be accounted for by periodic accelerations of the electrons passing over the surface of the grating. These accelerations are caused by electrostatic forces which in turn are due to the average spacecharge of sheets of elec trons reflected from the grating surface, so that in their space- charge structure the periodicity of the grating rulings is preserved.     

利用酶反应热效应检测过氧化氢酶活性

为了探索酶活性测定的新方法，降低酶活性常规测试中干扰因素的影响，提高酶活性测定的准确性，利用低电势电位差计及热电偶换能器检测过氧化氢酶活性，结果表明，测定的H2O2质量分数以9．6％为好，可以用于酶活性从0．5u至3．5u酶活力的检测，当H2O2质量分数在2．4％－7．2％时，酶反应速率与底物浓度有线性关系；当底物质量分数超过9．6％时，酶反应速率显现底物抑制的动力学特征。     

Energetic electrons in the magnetosphere of jupiter

Observations of energetic electrons ( greater, similar 0.07 million electron volts) show that the outer magnetosphere of Jupiter consists of a thin disklike, quasitrapping region extending from about 20 to 100 planetary radii (R(J)). This magnetodisk is confined to the vicinity of the magnetic equatorial plane and appears to be an approximate figure of revolution about the magnetic axis of the planet. Hard trapping is observed within a radial distance of about 20 R(J). The omnidirectional intensity J(0) of electrons with energy greater, similar 21 million electron volts within the region 3 r 20 R(J) is given by the following provisional expression in terms of radial distance r and magnetic latitude theta: J(0) = 2.1 x 10(8) exp[-(r/a) - (theta/b)(2)]. In this expression J(0) is particles per square centimeter per second; a = 1.52 R(J) for 3 相似文献