Serum Chloride Optical Sensors Based on Dynamic Quenching of the Fluorescence of Photo-Immobilized Lucigenin

This article describes the preparation and performance of an optical sensor for continuous measurement of chloride at extracellular (serum) levels (20–200mM). The sensor is based on dynamic quenching of the fluorescence of lucigenin which was photo-immobilized on a hydrogel. Quenching occurs via a collisional mechanism, and the decrease in fluorescence intensity on exposure to 100mM chloride typically is –60%. It allows the determination of chloride in the 1 to 200mM concentration range, with a precision of ±3mM at 120mM. Bromide, iodide and salicylate act as interferents, while the effect of pH and oxygen is negligibly small. The sensor displays strong fluorescence intensity, excellent reproducibility, long-term stability, response times in the order of 2–5min, and is used in a commercial serum and blood chloride analyzer.Received January 21, 2003; accepted April 6, 2003 Published online July 28, 2003     

Asymmetric Catalysis. Part 149 [1]. Synthesis of New Chiral Tridentate Ligands for Enantioselective Catalysis

Summary. The synthesis of new chiral tridentate ligands is reported which coordinate transition metals in a meridional way. The ligands contain a pyridine ring, an oxazoline ring, and a strongly coordinating diphenylphosphanyl group. The methionine-derived ligand forms a copper complex, which has been studied by X-ray crystallography. The new ligands were tested in models of enantioselective catalyses, such as hydrogenation of ketopantolactone, hydrosilylation of acetophenone, and transfer hydrogenation of acetophenone.X-ray structure analysesReceived March 4, 2003; accepted March 4, 2003 Published online August 18, 2003     

Percolation in strongly correlated systems: The massless Gaussian field

We derive a number of new results for correlated nearest neighbor site percolation onZ ^d. We show in particular that in three dimensions the strongly correlated massless harmonic crystal, i.e., the Gaussian random field with mean zero and covariance –, has a nontrivial percolation behavior: sites on whichS _x h percolate if and only ifh _c . with0 _c < . This provides the first rigorous example of a percolation transition in a system with infinite susceptibility.     

On a conjecture of R. E. Miles about the convex hull of random points

Denoty byp _d+i (B _d ,d+m) the probability that the convex hull ofd+m points chosen independently and uniformly from ad-dimensional ballB _d possessesd+i(i=1,...,m) vertices. We prove Mile's conjecture that, given any integerm, p _d+m (B _d ,d+m)»1 asd». This is obvious form=1 and was shown by Kingman form=2 and by Miles form=3. Further, a related result by Miles is generalized, and several consequences are deduced.Dedicated to Professor E. Halwaka on the occasion of his seventieth     

X-ray structure and variable temperature NMR spectra of [meso-triarylcorrolato]copper(III)

The diamagnetic square planar d(8) complexes [meso-arylcorrolato]copper(III) become paramagnetic upon warming, indicative of the equilibrium between the [corrolato]copper(III) and the [corrolato](+)* copper(II) forms of the complex. [meso-Triphenylcorrolato]copper(III) was structurally characterized and found to be saddled.     

Réductions chimique et électrochimique de 5H-benzopyranno[4,3-d]pyrimidines

The chemical reduction of 5H-[1]benzopyranno[4,3-d]pyrimidines with lithium aluminum hydrrde leads to 3,4-dihydro derivations. The electro-chemical reducation in acidic medium shows two monoelectronic cathodic waves. In netural or basic medium, substituted compounds in 2 position show a single bielectronic wave while two bielectronic waves are observed for unsubstituted compounds In all cases, preparative electrolysis lead to a hydrodimer in the 4,4′-positiom.     

A thiazole-containing tripodal ligand: synthesis, characterization, and interactions with metal ions and matrix metalloproteinases

A new tripodal ligand, tris[2-(((2-thiazolyl)methylidene)amino)ethyl]amine (Tatren), has been synthesized and characterized by NMR, IR, and UV-visible absorbance spectroscopy and elemental analysis. Tatren forms stable complexes with transition metal ions (Zn(2+), 1; Mn(2+), 2; Co(2+), 3) and the alkaline earth metal ions (Ca(2+), 4; Mg(2+), 5). Single-crystal X-ray structures of 1, 2, and 5 revealed six-coordinate chelate complexes with formula [M(Tatren)](ClO(4))(2) in which the metal centers are coordinated by three thiazolyl N atoms and three acyclic imine N atoms. Crystals of 1, 2, and 5 are monoclinic, P2(1)/c space group. Crystals of 4 are triclinic, P space group. The Ca(2+) complex is eight-coordinate with all N atoms of Tatren and one water molecule coordinated to the metal ion. Spectrophotometric titrations show that formation constants for the chelates of metal ions are >1 in methanol. Free Tatren inhibits the catalytic domain of matrix metalloproteinase-13 (MMP-13, collagenase-3) with K(i) = 3.5 +/- 0.6 microM. Molecular mechanics-based docking calculations suggest that one leg of Tatren coordinates to the catalytic Zn(2+) in MMPs-2, -9, and -13 with significant hydrogen bonding to backbone amide groups. High-level DFT calculations suggest that, in the absence of nonbonded interactions between Tatren and the enzyme, the most stable first coordination sphere of the catalytic Zn(2+) is achieved with three imidazolyl groups from His residues and two imine N atoms from one leg of Tatren. While complexes (1-3) do not inhibit MMP-13 to a significant extent, 4 does (K(i) = 30 +/- 10 microM). Hence, this study shows that tripodal chelating ligands of this class and their Ca(2+) complexes have potential as active-site inhibitors for MMPs.     

Use of solid-phase microextraction-capillary-gas chromatography (SPME-CGC) for the varietal characterization of wines by means of chemometrical methods

The extraction of wine aroma compounds was studied by direct-SPME (DI/SPME), headspace-SPME (HS/SPME) and multiple-headspace-extraction-SPME (MHE/SPME). The aromagrams obtained by HS/SPME-CGC were evaluated with chemometrical methods for the varietal classification of wines. Received: 25 July 1997 / Revised: 24 September 1997 / Accepted: 7 October 1997     

Speciation and biosynthetic variation in four dictyoceratid sponges and their cyanobacterial symbiont, Oscillatoria spongeliae

Four species of marine sponges (Phylum Porifera, Order Dictyoceratida), which contain the filamentous cyanobacterial symbiont Oscillatoria spongeliae, were collected from four locations in Palau. The halogenated natural products associated with the symbiont were characterized from each sample, revealing that each species contained either chlorinated peptides, brominated diphenyl ethers, or no halogenated compounds. Analysis of the host sponges and the symbionts indicated that each species of sponge contained a distinct strain of morphologically similar cyanobacteria. Although cospeciation may be present in this group, we have identified that at least one host switching event has occurred in this symbiosis. Only the strain of O. spongeliae in the sponge containing the chlorinated compounds possessed genes involved in the biosynthesis of chlorinated leucine precursors, indicating that the chemical variation observed in these animals has a genetic foundation.