Fungal laccase from Steccherinum ochraceum 1833 displays remarkable stability under different harsh conditions: organic/buffer mixtures, thermal treatment, and microwave radiation. The behavior is particularly significant in the light of the sharp inactivation observed for two different fungal laccases. Laccase from S. ochraceum 1833 also displays hyperactivation under mild thermal treatment (60 °C). Molecular dynamics simulations at 80 °C explained how this laccase retains the geometry of the electron transfer pathway, thereby assuring electron transfer through the copper ions and thus maintaining its catalytic activity at high temperature. Spectroscopic studies revealed that the thermal activation corresponds to specific conformational changes in the protein. The results indicate that this laccase is potentially applicable under denaturing conditions that might be beneficial for the biotransformation of recalcitrant substrates. 相似文献
Routing protocols are the binding force in mobile ad hoc network (MANETs) since they facilitate communication beyond the wireless
transmission range of the nodes. However, the infrastructure-less, pervasive, and distributed nature of MANETs renders them
vulnerable to security threats. In this paper, we propose a novel cluster-based trust-aware routing protocol (CBTRP) for MANETs
to protect forwarded packets from intermediary malicious nodes. The proposed protocol organizes the network into one-hop disjoint
clusters then elects the most qualified and trustworthy nodes to play the role of cluster-heads that are responsible for handling
all the routing activities. The proposed CBTRP continuously ensures the trustworthiness of cluster-heads by replacing them
as soon as they become malicious and can dynamically update the packet path to avoid malicious routes. We have implemented
and simulated the proposed protocol then evaluated its performance compared to the clustered based routing protocol (CBRP)
as well as the 2ACK approach. Comparisons and analysis have shown the effectiveness of our proposed scheme. 相似文献
Bridged ureasil precursors were synthesized by the reaction of either ethylenediamine (1 mol) or m‐xylylenediamine (1 mol) with isocyanatepropyltriethoxysilane (2 mol). Transparent polysilsesquioxane films were obtained by the hydrolytic condensation of the pure precursors or their co‐condensation in a 50:50 molar ratio. Films based on pure ureasil precursors showed a blue photoluminescent emission band assigned to the photoinduced proton‐transfer among H‐bonded urea groups and the subsequent radiative recombination of ionized groups. Films synthesized by the co‐condensation of both precursors exhibited a significant red‐shift of their absorption, excitation, and emission spectra, associated to de‐localization of H‐bonds, and a high absorption of UV‐radiation.
The Santa Ana River (SAR), CA and adjacent wetlands have been identified as potential sources of fecal indicator bacteria (FIB) to the surf zone at Huntington Beach, CA. A suite of fecal steroids, including coprostanol (COP), epicoprostanol (eCOP), cholesterol (CHOE), cholestanol (CHOA), alpha-cholestanone (aONE), beta-cholestanone (bONE), beta-sitosterol (bSIT), stigmasterol (STIG), stigmastanol (STAN), and campesterol (CAM), were used as chemical markers to examine whether sewage was a significant source of FIB within the lower Santa Ana River watershed. A total of 54 water samples were collected from three locations in the intertidal zone near the mouth of the Santa Ana River at different tidal stages. Steroid ratios in SAR samples were different from those found in raw and treated sewage from a local wastewater treatment plant or in nearby effluent plume and did not appear to be influenced by the sampling location, daily tides, and spring/neap tidal cycle. The characteristics of steroid ratios suggested a diagenetic ratherthan a biogenic source forthe COP content of the samples. The log-based concentrations of COP and FIB in the SAR samples were not significantly correlated, inconsistent with sewage being the source of FIB in the study area. In addition, multivariate statistical analysis showed that the concentrations of FIB were better correlated with bird fecal steroids than with the typical sewage sterols. The results implied that sewage was not a significant source of fecal steroids, and therefore perhaps FIB to the study area. Instead, birds may be one possible source of the intermittently high levels of FIB observed in the lower Santa Ana River watershed and the nearby surf zone. 相似文献
In recent years, a positive developmental role has been increasingly expected of civil society organizations. Focusing on non-governmental organizations (NGOs) and grass-roots organizations (GROs), the extent to which these organizations exist, adopt pro-poor strategies and have a positive influence in governmental processes in nine cities in Africa, Asia and Latin America is analysed. The findings demonstrate that a number of issues identified from the wider literature about the internal governance arrangements of NGOs and GROs, their commitment and ability to represent and address the needs of the poor, and their relationships with wider political and administrative processes are also a matter for concern at city level. While there are some successful development NGOs, many only operate on a small scale and many do not empower poor people and their organizations. Formal interactions between government and civil society organizations are apparently becoming more common, but informal exchanges between GROs, politicians and officials continue, and may in some circumstances be more productive in terms of delivering practical benefits to poor areas. However, such clientelist relations reinforce undemocratic leadership at community level and perpetuate differential treatment of low-income settlements. 相似文献
Type II diabetes mellitus (T2DM) is associated with β‐cell failure, which correlates with the formation of pancreatic islet amyloid deposits. The human islet amyloid polypeptide (hIAPP) is the major component of islet amyloid and undergoes structural changes followed by self‐association and pathological tissue deposition during aggregation in T2DM. There is clear evidence that the aggregation process is accelerated in the presence of particular lipid membranes. Whereas hIAPP aggregation has been extensively studied in homogeneous model membrane systems, especially negatively charged lipid bilayers, information on the interaction of hIAPP with heterogeneous model raft membranes has been missing until now. In the present study, we focus on the principles of aggregation and amyloid formation of hIAPP in the presence of model raft membranes. Time‐lapse tapping mode AFM and confocal fluorescence microscopy experiments followed membrane permeabilization and localization of hIAPP in the raft membrane. Together with the ThT and WST‐1 assay, the data revealed elevated cytotoxicity of hIAPP oligomers on INS‐1E cells.相似文献