Electrochemical reduction of oxygen on palladium nanocubes in acid and alkaline solutions

The electrocatalytic properties of cubic palladium nanoparticles towards the electrochemical reduction of oxygen were studied in acid and alkaline solutions and compared with those of spherical nanoparticles and bulk Pd. The synthesised Pd nanoparticles were characterised by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Electrooxidation of pre-adsorbed CO was employed for cleaning the palladium catalyst surface. Oxygen reduction was studied using the rotating disk electrode (RDE) method and enhanced electrocatalytic activity of Pd nanocubes was revealed both in acid and alkaline solutions, which was attributed to the prevalence of Pd(1 0 0) facets. The mechanism of oxygen reduction on Pd nanoparticles was similar to that on bulk Pd, the first electron transfer being the rate-limiting step, and the reaction predominantly followed a four-electron pathway in both solutions.     

The meaning of the future: Toward a more specific definition of possible selves.

Possible selves are traditionally defined as conceptions of our selves in future states. The author discusses the way the theory is used in the literature and argues that there is a need for a clearer definition, because there appear to be a number of common misinterpretations regarding possible selves. Important features of possible selves are discussed, in particular their nature as experienced meaning, their relation with the rest of the self-concept, and their social and cultural nature. It is suggested that agency is an important aspect of possible selves and that they can be seen as narratives. The clearer definition suggested is that possible selves are conceptions of our selves in the future, including, at least to some degree, an experience of being an agent in a future situation. Possible selves get vital parts of their meaning in interplay with the self-concept, which they in turn moderate, as well as from their social and cultural context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Polo-like kinase 1 as a target for human cytomegalovirus pp65 lower matrix protein

Human cytomegalovirus (HCMV) pp65 protein is the major constituent of viral dense bodies but is dispensable for viral growth in vitro. pp65 copurifies with a S/T kinase activity and has been implicated in phosphorylation of HCMV IE1 immediate-early protein and its escape from major histocompatibility complex 1 presentation. Furthermore, the presence of pp65 correlates with a virion-associated kinase activity. To clarify the role of pp65, yeast two-hybrid system (THS) screening was performed to identify pp65 cellular partners. A total of 18 out of 48 yeast clones harboring cDNAs for putative pp65 binding proteins encoded the Polo-like kinase 1 (Plk1) C-terminal domain. Plk1 behaved as a bona fide pp65 partner in THS control crosses, and the interaction was confirmed by in vitro binding experiments. Endogenous Plk1 was coimmunoprecipitated with pp65 from transiently transfected COS7 cells. In infected fibroblasts, Plk1 was coimmunoprecipitated with pp65 at late infection stages. Furthermore, Plk1 was detected within wild-type HCMV particles but not within the particles of a pp65-negative mutant (RVAd65). The hydrophilic region of pp65 was phosphorylated in vitro by Plk1. These results suggest that one function of pp65 may be to capture a cell kinase, perhaps in order to alter its activity, nucleotide preference, substrate specificity, or subcellular localization to the advantage of HCMV.     

Neuronopathic forms of Gaucher's disease

Neuronopathic Gaucher patients may have a wide variety of clinical manifestations and natural history, and can present with a range of degrees of severity of systemic disease and neurological deficit. The brain pathology of these patients has been well described, but the mechanism by which glucocerebrosidase deficiency leads to neuronal dysfunction is not yet understood. The almost 20 different mutations of the glucocerebrosidase gene that have been described in Type 2 and 3 Gaucher patients poorly predict the phenotype of individual patients. Enzyme replacement therapy (ERT), often at high doses, has been shown to reverse most of the systemic manifestations of this disease, but can rarely reverse the neurological deficits. Therefore, other forms of treatment, such as gene therapy or a more efficient and direct enzyme delivery to neurons, are being devised.     

Reconstitution of the Raf-1-MEK-ERK signal transduction pathway in vitro

Raf-1 is a serine/threonine kinase which is essential in cell growth and differentiation. Tyrosine kinase oncogenes and receptors and p21ras can activate Raf-1, and recent studies have suggested that Raf-1 functions upstream of MEK (MAP/ERK kinase), which phosphorylates and activates ERK. To determine whether or not Raf-1 directly activates MEK, we developed an in vitro assay with purified recombinant proteins. Epitope-tagged versions of Raf-1 and MEK and kinase-inactive mutants of each protein were expressed in Sf9 cells, and ERK1 was purified as a glutathione S-transferase fusion protein from bacteria. Raf-1 purified from Sf9 cells which had been coinfected with v-src or v-ras was able to phosphorylate kinase-active and kinase-inactive MEK. A kinase-inactive version of Raf-1 purified from cells that had been coinfected with v-src or v-ras was not able to phosphorylate MEK. Raf-1 phosphorylation of MEK activated it, as judged by its ability to stimulate the phosphorylation of myelin basic protein by glutathione S-transferase-ERK1. We conclude that MEK is a direct substrate of Raf-1 and that the activation of MEK by Raf-1 is due to phosphorylation by Raf-1, which is sufficient for MEK activation. We also tested the ability of protein kinase C to activate Raf-1 and found that, although protein kinase C phosphorylation of Raf-1 was able to stimulate its autokinase activity, it did not stimulate its ability to phosphorylate MEK.     

