Thermal decomposition reactions of nickel(II) complexes under quasi-equilibrium conditions

The stoichiometry of thermal decomposition and thermal (thermodynamic) stability was studied for the Werner clathrates [Ni(4-Mepy)₄(NCS)₂]·G, whereG = benzene(I), toluene(II) andp-xylene(III). The loss of the volatile components occurs in five steps in compounds I and II and in four steps in the complex III. According to the quasi-equilibrium data the thermodynamic stability of these compounds can be ordered in the following sequence: I<II<III. The increasing host-guest interaction (larger positive band shift in the visible spectra) was accompanied by increasing in the quasi-equilibrium temperature (T _D) for the complexes under study.     

Capillary electrophoresis of liposomes functionalized for protein binding

CE enabled assessing the attachment of hexa-histidine-tagged proteins to functionalized phospholipid liposomes. The liposomes were made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, phosphatidyl-ethanolamine, cholesterol and distearoyl-glycero-3-phosphoethanolamine-N-methoxy(polyethylene glycol) in a molar ratio of 29:26:40:5. The unilamellar vesicles, which had an average diameter of 170 nm, were labelled by inclusion of FITC-dextran for fluorescence detection. CE was carried out in poly(vinyl alcohol) (PVA)-coated capillaries at 25 degrees C with a BGE consisting of Tris-HCl (50 mM, pH 8.0). For conjugation of the liposomes with the proteins (soluble synthetic receptor fragments with molecular mass of 60 and 70 kDa, respectively), Ni(2+) was implanted into the vesicle surface by an anchor lipid containing a nitrilotriacetate acid (NTA) group as complexation agent for the metal ions. The difference in surface charge enabled the separation of the different species of interest by CE: plain vesicles, vesicles functionalised with Ni-NTA, vesicle-protein complexes and the species formed upon removal of the Ni-ions by complexation with EDTA. Loss of the Ni-ions resulted in the release of the proteins and the reappearance of the plain Ni-free NTA-liposome species in the electropherograms.     

Bioimprinted QCM sensors for virus detection—screening of plant sap

Surface imprinting techniques on polymer-coated quartz-crystal microbalances (QCM) have been used to detect tobacco mosaic viruses (TMV) in aqueous media. Molecularly imprinted polymers (MIP), tailor-made by self organisation of monomers around a template (TMV), were generated directly on the gold electrodes. Imprinted trenches on the polymer surface mimicking the shape and surface functionality of the virus serve as recognition sites for re-adsorption after washing out of the template. The sensors are applicable to TMV detection ranging from 100 ng mL^–1 to 1 mg mL^–1 within minutes. Furthermore, direct measurements without time-consuming sample preparation are possible in complex matrices such as tobacco plant sap.Dedicated to Professor Dr. W. Fresenius on the occasion of his 90th birthday     

Charge-reduced nano electrospray ionization combined with differential mobility analysis of peptides, proteins, glycoproteins, noncovalent protein complexes and viruses

This study explores the potential of a novel electrospray-based method, termed gas-phase electrophoretic mobility molecular analysis (GEMMA), allowing the molecular mass determination of peptides, proteins and noncovalent biocomplexes up to 2 MDa (dimer of immunglobulin M). The macromolecular ions were formed by nano electrospray ionization (ESI) in the 'cone jet' mode. The multiple charged state of the monodisperse droplets/ions generated was reduced by means of bipolar ionized air (generated by an alpha-particle source) to yield exclusively singly charged positive and negative ions as well as neutrals. These ions are separated subsequently at atmospheric pressure using a nano differential mobility analyzer according to their electrophoretic mobility in air. Finally, the ions are detected using a standard condensation particle counter. Data were expressed as electrophoretic mobility diameters by applying the Millikan equation. The measured electrophoretic mobility diameters, or Millikan diameters, of 32 well-defined proteins were plotted against their molecular weights in the range 3.5 to 1920 kDa and exhibited an excellent squared correlation coefficient (r(2) = 0.999). This finding allowed the exact molecular weight determination of large (glyco)proteins and noncovalent biocomplexes by means of this new technique with a mass accuracy of +/-5.6% up to 2 MDa at the femtomole level. From the molecular masses of the weakly bound, large protein complexes thus obtained, the binding stoichiometry of the intact complex and the complex stability as a function of pH, for example, can be derived. Examples of specific protein complexes, such as the avidin or catalase homo-tetramer, are used to illustrate the potential of the technique for characterization of high-mass biospecific complexes. A discussion of current and future applications of charge-reduced nano ESI GEMMA, such as chemical reaction monitoring (reduction process of immunglobulin G) or size determination of an intact virus, a supramolecular complex, and monitoring of partial dissociation of a human rhinoviruses, is provided.     

Coreflections in Algebraic Quantum Logic

Various generalizations of Boolean algebras are being studied in algebraic quantum logic, including orthomodular lattices, orthomodular po-sets, orthoalgebras and effect algebras. This paper contains a systematic study of the structure in and between categories of such algebras. It does so via a combination of totalization (of partially defined operations) and transfer of structure via coreflections.     

Influence of detergent additives on mobility of native and subviral rhinovirus particles in capillary electrophoresis

The electrophoretic properties of two human rhinovirus (HRV) serotypes, HRV2 and HRV14, their subviral particles, and their capsid proteins were investigated by CE using borate buffer, pH 8.3, as BGE and three different detergents as additives. In addition, the influence of modification of the capsid with an amine reactive fluorescent dye, Cy3.5, on migration in the electric field was assessed. We found that the reproducibility of the electrophoretic results was decisively dependent on the presence of the detergents above their respective CMC. As compared to the strong ionic detergent SDS, the nonionic, mild detergent dodecylpoly(ethyleneglycol ether) (D-PEG) efficiently and reproducibly resolved both, native viruses as well as subviral particles. Most of the analytes behaved as expected except native HRV2; this serotype showed a dramatically higher anionic mobility in SDS than in D-PEG. Additionally, its mobility decreased when each positive charge contributed from a lysine at the capsid surface was substituted by four negative charges upon derivatization with Cy3.5. We discuss the possibility that this effect is caused by differences in number and in arrangement of exposed lysines in the two serotypes leading to differences in the amount of bound SDS micelles.     

Recent developments in capillary and chip electrophoresis of bioparticles: Viruses, organelles, and cells

In appropriate aqueous buffer solutions, biological particles usually exhibit a particular electric surface charge due to exposed charged or chargeable functional groups (amino acid residues, acidic carbohydrate moieties, etc.). Consequently, these bioparticles can migrate in solution under the influence of an electric field allowing separation according to their electrophoretic mobilities or their pI values. Based on these properties, electromigration methods are of eminent interest for the characterization, separation, and detection of such particles. The present review discusses the research papers published between 2008 and 2010 dealing with isoelectric focusing and zone electrophoresis of viruses, organelles and microorganisms (bacteria and yeast cells) in the capillary and the chip format.