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1.
MA Jianhua LIN Weizhen WANG Wenfeng & YAO Side . College of Biology Engineering Jimei University Xiamen China . Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai China 《中国科学B辑(英文版)》2005,48(5):476-480
Many processes in organisms are involved in elec-tron transfer reaction, and radioactive effect, preven-tion and sensitization of radioactive injury are in-volved in it too. There exists a quantitative relation-ship between one-electron reduction potentia… 相似文献
2.
H. Bao S. Navaratnam B. J. Parsons G. O. Phillips 《Radiation Physics and Chemistry》1993,42(4-6):989-992
One-electron oxidation of the ferrous tris-PQ complex, a model for lipoxygenase, was attempted using oxidants such as •OH, N•3, Br•-2, Tl2+ and TlOH+. •OH was found to react with the complex with a bimolecular rate constant of (3.9±0.6)x109dm3mol-1s-1, a rate which is not very dissimilar to that for the reaction with the ligand PQ. However the product of the reaction was found to be a OH-adduct rather than a cation radical. No reaction was found to occur with N•3 or Br•-2. Both Tl2+ and TlOH+ reacted with the complex to form its oxidised species with rate constants of (7.0±1)x108dm3mol-1s-1 and (4.0±0.8)x108dm3mol-1s-1, respectively. From a comparison of the rate constants and the transient spectra it was concluded that the centre of oxidation is the ligand rather than the metal. 相似文献
3.
One-electron oxidation of thionine has been studied using specific oxidizing radicals such as Cl−Tl(II) and N3 generated by pulse radiolysis of aqueous solutions. The semioxidized thionine exhibited threepK’s indicating four conjugate acid-base forms. N3 radicals were found to be less efficient in oxidizing thionine as compared to Cl
2
−
, Tl2+ and Tl(OH)+. The rate constants for electron abstraction from thionine by Cl
2
−
, Tl2+, Tl(OH)+, Tl(OH)2 and N3 were evaluated. The spectra of different protonated forms of semioxidized thionine and the extinction coefficients at λmax are presented. Reaction of OH radicals with thionine gave transient products whose spectra and acid-base properties were
different from those of semioxidized thionine. The rate constant for formation of the product transient agrees well with competition
kinetic value for reaction of OH with thionine reported earlier. 相似文献
4.
~~Pulse radiolysis of one-electron oxidation of rare tricyclic nucleoside derivative@赵红卫$Shanghai Institute of Nuclear Research, Chinese Academy of Sciences! Shanghai 201800,China
@江致勤$Department of Chemistry, Tongji Unviersity!Shanghai 200092,China
@窦大营$Shanghai Institute of Nuclear Research, Chinese Academy of Sciences! Shanghai 201800,China
@吴铁一$Shanghai Institute of Nuclear Research, Chinese Academy of Sciences! Shanghai 201800,China
@王文锋$Shanghai… 相似文献
5.
M. Szadkowska-Nicze J. Mayer 《Journal of polymer science. Part A, Polymer chemistry》1998,36(8):1209-1215
A pulse radiolysis study of poly(methyl methacrylate) in the presence of pyrene has been carried out in the temperature range 100–295 K. The concentration of pyrene was changed from 10−3 to 10−1 mol dm−3. The absorption/emission spectra and kinetics of solute excited states and solute radical ions were investigated. It was found that pyrene excited states were formed as a result of their radical ion recombination in a time scale up to seconds. The decay of solute radical ions was influenced by photobleaching and can be described by a time-dependent rate constant. The activation energy of Py ions decay was temperature dependent and was equal to 35.7 and 1.2 kJ/mol for temperatures >Tγ and <Tγ, respectively, where Tγ ∼ 175 K represented the transition temperature responsible for γ-relaxation. The reaction mechanism was proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1209–1215, 1998 相似文献
6.
7.
