Determination of bisphenol A in human breast milk by HPLC with column-switching and fluorescence detection

A highly sensitive HPLC method was developed for the determination of xenoestrogenic compound, bisphenol A (BPA) in human breast milk samples. After a two-step liquid-liquid extraction, BPA was derivatized with fluorescent labeling reagent, 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl). The excess fluorescent reagent could be removed effectively using a column-switching system. The separation of DIB-BPA from endogenous materials in milk was carried out on two C(18) columns and fluorescence intensity was monitored at 475 nm with the excitation of 350 nm. A good linearity (r = 0.994) was observed of BPA in the concentration range of 0.2-5.0 ng mL(-1) in breast milk, and the detection limit was 0.11 ng mL(-1) at a signal-to-noise ratio of 3. Intra- and inter-day precision (RSD, %) were less than 8.7 and 10.4, respectively. Twenty-three breast milk samples of healthy lactating women were analyzed for the BPA concentration; the mean value was 0.61 +/- 0.20 ng mL(-1), with no correlation to the lipid content of milk samples.     

X-Ray Structure and Proton NMR Study of a Hexacoordinated Lithium Complex

The structure of the lithium complex with1,3,5-tris[oxymethylene(N,N-dicyclohexyl)carboxyamido]cyclohexanehas been determined by the X-ray method.The compound is triclinic, space group P¯1,a = 15.623(3), b = 19.279(4),c = 19.295(4)Å = 102.32(3), = 92.45(3), = 105.67(3)0, V = 5436(2)Å3, Z = 4. Itscomposition is represented by the formulaC48H82N3O6LiI 0.5H2O. The lithium cationis encapsulated in a polar pseudo-cavity of six oxygen atoms of the ligandmolecule and displays a distorted trigonal prism coordination. The conformationof the ligand in the solid state complex has been compared with the conformationof the complex in solution determined by 1H-NMR measurements.Supplementary data relevant to this publication have been deposited with the British Library, No. SUP 82224 (21 pages).     

Synthesis,characterization and antifungal activity of glycylglycine Schiff base complexes of 3d transition metal ions

Summary Two new Schiff bases, N-4-hydroxysalicylidene-glycylglycine (K·GGRS·H₂O), N-O-vanillal-glycylglycine (K· GGVS·3H₂O) and their manganese(II), cobalt(II), nickel(II) and copper(II) complexes have been synthesized and characterized by elemental analysis, t.g.a., molar conductance, i.r. and u.v. spectral studies. The ¹³Cn.m.r. spectrum of one of the Schiff base ligands has been recorded. The results show that the ligand is coordinated to the central metal ion via amide nitrogen, imino nitrogen, phenolic oxygen and carboxyl oxygen to form a quadridentate complexes. Some of the complexes exhibit strong inhibitory action towards Candida albicans and Cryptococcus neoformans.     

Fluorescence and aggregation behavior of poly(amidoamine) dendrimers peripherally modified with aromatic chromophores: the effect of dendritic architectures

PAMAM dendrimers of the zeroth to fifth generation (G0-5) have been peripherally modified with phenyl, naphthyl, pyrenyl, and dansyl chromophores. Their fluorescence behaviors are strongly affected by the dendritic architectures at different generations. These dendrimers modified with hydrophobic chromphores can self-organize into vesicular aggregates at the low generations G0-3 in water. The size and aggregation number of these vesicles decrease with increasing generation from G0 to G3. Critical aggregation concentration determined by fluorescence spectroscopy reveals that these aggregates can be favorably formed in the order of G3 > G2 > G1. In contrast to the vesicles made from traditional amphiphilic compounds, these dendrimer-based vesicles are very adhesive due to the H-bonding interaction and entanglement of dendritic branches located in the outer layer. A large number of multivesicle assemblies, i.e., "twins" and "quins" consisting of two and five vesicles, were clearly identifiable with transmission electron (TEM) and atomic force microscopy. For the dendrimers with peripheral pyrenyl chromophores, triangle-like vesicles were observed in water. The hydrophobic interphase thickness of the vesicular bilayer is ca. 2.0-3.2 nm determined by fluorescence resonance energy transfer methods, which agrees well with the thickness directly observed with TEM.     

微管蛋白聚合及其与紫杉醇作用的量热学研究

微管作为细胞骨架的主要成分之一，在细胞内执行许多功能.微管是一个动态的结构，既参与细胞运动和细胞内物质运输［‘个又感受、转导外界信号问的刺激产生相应灵敏的反应.尤其它是许多药物，如：紫杉醇（Taxol）、秋水仙素（Colchicine）、等作用的靶子问，因而，微管已成为筛