Alternating polyampholytes prepared by hydrolysis of copolymer of maleic anhydride and N-vinylsuccinimide

Alternating polyampholytes (MA-VA) containing two acidic groups and one basic group were prepared by the copolymerization of maleic anhydride (M₁) and N-vinylsuccinimide (M₂) at 60°C with AIBN as the initiator, followed by acid hydrolysis with 1N hydrochloric acid at 140°C for 24 hr. The monomer reactivity ratios r₁ and r₂ are 0.025 and 0.06, respectively. The structure of polymers was discussed on the basis of the data of their elementary, infrared (IR), and thermal analyses and the binding ability of heavy metal ion. Polyampholytes were soluble in strong acidic and basic media but were precipitated in the pH range 3–4. An isoelectric point at pH 3 was determined by potentiometric titration and the turbidimetric method. By thermal treatment above 205°C the polyampholyte turned quantitatively into a cyclized lactam. This suggests that the polyampholyte MA–VA has an intramolecular hydrogen bond between the amino and γ-carboxyl groups. The binding of Cu²⁺ and Hg²⁺ by the polyelectrolyte was evaluated by equilibrium dialysis.     

Magnetic susceptibility and specific heat of uranium double perovskite oxides Ba2MUO6 (M=Co, Ni)

Double perovskites Ba₂MUO₆ (M=Co, Ni) were prepared by the solid-state reaction. X-ray diffraction measurements show that both cobalt (nickel) and uranium ions are ordered in the NaCl type over the six-coordinate B sites of the perovskite ABO₃. Detailed magnetic susceptibility and specific heat measurements show that Ba₂CoUO₆ and Ba₂NiUO₆ order ferromagnetically at 9.1 and 25 K, respectively. From the analysis of the magnetic specific heat, the ground states of the Co²⁺ and Ni²⁺ ions were determined.     

Interaction between poly[(R)-3-hydroxybutyrate] depolymerase and biodegradable polyesters evaluated by atomic force microscopy

Adsorption of PHB depolymerase from Ralstonia pickettii T1 to biodegradable polyesters such as poly[(R)-3-hydroxybutyrate] (PHB) and poly(l-lactic acid) (PLLA) was investigated by atomic force microscopy (AFM). The substrate-binding domain (SBD) with histidines within the N-terminus was prepared and immobilized on the AFM tip surface via a self-assembled monolayer with a nitrilotriacetic acid group. Using the functionalized AFM tips, the force-distance measurements for polyesters were carried out at room temperature in a buffer solution. In the case of AFM tips with immobilized SBD and their interaction with polyesters, multiple pull-off events were frequently recognized in the retraction curves. The single rupture force was estimated at approximately 100 pN for both PLLA and PHB. The multiple pull-off events were recognized even in the presence of a surfactant, which will prevent nonspecific interactions, but reduced when using polyethylene instead of polyesters as a substrate. The present results provide that the PHB depolymerase adsorbs specifically to the surfaces of polyesters and that the single unbinding event evaluated here is mainly associated with the interaction between one molecule of SBD and the polymer surface.     

Elucidation of mechanism for living radical polymerization of styrene with N,N-diethyldithiocarbamate derivatives as iniferters by the use of spin trapping technique

The photodissociation of several N,N-diethyldithiocarbamate derivatives (RDC), i.e., benzyl, 1-phenylethyl, 2-phenylethyl, n-butyl, sec-, and tert-butyl N,N-diethyldithiocarbamates, was investigated by the spin trapping technique to elucidate the polymerization mechanism of styrene (St) with RDC as iniferters. The scission of RDC occured at two different C? S bonds depending on the structure of the alkyl groups of RDC and the cleavage manner was dominated by both resonance and steric effects. It has been confirmed that RDC generating an N,N-diethyldithiocarbamyl radical acts as an effective iniferter and induces the living radical polymerization of St in homogeneous system. The polymerizations of St with tetraethylthiuram disulfide and p-xylylene bis(N,N-diethyldithiocarbamate) were also discussed on the basis of the results of the spin trapping for RDC as the model compounds of the poly(St) chain ends. © 1994 John Wiley & Sons, Inc.     

Metabolism of ipriflavone (TC-80) in rats

Metabolic studies of ipriflavone (TC-80) in rats by gas-liquid chromatography-mass spectrometry led to the characterization of the following metabolites: the parent compound, 7-hydroxy-3-phenyl-4H-1-benzopyran-4-one, 7-hydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-one, 3-(4-hydroxyphenyl)-7-isopropoxy-4H-1-benzopyran-4-one, 2-(3-phenyl-4-oxo-4H-1-benzopyran-7-yl)oxypropionic acid, 2-[3-(4-hydroxyphenyl)-4-oxo-4H-1-benzopyran-7-yl]oxypropionic acid and 2-[3-(3-hydroxyphenyl)-4-oxo-4H-1-benzopyran-7-yl]oxypropionic acid. From the metabolites identified, TC-80 was shown to be metabolized primarily by oxidation. In vitro study using tissue slices of rats indicated that the above metabolic changes occurred exclusively in the liver. It was also demonstrated that the compound did not undergo metabolic conversion by gut flora of rats.     

