On the electropolishing and anodic oxidation of Ti-15Mo alloy

This paper presents research on modifying the surface of Ti-15Mo alloy using electropolishing and anodic passivation. The electropolishing process was carried out in solutions containing sulfuric acid, ethylene glycol, ammonium fluoride and oxalic acid. Whereas a voltage range from 20 to 100 V and a 1 M orthophosphoric acid solution were used during the anodic passivation. The influence of above mentioned processes parameters on the quality of the obtained oxide layer on Ti-15Mo alloy was investigated. The analysis of Ti-15Mo surface after modification was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), ellipsometry, and mechanical tests. Moreover, the corrosion resistance was investigated using a potentiostatic method in Ringer's solution. It was found that electropolishing leads to an increase in the surface homogeneity and to the form of an oxide layer, which consisted of TiO2 and MoO3. Whereas the oxide layers obtained during anodic passivation were characterized by different properties depending on the applied voltage. The anodic passivation at various voltages (20-100 V) increased the surface wettability (94.5°-87.6°) in comparison to the electropolished sample (97.5°). Moreover, the obtained oxide layer after anodization exhibited a high hardness. The electrolytic polishing and anodic passivation of Ti-15Mo also improved corrosion resistance of the alloy in contact with Ringer's solution. The sample anodized at 80 V presented the highest corrosion resistance by the smallest corrosion current density (1.4 nA cm-2) and the highest polarization resistance (37.4 MΩ cm2). © 2016 Elsevier Ltd. All rights reserved

Tubulin isoform composition tunes microtubule dynamics

Microtubules polymerize and depolymerize stochastically, a behavior essential for cell division, motility and differentiation. While many studies advanced our understanding of how microtubule-associated proteins tune microtubule dynamics in trans, we have yet to understand how tubulin genetic diversity regulates microtubule functions. The majority of in vitro dynamics studies are performed with tubulin purified from brain tissue. This preparation is not representative of tubulin found in many cell types. Here we report the 4.2Å cryo-EM structure and in vitro dynamics parameters of α1B/βI+βIVb microtubules assembled from tubulin purified from a human embryonic kidney cell line with isoform composition characteristic of fibroblasts and many immortalized cell lines. We find that these microtubules grow faster and transition to depolymerization less frequently compared to brain microtubules. Cryo-EM reveals that the dynamic ends of α1B/βI+βIVb microtubules are less tapered and that these tubulin heterodimers display lower curvatures. Interestingly, analysis of EB1 distributions at dynamic ends suggests no differences in GTP cap sizes. Lastly, we show that the addition of recombinant α1A/βIII tubulin, a neuronal isotype overexpressed in many tumors, proportionally tunes the dynamics of α1B/βI+βIVb microtubules. Our study is an important step towards understanding how tubulin isoform composition tunes microtubule dynamics

Insight into the Mechanisms of Adenovirus Capsid Disassembly from Studies of Defensin Neutralization

Defensins are effectors of the innate immune response with potent antibacterial activity. Their role in antiviral immunity, particularly for non-enveloped viruses, is poorly understood. We recently found that human alpha-defensins inhibit human adenovirus (HAdV) by preventing virus uncoating and release of the endosomalytic protein VI during cell entry. Consequently, AdV remains trapped in the endosomal/lysosomal pathway rather than trafficking to the nucleus. To gain insight into the mechanism of defensin-mediated neutralization, we analyzed the specificity of the AdV-defensin interaction. Sensitivity to alpha-defensin neutralization is a common feature of HAdV species A, B1, B2, C, and E, whereas species D and F are resistant. Thousands of defensin molecules bind with low micromolar affinity to a sensitive serotype, but only a low level of binding is observed to resistant serotypes. Neutralization is dependent upon a correctly folded defensin molecule, suggesting that specific molecular interactions occur with the virion. CryoEM structural studies and protein sequence analysis led to a hypothesis that neutralization determinants are located in a region spanning the fiber and penton base proteins. This model was supported by infectivity studies using virus chimeras comprised of capsid proteins from sensitive and resistant serotypes. These findings suggest a mechanism in which defensin binding to critical sites on the AdV capsid prevents vertex removal and thereby blocks subsequent steps in uncoating that are required for release of protein VI and endosomalysis during infection. In addition to informing the mechanism of defensin-mediated neutralization of a non-enveloped virus, these studies provide insight into the mechanism of AdV uncoating and suggest new strategies to disrupt this process and inhibit infection

In situ studies of particle deposition on non-transparent substrates

An oblique impinging-jet (OBIJ) cell was developed, suitable for colloid deposition studies at various interfaces including the practically significant case of non-transparent substrates. Particle transport conditions in the cell were quantitatively eva

Nonequivalent adsorption of pH-responsive dicephalic sugar surfactants at the air/solution interface

The present work contributes to the analysis of the effect of electrolyte and pH on the adsorption of dicephalic N-dodecyl-N,N-bis[(3-D-aldonylamido) propyl]amines (aldonyl = gluconyl and lactobionyl) at the air/water interface. The headgroup of these surfactants consists of two amide groups connected by a central tertiary amine, which may be protonated in an aqueous environment. We performed measurements of surface tension isotherms of aqueous solutions of the studied dicephalics in the presence of NaCl and NaOH and applied the STDE model for evaluation of the experimental results. They showed that the adsorption of the surfactants at the air/water interface was pH- and electrolyte- dependent, since addition of NaCl and NaOH had different effects on the surface activity and critical micelle concentration values (CMC). The theoretical model reflected well the surface tension isotherms obtained for a broad range of surfactants concentration, confirming the theoretical predictions concerning the protonation of tertiary amines, which was additionally supported by the measurements of solution pH

Influence of Polyelectrolyte Multilayer Films on Calcium Phosphate Nucleation

International audienc

Deposition/detachment of particles on plasma treated polymer surfaces

Deposition/detachment of inorganic pigments (BiVO4) by chemical bath deposition method (CBD) and polymer latex particles by impinging jet method on low temperature plasma treated polyethylene (PE), polypropylene (PP), polycarbonate (PC) and polystyrene (PS) were investigated. Bismuth vanadate (BiVO4) coatings on the commercial polymer substrates were prepared by the thermal treatment of aqueous solutions containing a bismuth (III) ethylenediaminetetra-acetate chelate and vanadium (V) species. Ability to study and quantify deposition/detachment processes is of a high scientific and industrial importance. In this paper the (so called "impinging jet") apparatus for study of adsorption of spherical colloidal particles on different types of surfaces under controlled hydrodynamic conditions is described. In this comunication a chemical bath deposition method and impinging jet method as a two novel advanced techniques are discussed