pH-dependent multiple morphologies of novel aggregates of carboxyl-terminated polymide in water

Rigid low-molecular-weight polyimide with two carboxyl ends (CPI) formed pH-dependent multiple morphologies including dimpled-beads, porous aggregates and vesicles via self-assembly in aqueous media. This is a rapid and conventional approach to a series of pH-dependent morphologies of mono-component aggregates based on a readily attainable rigid homopolymer.Received: 27 August 2004, Published online: 10 November 2004PACS: 81.16.Dn Self-assembly - 82.70.Uv Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems, (hydrophilic and hydrophobic interactions)     

New acetylenic glucosides from Bidens bipinnata LINNE

Two new acetylenic glucosides, 8Z-decaene-4,6-diyn-1-O-beta-D-glucopyranoside named bidenoside C, and 8E-decaene-4,6-diyn-3,10-dihydroxy-1-O-beta-D-glucopyranoside named bidenoside D, have been isolated from the aerial parts of Bidens bipinnata LINNE (Asterceae). These structures have been elucidated on the basis of spectroscopic methods.     

BRST quantization ofN = 2, 3, and 4 superconformal theories on higher-genus Riemann surfaces

Complex contour integral techniques, developed in a previous paper for theN=0 and 1 superconformal theories on higher-genus Riemann surfaces, are applied to a Becchi-Rouet-Stora-Tyutin (BRST) quantization procedure of superconformal theories withN=2, 3, and 4 super-Krichever-Novikov (KN) constraint algebras on a genus-g Riemann surface. The BRST charges of the superconformai theories are constructed and the nilpotency of the BRST charges is checked. The critical spacetime dimension and the intercepts are found for theN=2 and 4 cases. Also calculated are the central charge and the intercept for theN=3 case.     

Photochemical activities of plant photosystem I particles reconstituted into phosphatidylglycerol liposomes

Phosphatidylglycerol (PG) is the only anionic phospholipid in photosynthetic membrane and the important component of photosystem I (PSI). In this study, the interaction of PG with PSI particle from spinach was investigated by using reconstitution method. The results from the properties of electron transport, fluorescence emission, turbidity, and protein secondary structures in PSI complex incorporated into PG liposomes revealed the existence of PSI-PG interactions. A stimulation and an inhibition of oxygen uptake in PSI particle at a low and higher PG/chlorophyll mass ratio, respectively, were observed. Moreover, an additional enhancement and depression of electron flow in the PSI-PG complexes were occurred in the reaction medium containing CaCl2 at concentrations below and above 5 mM, the aggregation threshold of the reconstituted membranes, respectively. The results demonstrated that the maintenance of the structural optimization was needed for a stimulation of electron transport at a low PG/PSI mass ratio, while a decay of this PSI activity at high PG/PSI ratio was the result of inhibition of the energy transfer from LHCI to PSI reaction center induced by the dissociation of LHCI-680.     

Capacitive chemical sensor for fenvalerate assay based on electropolymerized molecularly imprinted polymer as the sensitive layer

A capacitive chemical sensor for fenvalerate is reported. By using ac impedance measurements the sensor has been based on the decrease in capacitance caused by the analyte used as the template in the formulation of an electropolymerized molecularly imprinted polymer as receptor layer. Improvement of the insulating properties of the sensor was investigated in detail. The capacitive sensor was prepared by a deposition of a self-assembled monolayer of 2-mercaptobenzimidazole (2-MBI) before electropolymerization of 2-MBI and subsequent treatment with n-dodecanethiol to eliminate pinholes and defects in the polymerized 2-MBI film. From the calibration curve concentrations of fenvalerate up to 9 g mL^–1 could be detected with a linear determination range up to 5 g mL^–1 and a detection limit of 0.36 g mL^–1. No significant interference was observed from common pyrethroid insecticides.     

Cd（Ⅱ）—SAF—DDMBA显色反应的研究及应用

研究了Cd(Ⅱ)与水杨基荧光酮(SAF)-溴化十二烷基二甲基苄铵(DDMBA)显色反应的条件,在表面活性剂DDMBA存在下,pH 10的硼砂-氢氧化钠缓冲介质中,Cd(Ⅱ)与SAF形成1:4紫红色配合物,配合物于570nm有最大吸收,表观摩尔吸光系数9.26×10~4,镉含量在0～6μg/25ml符合比耳定律,方法简便、灵敏,精密度高,准确度好,应用于铅渣中镉的测定,结果满意。