Drastically lowered protein adsorption on microbicidal hydrophobic/hydrophilic polyelectrolyte multilayers

Polyelectrolyte multilayer films assembled from a hydrophobic N-alkylated polyethylenimine and a hydrophilic polyacrylate were discovered to exhibit strong antifouling, as well as antimicrobial, activities. Surfaces coated with these layer-by-layer (LbL) films, which range from 6 to 10 bilayers (up to 45 nm in thickness), adsorbed up to 20 times less protein from blood plasma than the uncoated controls. The dependence of the antifouling activity on the nature of the polycation, as well as on assembly conditions and the number of layers in the LbL films, was investigated. Changing the hydrophobicity of the polycation altered the surface composition and the resistance to protein adsorption of the LbL films. Importantly, this resistance was greater for coated surfaces with the polyanion on top; for these films, the average zeta potential pointed to a near neutral surface charge, thus, presumably minimizing their electrostatic interactions with the protein. The film surface exhibited a large contact angle hysteresis, indicating a heterogeneous topology likely due to the existence of hydrophobic-hydrophilic regions on the surface. Scanning electron micrographs of the film surface revealed the existence of nanoscale domains. We hypothesize that the existence of hydrophobic/hydrophilic nanodomains, as well as surface charge neutrality, contributes to the LbL film's resistance to protein adsorption.     

Spreading and Wetting Behaviour of Trisiloxanes

Wetting and spreading processes which involve surfactant solutions are widely used in numerous industrial and practicalapplications nowadays.The performance of different non-ionic surfactants may vary significantly and so far superspreadersolutions show the most promising spreading ability.The addition of trisiloxane surfactants to water was proven to enhancewetting,even on hydrophobic surfaces,on which conventional surfactants seem to have little or no effect.Although theseextraordinary surfactants have been extensively studied over recent years,complete understanding of their underlying mechanismsand a suitable mathematical model are still lacking.Here we present a possible explanation for the impressive performanceof trisiloxane,which is compared to wetting enhancement of a conventional surfactant.Additionally,we will explain whythe hydrophobicity of the surface is a crucial factor for the spreading phenomenon.Light will be also shed on the effect of the pHof the solution to which surfactants are added.Finally,we will investigate long-term effects of the water environment on trisiloxanewetting ability and discuss if ageing may significantly affect their performance.     

Phosphorylation by Cdk1 Increases the Binding of Eg5 to Microtubules In Vitro and in Xenopus Egg Extract Spindles

Background

Motor proteins from the kinesin-5 subfamily play an essential role in spindle assembly during cell division of most organisms. These motors crosslink and slide microtubules in the spindle. Kinesin-5 motors are phosphorylated at a conserved site by Cyclin-dependent kinase 1 (Cdk1) during mitosis. Xenopus laevis kinesin-5 has also been reported to be phosphorylated by Aurora A in vitro.

Methodology/Principal Findings

We investigate here the effect of these phosphorylations on kinesin-5 from Xenopus laevis, called Eg5. We find that phosphorylation at threonine 937 in the C-terminal tail of Eg5 by Cdk1 does not affect the velocity of Eg5, but strongly increases its binding to microtubules assembled in buffer. Likewise, this phosphorylation promotes binding of Eg5 to microtubules in Xenopus egg extract spindles. This enhancement of binding elevates the amount of Eg5 in spindles above a critical level required for bipolar spindle formation. We find furthermore that phosphorylation of Xenopus laevis Eg5 by Aurora A at serine 543 in the stalk is not required for spindle formation.

Conclusions/Significance

These results show that phosphorylation of Eg5 by Cdk1 has a direct effect on the interaction of this motor with microtubules. In egg extract, phosphorylation of Eg5 by Cdk1 ensures that the amount of Eg5 in the spindle is above a level that is required for spindle formation. This enhanced targeting to the spindle appears therefore to be, at least in part, a direct consequence of the enhanced binding of Eg5 to microtubules upon phosphorylation by Cdk1. These findings advance our understanding of the regulation of this essential mitotic motor protein.     

Synthesis of some epoxy and/or N-oxy 17-picolyl and 17-picolinylidene-androst-5-ene derivatives and evaluation of their biological activity

Steroidal epoxy and/or N-oxy 17-picolyl and 17-picolinylidene-androst-5-ene derivatives have been prepared using 3beta,17beta-dihydroxy-17alpha-picolyl-androst-5-ene (1), 3beta-acetoxy-17-picolinylidene-androst-5-ene (2), and 3beta-hydroxy-17-picolinylidene-androst-5-ene (3) as synthetic precursors. The compounds 2 and/or 3 were reacted with m-chloroperoxybenzoic acid (MCPBA). The compounds synthesized from 2 were 17-picolinylidene-N-oxide 4, 5alpha,6alpha-epoxy and 5beta,6beta-epoxy-17-picolinylidene-N-oxide 5 and 6, and 5alpha,6alpha:17alpha,20alpha- and 5beta,6beta:17alpha,20alpha-diepoxy-N-oxide 7 and 8. Starting from compound 3, a mixture of 5alpha,6alpha-epoxy and 5beta,6beta-epoxy-17-picolinylidene 9 and 10, 5alpha,6alpha-epoxy and 5beta,6beta-epoxy-17-picolinylidene-N-oxide 11 and 12, and 5alpha,6alpha:17alpha,20alpha- and 5beta,6beta:17alpha,20alpha-diepoxy-N-oxide 13 and 14 were obtained. From compounds 15 and 18, obtained from 1 and 3 by the Oppenauer oxidation, the 4alpha,5alpha-epoxy and 4beta,5beta-epoxy derivatives 16, 17 and 20, 21 were prepared by oxidation with 30% H(2)O(2). Oxidation of 18 with MCPBA yielded only the N-oxide 19. The structures of compounds 15 and 18 were proved by the X-ray analysis. Compounds 1-6, 9, 15, 17, 18, and 21 were tested on activity against the enzyme aromatase. Antitumor activity against three tumor cell lines (human breast adenocarcinoma ER+, MCF-7, human breast adenocarcinoma ER-, MDA-MB-231, and prostate cancer PC3) was evaluated. Three tested compounds (1, 4, and 19) showed strong activity against PC3, the IC(50) values being in the range 0.55-10microM, whereas compound 17 showed strong activity against MDA-MB-231 (IC(50) 10.4microM).     

Perineurial Barrier Glia Physically Respond to Alcohol in an Akap200-Dependent Manner to Promote Tolerance

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Electroporation of cDNA/Morpholinos to targeted areas of embryonic CNS in <Emphasis Type="Italic">Xenopus</Emphasis>

Background  

Blastomere injection of mRNA or antisense oligonucleotides has proven effective in analyzing early gene function in Xenopus. However, functional analysis of genes involved in neuronal differentiation and axon pathfinding by this method is often hampered by earlier function of these genes during development. Therefore, fine spatio-temporal control of over-expression or knock-down approaches is required to specifically address the role of a given gene in these processes.