Preparation of metallochelating microbubbles and study on their site-specific interaction with rGFP-HisTag as a model protein

The histidine-metallochelating lipid complex is one of the smallest high affinity binding units used as tools for rapid noncovalent binding of histidine tagged molecules, especially recombinant proteins. The advantage of metallochelating complex over protein-ligand complexes (e.g., streptavidine-biotin, glutathiontransferase-glutathion) consists in its very low immunogenicity, if any. This concept for the construction of surface-modified metallochelating microbubbles was proved with recombinant green fluorescent protein (rGFP) containing 6His-tag. This protein is easy to be detected by various fluorescence techniques as flow cytometry and confocal microscopy. Microbubbles (MB) composed of DPPC with various contents of metallochelating lipid DOGS-NTA-Ni were prepared by intensive shaking of the liposome suspension under the atmosphere of sulfur hexafluoride. For this purpose, the instrument 3M ESPE CapMix was used. Various techniques (static light scattering, flow cytometry, and optical microscopy) were compared and used for the measurements of the size distribution of MB. All three methods demonstrated that the prepared MB were homogeneous in their size, and the mean diameter of the MB in various batches was within the range of 2.1-2.8 μm (the size range of 1-10 μm). The presence of large MB (8-10 μm) was marginal. Counting of MB revealed that the average amount of MB prepared of 10 mg of phospholipid equaled approximately 10(9) MB/mL. Lyophilized MB were prepared with saccharose as a cryoprotectant. These MB were shown to be stable both in vitro (the estimated half-live of the MB in bovine serum at 37 °C was 3-7 min) and in vivo (mouse). The stability of the MB was affected by molar content of DOGS-NTA-Ni. DPPC-based metallochelating MB provided a clear and very contrast image of the ventricular cavity soon after the injection. Site selective and stable binding of rGFP-HisTag (as a model of His-tagged protein) onto the surface of metallochelating MB was demonstrated by confocal microscopy.     

Oriented confined water induced by cationic lipids

We report on attenuated total reflection Fourier-transform infrared (ATR FTIR) spectroscopic measurements on oriented lipid multilayers of N,N-dimethyl-N,N-dioctadecyl-ammonium halides (DODAX, X = F, Cl, Br, I). The main goal of this study is the investigation of the structure and spectroscopic properties of water absorbed to these model membranes. Intensities of the water stretch absorptions were used to determine the amount of bound water. At high water activity, DODAF membranes bind ~11 water molecules/lipid while DODAC and DODAB adsorb 1-2 water/lipid and DODAI was hydrophobic. By adjustment of DODAF hydration to ~2 water molecules, stretching absorptions from water of the first hydration shell were accessible for the fluoride, chloride, and bromide analogs. The polarized measurements demonstrate highly confined and oriented water with infrared (IR) order parameters ranging from 0.2 to -0.4. Resolved IR water band components are attributed to different hydrogen-bonded populations. Complementary molecular dynamics simulations of DODAB strongly support the existence of differently hydrogen-bonded and oriented water within DODAB multilayers. A combination of both techniques was used for an assignment of water stretch band components to structures. The described cationic lipid systems are a prototype for a bottom-up approach to understand the IR spectroscopy of structured water at biological interfaces since they permit a defined increase of hydrophilic water-anionic interactions leading to extended water networks at membranes.     

Molecular order and dynamic mechanical behavior of polyurethanes based on liquid crystalline diol

