Antiviral agents of plant origin. III. Scopadulin, a novel tetracyclic diterpene from Scoparia dulcis L

The structure and stereochemistry of scopadulin, a novel aphidicolane-type diterpene isolated from Scoparia dulcis L. have been established from spectral data and single-crystal X-ray analysis of its acetone solvate.     

Conductometric titration of nitrate by formation of the silver-1,10-phenanthroline-nitrate ternary complex

Nitrate forms an insoluble ternary complex, Ag(phen)(2)NO(3), with silver in the presence of 1,10-phenanthroline (phen). A simple and direct conductometric titration of nitrate, based on the formation of this ternary complex, has been investigated. The sample solution is adjusted to pH 4.3 with acetate buffer and titrated with 0.1M Ag(phen)(+)(2) complex solution in 40% ethanol-water mixture. The relative error is less than 0.5% and relative standard deviation less than 0.4%. The effect of ammonium ion and urea has also been studied. The method has been successfully applied to determination of nitrate-nitrogen in fertilizer.     

PEGylated polyplex micelles from triblock catiomers with spatially ordered layering of condensed pDNA and buffering units for enhanced intracellular gene delivery

An A-B-C type triblock copolymer, tandemly aligning two types of polycations with different pKa values in a single polymer strand, was developed for the construction of novel polyplex micelles, satisfying a high DNA condensing ability as well as a proton buffering activity directed to elevating gene transfection. The micelle might feature the distinctive three-layered structure, where an inner polyplex layer of condensed pDNA with poly(l-lysine) (pKa approximately 9.4) as the C segment is successively wrapped with an intermediate layer of poly[(3-morpholinopropyl)aspartamide] (B segment) with a comparatively low pKa of approximately 6.2, to provide a buffering effect, and an outer PEG layer (A segment) as a biocompatible palisade.     

Indirect atomic-absorption spectrophotometric determination of phosphorus after flotation as the ion-pair of molybdophosphate with bis[2-(5-chloro-2-pyridylazo)-5-diethylaminophenolato]cobalt(III)

An atomic-absorption spectrophotometric method has been developed for the indirect determination of phosphorus. The calibration graph is linear over the range 0.025-0.2 mug of phosphorus. The relative standard deviation is 1.3% for 0.2 mug of phosphorus (6 replicates). The method has been applied to the determination of phosphate in natural water samples. The enhancement effect of acetone on the determination is discussed.     

Colominic acid: a novel chiral selector for capillary electrophoresis of basic drugs

Capillary zone electrophoresis was used for characterising nine samples of natural organic matter (NOM) using phosphate buffer (25 mM, pH 7) and various modifiers; methanol (50 mM), acetonitrile (10%,v/v), dimethyl sulfoxide (5%,v/v), and urea (5 M). Principal component analysis (PCA) was used to examine whether the electrophoretic profiles can be utilised as fingerprints for tracing the NOM samples to their source and/or type of location. It was found that all modifiers except methanol affect the electropherograms. Furthermore, it was found that the PCA analysis carried out on the electrophoretic profiles recorded in buffer solution modified by urea gave the best results for fingerprinting. The distribution of the fingerprints suggests a model for the humic substances in which all samples can be regarded as mixtures between two endmembers: autochtonous and allocthoneous NOM.     

Anion binding to a ferric porphyrin complexed with per-O-methylated beta-cyclodextrin in aqueous solution

5,10,15,20-Tetrakis(4-sulfonatophenyl)porphinato iron(III) (Fe(III)TPPS) forms a very stable 1:2 complex with heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TMe-beta-CD), whose iron(III) center is located at a hydrophobic cleft formed by two face-to-face TMe-beta-CD molecules. Various inorganic anions (X(-)) such as F(-), Cl(-), Br(-), I(-), N(3)(-), and SCN(-) coordinate to Fe(III)TPPS(TMe-beta-CD)(2) to form five-coordinate high-spin Fe(III)TPPS(X)(TMe-beta-CD)(2), while no coordination occurs with ClO(4)(-), H(2)PO(4)(-), NO(3)(-), and HSO(4)(-). Except for F(-), none of the anions investigated coordinate to Fe(III)TPPS in the absence of TMe-beta-CD due to extensive hydration to the anions as well as to Fe(III)TPPS. The present system shows a high selectivity toward the N(3)(-) anion. The thermodynamics suggests that Lewis basicity, hydrophilicity, and shape of an X(-) anion are the main factors to determine the stability of the Fe(III)TPPS(X)(TMe-beta-CD)(2) complex.     

13C- and 1H-NMR and FTIR spectroscopic evidence for aggregate formation of organosilanes in toluene

 Changes in the ¹³C and ¹H NMR chemical shifts of the silane coupling agent (3-aminopropyltri-ethoxysilane, APTS) in toluene, which were detected as the concentration of APTS increased, have been interpreted in terms of the formation of micelles and the presence of a critical micelle concentration (CMC) equal to ca. 0.47 mol 1^-1. For the protons of the n-propyl segment, ¹H NMR splitting patterns have been analyzed and conformations of the propyl segment have been discussed. Plots of relative absorbance of the two NH₂ stretch IR bands at 3324 and 3384 cm^-1 against concentration provided an inflection point (corresponding to the CMC) at a value equal to 0.46 mol 1^-1. Thus, consideration of the interaction of APTS with a surface must take into account the presence of both APTS aggregates as well as APTS monomers. Received: 16 August 1996 Accepted: 26 September 1996     

Infrared and raman studies on the phase structure of barium ethyl(octyl)phosphate-water system

Barium ethyl(alkyl)phosphates, as new simple surfactants ((C₂H₅O)(RO)-PO ₂ ^– )₂Ba²⁺ with various chain length ofR, were synthesized. The infrared spectra in the CH stretching region were measured for these surfactants in the solid state and in aqueous solution, and assignments were made. In particular, the ordering and environment of octyl chains in the different phases of the barium ethyl(octyl)phosphate-water system were studied by the Fourier-transform-infrared and Raman spectra. The CH stretching bands in the infrared spectra reflected the ordering and environment of octyl chains in each phase. The Raman band connected to the PO ₂ ^– symmetric stretching mode was sensitively shifted. This was caused by the change of aggregation structures with different Ba²⁺...PO ₂ ^– interaction. The infrared band arising from the PO ₂ ^– antisymmetric stretching mode was insensitive to the phase structures. The C–C stretching region in the infrared spectra was used to discuss the ordering of each phase.