ABSTRACT Four computer codes based on the Discrete Dipole Approximation are compared against each... more ABSTRACT Four computer codes based on the Discrete Dipole Approximation are compared against each other and against exact solutions for five different scattering geometries. The interest is in the accuracy of intensity and linear polarization values the codes produce and in the computational time needed.
ABSTRACT We performed extensive simulations of light scattering by granulated coated sphere model... more ABSTRACT We performed extensive simulations of light scattering by granulated coated sphere model using the discrete dipole approximation and varying model parameters in the ranges of sizes and refractive indices of granulated blood cells. We compared these results with predictions of Maxwell-Garnett effective medium theory and independent scattering approximation. Extinction efficiency and Mueller matrix element S11, averaged over azimuthal angles, are accurately described by one of the approximations, except for the intermediate range of polar angles. We discuss dependence of S11 on granule diameter for any fixed angle, showing a distinct maximum, with respect to the solution of the inverse light scattering problem.
Magnesium sulfate (MgSO4) is widely used in medicine but molecular mechanisms of its protection t... more Magnesium sulfate (MgSO4) is widely used in medicine but molecular mechanisms of its protection through influence on erythrocytes are not fully understood and are considerably controversial. Using scanning flow cytometry, in this work for the first time we observed experimentally (both in situ and in vitro) a significant increase of HCO3(-)/Cl(-) transmembrane exchange rate of human erythrocytes in the presence of MgSO4 in blood. For a quantitative analysis of the obtained experimental data, we introduced and verified a molecular kinetic model, which describes activation of major anion exchanger Band 3 (or AE1) by its complexation with free intracellular Mg(2+) (taking into account Mg(2+) membrane transport and intracellular buffering). Fitting the model to our in vitro experimental data, we observed a good correspondence between theoretical and experimental kinetic curves that allowed us to evaluate the model parameters and to estimate for the first time the association constant of Mg(2+) with Band 3 as KB~0.07mM, which is in agreement with known values of the apparent Mg(2+) dissociation constant (from 0.01 to 0.1mM) that reflects experiments on enrichment of Mg(2+) at the inner erythrocyte membrane (Gunther, 2007). Results of this work partly clarify the molecular mechanisms of MgSO4 action in human erythrocytes. The method developed allows one to estimate quantitatively a perspective of MgSO4 treatment for a patient. It should be particularly helpful in prenatal medicine for early detection of pathologies associated with the risk of fetal hypoxia.
ABSTRACT Four computer codes based on the Discrete Dipole Approximation are compared against each... more ABSTRACT Four computer codes based on the Discrete Dipole Approximation are compared against each other and against exact solutions for five different scattering geometries. The interest is in the accuracy of intensity and linear polarization values the codes produce and in the computational time needed.
ABSTRACT We performed extensive simulations of light scattering by granulated coated sphere model... more ABSTRACT We performed extensive simulations of light scattering by granulated coated sphere model using the discrete dipole approximation and varying model parameters in the ranges of sizes and refractive indices of granulated blood cells. We compared these results with predictions of Maxwell-Garnett effective medium theory and independent scattering approximation. Extinction efficiency and Mueller matrix element S11, averaged over azimuthal angles, are accurately described by one of the approximations, except for the intermediate range of polar angles. We discuss dependence of S11 on granule diameter for any fixed angle, showing a distinct maximum, with respect to the solution of the inverse light scattering problem.
Magnesium sulfate (MgSO4) is widely used in medicine but molecular mechanisms of its protection t... more Magnesium sulfate (MgSO4) is widely used in medicine but molecular mechanisms of its protection through influence on erythrocytes are not fully understood and are considerably controversial. Using scanning flow cytometry, in this work for the first time we observed experimentally (both in situ and in vitro) a significant increase of HCO3(-)/Cl(-) transmembrane exchange rate of human erythrocytes in the presence of MgSO4 in blood. For a quantitative analysis of the obtained experimental data, we introduced and verified a molecular kinetic model, which describes activation of major anion exchanger Band 3 (or AE1) by its complexation with free intracellular Mg(2+) (taking into account Mg(2+) membrane transport and intracellular buffering). Fitting the model to our in vitro experimental data, we observed a good correspondence between theoretical and experimental kinetic curves that allowed us to evaluate the model parameters and to estimate for the first time the association constant of Mg(2+) with Band 3 as KB~0.07mM, which is in agreement with known values of the apparent Mg(2+) dissociation constant (from 0.01 to 0.1mM) that reflects experiments on enrichment of Mg(2+) at the inner erythrocyte membrane (Gunther, 2007). Results of this work partly clarify the molecular mechanisms of MgSO4 action in human erythrocytes. The method developed allows one to estimate quantitatively a perspective of MgSO4 treatment for a patient. It should be particularly helpful in prenatal medicine for early detection of pathologies associated with the risk of fetal hypoxia.
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Papers by Maxim Yurkin