Optimum sample medium for single-nucleotide polymorphism and mutation detection by capillary electrophoresis

Capillary electrophoresis (CE) is a versatile analytical platform widely used for nucleic acids analysis. Its applications in research and diagnostics include scanning and screening for mutations and polymorphisms by such reliable methods as single-strand conformation polymorphism (SSCP), heteroduplex analysis (HA), and combined SSCP/HA. This study, aimed at the further development of these methods, is focused on detailed sample-media characteristics. Factors affecting single-strand conformer stability and DNA intake efficiency were analyzed. The sample media optimal for efficient mutation or SNP detection were determined, and complex SSCP-CE patterns arising from unpurified PCR products were explained. It turns out, that the nondenaturing aqueous media assure both efficient DNA intake, and single-strand conformers stability required for the SSCP and combined SSCP/HA. The results of this study are applicable to all these areas of biomedical research, in which capillary electrophoresis is used for the characterization of nucleic acids.     

Dramatic decrease of the cis content and molecular weight of cis‐transoidal polyphenylacetylene at 23 °C in solutions prepared in air

The thermal cis–trans isomerization of cis‐transoidal polyphenylacetylene (PPA) synthesized with Noyori's catalyst [Rh(C?CPh)(norbornadiene)(PPh₃)₂] has been investigated under both ambient and inert atmospheres in solution and in bulk. In all cases, an intramolecular cyclization results in cis–trans isomerization, and subsequent chain cleavage produces 1,3,5‐triphenylbenzene. This reaction is accelerated by the presence of air, particularly when the reaction takes place in solution. Decreases in the cis content and molecular weight show that the intramolecular cyclization process takes place at 23 °C in solution. The mechanism of this reaction is identical to that reported previously for cis‐cisoidal and cis‐transoidal PPA synthesized with Ziegler–Natta catalysts. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3212–3220, 2002     

Proper holomorphic mappings of the spectral unit ball

We prove an Alexander type theorem for the spectral unit ball showing that there are no non-trivial proper holomorphic mappings in , .

     

Synthesis and solid-state study of supramolecular host-guest assemblies: Bis[6-O,6-O'-(1,2:3,4-diisopropylidene-alpha-D-galactopyranosyl)thiophosphoryl] dichalcogenides

A complementary approach for studying structural details of complex solid materials formed by symmetrical and unsymmetrical dichalcogenides, which employs both X-ray diffraction (XRD) and solid-state NMR (SS NMR), is presented. The new diagnostic technique allows reversible crystallographic space group change and very subtle distortion of host geometry to be followed during guest migration in the crystal lattice. Bis[6-O,6-O'-(1,2:3,4-diisopropylidene-alpha-D-galactopyranosyl)]thiophosphoryl selenenyl sulfide, a representative of wheel-and-axle host (WAAH) molecules, can be synthesized in the solid state by grinding and gentle heating of disulfide 1 and diselenide 2. Full characterization of disulfide 1 in the solid phase has been reported (J. Org. Chem. 1995, 60, 2549). In the current work, the synthesis and both XRD and SS NMR studies of the isostructural diselenide substrate 2 are presented. A (31)P cross polarization magic angle spinning experiment is employed to follow the progress of synthesis of selenenyl sulfide 3 in the solid state. It is concluded that selenenyl sulfide exists in equilibrium with disulfide and diselenide in a 1:1:1 ratio in both the liquid and the powdered solid. A mixture of isostructural dichalcogenides crystallized from different solvents form three-component host-guest inclusion complexes with columnar architecture. In the host-guest complex of diselenide 2 with toluene (space group C2), columns of host molecules are in parallel orientations along all the axes, whereas in the structures of diselenide 2 with propan-2-ol and propan-1-ol (space group P3 2), the columns of host molecules lay along the 3-fold symmetry axis. Thermal processes effecting structural changes in the host lattice and the kinetics of reversible guest molecule diffusion were investigated using SS NMR spectroscopy. Finally, the Se/S scrambling phenomenon and limitations in the X-ray structure refinement of organic compounds containing selenium and sulfur in chains are discussed.     

‘Gate effect’ in molecularly imprinted polymers: the current state of understanding

The so-called ‘gate effect’ is frequently used in electrochemical signal transduction for chemosensing developed using recognition units based on molecularly imprinted polymers (MIPs). A vast majority of different reported MIP electroanalytical systems makes the gate effect definition difficult to be established precisely, thus resulting in ambiguity and complexity. In the MIP literature, the gate effect is predominantly considered as an electrode–electrolyte phenomenon, which depends on the MIP film nature. However, most of the reports do not describe or confirm the origin of this effect. The present review critically evaluates representative original articles on the subject to increase understanding the origin of the gate effect operation in MIP-based electrochemical chemosensors.     

