These islands encode for two different type III secretion systems (TTSS) [4]. The TTSS is responsible for enabling pathogenic Salmonella to transfer virulence factors into the host, allowing it to invade and hijack the host cellular Small molecule library price processes [4, 5]. SPI1 encodes for the TTSS1, responsible for the invasion of the host’s intestinal cells, while SPI2 encodes for the TTSS2, responsible for the survival and proliferation of the bacteria within the host cells [6]. Overall, the TTSS consists of more than 20

proteins including soluble cytoplasmic proteins, integral membrane proteins and outer membrane proteins [5]. The outer membrane proteins are influential in how bacteria interact with each other and with its immediate environment and are actively involved in both the uptake of nutrients and the transport of toxic by-products out of the cell [7]. More importantly, these surface exposed proteins play

Y-27632 in vitro a critical role in pathogenic processes such as motility, adherence and colonisation of the host cells, injection of toxins and cellular proteases, as well as the formation of channels for the removal of antibiotics (antibiotic resistance) [8, 9]. Therefore these functions make outer membrane proteins attractive targets for the development of antimicrobial drugs and vaccines [10, 11]. However, it is well documented that the isolation and characterisation of outer membrane proteins oxyclozanide has been fraught with difficulty for use in conventional proteomic techniques such as 2D gel electrophoresis (2D GE) due to their association with the membrane or peptidoglycan and relative low abundance when compared to the whole cell complex [7, 8, 12]. Work carried out by Molloy et al attempted to characterise OMPs using 2D GE with the addition of the zwitterionic detergent Amidosulfobetaine-14

(ASB-14) in the rehydration buffer with some degree of success [13]. In addition, several strategies have been developed to try and enrich samples in favour of outer membrane proteins based on differential solubilisation using detergents such as Triton X-100 [14] and sarcosyl [15], chemical enrichment such as sodium carbonate [13] and surface labelling such as biotinylation [16, 17]. However, each strategy fails to remove all contaminants such as cytosolic and ribosomal proteins. New gel-free proteomic approaches such as two dimensional liquid chromatography – tandem mass spectrometry (2D-LC-MS/MS) have been developed for the downstream analysis of complex protein mixtures and are able to overcome the limitations gel based proteomics face especially when dealing with membrane associated proteins [18]. However, these new methods do not focus on preliminary sample preparation where the outer membrane proteins are separated from the rest of the cell protein complex prior to mass spectrometry analysis.