Collusion-Resistant Audio Fingerprinting System in the Modulated Complex Lapped Transform Domain

Collusion-resistant fingerprinting paradigm seems to be a practical solution to the piracy problem as it allows media owners to detect any unauthorized copy and trace it back to the dishonest users. Despite the billionaire losses in the music industry, most of the collusion-resistant fingerprinting systems are devoted to digital images and very few to audio signals. In this paper, state-of-the-art collusion-resistant fingerprinting ideas are extended to audio signals and the corresponding parameters and operation conditions are proposed. Moreover, in order to carry out fingerprint detection using just a fraction of the pirate audio clip, block-based embedding and its corresponding detector is proposed. Extensive simulations show the robustness of the proposed system against average collusion attack. Moreover, by using an efficient Fast Fourier Transform core and standard computer machines it is shown that the proposed system is suitable for real-world scenarios.     

Optimizing lectin-carbohydrate interactions: improved binding of divalent α-mannosylated ligands towards Concanavalin A

The synthesis and binding properties to Jack bean phytohaemagglutinin in (Concanavalin A, Con A) of a new family of divalent α-D-mannopyranoside ligands are described. The synthesis of these ligands is based on the coupling of commercially available diamines to p-isothiocyanatophenyl 2,3,4,6 tetra-O-acetyl-α-D-mannopyranoside (4). The resulting dimers 6, 15 to 22 and 30 were tested for their relative inhibitory potency by solid-phase enzyme-linked lectin assays (ELLA) using methyl α-D-mannopyranoside as standard. Divalent mannosylated ligand 35 bearing a non-aromatic aglycon was also tested for comparison purposes. Concentrations necessary for 50% inhibition (IC50s) of binding of yeast mannan to Jack bean phytohaemagglutinin (Con A) were determined. The inhibitions showed dimers to be approximately 10- to 90-fold more potent than methyl α-D-mannopyranoside. Variations in the intra-mannosyl distance proved to be an important factor for optimum binding. This revised version was published online in November 2006 with corrections to the Cover Date.     

Establishment of quantitative RNAi-based forward genetics in Entamoeba histolytica and identification of genes required for growth

While Entamoeba histolytica remains a globally important pathogen, it is dramatically understudied. The tractability of E. histolytica has historically been limited, which is largely due to challenging features of its genome. To enable forward genetics, we constructed and validated the first genome-wide E. histolytica RNAi knockdown mutant library. This library allows for Illumina deep sequencing analysis for quantitative identification of mutants that are enriched or depleted after selection. We developed a novel analysis pipeline to precisely define and quantify gene fragments. We used the library to perform the first RNAi screen in E. histolytica and identified slow growth (SG) mutants. Among genes targeted in SG mutants, many had annotated functions consistent with roles in cellular growth or metabolic pathways. Some targeted genes were annotated as hypothetical or lacked annotated domains, supporting the power of forward genetics in uncovering functional information that cannot be gleaned from databases. While the localization of neither of the proteins targeted in SG1 nor SG2 mutants could be predicted by sequence analysis, we showed experimentally that SG1 localized to the cytoplasm and cell surface, while SG2 localized to the cytoplasm. Overexpression of SG1 led to increased growth, while expression of a truncation mutant did not lead to increased growth, and thus aided in defining functional domains in this protein. Finally, in addition to establishing forward genetics, we uncovered new details of the unusual E. histolytica RNAi pathway. These studies dramatically improve the tractability of E. histolytica and open up the possibility of applying genetics to improve understanding of this important pathogen.     

Synthesis of 4(3H)quinazolinimines with selective cytotoxic effect on human acute promyelocytic leukemia cells

We synthesized a new family of six 4(3H)quinazolinimines based on the reaction between (E)-N-(2-cyanophenyl)benzimidoyl chloride and substituted anilines reaching the formation of their corresponding C2, N3-substituted quinazoliniminium chlorides. This method provides novel, direct and flexible access to diverse substituted 4(3H)quinazolinimines.New compounds obtained following the proposed synthesis were fully characterized and, including the thirteen 4(3H)quinazolinimines synthesized by this method and previously reported by us, were used to study its cytotoxic effect on neoplastic cell lines. The mechanism involved in cell toxicity was also studied. Results showed that these compounds were highly cytotoxic, in particular on Human Promyelocytic Leukemia cells (HL60) and Chronic Myelogenous Leukemia cells (K562) when compared with conventional antineoplastic drugs such as etoposide and cisplatin. The mechanism associated to cytotoxic effect was mainly apoptosis, which not was decreased by antioxidant addition, thereby suggesting that the compounds exert apoptotic death through a mechanism unrelated with oxidative stress.     

The evolution of siderophore production as a competitive trait

Microbes have the potential to be highly cooperative organisms. The archetype of microbial cooperation is often considered to be the secretion of siderophores, molecules scavenging iron, where cooperation is threatened by “cheater” genotypes that use siderophores without making them. Here, we show that this view neglects a key piece of biology: siderophores are imported by specific receptors that constrain their use by competing strains. We study the effect of this specificity in an ecoevolutionary model, in which we vary siderophore sharing among strains, and compare fully shared siderophores with private siderophores. We show that privatizing siderophores fundamentally alters their evolution. Rather than a canonical cooperative good, siderophores become a competitive trait used to pillage iron from other strains. We also study the physiological regulation of siderophores using in silico long‐term evolution. Although shared siderophores evolve to be downregulated in the presence of a competitor, as expected for a cooperative trait, privatized siderophores evolve to be upregulated. We evaluate these predictions using published experimental work, which suggests that some siderophores are upregulated in response to competition akin to competitive traits like antibiotics. Although siderophores can act as a cooperative good for single genotypes, we argue that their role in competition is fundamental to understanding their biology.