Structural Basis for Antimicrobial Activity of Lasiocepsin

Lasiocepsin is a unique 27‐residue antimicrobial peptide, isolated from Lasioglossum laticeps (wild bee) venom, with substantial antibacterial and antifungal activity. It adopts a welldefined structure consisting of two α‐helices linked by a structured loop. Its basic residues form two distinct positively charged regions on the surface whereas aliphatic side chains contribute to solvent‐accessible hydrophobic areas, thus emphasising the amphipathic character of the molecule. Lasiocepsin structurally belongs to the ShK family and shows a strong preference for anionic phospholipids; this is further augmented by increasing concentrations of cardiolipin, such as those found at the poles of bacterial cells. The membrane‐permeabilising activity of the peptide is not limited to outer membranes of Gram‐negative bacteria. The peptide interacts with phospholipids initially through its N terminus, and its degree of penetration is strongly dependent on the presence of cardiolipin.     

Variation in Preen Oil Composition Pertaining to Season,Sex, and Genotype in the Polymorphic White-Throated Sparrow

Evidence for the the ability of birds to detect olfactory signals is now well documented, yet it remains unclear whether birds secrete chemicals that can be used as social cues. A potential source of chemical cues in birds is the secretion from the uropygial gland, or preen gland, which is thought to waterproof, maintain, and protect feathers from ectoparasites. However, it is possible that preen oil also may be used for individual recognition, mate choice, and signalling social/sexual status. If preen oil secretions can be used as socio-olfactory signals, we should be able to identify the volatile components that could make the secretions more detectable, determine the seasonality of these secretions, and determine whether olfactory signals differ among relevant social groups. We examined the seasonal differences in volatile compounds of the preen oil of captive white-throated sparrows, Zonotrichia albicollis. This species is polymorphic and has genetically determined morphs that occur in both sexes. Mating is almost exclusively disassortative with respect to morph, suggesting strong mate choice. By sampling the preen oil from captive birds in breeding and non-breeding conditions, we identified candidate chemical signals that varied according to season, sex, morph, and species. Linear alcohols with a 10–18 carbon chains, as well as methyl ketones and carboxylic acids, were the most abundant volatile compounds. Both the variety and abundances of some of these compounds were different between the sexes and morphs, with one morph secreting more volatile compounds in the non-breeding season than the other. In addition, 12 compounds were seasonally elevated in amount, and were secreted in high amounts in males. Finally, we found that preen oil signatures tended to be species-specific, with white-throated sparrows differing from the closely related Junco in the abundances and/or prevalence of at least three compounds. Our data suggest roles for preen oil secretions and avian olfaction in both non-social as well as social interactions.     

Electrospun Poly(styrene) Fibers as a Protection for the First- and the Second-Generation Grubbs’ Catalyst

The study presents a novel method for protection of the first- and the second-generation Grubbs’ catalyst, by incorporation in poly(styrene) fibers through electrospinning technique. Both catalysts are sensitive to the presence of the amine hardeners in the epoxy-based self-healing composites and require protection from deactivation to retain their ability to promote polymerization reaction of the healing agent. Comparison of healing efficiencies of both catalysts suggested that poly(styrene) fibers offer better protection and dispersion for the first-generation Grubbs’ catalyst, although all the samples exhibited high-healing efficiency. Difference in stereoselectivity between two catalysts was also indicated.     

Ion Electrodiffusion Governs Silk Electrogelation

Silk electrogelation involves the transition of an aqueous silk fibroin solution to a gel state (E-gel) in the presence of an electric current. The process is based on local pH changes as a result of water electrolysis - generating H(+) and OH(-) ions at the (+) and (-) electrodes, respectively. Silk fibroin has a pI=4.2 and when local pH相似文献   

Charge Photogeneration in Few‐Layer MoS2

The 2D semiconductor MoS₂ in its mono‐ and few‐layer form is expected to have a significant exciton binding energy of several 100 meV, suggesting excitons as the primary photoexcited species. Nevertheless, even single layers show a strong photovoltaic effect and work as the active material in high sensitivity photodetectors, thus indicating efficient charge carrier photogeneration. Here, modulation spectroscopy in the sub‐ps and ms time scales is used to study the photoexcitation dynamics in few‐layer MoS₂. The results suggest that the primary photoexcitations are excitons that efficiently dissociate into charges with a characteristic time of 700 fs. Based on these findings, simple suggestions for the design of efficient MoS₂ photovoltaic and photodetector devices are made.     