Videodensitometry in the diagnosis of aortic incompetence

The videodensitometer has been used in a group of 20 patients with aortic incompetence and incompetence combined with stenosis. The method appears effective in the preoperative evaluation of the valvular and ventricular function of the patient. It gives objective and probably more accurate information of the regurgitation fraction and the ejection fraction than the commonly used semiquantitative methods. The method is simple to use and needs no technical changes in the roentgen equipment.     

Activated polo-like kinase Plx1 is required at multiple points during mitosis in Xenopus laevis

Entry into mitosis depends upon activation of the dual-specificity phosphatase Cdc25C, which dephosphorylates and activates the cyclin B-Cdc2 complex. Previous work has shown that the Xenopus polo-like kinase Plx1 can phosphorylate and activate Cdc25C in vitro. In the work presented here, we demonstrate that Plx1 is activated in vivo during oocyte maturation with the same kinetics as Cdc25C. Microinjection of wild-type Plx1 into Xenopus oocytes accelerated the rate of activation of Cdc25C and cyclin B-Cdc2. Conversely, microinjection of either an antibody against Plx1 or kinase-dead Plx1 significantly inhibited the activation of Cdc25C and cyclin B-Cdc2. This effect could be reversed by injection of active Cdc25C, indicating that Plx1 is upstream of Cdc25C. However, injection of Cdc25C, which directly activates cyclin B-Cdc2, also caused activation of Plx1, suggesting that a positive feedback loop exists in the Plx1 activation pathway. Other experiments show that injection of Plx1 antibody into early embryos, which do not require Cdc25C for the activation of cyclin B-Cdc2, resulted in an arrest of cleavage that was associated with monopolar spindles. These results demonstrate that in Xenopus laevis, Plx1 plays important roles both in the activation of Cdc25C at the initiation of mitosis and in spindle assembly at late stages of mitosis.     

Atlantic salmon skin and fillet color changes effected by perimortem handling stress, rigor mortis, and ice storage

ABSTRACT:  The changes in skin and fillet color of anesthetized and exhausted Atlantic salmon were determined immediately after killing, during rigor mortis, and after ice storage for 7 d. Skin color (CIE L *, a *, b *, and related values) was determined by a Minolta Chroma Meter. Roche Salmo Fan™ Lineal and Roche Color Card values were determined by a computer vision method and a sensory panel. Before color assessment, the stress levels of the 2 fish groups were characterized in terms of white muscle parameters (pH, rigor mortis, and core temperature). The results showed that perimortem handling stress initially significantly affected several color parameters of skin and fillets. Significant transient fillet color changes also occurred in the prerigor phase and during the development of rigor mortis. Our results suggested that fillet color was affected by postmortem glycolysis (pH drop, particularly in anesthetized fillets), then by onset and development of rigor mortis. The color change patterns during storage were different for the 2 groups of fish. The computer vision method was considered suitable for automated (online) quality control and grading of salmonid fillets according to color.     

Pt nanoparticles sputter-deposited on TiO2/MWCNT composites prepared by atomic layer deposition: Improved electrocatalytic activity towards the oxygen reduction reaction and durability in acid media

Acid-treated multi-walled carbon nanotubes (MWCNTs) were decorated with TiO₂ using the atomic layer deposition (ALD) technique followed by uniform distribution of platinum nanoparticles (PtNPs) through magnetron sputtering. Surface analyses were performed by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical decontamination and characterization of the Pt-TiO₂/MWCNT electrodes were carried out by CO stripping followed by cyclic voltammetry in acid media. The oxygen reduction reaction (ORR) was studied in O₂-saturated 0.05 M H₂SO₄ solution using the rotating disk electrode (RDE) method. Durability of the prepared catalysts was examined by repetitive potential cycling. Electrochemical data obtained was analyzed and compared to that of the commercial Pt/C catalyst. It was revealed that the Pt-TiO₂/MWCNT catalysts possess higher ORR activity and better durability as compared to that of the commercial Pt/C.