Neutrophil Activation by Mineral Microparticles Coated with Methylglyoxal-Glycated Albumin.

Hyperglycemia-induced protein glycation and formation of advanced glycation end-products (AGEs) plays an important role in the pathogenesis of diabetic complications and pathological biomineralization. Receptors for AGEs (RAGEs) mediate the generation of reactive oxygen species (ROS) via activation of NADPH-oxidase. It is conceivable that binding of glycated proteins with biomineral particles composed mainly of calcium carbonate and/or phosphate enhances their neutrophil-activating capacity and hence their proinflammatory properties. Our research managed to confirm this hypothesis. Human serum albumin (HSA) was glycated with methylglyoxal (MG), and HSA-MG was adsorbed onto mineral microparticles composed of calcium carbonate nanocrystals (vaterite polymorph, CC) or hydroxyapatite nanowires (CP). As scopoletin fluorescence has shown, H2O2 generation by neutrophils stimulated with HSA-MG was inhibited with diphenyleneiodonium chloride, wortmannin, genistein and EDTA, indicating a key role for NADPH-oxidase, protein tyrosine kinase, phosphatidylinositol 3-kinase and divalent ions (presumably Ca2+) in HSA-MG-induced neutrophil respiratory burst. Superoxide anion generation assessed by lucigenin-enhanced chemiluminescence (Luc-CL) was significantly enhanced by free HSA-MG and by both CC-HSA-MG and CP-HSA-MG microparticles. Comparing the concentrations of CC-bound and free HSA-MG, one could see that adsorption enhanced the neutrophil-activating capacity of HSA-MG.

Free energy profiles of amino acid side chain analogs near water-vapor interface obtained via MD simulations.

Solvation of 13 neutral amino acid side chain analogs at water-vapor interface was studied by computing high precision free energy profiles of the molecules across the interface using molecular dynamics (MD) simulations. The SPC water model (Berendsen, H. J. C., Postma, J. P. M., van Gunsteren, W. F., Hermans, P. A. K. J., Dixon, R., Cornell, W., Fox, T., Chipot, C., Pohorille, A. In: Wilkinson, A., Weiner, P. and van Gunsteren, W. F. editors. Intermolecular Forces, 1981, 3, 331) and OPLS-AA (Jorgensen et al., J Am Chem Soc, 1996, 118, 11225) potential parameter sets were used. A rigorous approach for the computation of high precision free energy profiles at water-vapor interface using constraint force technique is implemented. Methodology of obtaining high precision potential of mean force (PMF) profiles free of simulation artifacts in MD simulations is outlined and discussed. The accuracy of the calculations is examined by comparing the hydration free energies of studied solutes obtained from PMF calculations and separately using Bennett acceptance ratio technique by decoupling solvent-solute interactions in the bulk. All molecules exhibit a free energy minimum at interface. No significant desolvation barrier is observed for any of the studied species. Adsorption energies for studied molecules at water-vapor interface are estimated and compared with experimental observations. We find that for modeled neutral compounds pronounced surface influence on solute solvation vanishes already at 6-7 A behind the water surface as the solvation free energy approaches the bulk value. The possibility of force field refinement using adsorption free energies is outlined.

Multidimensional stochastic approximation Monte Carlo.

Stochastic Approximation Monte Carlo (SAMC) has been established as a mathematically founded powerful flat-histogram Monte Carlo method, used to determine the density of states, g(E), of a model system. We show here how it can be generalized for the determination of multidimensional probability distributions (or equivalently densities of states) of macroscopic or mesoscopic variables defined on the space of microstates of a statistical mechanical system. This establishes this method as a systematic way for coarse graining a model system, or, in other words, for performing a renormalization group step on a model. We discuss the formulation of the Kadanoff block spin transformation and the coarse-graining procedure for polymer models in this language. We also apply it to a standard case in the literature of two-dimensional densities of states, where two competing energetic effects are present g(E_{1},E_{2}). We show when and why care has to be exercised when obtaining the microcanonical density of states g(E_{1}+E_{2}) from g(E_{1},E_{2}).