The Space Confinement Approach Using Hollow Graphitic Spheres to Unveil Activity and Stability of Pt‐Co Nanocatalysts for PEMFC

The performance of polymer electrolyte fuel cells is strongly correlated to the electrocatalytic activity and stability. In particular, the latter is the result of an interplay between different degradation mechanisms. The essential high stability, demanded for real applications, requires the synthesis of advanced electrocatalysts that withstand the harsh operation conditions. In the first part of this study, the synthesis of oxygen reduction electrocatalysts consisting of Pt‐Co (i.e., Pt₅Co, Pt₃Co, and PtCo) alloyed nanoparticles encapsulated in the mesoporous shell of hollow graphitic spheres (HGS) is reported. The mass activities of the activated catalysts depend on the initial alloy composition and an activity increase on the order of two to threefold, compared to pure Pt@HGS, is achieved. The key point of the second part is the investigation of the degradation of PtCo@HGS (showing the highest activity). Thanks to pore confinement, the impact of dissolution/dealloying and carbon corrosion can be studied without the interplay of other degradation mechanisms that would induce a substantial change in the particle size distribution. Therefore, impact of the upper potential limit and the scan rates on the dealloying and electrochemical surface area evolution can be examined in detail.     

Furanocembranoids from the Soft Corals Sinularia asterolobata and Litophyton arboreum

The new cembranoid diterpene danielid ( 1 ) along with 3α‐ethoxyfuranocembranoid 2 , pukalide ( 3 ), 13α‐acetoxypukalide ( 4 ), furanocembranoid 5 , and furanosesquiterpene 6 have been isolated from the soft coral Sinularia asterolobata. The furanocembranoid diterpene 11β,12β‐epoxypukalide ( 7 ) and the sesquiterpene (?)‐bicyclogermacrene ( 8 ) have been obtained from the soft coral Litophyton arboreum. The structures were elucidated primarily by NMR spectroscopy. The furanocembranoids 2, 4 , and 5 show good antiproliferative activities against the cell lines L‐929 and K‐562, and weak cytotoxic effects on HeLa cells.     

Modeling volatile isoprenoid emissions--a story with split ends.

Accurate prediction of plant-generated volatile isoprenoid fluxes is necessary for reliable estimation of atmospheric ozone and aerosol formation potentials. In recent years, significant progress has been made in understanding the environmental and physiological controls on isoprenoid emission and in scaling these emissions to canopy and landscape levels. We summarize recent developments and compare different approaches for simulating volatile isoprenoid emission and scaling up to whole forest canopies with complex architecture. We show that the current developments in modeling volatile isoprenoid emissions are "split-ended" with simultaneous but separated efforts in fine-tuning the empirical emission algorithms and in constructing process-based models. In modeling volatile isoprenoid emissions, simplified leaf-level emission algorithms (Guenther algorithms) are highly successful, particularly after scaling these models up to whole regions, where the influences of different ecosystem types, ontogenetic stages, and variations in environmental conditions on emission rates and dynamics partly cancel out. However, recent experimental evidence indicates important environmental effects yet unconsidered and emphasize, the importance of a highly dynamic plant acclimation in space and time. This suggests that current parameterizations are unlikely to hold in a globally changing and dynamic environment. Therefore, long-term predictions using empirical algorithms are not necessarily reliable. We show that process-based models have large potential to capture the influence of changing environmental conditions, in particular if the leaf models are linked with physiologically based whole-plant models. This combination is also promising in considering the possible feedback impacts of emissions on plant physiological status such as mitigation of thermal and oxidative stresses by volatile isoprenoids. It might be further worth while to incorporate main features of these approaches in regional empirically-based emission estimations thereby merging the "split ends".     

The new method ‘micromapping’, a means to study species-specific associations and exclusions of ectomycorrhizae

Ectomycorrhizae (ECM) are obligate symbiotic associations between higher fungi and most tree species of the temperate and boreal forests, and of some tree families in tropical areas. As the anatomical features of these symbiotic organs are very diverse and suggested to improve tree growth differently efficient, their frequency and natural distribution in the soil, as well as the differentiation and amount of their substrate exploiting extramatrical mycelia, are of special ecological interest. The soil with its heterogeneous assemblage of micro-niches certainly provokes ectomycorrhizal fungi to compete for such microsites. We therefore applied the method ‘micromapping’ to record the ECM in their natural position with the following question in mind: Do indicators exist for an exclusion of or an association with other ectomycorrhizal species or not? Thoroughly excavated and carefully cleaned ectomycorrhizae of the O_F horizon of a Picea abies stand were drawn in their natural position on perspex plates of 5 × 5 cm mapping area (McMp) with ink of different colours. They were afterwards removed and specified. Following scanning of the McMp, a special computer program was applied to analyse their distribution. The spatial relations of the ECM were calculated according to the ‘growing grid method’. The preliminary results suggest that the ECM of Russula ochroleuca and Piceirhiza internicrassihyphis show no common occurrence within short distances. This possibly applies also for Russula ochroleuca in comparison to Piceirhiza cinnbadiosimilis, for Elaphomyces granulatus in comparison to Xerocomus badius, and Lactarius decipiens in comparison to Piceirhiza cinnbadiosimilis. Cortinarius obtusus with Piceirhiza internicrassihyphis, and Piceirhiza internicrassihyphis with Xerocomus badius, indicate, however, rather high values of common occurrence. Due to the small number of replications, the standard deviations are high. More detailed investigations are therefore necessary before definite conclusions can be made. This method, however, apparently provides a useful tool to analyse spatial relations of ECM in the soil. Possible reasons for exclusions and associations of ECM are briefly discussed.     

