缓蚀剂对金属钆在水介质中腐蚀行为的影响

采用失重法、腐蚀电化学方法研究了NaOH、NH4OH、单宁酸和苯并三氮唑等缓蚀剂对金属钆在水介质中腐蚀行为的影响。在没有缓蚀剂的情况下,钆在水中发生明显的点蚀,腐蚀速度为0.152g.m-2.h-1。NaOH能有效地控制金属钆在水介质中的腐蚀,经8880h的长时间浸泡,钆表面依然呈现明显的金属光泽,没有失重与点蚀发生。当采用NaOH调节苯并三氮唑(BTA)溶液的pH值接近中性时,钆在其中长时间浸泡,同样没有失重发生,表观没有发现点蚀发生。选择合适的缓蚀剂,使得钆能够在水介质中不发生腐蚀,保证了磁制冷机的长时间正常运转。     

Photophysical properties of the extract of endometallofullerenes La@C2n inortho-dichlorobenzene. Picosecond laser photolysis

The kinetics of relaxation of optical anisotropy induced by polarized light in endometallofullerenes La@C_2n inortho-dichlorobenzene was studied by picosecond laser photolysis. Decay of the optical absorption signal due to the excited states of La@C_2n follows the biexponential law with two values of relaxation time:t ₁=35±3 ps andt ₂=1100±200 ps. The lifetimet or decay of the optical anisotropy is 19±5 ps and determined by the orientational diffusion of La@C_2n . The experimentally determined lifetime of optical anisotropy agrees satisfactorily with the value yielded by the theoretical model of orientational diffusion under slip boundary conditions at the interface of the La@C_2n molecule with the solvent. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya No. 10, pp. 1921–1923, October, 1999.     

Cd2+离子诱导的DNA构象变化

近年来,Cd^2 由于其在生物化学、临床医学、环境和农业科学等领域的重要性而受到了极大的关注^[1]。同其它金属离子一样,Cd^2 离子能与蛋白和其它生物分子反应从而影响动物和人类的器官,如肺、前列腺、睾丸、心脏、肝和肾等的正常生理活动^[2-4]。日本的痛痛病就是由于Cd^2 引起的骨软化和肾小管功能障碍造成的。但是从分子水平上对Cd^2 与生物大分子的相互作用机制的研究还较少。本文对Cd^2 与鲑鱼精DNA的相互作用及其对DNA构象的影响进行了初步研究。结果表明,Cd^2 可与DNA发生作用,并且使DNA构象发生变化。     

钛合金在FGD系统中的腐蚀行为研究

商用纯钛试片实地悬挂于排烟脱硫 (FGD)系统中的冷却器、除尘塔、吸收塔、加热器等不同位置 ,经历 2 71d现场重量损失试验后 ,观察得知商用纯钛在 4个位置均有良好之耐蚀性 (腐蚀速率 1mpy) ,且以在除尘塔中的腐蚀速率最低 (mpy值为 0 ) ,加热器中的腐蚀速率最高 (mpy值为0 .58) .SEM观察结果显示钛在加热器中有孔蚀现象 .ESCA分析结果得知 :在加热器位置中钛生成硝酸盐 ,在除尘塔位置中钛表面未发现钛化物而有碳酸钙厚膜覆盖 .在通氮气及通氧气之绿色溶液中进行直流电动态极化以探讨钛在FGD系统中不同位置腐蚀行为之差异     

膜电阻对自组装膜修饰电极电化学行为的影响

应用循环伏安和交流阻抗技术研究了 16烷基硫醇自组装膜修饰的金电极在Fe(CN) 63 - /Fe(CN) 64 - 溶液中的电化学行为 .无“针孔”缺陷的自组装膜对溶液与基底间的界面电子转移具有强烈的阻碍作用 ,当过电位较大时 ,In(I/ η)对 η1/2 之间具有良好的线性关系 .通过对Au/SAM /Hg模拟体系的电流———电压曲线进行测定 ,得到了自组装膜膜电阻的特征 .指出由于膜电阻的存在 ,自组装膜修饰电极在Fe(CN) 63 - /Fe(CN) 64 - 溶液中的行为实质上反映了膜自身的电阻特征     

Study of the effect of Cal-Red on the secondary structure of human serum albumin by spectroscopic techniques

