Modification of polysulfone ultrafiltration membranes with UV irradiation and hydrophilicity increasing agents

Hydrophobic polysulfone UF membranes were modified with UV irradiation and hydrophilicity increasing agents. The modifications were tested with 0.5% whey-protein solution and 0.05% lysozyme solution at pH 6 and with 0.05% bovine serum albumin solution at various pH values. UV irradiation increased flux and the hydrophilicity of the membranes. The flux increases obtained varied with pH and modification agents used and could be more than 400% compared to unmodified conditions without any loss in retention. The best retentions were obtained at pH values, where both the protein and the membrane had the same charge, and a strong electrostatic repulsion was obtained. The pores enlarged to fixed sizes, which depended on the sizes of the proteins and the range of double layer forces between proteins and membranes at different states of charge density.     

Stair motifs at protein-DNA interfaces: nonadditivity of H-bond, stacking, and cation-pi interactions

At the interface between protein and double-stranded DNA, stair motifs simultaneously involve three different types of pairwise interactions: aromatic base stacking, hydrogen bonding, and cation-pi. The relative importance of these interactions is studied in the stair motif occurring in the 1TC3 crystal structure, which involves an arginine and two stacked guanines, by means of Hartree-Fock (HF) and M?ller-Plesset energy and free energy calculations, including vibrational, rotational, translational contributions, both in a vacuum and various solvents. The results obtained show an anti-cooperative tendency of the HF energy and vibrational free energy terms, and the cooperativity of the rotational, translational, and solvation free energies. Hence, the cooperativity of the stair motif interactions, in the context of protein-DNA recognition, can be viewed as arising from the environment.     

Detoxification of VX and Other V‐Type Nerve Agents in Water at 37 °C and pH 7.4 by Substituted Sulfonatocalix[4]arenes

Sulfonatocalix[4]arenes with an appended hydroxamic acid residue can detoxify VX and related V‐type neurotoxic organophosphonates with half‐lives down to 3 min in aqueous buffer at 37 °C and pH 7.4. The detoxification activity is attributed to the millimolar affinity of the calixarene moiety for the positively charged organophosphonates in combination with the correct arrangement of the hydroxamic acid group. The reaction involves phosphonylation of the hydroxamic acid followed by a Lossen rearrangement, thus rendering the mode of action stoichiometric rather than catalytic. Nevertheless, these calixarenes are currently the most efficient low‐molecular‐weight compounds for detoxifying persistent V‐type nerve agents under mild conditions. They thus represent lead structures for novel antidotes that allow treatment of poisonings by these highly toxic chemicals.     

Monitoring of small‐scale anionic polymerization of caprolactam; a method to be used in an additive manufacturing process

The anionic polymerization of caprolactam using small quantities of reactants was investigated as part of a project aimed at producing polyamide parts by additive manufacturing. Various methods were used to monitor the polymerization and crystallization processes. Drop on drop small‐scale polymerization was carried out on a hot surface and monitored by Fourier transform infrared, which showed that PA6 had been polymerized successfully. PA6 synthesis was carried out in a differential scanning calorimetry cell to monitor the exothermic and endothermic processes during polymerization, and the processes were also observed by hot stage microscopy. It was found that polymerization and crystallization occurred simultaneously at slow heating rates. The amount of crystallinity produced during polymerization decreased as the heating rate increased. Copyright © 2013 John Wiley & Sons, Ltd.     

Fuel cell catalyst degradation on the nanoscale

A newly developed methodology for examining fuel cell catalyst degradation is introduced. In contrast to the conventional, destructive TEM investigation procedure, this methodology enables the observation of corrosion processes of the same catalyst region repeatedly. In particular we demonstrate the impact of a potential cycling treatment on a carbon-supported platinum catalyst, and propose a new corrosion mechanism for fuel cell catalyst degradation. Under the applied harsh conditions, whole Pt particles detach from the support and dissolve into the electrolyte without re-deposition.     

Validation of an MPC Polymer Coating to Attenuate Surface‐Induced Crosstalk between the Complement and Coagulation Systems in Whole Blood in In Vitro and In Vivo Models

Artificial surfaces that come into contact with blood induce an immediate activation of the cascade systems of the blood, leading to a thrombotic and/or inflammatory response that can eventually cause damage to the biomaterial or the patient, or to both. Heparin coating has been used to improve hemocompatibility, and another approach is 2‐methacryloyloxyethyl phosphorylcholine (MPC)‐based polymer coatings. Here, the aim is to evaluate the hemocompatibility of MPC polymer coating by studying the interactions with coagulation and complement systems using human blood in vitro model and pig in vivo model. The stability of the coatings is investigated in vitro and MPC polymer‐coated catheters are tested in vivo by insertion into the external jugular vein of pigs to monitor the catheters' antithrombotic properties. There is no significant activation of platelets or of the coagulation and complement systems in the MPC polymer‐coated one, which was superior in hemocompatibility to non‐coated matrix surfaces. The protective effect of the MPC polymer coat does not decline after incubation in human plasma for up to 2 weeks. With MPC polymer‐coated catheters, it is possible to easily draw blood from pig for 4 days in contrast to the case for non‐coated catheters, in which substantial clotting is seen.