Isolation of swinholide A and related glycosylated derivatives from two field collections of marine cyanobacteria

[structure: see text] Chemical investigation of two field collections of marine cyanobacteria has led to the discovery of two new cytotoxic natural products, ankaraholides A (2) and B (3), along with the known compound swinholide A (1). Since swinholide-type compounds were previously localized to the heterotrophic bacteria of sponges, these findings raise intriguing questions about their true metabolic source.     

Persistent droplet motion in liquid-liquid dewetting

When a nonvolatile liquid film dewets from a partly compatible liquid substrate, the advancing dewetting front leaves behind droplets formed through a Rayleigh instability mechanism at its rim. We have found that these droplets continue to move in the direction of the dewetting front for extended periods (of order one day) with an initial droplet velocity varying linearly with the droplet size, and a displacement varying logarithmically with time. We attribute this persistent motion to a transient surface tension gradient on the substrate liquid surface trailing the dewetting front.     

UV laser ablation of GdCa4O(BO3)3 (GdCOB) investigated by Fourier transform ion cyclotron resonance mass spectrometry

The ions generated by laser ablation (LA) of calcium and gadolinium oxoborate GdCa4O(BO3)3 (GdCOB) were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS), a powerful tool for the characterization of ionic species produced by laser interaction with solid material. In order to better understand the matter transfer and the mechanism of thin film growth by pulsed-laser deposition (PLD), cationic and anionic clusters generated by UV laser ablation of GdCOB bulk material were studied. Laser ablation of GdCOB leads to the formation of various cluster ions which result from association of CaO, BO and B2O3 building blocks (BB) with different charge carriers (CC): H+, BO+, GdO+ in positive ion mode, and BO2-, OK-, OH-, Cl-, WO3- in negative ion mode. LA-FTICRMS investigations allow us to assign a valence state to each metallic atom included in each BB. A +II chemical state may be associated with calcium and +II and +III ones to boron. UV laser ablation of GdCOB therefore induces reduction processes of boron species in the gas phase. The oxygen reactive atmosphere used during PLD experiments allows the growth of stoichiometric thin films by fixation of oxygen on the ablated species.     

Arrays for the combinatorial exploration of cell adhesion

A new method for the fabrication of arrays of self-assembled monolayers (SAMs) of alkane thiols (ATs) on gold to combinatorially assay surfaces for cell adhesion is reported. A fluorous SAM, which is both cytophobic and solvophobic, was used as the background between the array features. The resulting solvophobic background permits the application of an assembly after conjugation strategy for fabrication. SAMs containing mixtures of ATs and peptide-terminated ATs were generated. Multiple cell types demonstrated differential and specific binding to these surfaces. Additionally, pluripotent human embryonic stem cells proliferated on surfaces generated by this method.     

Variable temperature system using vortex tube cooling and fiber optic temperature measurement for low temperature magic angle spinning NMR

We describe the construction and operation of a variable temperature (VT) system for a high field fast magic angle spinning (MAS) probe. The probe is used in NMR investigations of biological macromolecules, where stable setting and continuous measurement of the temperature over periods of several days are required in order to prevent sample overheating and degradation. The VT system described is used at and below room temperature. A vortex tube is used to provide cooling in the temperature range of -20 to 20 degrees C, while a liquid nitrogen-cooled heat exchanger is used below -20 degrees C. Using this arrangement, the lowest temperature that is practically achievable is -140 degrees C. Measurement of the air temperature near the spinning rotor is accomplished using a fiber optic thermometer that utilizes the temperature dependence of the absorption edge of GaAs. The absorption edge of GaAs also has a magnetic field dependence that we have measured and corrected for. This dependence was calibrated at several field strengths using the well-known temperature dependence of the (1)H chemical shift difference of the protons in methanol.     

Support Varieties for Selfinjective Algebras

Support varieties for any finite dimensional algebra over a field were introduced in (Proc. London Math. Soc. 88 (3) (2004) 705–732) using graded subalgebras of the Hochschild cohomology ring. We mainly study these varieties for selfinjective algebras under appropriate finite generation hypotheses. Then many of the standard results from the theory of support varieties for finite groups generalize to this situation. In particular, the complexity of the module equals the dimension of its corresponding variety, all closed homogeneous varieties occur as the variety of some module, the variety of an indecomposable module is connected, the variety of periodic modules are lines and for symmetric algebras a generalization of Webbs theorem is true. As a corollary of a more general result we show that Webbs theorem generalizes to finite dimensional cocommutative Hopf algebras.Received November 2003Mathematics Subject Classifications (2000) Primary: 16E40, 16G10, 16P10, 16P20; Secondary: 16G70.     

Metal-chelating nanoparticles as selective fluorescent sensor for Cu2+

A fluorescent sensor for Cu(2+) at the nanomolar level in water has been designed by associating a BODIPY fluorophore and a selective ligand (cyclam) in ultrafine polymer nanoparticles.     

Sweet success: Ionic liquids derived from non-nutritive sweeteners

The anions of the sweeteners saccharin and acesulfame form ionic liquids when paired with a variety of organic cations.