A Whitney-stratified curve in with multiple-point projections

We construct a compact Whitney-stratified curve in , such that each of its plane projections has an infinite number of multiple points.

     

Effect of a Phosphazene Base on the Diastereoselectivity of Addition of alpha-Sulfonyl Carbanions to Butyraldehyde and Isopropylideneglyceraldehyde

The effect of tBuP4, a strong and cation-free base, on the yield and diastereoselectivity of additions of thus formed "naked" alpha-sulfonyl carbanions to achiral butyraldehyde and chiral isopropylideneglyceraldehyde was studied. It has been found that with tBuP4 a reasonable yield ( approximately 55%) and a slightly better diastereoselectivity (72% of the anti diastreomer) are obtained with achiral and nonfunctionalized butyraldehyde while with isopropylideneglyceraldehyde the use of tBuP4 allowed us to greatly increase the yields (up to 95-100%) and the diastereoselectivities (83-89% of a single diastereomer over the four possible diastereomers). It was also shown that the extra oxygen atom in the alpha-position plays a determinant role in this effect.     

Novel alkaloids of the aaptamine class from an Indonesian marine sponge of the genus Xestospongia

Four novel alkaloids of the aaptamine class have been isolated in addition to the known aaptamine, isoaaptamine, demethyl(oxy)aaptamine and its dimethylketal from an unidentified species of Indonesian marine sponge of the genus Xestospongia. Their structures were elucidated on the basis of detailed 1D and 2D NMR spectroscopic data. Their antimicrobial activity was tested towards Gram (+) (S. aureus), Gram (−) (E. coli, V. anguillarum) bacterial strains, a fungus (C. tropicalis); their cytotoxic activity was evaluated against KB cells.     

The effect of first-stage polymer Tg on the morphology and thermomechanical properties of structured polymer latex particles

A series of heterogeneous latexes having stage ratios of 40:60 between the first and second stage polymers were prepared by emulsion polymerization. The first-stage polymers were non-polar S-BuA with T_gs ranging from + 100 °C to + 20 °C and the second stage polymer was polar MMA–BuA–MAA having a T_g of 20 °C. The latex particle morphologies were studied using TEM and the thermomechanical properties of the resulting latex films were studied with DSC and DMA. Calculated diffusion rates for propagating species during the reactions were correlated to the observed morphologies and to the amount of interphase in the latex particles. To cite this article: O.J. Karlsson et al., C. R. Chimie 6 (2003).     

Transport, retention and fluorescent measurement of single biological cells studied in microfluidic chips

Cellular manipulation and fluorescent measurement were performed on two types of biological cells. First, transport and retention of yeast cells were demonstrated on a glass microfluidic chip, which consists of special U-shaped microstructures. These microstructures have the openings parallel to the liquid flow and weirs perpendicular to the flow. These allow the retention of yeast cells in the U-shaped pocket and drainage of liquid over the weirs. Thereafter, the same chip was used to carry out real-time fluorescent measurement for the cellular changes in single Jurkat T cells. In this case, the Jurkat cells were localized inside the straight portion of a microchannel. Fluorescent imaging on the same, single suspension cell was carried out to study two cellular processes occurring in viable cells, (1) the intracellular conversion of fluorescein diacetate (FDA) to fluorescein; (2) the degradation of an inhibitory protein, IkappaB, as involved in the NF-kappaB signalling pathway. In the former, the increase in fluorescent intensity of single Jurkat T cells (due to fluorescein formation) was measured; whereas in the latter, the decrease in the fluorescent intensity of a single transfected Jurkat cell (due to the degradation of the IkappaB-EGFP fusion protein) was monitored. In addition, we employed a Jurkat cell expressed with IkappaB-EGFP to probe any possible action of an herbal compound, isoliquiritigenin (IQ), on the degradation of IkappaB-EGFP. These examples have demonstrated that Jurkat cells remain viable within microfluidic channels for cellular studies and that the microfluidic chip can facilitate monitoring of cellular changes of biological cells at the single cell level and in the same cell.     

Is ferromagnetism an intrinsic property of the CuII/GdIII couple? 1. Structures and magnetic properties of two novel dinuclear complexes with a mu-phenolato-mu-oximato (Cu,Gd) core

Two original dinuclear (Cu(II),Gd(III)) complexes (1 and 2) deriving from polydentate nonsymmetrical Schiff base ligands LiH2 have been prepared. Formally they differ by the length of the diamino chain. They crystallize in the orthorhombic Pbca (No. 61) (1) and in the monoclinic P2(1/n) (No. 14) (2) space groups. The cell parameters are a = 12.6295(7) A, b = 20.7894(9) A, c = 18.3301(13) A, and Z = 8 for 1 and a = 12.7246(16) A, b = 13.5691(17) A, c = 14.5310(19) A, beta = 94.629(16) degrees , and Z = 4 for 2. These structural studies show that in both complexes the CuII and GdIII ions are doubly bridged by a phenolato oxygen atom and an oximato (N-O) pair. The bridging network is not planar. The more important distortions are observed for the complex having the larger diamino chain. Unexpectedly the latter complex presents an antiferromagnetic interaction, but the related J value is small (J approximately equal to -0.49 cm(-1)). In the former complex the interaction is ferromagnetic (J approximately equal to 3.5 cm(-1)) as it is for complexes containing (CuO2Gd) bridging cores which yield J values varying from 1.4 to 10.1 cm(-1).     

The elusive atomic rationale for DNA base pair stability

A systematic analysis of the electrostatic interaction between 27 natural DNA base pairs was carried out, based on ab initio correlated wave functions and the topology of the electron density. Using high rank multipole moments we show that the atomic partitioning of the interaction energy contains many substantial contributions between distant atoms. Profiles of cumulative energy versus internuclear distance show large fluctuations and provide an electrostatic fingerprint of the partitioning of interaction energy in a complex. A quantified comparison between each pair of energy profiles, one for each base pair, makes clear that there is no correlation between the total base pair interaction energy and the shape of the profile. In other words, base pairs with similar interaction energy are not stable for the same reasons in terms of atomic partitioning. In summary, simple rules to rationalize the pattern of energetic stability of naturally occurring base pairs in terms of subsets of atoms are elusive. Our work cautions against inappropriate use of Jorgensen's secondary interaction hypothesis.