Channel Assignment with Separation for Interference Avoidance in Wireless Networks

Given an integer $\sigma > 1$, a vector $(\delta_1, \delta_2, \ldots, \delta_{\sigma-1})$ of nonnegative integers, and an undirected graph $G=(V,E)$, an $L(\delta_1, \delta_2, \ldots,\delta_{\sigma-1})$-coloring of $G$ is a function $f$ from the vertex set $V$ to a set of nonnegative integers such that $| f(u) -f(v) | \ge \delta_i$, if $d(u,v) = i, \ 1 \le i \le \sigma-1, \$ where $d(u,v)$ is the distance (i.e. the minimum number of edges) between the vertices $u$ and $v$. An optimal $L(\delta_1, \delta_2, \ldots,\delta_{\sigma-1})$-coloring for $G$ is one using the smallest range $\lambda$ of integers over all such colorings. This problem has relevant application in channel assignment for interference avoidance in wireless networks, where channels (i.e. colors) assigned to interfering stations (i.e. vertices) at distance $i$ must be at least $\delta_i$ apart, while the same channel can be reused in vertices whose distance is at least $\sigma$. In particular, two versions of the coloring problem -- $L(2,1,1)$, and $L(\delta_1, 1, \ldots,1)$ -- are considered. Since these versions of the problem are $NP$-hard for general graphs, efficient algorithms for finding optimal colorings are provided for specific graphs modeling realistic wireless networks including rings, bidimensional grids, and cellular grids

A Burkholderia pseudomallei toxin inhibits helicase activity of translation factor eIF4A

The structure of BPSL1549, a protein of unknown function from Burkholderia pseudomallei, reveals a similarity to Escherichia coli cytotoxic necrotizing factor 1. We found that BPSL1549 acted as a potent cytotoxin against eukaryotic cells and was lethal when administered to mice. Expression levels of bpsl1549 correlate with conditions expected to promote or suppress pathogenicity. BPSL1549 promotes deamidation of glutamine-339 of the translation initiation factor eIF4A, abolishing its helicase activity and inhibiting translation. We propose to name BPSL1549 Burkholderia lethal factor 1

Are bacterial vaccine antigens T-cell epitope depleted?

For many infectious diseases, protective immunity can be elicited by vaccination with pathogen-derived proteins. Peptides derived from these proteins are bound to major histocompatibility complex (MHC) molecules and presented to T-cell receptors to stimulate an immune response. We show here that, paradoxically, bacterial proteins known experimentally to elicit a protective immune response are relatively depleted in peptides predicted to bind to human MHC alleles. We propose three nonconflicting reasons for this: the lack of precision of current predictive software, the low incidence of hydrophobic residues in vaccine antigens or evolutionary pressure exerted on bacteria by the immune system. We suggest that there is little value in predicting candidate vaccines based on high MHC-binding epitope density

Transcriptional profiles of Burkholderia pseudomallei reveal the direct and indirect roles of Sigma E under oxidative stress conditions

10.1186/1471-2164-15-787BMC Genomics15178

Comparison of a nontoxic variant of Clostridium perfringens alpha-toxin with the toxic wild-type strain

The alpha-toxin produced by Clostridium perfringens is one of the best-studied examples of a toxic phospholipase C. In this study, a nontoxic mutant protein from C. perfringens strain NCTC8237 in which Thr74 is substituted by isoleucine (T74I) has been characterized and is compared with the toxic wild-type protein. Thr74 is part of an exposed loop at the proposed membrane-interfacing surface of the toxin. The mutant protein had markedly reduced cytotoxic and myotoxic activities. However, this substitution did not significantly affect the catalytic activity towards water-soluble substrate or the overall three-dimensional structure of the protein. The data support the proposed role of the 70-90 loop in the recognition of membrane phospholipids. These findings also provide key evidence in support of the hypothesis that the hydrolysis of both phosphatidylcholine and sphingomyelin are required for the cytolytic and toxic activity of phospholipases