Syntheses of anthraquinone capped hairpin DNAs and electrochemical redox responses from their self-assembled monolayers on gold electrode

An anthraquinone (AQ) based DNA linker and hairpin-forming DNAs linked by the AQ linker with variable A-T base pairs were synthesized for the investigation of electron transfer through double helical DNA (DNA-ET) in self-assembled monolayers (SAMs). The spectroscopic analysis of absorption spectra indicated that the AQ of the hairpin DNA stacked with adjacent A-T base pair. Electrochemical redox response due to the AQ was observed from the hairpin DNA immobilized on gold electrode, thus the hairpin DNA is suitable for the investigation of DNA-ET in SAMs.     

Synthesis of zigzag-chain and cyclic-octanuclear calcium complexes and hexanuclear bulky aryl-phosphate sodium complexes with ortho-amide groups: structural transformation involving a network of inter- and intramolecular hydrogen bonds

Three new polynuclear Ca(II)- and Na(I) phosphate complexes with two strategically oriented bulky amide groups, 2,6-(PhCONH)(2)C(6)H(3)OPO(3)H(2), were synthesized, including one with a zigzag-chain, [Ca(II)[O(3)POC(6)H(3)-2,6-(NHCOPh)(2)](H(2)O)(4)(EtOH)](n), a cyclic-octanuclear form, [Ca(II)(8)[O(3)POC(6)H(3)-2,6-(NHCOPh)(2)](8)(O=CHNMe(2))(8)(H(2)O)(12)], and a hexanuclear complex, (NHEt(3))[Na(3)[O(3)POC(6)H(3)-2,6-(NHCOPh)(2)](2)(H(2)O)(MeOH)(7)]. X-ray crystallography revealed that all have an unsymmetric ligand position due to the bulky amide groups. A dynamic transformation of the Ca(II) zigzag-chain structure to the cyclic-octanuclear complex was induced by changing coordination of DMF molecules, which caused a reorganization of the intermolecular/intramolecular hydrogen bond network.     

Substitution effect,absorption, and fluorescence behaviors of 11,12-benzo-1,7,10,13-tetraoxa-4-aza- cyclopentadec-11-ene (benzoaza-15-crown-5) derivatives upon cation complexation in solvent extraction

Substitution effect, absorption, and fluorescence behaviors of some benzoaza-15-crown-5 derivatives upon cation complexation in solvent extraction were studied. The introduction of a substituent on the nitrogen atom in benzoaza-15-crown-5 enhanced extractabilities in the solvent extraction of aqueous alkali metal picrates. The nondonating substituents raised the cation selectivity for Na(+) over K(+), but the donating substituents reduced the cation selectivity. The absorption and fluorescence spectral behavior was different with the alkali metal cations.     

Doppler-free two-photon excitation spectroscopy and the Zeeman effects. Perturbations in the 14(0)1 and 1(0)(1)14(0)1 bands of the S1 <-- S0 transition of C6D6

Doppler-free two-photon excitation spectra and the Zeeman effects for the 1 band of the S1 1B2u <-- S0 1A1g transition in gaseous benzene-d6 were measured. Although the spectral lines were strongly perturbed, almost all of the lines near the band origin could be assigned. From a deperturbation analysis, the perturbation near the band origin was identified as originating from an anharmonic resonance interaction. Perturbation centered at K = 28-29 in the 14(0)1 band was analyzed, and it was identified as originating from a perpendicular Coriolis interaction. The symmetry and the assignment of the perturbing state proposed by Schubert et al. (Schubert, U.; Riedle, E.; Neusser, H. J. J. Chem. Phys. 1989, 90, 5994.) were confirmed. No perturbation originating from an interaction with a triplet state was observed in both bands. From the Zeeman spectra and the analysis, it is demonstrated that rotationally resolved levels are not mixed with a triplet state. The intersystem mixing is not likely to occur at levels of low excess energy in the S1 state of an isolated benzene. Nonradiative decay of an isolated benzene in the low vibronic levels of the S1 state will occur through the internal mixing followed by the rotational and vibrational relaxation in the S0 state.     

Effect of Metallic Oxides Containing Composite Electrodes on Crystallization and Ferroelectric Properties of Pb(Zr0.52,Ti0.48)O3 Thin Films Deposited by the Sol-Gel Method

In order to suppress polarization fatigue and decrease the leakage current of the PZT capacitor, composite electrodes consisting of MO₂ (RuO_x or IrO_x) as an effective diffusion barrier and considerably large amounts of Pt were deposited by magnetron co-sputtering to yield heterostructured PZT capacitors, Pt/(Pt+MO₂)//PZT(52/48)//(Pt+MO₂)/(Pt+M)/M/Pt/Ti(Ta)/SiO₂/Si(1 0 0), and the crystallinity and the orientation, the morphology of the surface and the cross section, and the composition depth profile of the PZT capacitor were examined by XRD analysis, SEM and AES, respectively, and the ferroelectric properties were measured. The results indicated that by adjusting the distribution and composition of the RuO₂ phase, the polarization loss of the PZT capacitor can be suppressed to as small as 5% after polarization reversals of 10⁹ while maintaining the effective polarization dP_r = P_r* – P_r ^{^} at 15 C/cm². The suppression of the polarization fatigue was found more effective with (Pt+IrO₂) electroding than (Pt+RuO₂) electroding. The leakage current of the PZT capacitor electroded with (Pt+MO₂) was a little larger than that of the PZT capacitor with Pt electrode. The possible reason was suggested.