The effect of Cal-Red on the structure of human serum albumin (HSA) was studied using Resonance light scattering (RLS), Fourier transformed Infrared (FT-IR) and Circular dichroism (CD) spectroscopic methods. The RLS spectroscopic results show that the RLS intensity of HSA was significantly increased in the presence of Cal-Red. The binding parameters of HSA with Cal-Red were studied at different temperatures of 289, 299, 309 and 319 K at pH 4.1. It is indicated by the Scatchard plots that the binding constant K decreased from 4.03 × 10⁸ to 7.59 × 10⁷ l/mol and the maximum binding number N decreased from 215 to 152 with increasing the temperature, respectively. The binding process was exothermic and spontaneous, as indicated by the thermodynamic analyses, and the major part of the binding energy is hydrophobic interaction. The enthalpy change ΔH⁰, the free energy change ΔG⁰ and the entropy change ΔS⁰ of 289 K were calculated to be −42.75 kJ/mol, −47.56 kJ/mol and 16.66 J/mol K, respectively. The alterations of protein secondary structure in the presence of Cal-Red in aqueous solution were quantitatively calculated from FT-IR and CD spectroscopy with reductions of -helices content about 5%, β-turn from 10% to 2% and with increases of β-sheet from 38% to 51%.     

利福布汀与人血清白蛋白相互作用的光谱研究

用荧光光谱法和圆二色谱法研究了利福布汀(RB)与人血清白蛋白(HSA)的相互作用. 结果表明, RB与HSA之间的相互作用主要是疏水作用, 作用机制是静态猝灭与动态猝灭的结合. 其结合常数(Ka)在106数量级, 说明RB和HSA有很强的结合. 此外, 探讨了金属离子(Cu2+, Zn2+, Mg2+ 和Ca2+)对RB与HSA结合常数的影响. 同步荧光光谱和圆二色谱数据表明, RB可导致HSA的构象改变.     

Spin Polarization at Organic-Ferromagnetic Interface: E ect of Contact Con guration

Based on ab initio theory, the interfacial spin polarization of a benzene-dithiolate molecule vertically adsorbed on a nickel surface is investigated by adopting di erent microscopic con-tact con gurations. The results demonstrate a strong dependence of the interfacial spin polarization on the contact con guration, where the sign of spin polarization may vary from positive to negative with the change of contact con guration. By analyzing the projected density of states, an interfacial orbital hybridization between the 3d orbital of the nickel atom and the sp3 hybridized orbital of the sulfur atom is observed. We also simulated the interfacial adsorption in mechanically controllable break junction experiments. The magne-toresistance obtained from Julliere model is about 27% based on the calculated interfacial spin polarization, which is consistent with experimental measurement.     

Electrocatalytic Oxidation of Calcium Folinate on Carboxyl Graphene Modified CuxO/Cu Electrode

Carboxyl graphene modified Cu_xO/Cu electrode was fabricated. The bare copper electrode was firstly anodic polarized in 1.0 mol/L NaOH solution in order to get Cu_xO nanoparticles, then the carboxyl graphene (CG) was electrodeposited on the Cu_xO/Cu electrode by cyclic potential sweeping. The electrocatalytic oxidation behaviors of calcium folinate (CF) at the graphene modified Cu_xO/Cu electrode were investigated by cyclic voltammetry. A positive scan polarization reverse catalytic voltammetry was used to obtain the pure catalytic oxidation current. The graphene modified Cu_xO/Cu electrode was served as the electrochemical sensor of CF, a highly sensitivity of 22.0 μA·(μmol/μL)^-1cm^-2 was achieved, and the current response was linear with increasing CF concentration in the range of 2.0×10^-7 mol/L to 2.0×10^-5 mol/L, which crossed three orders of magnitude, and the detection limit was found 7.6×10^-8 mol/L (S/N=3). In addition, the proposed sensor was successfully applied in determination of CF in drug sample.     

Rational Design of [13C,D14]Tert‐butylbenzene as a Scaffold Structure for Designing Long‐lived Hyperpolarized 13C Probes

Dynamic nuclear polarization (DNP) is a technique to polarize the nuclear spin population. As a result of the hyperpolarization, the NMR sensitivity of the nuclei in molecules can be dramatically enhanced. Recent application of the hyperpolarization technique has led to advances in biochemical and molecular studies. A major problem is the short lifetime of the polarized nuclear spin state. Generally, in solution, the polarized nuclear spin state decays to a thermal spin equilibrium, resulting in loss of the enhanced NMR signal. This decay is correlated directly with the spin‐lattice relaxation time T₁. Here we report [¹³C,D₁₄]tert‐butylbenzene as a new scaffold structure for designing hyperpolarized ¹³C probes. Thanks to the minimized spin‐lattice relaxation (T₁) pathways, its water‐soluble derivative showed a remarkably long ¹³C T₁ value and long retention of the hyperpolarized spin state.