Rational Design of Tryptophan‐Rich Antimicrobial Peptides with Enhanced Antimicrobial Activities and Specificities

Trp‐rich antimicrobial peptides play important roles in the host innate defense mechanism of many plants and animals. A series of short Trp‐rich peptides derived from the C‐terminal region of Bothrops asper myothoxin II, a Lys49 phospholipase A₂ (PLA₂), were found to reproduce the antimicrobial activities of their parent molecule. Of these peptides, KKWRWWLKALAKK—designated PEM‐2—was found to display improved activity against both Gram‐positive and Gram‐negative bacteria. To improve the antimicrobial activity of PEM‐2 for potential clinical applications further, we determined the solution structure of PEM‐2 bound to membrane‐mimetic dodecylphosphocholine (DPC) micelles by two‐dimensional NMR methods. The DPC micelle‐bound structure of PEM‐2 adopts an α‐helical conformation and the positively charged residues are clustered together to form a hydrophilic patch. The surface electrostatic potential map indicates that two of the three tryptophan residues are packed against the peptide backbone and form a hydrophobic face with Leu7, Ala9, and Leu10. A variety of biophysical and biochemical experiments, including circular dichroism, fluorescence spectroscopy, and microcalorimetry, were used to show that PEM‐2 interacted with negatively charged phospholipid vesicles and efficiently induced dye release from these vesicles, suggesting that the antimicrobial activity of PEM‐2 could be due to interactions with bacterial membranes. Potent analogues of PEM‐2 with enhanced antimicrobial and less pronounced hemolytic activities were designed with the aid of these structural studies.     

Characterization of poly(vinyl alcohol) grafted with acrylic acid and methylmethacrylate using a Ce(IV) glucose redox system

Poly(vinyl alcohol) (PVA) is a well-known biomedical polymer and is biocompatible. Methylmethacrylate and acrylic acid monomers were grafted onto PVA using a Ce(IV)–glucose redox system at three different temperatures (35, 45, and 55°C) under nitrogen atmosphere. More than 80% grafting could be achieved in the process. The grafted PVA was characterized through infrared spectra, thermal decomposition studies [thermogravimetric analysis (TGA) and decomposition thermal grafting (DTG)], differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The thermal stability and other properties of grafted PVA related to medical applications was found to be better than those of ungrafted PVA. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 677–683, 1999     

Multiple metal coordinating behaviour of the tetrapodal ligand 1,1,1,1-tetrakis[(salicylaldimino)methyl]methane

The tetrapodal ligand 1,1,1,1-tetrakis[(salicylaldimino)methyl]methane (H₄tsam) has been introduced for the first time for metal complexation. Two zinc(II) complexes[Zn₂(tsam)] (1) and [Zn₃(Htsam)₂]·2C₇H₈ (2) have been obtained by reacting zinc acetylacetonate with the ligand in the presence of triethylamine, while a cobalt(III) complex [Co(Htsam)]·CH₃CN·H₂O (3) is obtained when Co(ClO₄)₂·6H₂O is reacted in air. All the compounds have been characterized by their elemental analyses and ESI-MS, IR, UV-VIS and ¹H NMR spectra. The X-ray crystal structures of H₄tsam, 2 and 3 have been determined. Compounds 1 and 2 exhibit fluorescence in solution and the lifetimes of their luminescence decay have been measured. Thermal analysis (TGA, DTA) of 2 with regard to loss of encapsulated toluenes and redox behaviour of 3 have been studied.     

Synthesis,characterization, and antimicrobial properties of novel quaternary amine methacrylate copolymers

A novel amine methacrylate monomer trimethylolpropane trimethacrylate–piperazine–ethyleneglycol dimethacrylate (TMPTMA‐PPZ‐EGDMA) was synthesized by amination of trimethylolpropane trimethacrylate (TMPTMA) with excess of piperazine (PPZ) followed by reaction with ethyleneglycol dimethacrylate (EGDMA). Copolymerization of TMPTMA‐PPZ‐EGDMA with 2‐hydroxyethyl methacrylate (HEMA) was carried out by free radical polymerization using ammonium persulfate (APS) and N,N,N′,N′‐tetramethyl ethylenediamine (TEMED) as a redox initiator. The copolymers obtained were then quaternized with 1‐iodooctane. The monomers were characterized by FTIR and ¹H NMR spectral studies. The molecular weights and polydispersity values of the monomers were determined with gel permeation chromatography. Quaternized copolymers containing more than 20% amine methacrylate monomer showed microporosity in the range of 9.9–10.4 μm. The antibacterial activity of the quaternized copolymers against Escherichia coli and Staphylococcus aureus was studied using UV–vis spectrophotometer and scanning electron microscopy. Quaternized copolymers showed broad‐spectrum contact‐killing antibacterial properties without releasing any active agent as checked by iodide selective ion meter. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Early Stage Automatic Strategy for Power-Aware Signal Processing Systems Design