Computing global and diffuse solar hourly irradiation on clear sky. Review and testing of 54 models

Fifty-four broad band models for computation of global and diffuse irradiance on horizontal surface are shortly presented and tested. The input data for these models consist of surface meteorological data, atmospheric column integrated data and data derived from satellite measurements. The testing procedure is performed for two meteorological stations in Romania (South-Eastern Europe). The testing procedure consists of forty-two stages intended to provide information about the sensitivity of the models to various sets of input data. There is no model to be ranked “the best” for all sets of input data. Very simple models as well as more complex models may belong to the category of “good models”. The best models for solar global radiation computation are, on equal-footing, ESRA3, Ineichen, METSTAT and REST2 (version 81). The second best models are, on equal-footing, Bird, CEM and Paulescu & Schlett. The best models for solar diffuse radiation computation are, on equal-footing, ASHRAE2005 and King. The second best model is MAC model. The best models for computation of both global and diffuse radiation are, on equal-footing, ASHRAE 1972, Biga, Ineichen and REST2 (version 81). The second best is Paulescu & Schlett model.     

Composition and antibacterial activities of essential oils of seven Ocimum taxa

GC/MS was used to identify compounds of essential oils from seven Ocimum taxa (O. americanum L., O. basilicum L., O. campechianum Mill., O. x citriodorum Vis., O. kilimandscharicum Baker ex Gürke and three botanical varieties and cultivars of Ocimum basilicum L.: ‘Genovese’, var. difforme and var. purpurascens). Preliminary screening of their antibacterial activity was done against a number of common pathogens (Enterococcus faecalis, Enterococus faecium, Escherichia coli 0157:H7, Listeria monocytogenes, Listeria ivanovii, Proteus vulgaris, Staphylococcus aureus, Staphylococcus epidermis) using the filter paper disc agar diffusion technique, while further analyses were done by modification of the disc diffusion method. A broad variation in the antibacterial properties of investigated essential oils was observed. E. coli 0157:H7 was inhibited by O. basilicum ‘Genovese’ essential oil, while Ocimum americanum and Ocimum x citriodorum essential oils were the most effective against Enterococcus faecalis, Enterococcus faecium, P. vulgaris, S. aureus and S. epidermis.     

Liposomes as Carriers of Antimicrobial Drugs

Liposome are promising drug carrier systems being developed. Their successful use in the treatment of several diseases demonstrates that a solid rationale for clinical development of liposomes as antimicrobial drug carriers can be established. There are a number of potential drug candidates for liposome encapsulation. The involvement of several biotechnology companies has culminated in the design and licensing of formulations for the treatment of certain microbial infections and cancers. Understanding of liposome behavior in the body and of the physicochemical mechanisms involved in the interaction of liposome, drug, and cellular targets is essential for their future applications.     

Measuring linearity of planar point sets

Our goal is to design algorithms that give a linearity measure for planar point sets. There is no explicit discussion on linearity in literature, although some existing shape measures may be adapted. We are interested in linearity measures which are invariant to rotation, scaling, and translation. These linearity measures should also be calculated very quickly and be resistant to protrusions in the data set. The measures of eccentricity and contour smoothness were adapted from literature, the other five being triangle heights, triangle perimeters, rotation correlation, average orientations, and ellipse axis ratio. The algorithms are tested on 30 sample curves and the results are compared against the linear classifications of these curves by human subjects. It is found that humans and computers typically easily identify sets of points that are clearly linear, and sets of points that are clearly not linear. They have trouble measuring sets of points which are in the gray area in-between. Although they appear to be conceptually very different approaches, we prove, theoretically and experimentally, that eccentricity and rotation correlation yield exactly the same linearity measurements. They however provide results which are furthest from human measurements. The average orientations method provides the closest results to human perception, while the other algorithms proved themselves to be very competitive.