Study on the reaction of triple helix poly(A:2I) with Cu~(2+)

The effect of Cu2+ on the triple-stranded helical structure of poly(A:2I) was studied by means of circular dichroism spectral method with the help of ultraviolet spectral and ethidium bromide fluorescence probe methods. It was found that Cu2+ destabilizes the structure of the triple helix poly(A:2I) and induces its structural transformations, meanwhile, the transformations can be partially reversed by a higher NaCl concentration. The structural transformations may be expressed by the following scheme: poly(A:2I) - poly(A:I) + poly(I)- poly(A) + 2poly(I)     

Syntheses, properties and structures of copper and nickel complexes of 6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate

The reaction of CuCl2-2H2O or NiCl2.6H2O with K2(C5H6S4) [potassium salt of 6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate] under nitrogen atmosphere resulted in the isolation of [Cu(C5H6S4)2]- or [Ni(C5H6S4)2]- as the tetrabutylammonium salt. Both complexes show characteristic IR and UV-Vis absorptions of transition metal dithiolenes. Cyclic voltammograms contain two waves indicating a two step electrochemical procedure [M(C5H6S4)2]0 = [M(C5H6S4)2]1-= [M(C5H6S4)2]2-. Single crystal structure study has been carried out on the nickel complex. Crystal of [Bu4N][Ni(C5H6S4)2] belongs to monoclinic space group P21/c with a=17.576(5), 6=10.883(2), c=17.773(4) A,B=91.07(2)0, Z=4, and o(calcd.)=1.348 g/cm3. Final result is R=0.059 for 2959 reflections. The NiS4 core exhibits square planar coordination with average Ni-S bond length of 2.134(5) A. There are not anion pairs in crystal. The anions stack along a and c axes while the cations intercalate in them. The nearest S-S contact is 4.429 A. The solid powder ESR s     

ICP-MS测定三七中铬、砷、汞、镉和铅的测量不确定度的评估

合理评估ICP-MS测定三七中铬、砷、汞、镉、铅的测量不确定度,对测试方法的每一步骤进行不确定度的分析评估.     

Thermodynamics of mixture of boric acid with lithium borate and chloride

The first thermodynamic dissociation constants of boric acid in aqueous solution of lithium chloride with borate at five different temperatures from 278.15 to 318.15 K were evaluated from emf values of the cell without liquid junction potential with the improved extrapolation and polynomial approximation on the basis of Pitzer's theory. Values obtained from both methods are in good agreement with each other. Pitzer's parameters β(0) and β(1) of LiB(OH)4 and other thermodynamic quantities of dissociation process of boric acid are obtained. Results have been discussed.