Manganese(II) o ctacyanotungstate(V)-based magnet containing a noncoordinated aromatic molecule

We have prepared a pillared layer magnetic material containing a noncoordinated aromatic molecule, [{MnII(pyrimidine)(H2O)}2{MnII(H2O)2}{WV(CN)8}2](pyrimidine)2.2H2O. This compound has one-dimensional channels (6.2 x 2.1 A) that are occupied by noncoordinated pyrimidine. The magnetization versus temperature plots showed the magnetic phased transition temperature (TC) was 47 K. The magnetization versus external magnetic field plots showed that the saturation magnetization (MS) value was 13.0 muB at 2 K. This MS value indicates that an antiferromagnetic interaction operates between the WV (S = 1/2) and MnII (S = 5/2) ions. The magnetic hysteresis loop showed that the coercive field (HC) was 17 G at 2 K.     

Analysis of the interaction between human plasma fibronectin and gelatin by affinity electrophoresis

The interaction between human plasma fibronectin and gelatin was analyzed by affinity electrophoresis, in which the fibronectin was subjected to electrophoresis in a 4% polyacrylamide gel in the presence and absence of gelatin, as an affinity ligand, and the fibronectin band was stained by an immunoblotting method. The apparent dissociation constants (Kd) of fibronectin for gelatin were calculated from affinity plots based on the original affinity equation at different pHs, urea concentrations, and temperatures. The fibronectin exhibited much lower affinity in the presence of urea. The Kds at 37 degrees C were 1.49 X 10(-7) M, 2.50 X 10(-6) M, and 3.58 X 10(-6) M with 2 M, 3 M, and 4 M urea, respectively. The van't Hoff plots of Kd values against absolute temperature (T) showed that the value of log Kd decreased in proportion to the increase in the value of 1/T within the range of 15-50 degrees C. The standard enthalpy, the standard free energy change at 37 degrees C, and the entropy change at 37 degrees C for association were calculated to be -124.7 kJ/mol, -33.23 kJ/mol, and -295.1 J/mol/deg, respectively. These results suggest that a hydrophilic interaction, such as hydrogen bond or van der Waals interaction, plays an important role in the binding of plasma fibronectin to gelatin.     

Ab initio MO Calculations of benzene + TCNE and naphthalene + TCNE complexes with STO-3G π-split basis set

Ab initio SCF MO calculations have been carried out on benzene + TCNE (tetracyanoethylene) and naphthalene + TCNE complexes with the STO -3G, STO -3G π-split (STO -3G for π orbitals and a split basis for π orbitals), and 4–31G basis sets. The interaction energy, gross charges, dipole moment, and the electron density in the middle plane of the complexes have also been evaluated. The STO -3G π-split basis set is appropriate for the calculation of large π–π stacking complexes from two points of view, production of reliable results and ease of computations. The approximation scheme based on the semiorthogonalized orgitals is revealed to be very efficient to save CPU time and storage in such calculations. The stable conformation and the charge-transfer interaction of the two complexes are discussed on the basis of the calculated quantities.     

Improvement of an integral approximation scheme based on semiorthogonalized orbitals

In a previous paper, a scheme of integral approximation was proposed, in which a large number of two-electron integrals containing a certain kind of orbital pairs, i.e., weakly related pairs, can be neglected. A new criterion for partitioning orbital pairs into two groups, i.e., strongly and weakly related pairs, is introduced in order to allow for neglect of more integrals without sacrificing the accuracy of a computation. Test calculations on the BH₃? C₂H₄ complex show that by the use of the new version, results of roughly the same accuracy as was obtained by the old version is obtained by retaining 80% of the integrals used in the old version. This kind of saving is more significant for larger molecules. For example, in a calculation on Cu-porphine with 203 CGTO 'S , the revised version will require about 2.0 × 10⁶ integrals, while the original version will require about 4.5 × 10⁶. And these two approximate calculations are expected to give the results of roughly the same accuracy.     

Development of hydrophilic fluorogenic derivatization reagents for thiols: 4-(N-acetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole and 4-(N-trichloroacetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole

Sensitive, reactive, and hydrophilic fluorogenic reagents for thiols with the benzofurazan skeleton, 4-(N-acetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (AcABD-F) and 4-(N-trichloroacetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (TCAcABD-F) have been developed. These reagents reacted with thiols within 10 min at 60 degrees C. AcABD-F and TCAcABD-F themselves do not fluoresce but are strongly fluorescent after the reaction with thiol compounds. The generated derivatives were highly water-soluble, since they dissociated a proton and ionized in the neutral pH region. The derivatives with four biologically important thiol compounds were separated on a reversed-phase HPLC column and detected fluorometrically at 504 nm with excitation at 388 nm. The detection limit attained for homocysteine with AcABD-F was 25 fmol on column (11 nM) (signal-to-noise ratio = 3), and that for glutathione with TCAcABD-F was 45 fmol on column (20 nM).     

The electrochemistry and determination of Ligustrazine hydrochloride

Ligustrazine is one of the active ingredients contained in Ligusticum chuanxiong Hort. (Umbelliferae), which is widely used in traditional Chinese medicine for the treatment of cardiovascular problems. In this work, the electrochemistry of Ligustrazine hydrochloride (LZC) and its determination are investigated. The detection limit is estimated to be 8.0×10^–8 M, with three linear ranges from 1.0×10^–6 to 1.0×10^–4 M, 1.0×10^–4 to 5.0×10^–4 M, and 6.5×10^–4 to 1.6×10^–3 M. The method has been proved to be highly sensitive, selective, and stable, and has been successfully applied to determining LZC in LZC injections.     

Electrocatalytic Oxidation of Amines on a Mediator‐Modified Electrode by Electrochemical Copolymerization of Nitroxyl Radical Precursor Containing Pyrrole Side Chain and Bithiophene

This paper describes the electrocatalytic oxidation of amines on TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl)‐modified electrodes prepared by electrochemical copolymerization of TEMPO precursor containing pyrrole side chain and 2,2′‐bithiophene. The modified electrode exhibits electrocatalytic activity for the oxidation of primary and secondary amines. Cyclic voltammetric studies showed that the peak current of the cyclic voltammogram increased linearly with increasing concentration of amine in the sample solution.