Promiscuity in Rab-SNARE interactions

Fusion of post-Golgi secretory vesicles with the plasma membrane in yeast requires the function of a Rab protein, Sec4p, and a set of v- and t-SNAREs, the Snc, Sso, and Sec9 proteins. We have tested the hypothesis that a selective interaction between Sec4p and the exocytic SNAREs is responsible for ensuring that secretory vesicles fuse with the plasma membrane but not with intracellular organelles. Assembly of Sncp and Ssop into a SNARE complex is defective in a sec4-8 mutant strain. However, Snc2p binds in vivo to many other syntaxin-like t-SNAREs, and binding of Sncp to the endosomal/Golgi t-SNARE Tlg2p is also reduced in sec4-8 cells. In addition, binding of Sncp to Ssop is reduced by mutations in two other Rab genes and four non-Rab genes that block the secretory pathway before the formation of secretory vesicles. In an alternate approach to look for selective Rab-SNARE interactions, we report that the nucleotide-free form of Sec4p coimmunoprecipitates with Ssop. However, Rab-SNARE binding is nonselective, because the nucleotide-free forms of six Rab proteins bind with similar low efficiency to three SNARE proteins, Ssop, Pep12p, and Sncp. We conclude that Rabs and SNAREs do not cooperate to specify the target membrane.     

Erythropoietin in the General Population: Reference Ranges and Clinical,Biochemical and Genetic Correlates

Background

Although erythropoietin has been used for decades in the treatment of anemia, data regarding endogenous levels in the general population are scarce. Therefore, we determined erythropoietin reference ranges and its clinical, biochemical and genetic associations in the general population.

Methods

We used data from 6,777 subjects enrolled in the Prevention of REnal and Vascular ENd-stage Disease (PREVEND) study. Fasting venous blood samples were obtained in the morning from all participants from 2001–2003. Serum erythropoietin concentrations were measured using a fully automated chemiluminescent enzyme-labeled immunometric assay. A genome-wide association study was performed to identify genetic determinants.

Results

Mean age (± SD) was 53 ± 12 years and 50% were female. Median (IQR) erythropoietin concentrations were 7.6 (5.8–9.9) IU/L in men and 7.9 (6.0–10.6) IU/L in women. A strong positive correlation was found between erythropoietin and waist circumference, glucose and systolic blood pressure (all P < 0.05). In subjects with normal renal function there was a strong exponential relation between hemoglobin and erythropoietin, whereas in renal impairment (eGFR < 60 mL/min/1.73m^²) this relation was linear (men) or absent (women) (P < 0.001 for interaction). Single-nucleotide polymorphisms at the HBS1L-MYB locus were shown to be related to erythropoietin levels (P < 9x10^-21), more significantly than other erythrocyte parameters.

Conclusion

We provide age-specific reference ranges for endogenous serum erythropoietin. Erythropoietin levels are positively associated with the components of the metabolic syndrome, except cholesterol. We show that even mild renal failure blunts erythropoietin production and propose the HBS1L-MYB locus as a regulator of erythropoietin.     

The Nicotiana tabacum plasma membrane aquaporin NtAQP1 is mercury-insensitive and permeable for glycerol

A new aquaporin from Nicotiana tabacum (cv. Samsun) was characterized. It shares sequence homology to the Arabidopsis thaliana PIP1 protein family. By two-phase partitioning and immunoblot analysis, plasma membrane localization could be demonstrated. The corresponding mRNA is highly abundant in roots and flowers, while it is rarely expressed in leaves and stems. Functional expression in Xenopus oocytes revealed that NtAQP1 can mediate glycerol transport in addition to water flow. However, NtAQP1 is impermeable for Na+, K+ and Cl- ions. The water permeability and selectivity could not be modulated by addition of mercurials or the activity of cAMP-dependent protein kinases.