1. Investigación

The metabolome is the complete set of small molecules coming from protein activity (anabolism and catabolism) in living systems. They have a broad range of chemical structures and physico-chemical properties and therefore different analytical methodologies are necessary. Highly polar metabolites, such as sugars and most amino acids are not retained by conventional reversed phase liquid (RP-LC) chromatography columns. Without sufficient retention, coelution may result in identification problems while the detection of compounds by mass spectrometry at low concentrations may also be problematic due to ion suppression. In order to retain compounds based on their hydrophilicity, polar stationary phases and hydrophilic interaction liquid chromatography (HILIC) provide a complementary tool to RP-LC for untargeted comprehensive metabolite fingerprinting. However, robustness of the methods is still limiting their applications. This review focuses on sample pre-treatment, stationary phases, analytical methods and applications for polar compound analysis in biological matrices.

Titania (TiO2)-based nanocomposites subjected to light excitation are remarkably effective in eliciting microbial death. However, the mechanism by which these materials induce microbial death and the effects that they have on microbes are poorly understood. Here, we assess the low dose radical-mediated TiO2 photocatalytic action of such nanocomposites and evaluate the genome/proteome-wide expression profiles of Pseudomonas aeruginosa PAO1 cells after two minutes of intervention. The results indicate that the impact on the gene-wide flux distribution and metabolism is moderate in the analysed time span. Rather, the photocatalytic action triggers the decreased expression of a large array of genes/proteins specific for regulatory, signalling and growth functions in parallel with subsequent selective effects on ion homeostasis, coenzyme-independent respiration and cell wall structure. The present work provides the first solid foundation for the biocidal action of titania and may have an impact on the design of highly active photobiocidal nanomaterials.