Preparation of highly accessible mordenite coatings on ceramic monoliths at loadings exceeding 50% by weight

A mordenite layer with a high accessibility has been synthesised on cordierite monolith supports; substantial loadings of mordenite were achieved (above 50 wt%) under the synthesis conditions used.     

Effects of sample preservation and storage on mercury speciation in natural stream water

Despite an increasing focus on low level methods for determination of mercury species in water over the last decades, few studies have paid attention to direct effects of different sample preparation methods (i.e. preservation techniques) on natural freshwater samples. In this study we show how different preservation techniques give significantly different concentrations of total and methylmercury in freshwaters (9 and 14% on average, respectively). Natural stream samples from a forested lake catchment were studied. Mean stream sample concentrations of total (3.6 ng/L) and methylmercury (0.06 ng/L) reflect levels typical for pristine humic boreal catchments. The main reason for the observed average differences in total and methylmercury concentrations is the use of one instead of two sample bottles and timing of sample acidification, respectively.     

Quantitative detection of well-based DNA array using switchable lanthanide luminescence

In this report a novel wash-free method for multiplexed DNA detection is demonstrated employing target specific probe pairs and switchable lanthanide luminescence technology on a solid-phase array. Four oligonucleotide capture probes, conjugated at 3′ to non-luminescent lanthanide ion carrier chelate, were immobilized as a small array on the bottom of a microtiter plate well onto which a mix of corresponding detection probes, conjugated at 5′ to a light absorbing antenna ligand, were added. In the presence of complementary target nucleic acid both the spotted capture probe and the liquid-phase detection probe hybridize adjacently on the target. Consequently the two non-luminescent label molecules self-assemble and form a luminescent mixed lanthanide chelate complex. Lanthanide luminescence is thereafter measured without a wash step from the spots by scanning in time-resolved mode. The homogeneous solid-phase array-based method resulted in quantitative detection of synthetic target oligonucleotides with 0.32 nM and 0.60 nM detection limits in a single target and multiplexed assay, respectively, corresponding to 3× SD of the background. Also qualitative detection of PCR-amplified target from Escherichia coli is described.     

On the leading principal minors of direct products

A result is given, relating the leading principal minors of a direct product of matrices to the leading principal minors of the matrices     

DNA-controlled assembly of soft nanoparticles

Immobilization of DNA (encoding) on solid nanoparticles requires surface chemistry, which is well established for gold surfaces but often tedious and not generally applicable for many other inorganic surface materials. While substantial effort has been devoted to expanding surface chemistry techniques for solid nanoparticles, considerably less attention has been given to the development of noncovalent attachment of DNA to soft nanoparticles, like liposomes. Here we report a DNA-controlled assembly of liposomes in solution and on solid supported membranes, this process displays remarkably sharp thermal transitions from an assembled to a disassembled state, allowing application of DNA-controlled liposome assembly for the detection of polynucleotides (e.g., DNA) with single mismatch discrimination power. The method is based on a single DNA strand (contains two lipid membrane anchors), which is able to noncovalently attach to a liposome surface. This design enables detection of biological polynucleotide targets as the complementary strand can be unmodified DNA and RNA strands.     

Spontaneous reduction of mixed 2,2'-bipyridine/methylamine/chloro complexes of Pt(IV) in water in the presence of light is accompanied by complex isomerization, loss of methylamine, and formation of a strong oxidant, presumably HOCl

Three 2,2'-bipyridine (2,2'-bpy) complexes of Pt(IV) have been synthesized, characterized by X-ray crystallography, and their solution behavior in D(2)O studied by (1)H NMR spectroscopic analysis: mer-[PtCl(3)(2,2'-bpy)(MeNH(2))]ClH(2)O (4), trans-[PtCl(2)(2,2'-bpy)(MeNH(2))(2)]Cl(2) (5), and trans-[Pt (2,2'-bpy)(MeNH(2))(2)(OH)(2)]Cl(2) (6; MeNH(2)=methylamine). Complexes 4 and 5 undergo hydrolysis of the Cl(-) ions, both in the dark and daylight, as evident from a drop in the pH value. Two solvolysis products were detected in the case of 4, which is indicative of species with equatorial and axial OH(-) groups. The hydrolysis reaction of 5 implies that an axial Cl(-) group is replaced by an OH(-) moiety; in contrast, 6 remains virtually unaffected. Ordinary daylight, in particular irradiation with a 50-W halogen lamp, initially causes ligand-isomerization processes, which are followed by the reduction of 4 and 5 to Pt(II) species. This reduction of 4 and 5 is accompanied by the formation of hypochlorous acid, as demonstrated qualitatively in the decoloration test of indigo, and loss of MeNH(2), which is particularly pronounced in the case of 5. The formation of Pt(II) compounds is established on the basis of the J coupling constants of (195)Pt with selected (1)H NMR resonances. The results obtained herein are possibly also relevant to the chemistry of Cl-containing Pt(IV) antitumor agents and their reactions with DNA.     

Bowl adamanzanes--bicyclic tetraamines: syntheses and crystal structures of complexes with cobalt(III) and chelating coordinated oxo-anions

Seven cobalt(III) complexes of the macrobicyclic tetraamine ligand [2(4).3(1)]adamanzane ([2(4).3(1)]adz) are reported along with the crystal structure of six of these complexes. The solid state and solution structures are discussed, and a detailed assignment of the NMR spectra of the sulfato complex is provided. Four of the seven complexes contain a chelate coordinating oxo-anion (sulfate, formiate, nitrate, carbonate). Equilibration of these species with the corresponding diaqua complex is generally slow. The rates of equilibration in 5 mol dm(-3) perchloric acid at 25 degrees C have been measured, yielding half lives of 20 min, 10 min and 3 h for the sulfato, formiato and carbonato species respectively. The corresponding reaction for the nitrato complex occurs with a half life of less than 3 min. The concentration acid dissociation constant for the Co([2(4).3(1)]adz)(HCO(3))(2+) ion has been measured to K(a) = 0.33 mol dm(-3) [25 degrees C, I = 2 mol dm(-3)] and K(a) = 0.15 mol dm(-3) [25 degrees C, I = 5 mol dm(-3)]. The propensity for coordination of sulfate was found to be large enough for a quantitative conversion of the carbonato complex to the sulfato complex to occur in 3 mol dm(-3) triflic acid containing a small sulfate contamination. On this basis the decarboxylation in 5 mol dm(-3) triflic acid of the corresponding cobalt(III) carbonato complex of the larger macrobicyclic tetraamine ligand [3(5)]adz was reinvestigated and found to lead to the sulfato complex as well. The difference in exchange rate of the oxo-anion ligands for the cobalt(III) complexes of the two adamanzane ligands is discussed and attributed to fundamental differences in the molecular structure where an inverted configuration of the secondary non-bridged amine groups is seen for the complexes of the larger [3(5)]adz ligand. The high affinity for chelating coordination of oxo-anions for these two cobalt(iii)-adamanzane-moieties is rationalised on basis of the N-Co-N angles. N-Co-N angles are compared for a series of adamanzane complexes, and the structural consequences are discussed.