Badri Z. Momeni Nastaran Fathi Maliheh Shafiei Fahimeh Ghasemi Frank Rominger 《Journal of Coordination Chemistry》2016,69(18):2697-2706
The reaction of a mixture of cis and trans-[PtCl2(SMe2)2] with 4,7-phen (4,7-phen = 4,7-phenanthroline) in a molar ratio of 1 : 1 or 2 : 1 resulted in the formation of mono and binuclear complexes trans-[PtCl2(SMe2)(4,7-phen)] (1) and trans-[Pt2Cl4(SMe2)2(μ-4,7-phen)] (2), respectively. The products have been fully characterized by elemental analysis, 1H, 13C{1H}, HHCOSY, HSQC, HMBC, and DEPT-135 NMR spectroscopy. The crystal structure of 1 reveals that platinum has a slightly distorted square planar geometry. Both chlorides are trans with a deviation from linearity 177.66(3)°, while the N–Pt–S angle is 175.53(6)°. Similarly, the reaction of a mixture of cis and trans-[PtBr2(SMe2)2] with 4,7-phen in a 1 : 1 or 2 : 1 mole ratio afforded the mono or binuclear complexes trans-[PtBr2(SMe2)(4,7-phen)] (3) and trans-[Pt2Br4(SMe2)2(μ-4,7-phen)] (4), respectively. The crystal structure of trans-[Pt2Br4(SMe2)2(μ-4,7-phen)].C6H6 reveals that 4,7-phen bridges between two platinum centers in a slightly distorted square planar arrangement of the platinum. In this structure, both bromides are trans, while the PtBr2(SMe2) moieties are syn to each other. NMR data of mono and binuclear complexes of platinum 1–4 show that the binuclear complexes exist in solution as a minor product, while the mononuclear complexes are major products. 相似文献
8.
4-氯酚稀水溶液的脉冲辐解研究 总被引:10,自引:0,他引:10
利用脉冲电子束进行了多种条件下4-氯酚稀水溶液的脉冲辐解研究,对其瞬态光谱中的主要吸收峰作了归属,并初步考察了这些瞬态物种的生长、衰减等行为,研究表明,·OH基与4-氯酚在碱性条件下反应生成氯代酚氧基,速率常数为4.14×10^9L/(mol·s),在酸性条件下要经过OH-adducts;H原子与4-氯酚反应生成H-adducts的速率常为2.0×10^9L/(mol·s),产物可通过双分子二级反应逐步脱氯;eaq^-可直接从4-氯酚分子夺氯,反应速率常数为1.82×10^9/L(mol·s)。 相似文献
9.
At near neutral pH (approx. 5.5), the OH-adduct of chlorogenic acid (CGA), formed on pulse radiolysis of N2O-saturated aqueous CGA solutions (λ
max = 400 and 450 nm) with k = 9 × 109 dm3 mol−1 s−1, rapidly eliminates water (k = 1 × 103 s−1) to give a resonance-stabilized phenoxyl type of radical. Oxygen rapidly adds to the OH-adduct of CGA (pH 5.5) to form a
peroxyl type of radical (k = 6 × 107 dm3 mol−1 s−1). At pH 10.5, where both the hydroxyl groups of CGA are deprotonated, the rate of reaction of · OH radicals with CGA was
essentially the same as at pH 5.5, although there was a marked shift in the absorption maximum to approx. 500 nm. The CGA
phenoxyl radical formed with more specific one-electron oxidants, viz., Br
2
·−
and N
3
·
radicals show an absorption maximum at 385 and 500 nm, k ranging from 1–5.5 × 109 dm3 mol−1 s−1. Reactions of other one-electron oxidants, viz., NO
2
·
, NO· and CCl3OO· radicals, are also discussed. Repair rates of thymidine, cytidine and guanosine radicals generated pulse radiolytically at
pH 9.5 by CGA are in the range of (0.7–3) × 109 dm3 mol−1 s−1. 相似文献
10.
The formation of neutral Tl2 (λmax = 390 nm) and Tl4 (λmax = 360 nm) clusters in dilute aqueous solutions of Tl2SO4 containing formate ions was found by pulse radiolysis. The rate constants for the recombination of Tl0 atoms and Tl2 clusters are equal to 1.5·1010 L mol−1 s−1 and 1.0·1010Lmol−1 s−1 (±30%), respectively, and the extinction coefficient of Tl2 at 390 nm is −6.0·103 L mol−1 cm−1
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2367–2369, December, 1999. 相似文献
11.
