Dissolved organic nitrogen and its biodegradable portion in a water treatment plant with ozone oxidation.

Biodegradability of dissolved organic nitrogen (DON) has been studied in wastewater, freshwater and marine water but not in drinking water. Presence of biodegradable DON (BDON) in water prior to and after chlorination may promote formation of nitrogenous disinfectant by-products and growth of microorganisms in the distribution system. In this study, an existing bioassay to determine BDON in wastewater was adapted and optimized, and its application was tested on samples from four treatment stages of a water treatment plant including ozonation and biologically active filtration.

Membrane modulates affinity for calcium ion to create an apparent cooperative binding response by annexin a5.

Isothermal titration calorimetry was used to characterize the binding of calcium ion (Ca²⁺) and phospholipid to the peripheral membrane-binding protein annexin a5. The phospholipid was a binary mixture of a neutral and an acidic phospholipid, specifically phosphatidylcholine and phosphatidylserine in the form of large unilamellar vesicles. To stringently define the mode of binding, a global fit of data collected in the presence and absence of membrane concentrations exceeding protein saturation was performed.

Peripheral protein organization and its influence on lipid diffusion in biomimetic membranes.

Protein organization on biomembranes and their dynamics are essential for cellular function. It is not clear, however, how protein binding may influence the assembly of underlying lipids or how the membrane structure leads to functional protein organization. Toward this goal, we investigated the effects of annexin a5 binding to biomimetic membranes using fluorescence imaging and correlation spectroscopy.

Protein-lipid interactions role of membrane plasticity and lipid specificity on peripheral protein interactions.

Lipid mixtures are inherently nonrandom as each lipid species differs slightly in its chemical structure. A protein associates not with a lipid but with a membrane comprised of lipids where the chemical activities of each lipid is determined by the composition of the mixture. There can be selectivity in this association because a protein can enhance the underlying tendency of lipids to be heterogeneously distributed.