Electrochemically synthesized polymers in molecular imprinting for chemical sensing

This critical review describes a class of polymers prepared by electrochemical polymerization that employs the concept of molecular imprinting for chemical sensing. The principal focus is on both conducting and nonconducting polymers prepared by electropolymerization of electroactive functional monomers, such as pristine and derivatized pyrrole, aminophenylboronic acid, thiophene, porphyrin, aniline, phenylenediamine, phenol, and thiophenol. A critical evaluation of the literature on electrosynthesized molecularly imprinted polymers (MIPs) applied as recognition elements of chemical sensors is presented. The aim of this review is to highlight recent achievements in analytical applications of these MIPs, including present strategies of determination of different analytes as well as identification and solutions for problems encountered.     

Structure and dynamics of L-selenomethionine in the solid state

L-selenomethionine 1 crystallizes in P2(1) space group with two molecules in the asymmetric unit. Solid-state NMR spectroscopy is used for searching of structure and dynamics of 1 in the crystal lattice. The distinct molecular motion of side chains for A and B molecules of 1 is apparent from measurements of relaxation parameters (1H 1rho, 13C T1) and analysis of CSA data (2D-PASS experiment). The 13C delta(ii) and 77Se delta(ii) parameters are correlated with theoretical shielding parameters obtained by means DFT GIAO calculations. Attempt to explain the mechanism of phase transition of crystals of 1 at 313K is presented.     

Oxidative extraction versus total decomposition of soil in the determination of thallium

An aqua regia extraction and a total decomposition of soil were compared in terms of thallium determination. A sequential extraction of soil, according to the BCR protocol, was also performed for additional information on thallium distribution in soil fractions. Certified reference material—soil GBW 07401 of Chinese origin, containing 1 ± 0.2 ppm of thallium was used in these experiments. Thallium was determined by flow injection-differential pulse-anodic stripping voltammetry (FI-DP-ASV). Only 35% of total thallium was extracted in the aqua regia extraction, while the total decomposition led to satisfactory recovery. The sequential extraction showed that only 5% of thallium in GBW 07401 is dissolvable in the four BCR procedure fractions, and that 95% of the element is entrapped in the residual parent matter. These results show that the aqua regia extraction does not ensure complete thallium extraction from soil. Surprisingly, the total decomposition is significantly less time consuming than the aqua regia extraction.     

Investigation of NeutrAvidin-tagged liposomal nanovesicles as universal detection reagents for bioanalytical assays

Ligand-tagged liposomes, obtained by covalent conjugation of ligands to the liposomal surface, have been widely used as detection reagents in bioanalytical assays. A non-covalent conjugation method where IgG was attached to protein G-tagged liposomes has been recently utilized. To enlarge the application of non-covalent methods to a greater variety of ligands, including peptides, proteins, and nucleic acids, we developed and optimized a new method for the preparation of NeutrAvidin-tagged liposomes with subsequent attachment of biotinylated ligands. Two assays were used to investigate the feasibility of NeutrAvidin-tagged liposomes. The first assay was a competitive immunoassay for detecting rabbit antibodies, while the second assay was a sandwich hybridization assay for detecting a synthetic target: a DNA fragment of Erwinia amylovora. To produce the immunoliposomes for the detection of rabbit IgG, NeutrAvidin was covalently tagged to the liposomal surface at four different starting molar percentages (0.1, 0.2, 0.4, and 0.8). The biotinylated goat anti-rabbit IgG at three different molar ratios of biotin to IgG (5, 10, and 20) were then attached to the NeutrAvidin-tagged liposomes by using two different molar ratios of goat anti-rabbit IgG to NeutrAvidin (1 and 5). After the comparison of all 24 combinations, the best result was obtained with the 0.1 starting molar percentage of NeutrAvidin, 20 as the molar ratio of biotin to goat IgG, and 1 as molar ratio of IgG to NeutrAvidin. Under these optimized conditions, the limit of detection (LOD) for rabbit IgG was 38 pmol/mL. Moreover, the best combination for the sandwich hybridization assay was with the 0.1 starting molar percentage of NeutrAvidin-tagged liposomes and when the molar ratio of biotinylated reporter probe to NeutrAvidin was equal to 1. The LOD for the synthetic target DNA fragment of E. amylovora was ca. 30 pmol/mL. Both assays could be completed in about 30 min without the requirement of sophisticated equipment or techniques. Therefore, these two assays have successfully demonstrated the feasibility of NeutrAvidin-tagged liposomal nanovesicles as a universal reagent for the attachment of different types of biotinylated ligands in a fast and easy coupling process. In addition, these ligand-tagged liposomes have the potential for wide use in different types of bioanalytical assays.     

Almost Kähler A-Structures on Twistor Bundles

The aim of this paper is to give examples of compact almost Kähler A-manifolds.