12.
Pulse radiolysis of epicatechin in aqueous solution has been done to investigate the reactions of epicatechin derived phenoxy radical (EpO) at neutral pH. EpO was generated by N3 reacting toward EpOH, the rate constant was measured to be 3 × 108 dm3 mol−1 s−1. The biomolecular termination of EpO is rather slow ((2k < × 106 dm3 mol−1 s−1) and results in products exhibiting strong visible absorption around 450 nm. No reactions have been observed for EpO with O2 and O2 in the time scale of pulse radiolysis (0.01 s), suggesting the bimolecular rate constant are less than 104 and 5 × 106 dm3 mol−1 s−1, respectively. 相似文献
13.
Atanu Barik K. Indira Priyadarsini Hari Mohan 《Research on Chemical Intermediates》2006,32(9):837-845
Reactions of peroxyl radicals and peroxynitrite with o-vanillin (2-hydroxy 3-methoxy benzaldehyde), a positional isomer of
the well-known dietary compound vanillin, were studied to understand the mechanisms of its free radical scavenging action.
Trichloromethylperoxyl radicals (CCl3O
2
·
) were used as model peroxyl radicals and their reactions with o-vanillin were studied using nanosecond pulse radiolysis technique
with absorption detection. The reaction produced a transient with a bimolecular rate constant of approx. 105 M−1s−1, having absorption in the 400–500 nm region with a maximum at 450 nm. This spectrum looked significantly different from that
of phenoxyl radicals of o-vanillin produced by the one-electron oxidation by azide radicals. The spectra and decay kinetics
suggest that peroxyl radical reacts with o-vanillin mainly by forming a radical adduct. Peroxynitrite reactions with o-vanillin
at pH 6.8 were studied using a stopped-flow spectrophotometer. o-Vanillin reacts with peroxynitrite with a bimolecular rate
constant of 3 × 103 M−1s−1. The reaction produced an intermediate having absorption in the wavelength region of 300–500 nm with a absorption maximum
at 420 nm, that subsequently decayed in 20 s with a first-order decay constant of 0.09 s−1. The studies indicate that o-vanillin is a very efficient scavenger of peroxynitrite, but not a very good scavenger of peroxyl
radical. The reactions take place through the aldehyde and the phenolic OH group and are significantly different from other
phenolic compounds. 相似文献
14.
15.
Mustafa Soylak Aslihan Temeltas 《International journal of environmental analytical chemistry》2016,96(9):862-871
A solid-phase extraction procedure for Pb(II) and Cd(II) as 2,9 dimethyl-4,7-diphenyl-1,10-phenanthroline complexes on activated carbon cloth (ACC) has been established. In the determination step, flame atomic absorption spectrometry (FAAS) was used. The optimum conditions for pH, type and volume of eluent, volume of sample solution, flow rates of eluent, sample solution and matrix effect were determined. For quantitative recovery of the analyte ions, refereed optimum values are as follows: amount of ACC, 0.4 g; pH, 6.0 and eluent, 10 mL 3 M HNO3. To test the accuracy of the method, a certified reference material (CRM) analysis and add-recovery methods were performed. The developed method was applied for the determination of the analyte elements in water and vegetable samples. 相似文献
16.
The 1,10-phenanthroline (phen) complexes of Co(II), Ni(II), Cu(II) and
Cd(II) orotates were synthesized and characterized by elemental analysis,
magnetic susceptibility, spectral methods (UV-vis and FTIR) and thermal analysis
techniques (TG, DTG and DTA). The Co(II), Ni(II), Cu(II) and Cd(II) ions in
diaquabis(1,10-phenanthroline)metal(II) diorotate octahedral complexes [M(H2O)2(phen)2](H2Or)2·nH2O
(M=Co(II), n=2.25; Ni(II), n=3;
Cu(II) and Cd(II), n=2) are coordinated
by two aqua ligands and two moles of phen molecules as chelating ligands through
their two nitrogen atoms. The monoanionic orotate behaves as a counter ion
in the complexes. On the basis of the first DTGmax,
the thermal stability of the hydrated complexes follows the order: Cd(II),
68°C 68°C 相似文献
17.