Complexity management, portability and long term adaptivity are common challenges in different fields of embedded systems, normally colliding with the needs of efficient resource utilization and power balance. Image/signal processing systems, though required to offer a large variety of complex functions, have also to deal with battery-life limitations. Wearable signal processing systems, for example, should provide high performance and support new generation standards without compromising their portability and their long-term usability. These constraints challenge hardware designers: early stage trade-off analysis and power management automated techniques are helpful to guarantee a reasonable time-to-market. In the field of video codec specifications, the MPEG standard known as Reconfigurable Video Coding (RVC) framework addresses functional complexity and adaptivity leveraging on the intrinsic modularity of the dataflow model of computation, but it still lacks in offering power management support. The main contribution of this work is providing an automatic early-stage power management methodology to be adopted within the MPEG-RVC context. Starting from different high-level specifications, our mapping methodology identifies directly on the high-level models disjointed homogeneous logic clock regions, where the platform resources can be enabled/disabled together without affecting the overall system performance. To extend its usability to the RVC community, we have integrated this methodology within the Multi-Dataflow Composer (MDC) tool. MDC is a tool for on-the-fly reconfigurable signal processing platforms deployment. In this paper, we extended MDC to address power-aware multi-context systems. To prove the effectiveness of our work, a coprocessor for image and video processing acceleration has been assembled. This latter has been synthesized on a 90 nm ASIC technology, where demonstrated up to 90 % of reduction in the dynamic power consumption on different dataflow-intensive applications. The coprocessor has been implemented also on FPGA, confirming, partially, the benefits of adopting the proposed methodology.     

Hydrotreating of Gas Oil,Jatropha Oil,and Their Blends Using a Carbon Supported Cobalt-Molybdenum Catalyst

Hydrotreating of Jatropha oil and Jatropha oil blended gas oil feeds were studied under diesel hydrotreating conditions using Cobalt-Molybdenum catalyst on activated carbon. The experiments were carried out in pilot plant for more than 90 days first with gas oil, followed by 5%, 10%, and 20% Jatropha oil in gas oil and finally with Jatropha oil alone. Deactivation of the catalyst was not observed up to hydrotreating of 20 wt% Jatropha oil in gas oil, but, the reactor pressure shoots up after seven days of running neat Jatropha oil. The liquid products were characterized by GC-MS analysis, distillation, density, sulfur, nitrogen, and Cetane Index.     

Unsteady compressible boundary layer flow on the stagnation line of an infinite swept cylinder

Summary Numerical solutions of flow and heat transfer process on the unsteady flow of a compressible viscous fluid with variable gas properties in the vicinity of the stagnation line of an infinite swept cylinder are presented. Results are given for the case where the unsteady temperature field is produced by (i) a sudden change in the wall temperature (enthalpy) as the impulsive motion is started and (ii) a sudden change in the free-stream velocity. Solutions for the simultaneous development of the thermal and momentum boundary layers are obtained by using quasilinearization technique with an implicit finite difference scheme. Attention is given to the transient phenomenon from the initial flow to the final steady-state distribution. Results are presented for the skin friction and heat transfer coefficients as well as for the velocity and enthalpy profiles. The effects of wall enthalpy parameter, sweep parameter, fluid properties and transpiration cooling on the heat transfer and skin friction are considered.     

Cu–Zn–Al based catalysts for low temperature bioethanol steam reforming by solar energy

Bioethanol steam reforming is one of the most promising route to produce hydrogen from a renewable liquid biofuel. Activity of two Cu–Zn–Al based catalysts was investigated at low temperatures, ranging from 420 to 500 °C, in view of temperature limitations associated with solar energy supply by parabolic trough technology. At 450 °C the space velocity effect was also investigated, by varying the weight hourly space velocity (WHSV) from 1.67 to 3.32 h⁻¹. In each experimental conditions, together with the expected hydrogen and carbon dioxide, also methane, ethylene, acetaldehyde and diethylether were detect as products, so indicating the presence of several parallel reaction pathways. A good selectivity to ethanol reforming was obtained only at 500 °C (with values of the H₂/CO₂ mol ratio of 3.4 and 4.5) with both catalysts, while at lower temperatures alcohol dehydration into acetaldehyde seemed to be the main reaction.     

Metric and trigonometric pruning for clustering of uncertain data in 2D geometric space

We study the problem of clustering data objects with location uncertainty. In our model, a data object is represented by an uncertainty region over which a probability density function (pdf) is defined. One method to cluster such uncertain objects is to apply the UK-means algorithm [1], an extension of the traditional K-means algorithm, which assigns each object to the cluster whose representative has the smallest expected distance from it. For arbitrary pdf, calculating the expected distance between an object and a cluster representative requires expensive integration of the pdf. We study two pruning methods: pre-computation (PC) and cluster shift (CS) that can significantly reduce the number of integrations computed. Both pruning methods rely on good bounding techniques. We propose and evaluate two such techniques that are based on metric properties (Met) and trigonometry (Tri). Our experimental results show that Tri offers a very high pruning power. In some cases, more than 99.9% of the expected distance calculations are pruned. This results in a very efficient clustering algorithm. ¹