Study of complexes between lysozyme and sodium alkyl sulfates in the solid state

Complexes between lysozyme and sodium alkyl sulfates (decyl, dodecyl, tetradecyl and hexadecyl) in the solid state were prepared by mixing aqueous solutions of lysozyme and of the surfactant, separating the precipitated complex and purifying it. The stoichiometry of the complexes was investigated by elemental analysis and was found to correspond to about 8ǃ alkyl sulfate ions per lysozyme. Low- and wide-angle X-ray scattering were used to investigate the structure of the complexes. The scattering curves showed one fairly large scattering maximum, revealing a low state of organization of the complexes. The characteristic length characterizing the complexes was calculated from the value of the wave vector corresponding to the maximum of the scattered intensity. This length increased by about 0.233 nm per additional methylene group in the surfactant alkyl chain. A model where spherical aggregates of alkyl sulfate ions are arranged in a disordered simple cubic structure, dispersed in a matrix of lysozyme, provides a possible explanation of the results.     

Far-infrared and mid-infrared absorption in (Bi,Pb)-Sr-(Ca,Y)-Cu-O

The reflectivities of seven films belonging to the Bi-Sr-Ca-Cu-O family, with T_c ranging from 60 to 95 K, and of a single crystal of insulating Bi-Sr-Y-Cu-O, have been measured at room temperature in the normal phase. The optical conductivity has been analyzed in terms of Drude (D), mid-infrared (MIR), and charge-transfer (CT) contributions. As T_c increases, the spectral weight within the charge-transfer gap (D+MIR) increases. Meanwhile, the peak frequency of the MIR band moves towards the far-infrared and the optical conductivity becomes more similar to that of a normal metal.     

Linear Relationship between 13C NMR Chemical Shifts and the Bending of sp-Carbon Chains

Polyynes show a strictly linear relationship between the energy impact and the bending of the polyyne chain. The energy, which is necessary to bend the acetylenic chain, decreases with the increasing number of acetylene units. A deviation from linearity in polyynes can be realized in solution by violation of the mutual-exclusion principle between IR and Raman spectra. However, there is still no possibility to measure the extent of the nonlinearity in solution. Herein, we show that the ¹³C NMR spectroscopy represents an appropriate tool for this as we found an almost perfect linear relationship between the bending of the alkyne chain and the change of the chemical shift of the outer acetylenic carbon atoms. By using molecular bows in which the alkyne chain can be bent by switching the azobenzene unit, this correlation can be proved experimentally. In the future, this correlation should enable the determination of the extent of the bending and the strain energy in polyynes. Consequently, polyynes could be employed as probes for measuring further molecular forces.     

Pearlite revisited

Zener’s model of pearlite transformation in steels can be viewed as the prototype of many microstructure evolution models in materials science. It links principles of thermodynamics and kinetics to the scale of the microstructure. In addition it solves a very practical problem: How the hardness of steel is correlated to the conditions of processing. Although the model is well established since the 1950s, quantitative explanation of growth kinetics was missing until very recently. The present paper will shortly review the classical model of pearlite transformation. Zener’s conjecture of maximum entropy production will be annotated by modern theoretical and experimental considerations of a band of stable (sometimes oscillating) states around the state of maximum entropy production. Finally, an explanation of the growth kinetics observed in experiments is proposed based on diffusion fluxes driven by stress gradients due to large transformation strain.     

Preparation of Novel,Functionalized 1,10-Phenanthrolines

The preparation of hydrophilic 2,9-dialkyl-1,10-phenanthrolines, including phenanthroline-5-sulfonic acids and phenanthrolines with side chain functionality is described. Nucleophilic aromatic substitution chemistry is used to obtain regiochemically defined phenanthroline sulfonic acids by much simpler means than have been available in the past.     

Nanoparticle targeting at cells

Gold nanoparticles have been used for analytical and biomedical purposes for many years. In fact, the labeling of targeting molecules with nanoparticles has revolutionized the visualization of cellular or tissue components by electron microscopy. We report in this study the derivatization of tiopronin-protected nanoparticles with ethylenediamine and poly(ethylene glycol) bis(3-aminopropyl) terminated and their functionalization with the GRGDSP peptide sequence by a straightforward and economical methodology. The particles were subsequently tested in vitro with a human fibroblast cell line to determine the biocompatibility, and the cell-particle interactions, using fluorescence and scanning electron microscopies. The results indicate that tiopronin gold nanoparticles aggregate due to culture medium proteins, whereas the tiopronin gold nanoparticles derivatized with ethylenediamine induce endocytosis, and the same nanoparticles derivatized with poly(ethylene glycol) derivative promote particle-cell adhesion.     

Air-trapping on biocompatible nanopatterns

The occurrence of air-trapping inside poly-eta-caprolactone nanopits was investigated by measuring the contact angles of water droplets on a set of defined nanotopographies. It is shown that the advancing angles follow the Cassie-Baxter theory, thus revealing the presence of air bubbles inside the biodegradable nanopatterns. The importance of these observations for the definition of hydrophilicity/hydrophobicity and in the context of in vitro cell behavior is discussed.     

Effect of protein relaxation on electron transfer from the cytochrome subunit to the bacteriochlorophyll dimer in Rps. sulfoviridis reaction centers within mixed adiabatic/nonadiabatic model

The broad set of nonexponential electron transfer (ET) kinetics in reaction centers (RC) from Rhodopseudomonas sulfoviridis in temperature range 297-40 K are described within a mixed adiabatic/nonadiabatic model. The key point of the model is the combination of Sumi-Marcus and Rips-Jortner approaches which can be represented by the separate contributions of temperature-independent vibrational (v) and temperature-dependent diffusive (d) coordinates to the preexponential factor, to the free energy of reaction DeltaG=DeltaG(v)+DeltaG(d)(T) and to the reorganization energy lambda=lambda(v)+lambda(d)(T). The broad distribution of protein dielectric relaxation times along the diffusive coordinate is considered within the Davidson-Cole formalism.