Synthesis of the liquid crystalline (LC) diol 6,6′-[ethylenebis(l,4-phenylene-oxy)]-dihexanol (I) is described. The structure of polyurethanes prepared from diol I and 4,4′-methylenedi(phenyl isocyanate) (MDI), 4,4′-methylenedi(cyclohexyl isocyanate) (HMDI), or 2(4)-methyl-l,3-phenylene diisocyanate (TDI) at 1:1 molar ratios of isocyanate and hydroxy groups is studied by dynamic mechanical spectroscopy, differential scanning calorimetry (DSC), polarizing microscopy, and x-ray scattering. The polymer prepared from HMDI and the diol (I/HMDI) shows, on cooling, thermal behavior typical of amorphous polymers. A frequency-temperature superposition could be applied to the mechanical data, and the horizontal shift factor satisfied the Williams-Landel-Ferry (WLF) equation. A more-complex thermal behavior was found for I/HMDI polymer during subsequent heating; above 70°C, the formation of an ordered structure takes place, and this structure melts at about 120°C. Complex thermal behavior is exhibited by I/TDI polymer. On cooling its melt, the polymer forms a nematic phase at about 80°C, which freezes into the LC glassy state. On heating, the mesophase melts, and. subsequently, a better-ordered smectic phase is formed at 95°C, which melts at 120°C. This structure buildup is accompanied by a rapid increase in storage modulus G′, and the sample shows thermorheologically complex mechanical behavior. The polymer formed from the diol and MDI (I/MDI) exhibits a most-complex thermal behavior. On cooling and heating, four transitions can be detected in its thermal mechanical behavior, and the structure of the polymer is strongly dependent on its thermal history.     

Spin–orbit coupling in biradicals. 5. Zero-field splitting in triplet dimethylnitrenium,dimethylphosphenium and dimethylarsenium cations

The spin dipole–spin dipole and spin–orbit coupling contributions to the zero-field splitting parameters D and E of [CH₃–N–CH₃]⁺, [CH₃–P–CH₃]⁺, and [CH₃–As–CH₃]⁺ have been calculated from CASSCF(14,14)/cc-pVTZ wave functions and the Breit–Pauli Hamiltonian at T₁ B3LYP/cc-pVTZ optimized geometries. The spin–orbit coupling contributions represent a minor correction for the dimethylnitrenium cation, which has a triplet ground state. They dominate the spin–spin terms by an order of magnitude in the dimethylphosphenium cation and by more than two orders of magnitude in the dimethylarsenium cation, both of which have a singlet ground state. The properties of all these biradicaloids follow expectations based on the simple algebraic 2-in-2 model of biradical structure.     

A calculator‐based computational approach Part 3. The differentiation

This paper extends the themes on the computational approach discussed in Parts 1 and 2 to the differentiation of functions. One theme is that constructing diagrams for programs using a calculator helps students to visualize processes and thus acquire the concepts involved. The ability to construct diagrams for a given problem is identical to that of programming a calculator to solve the problem. However, in this case constructing the diagram for derivatives from the diagram of the function also represents the ability to teach a calculator how to perform formal differentiation. A second theme is that the approach promotes sequential or procedural thinking which is important in both programming and mathematics. A third theme is that the approach permits the generation of many subproblems, thereby encouraging one to pose questions rather than merely to solve those set by others. Consequently, it becomes clear that the approach has wider applications in the learning of mathematics.     

On a Relation Between Potentials for Pluriharmonic Maps and Para-Pluriharmonic Maps

In this paper, we show that one can interrelate pluriharmonic maps with para-pluriharmonic maps by means of the loop group method. As an appendix, we give examples for the interrelation between pluriharmonic maps and para-pluriharmonic maps. Moreover, we investigate the relation among CMC-surfaces by use of such maps.     

Direct synthesis of inverse hexagonally ordered diblock copolymer/polyoxometalate nanocomposite films

Nanostructured inverse hexagonal polyoxometalate composite films were cast directly from solution using poly(butadiene-block-2-(dimethylamino)ethyl methacrylate) (PB-b-PDMAEMA) diblock copolymers as structure directing agents for phosphomolybdic acid (H(3)[PMo(12)O(40)], H(3)PMo). H(3)PMo units are selectively incorporated into the PDMAEMA domains due to electrostatic interactions between protonated PDMAEMA and PMo(3-) anions. Long solvophilic PB chains stabilized the PDMAEMA/H(3)PMo aggregates in solution and reliably prevented macrophase separation. The choice of solvent is crucial. It appears that all three components, both blocks of the diblock copolymer as well as H(3)PMo, have to be soluble in the same solvent which turned out to be tetrahydrofuran, THF. Evaporation induced self-assembly resulted in highly ordered inverse hexagonal nanocomposite films as observed from transmission electron microscopy and small-angle X-ray scattering. This one-pot synthesis may represent a generally applicable strategy for integrating polyoxometalates into functional architectures and devices.