A sensing system for the rapid on-line screening of lipids and biomembrane active compounds in water samples has been successfully developed. The sensor consists of a flow cell and incorporated wafer-based device with on-chip mercury on platinum (Pt/Hg) working electrode and platinum (Pt) auxiliary and pseudo-reference electrodes. To optimise system performance, the following experiments were carried out: (i) Deposition and removal of phospholipid layers on and from Pt/Hg electrodes respectively, (ii) Effect of electrode size on signal, (iii) Monitoring of different phospholipids deposited in flow cell and, (iv) Detection of phospholipid monolayer interaction with representative compounds. The results showed that: (i) Miniaturisation and ruggedisation of the mercury (Hg)/phospholipid system has been successfully achieved, (ii) Rapid cyclic voltammetry facilitates repetitive dioleoyl phosphatidylcholine (DOPC) monolayer formation on Hg from aqueous DOPC dispersion and, (iii) The device responds selectively to organic compounds injected into electrolyte flow.
The paper describes the detection of carbohydratelectin interaction on graphene-on-metal surface plasmon resonance (SPR) interfaces. Graphene-coated gold-based SPR interfaces were formed through the transfer of large-area graphene grown by chemical vapor deposition (CVD) on polycrystalline Cu foils. The method allowed successful transfer of single-and double-layered graphene sheets onto the SPR interfaces in a reproducible manner. Functionalization of the graphene interface with mannose was achieved by simple immersion into a mannose aqueous solution (100 mM), resulting in noncovalent interactions between the aromatic ring structure of graphene and mannose. The utility of the carbohydrate-modified graphene-on-gold interface for the selective and sensitive detection of carbohydrate-lectin interactions was demonstrated using model lectins from Lens culinaris (LC) and Triticum vulgaris (TV). While LC lectin binds specifically to mannopyranoside units, TV lectin has an affinity for N-acetyl glucosamine and sialic acid residues.
We characterize the distribution of oceanic phosphorus-containing lipids (PL) in the Northeast Atlantic by Iatroscan thin layer chromatography and high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Phospholipids are a small but significant fraction of oceanic particulate organic carbon (POC) (1.5%). We describe the distribution of 1,862 PL compounds in total, of which only ~27% have elemental compositions that match those found in the Nature Lipidomics Gateway database (e.g., phosphatidylglycerol (PG), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidic acid (PA), phosphatidyl serine (PS), and phosphatidylinositol (PI)). The highest phospholipid concentration is found in the epipelagic, which reflects primary production in that depth horizon. Depthrelated PL removal was the strongest for PL signals that match database-reported (known) lipids and was lower for saturated non-database (novel) matched PL. The transformation of known PL is marked by depth-related increase in saturation with PA that is assumed to be generated as the earliest transformation product of PL. Novel unsaturated P-lipids likely originate from both PL transformation processes and insitu biological production at the surface layer. Novel PL are dominated by unsaturated compounds for which unsaturation increased between the epipelagic (average molecular double bond equivalents, DBE=5) and the abyssopelagic (average DBE=6.7) zones. Additionally, those compounds increase in both average molecular weight and contribution to all lipid content with increasing depth, likely from crosslinking of unsaturated compounds. Our data indicate that novel PL are selectively preserved with depth and therefore are P and C carriers to the deep Atlantic. We demonstrate that a full appreciation of
Environmental context. Polycyclic aromatic hydrocarbons (PAHs) are potentially carcinogenic and mutagenic compounds found in the atmosphere, soil, sediments and water. They can bioaccumulate in marine organisms where they pose a threat to the health of the organisms. We are developing a low-cost and simple electrochemical method to monitor the concentrations of these compounds in the aquatic environment.Abstract. A new sensing system for polycyclic aromatic hydrocarbons (PAHs) in waters is being developed. The system consists of a wafer-based device with a chip-based mercury on platinum microelectrode as a working electrode and a platinum auxiliary electrode, incorporated into a flow cell system with an external reference electrode. The Hg microelectrode was coated with a phospholipid-triglyceride mixed layer and interactions between anthracene, phenanthrene, pyrene and fluoranthene and the layer were monitored using rapid cyclic voltammetry. The layer proved sensitive to interactions with PAHs in 'organic matter free' seawater, with respective detection limits of 0.33, 0.35, 0.15 and 0.32 mg L À1 for phenanthrene, pyrene, anthracene and fluoranthene. Tested interferences, such as sodium humate, dextran T-500 and bovine serum albumin, representing humic substances, polysaccharides and proteins, did not have an influence on the layer response. The system was also tested with a river water sample where concentrations of PAHs were determined using the standard addition method and compared with the results obtained by using gas chromatographymass spectrometry (GC-MS). The concentration of total PAHs obtained by the standard addition method is ,80 % lower compared with the results obtained by GC-MS analysis. The difference is explained by the fact that the electrochemical method measures water-soluble and free PAHs whereas the chromatographic method measures both dissolved and particulate-organic PAHs.
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