熔融萘萃取铁(Ⅱ)-4,7-二苯基-1,10-菲啰啉-四苯硼酸盐三元络合物光度法测定铁 总被引:1,自引:0,他引:1
研究了以熔融萘作为萃取剂,以4,7 二苯基 1,10 菲口罗啉作为显色剂,测定天然水中微量铁的分光光度法。在pH4的条件下,铁(Ⅱ)与4,7 二苯基 1,10 菲口罗啉和四苯硼酸盐能够形成红色三元络合物。在熔融萘存在下,此络合物可以迅速萃入熔融萘。将含有络合物的萘冷却、固化、分离,配制成25mL丙酮溶液,对其进行分光光度分析。实验表明,该络合物最大吸收波长为534nm,摩尔吸光系数和桑德尔灵敏度分别为2×104L·mol-1·cm-1和0.0025μg/cm2,铁(Ⅱ)的质量浓度在0~2 0μg/mL的范围内符合比耳定律。大多数常见离子不干扰测定。已应用于天然水中微量铁的测定。 相似文献
18.
The radiation polymerization of vinylpyrrolidone (VP) in aqueous solution was studied. For pulse radiolysis experiments, absorption and light scattering detection were used to measure the nature and concentration of reacting species. Some aspects of these detection methods in relation to the kinetic measurements in the radiation-induced polymerization reactions were discussed. The absorption spectra of intermediates were taken. The decay of the transient species follows second-order kinetics with the rate constant depending on the VP concentration. The growth of the absorbance and intensity of scattered light in the concentrated VP solution (9,4 × 10−1 mol dm−3) occur both in the same timescale. 相似文献
19.
One-electron reduction of thionine has been studied by using the technique of nanosecond pulse radiolysis and kinetic spectrophotometry.
H,e
aq
−
as well as radicals derived from methanol, ethanol, isopropanol, THF, dioxane andt-butanol by H atom abstraction were used as reductants. The rate constants for the transfer of electrons from these radicalts
to thionine were directly determined from the pseudo first-order formation rates of the product, semithionine and the one-electron
reduction potential of thionine estimated. The absorption spectrum of semithionine in its different conjugate acid-base forms
was found to be in agreement with previously reported spectra and the decay of the species was second order. By monitoring
transient absorbance changes as a function of pH, twopK
a values were observed and, based on the effect of ionic strength on the second-order decay constants of the species were assigned
to the equilibria described. 相似文献
20.
Rafał Kocia 《国际化学动力学杂志》2019,51(12):958-964
Radiation-induced processes in oxygenated ionic liquid (IL) methyltributylammonium bis[(trifluoromethyl)sulfonyl]imide ([MeBu3N][NTf2]) solutions containing p-terphenyl (TP) were investigated by the nanosecond pulse radiolysis with UV-vis detection. The transient absorption spectra generated in these solutions were assigned to radical anions (TP•−), radical cations (TP•+), and triplet excited states (3TP*). Saturation of [MeBu3N][NTf2] solutions with oxygen (O2) efficiently eliminates solvated electrons (esolv−); however, it does not decrease significantly the radiation chemical yield of TP•−, which are mainly formed in a reaction of TP with presolvated electrons (epresolv−). On the other hand, the lifetime of TP•− decreases significantly due to their reaction with O2. The TP•+ is formed in a reaction of electron-deficient centers of the IL (IL⊕) with TP. Their radiation chemical yield and lifetime are not affected by the presence of O2; however, they are decreased by the presence of triethylamine (TEA). The 3TP* are formed in a reaction of excited states of ionic liquid (IL*) with TP. The presence of O2 and TEA effectively eliminates 3TP* in the time domain >1 μs. 相似文献