The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Mario Suwalsky - One of the best experts on this subject based on the ideXlab platform.
-
an in vitro study on the antioxidant capacity of usnic acid on human erythrocytes and Molecular Models of its membrane
Biochimica et Biophysica Acta, 2015Co-Authors: Mario Suwalsky, Fernando Villena, Malgorzata Jemiolarzeminska, C Astudillo, Maria Jose Gallardo, Juan Pablo Staforelli, Kazimierz StrzalkaAbstract:Usnic acid (UA) has been associated with chronic diseases through its antioxidant action. Its main target is the cell membrane; however, its effect on that of human erythrocytes has been scarcely investigated. To gain insight into the Molecular mechanisms of the interaction between UA and cell membranes human erythrocytes and Molecular Models of its membrane have been utilized. Dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were chosen as representative of phospholipid classes located in the outer and inner monolayers of the erythrocyte membrane, respectively. Results by X-ray diffraction showed that UA produced structural perturbations on DMPC and DMPE bilayers. DSC studies have indicated that thermotropic behavior of DMPE was most strongly distorted by UA than DMPC, whereas the latter is mainly affected on the pretransition. Scanning electron (SEM) and defocusing microscopy (DM) showed that UA induced alterations to erythrocytes from the normal discoid shape to echinocytes. These results imply that UA molecules were located in the outer monolayer of the erythrocyte membrane. Results of its antioxidant properties showed that UA neutralized the oxidative capacity of HClO on DMPC and DMPE bilayers; SEM, DM and hemolysis assays demonstrated the protective effect of UA against the deleterious oxidant effects of HClO upon human erythrocytes.
-
structural effects of the solanum steroids solasodine diosgenin and solanine on human erythrocytes and Molecular Models of eukaryotic membranes
Biochimica et Biophysica Acta, 2014Co-Authors: Marcela Manriquemoreno, Fernando Villena, Julian Londonolondono, Malgorzata Jemiolarzeminska, Kazimierz Strzalka, Marcia Avello, Mario SuwalskyAbstract:Abstract This report presents evidence that the following Solanum steroids: solasodine, diosgenin and solanine interact with human erythrocytes and Molecular Models of their membranes as follows: a) X-ray diffraction studies showed that the compounds at low molar ratios (0.1–10.0 mol%) induced increasing structural perturbation to dimyristoylphosphatidylcholine bilayers and to a considerable lower extent to those of dimyristoylphosphatidylethanolamine; b) differential scanning calorimetry data showed that the compounds were able to alter the cooperativity of dimyristoylphosphatidylcholine, dimyristoylphosphatidylethanolamine and dimyristoylphosphatidylserine phase transitions in a concentration-dependent manner; c) in the presence of steroids, the fluorescence of Merocyanine 540 incorporated to the membranes decreased suggesting a fluidization of the lipid system; d) scanning electron microscopy observations showed that all steroids altered the normal shape of human erythrocytes inducing mainly echinocytosis, characterized by the formation of blebs in their surfaces, an indication that their molecules are located into the outer monolayer of the erythrocyte membrane.
-
effects of an antimalarial quinazoline derivative on human erythrocytes and on cell membrane Molecular Models
Biochimica et Biophysica Acta, 2012Co-Authors: Yareli Rojasaguirre, Francisco Hernandezluis, Cesar Mendozamartinez, Carlos P Sotomayor, Luis F Aguilar, Fernando Villena, Ivan Castillo, David J Hernandez, Mario SuwalskyAbstract:Plasmodium, the parasite which causes malaria in humans multiplies in the liver and then infects circulating erythrocytes. Thus, the role of the erythrocyte cell membrane in antimalarial drug activity and resistance has key importance. The effects of the antiplasmodial N(6)-(4-methoxybenzyl)quinazoline-2,4,6-triamine (M4), and its inclusion complex (M4/HPβCD) with 2-hydroxypropyl-β-cyclodextrin (HPβCD) on human erythrocytes and on cell membrane Molecular Models are herein reported. This work evidences that M4/HPβCD interacts with red cells as follows: a) in scanning electron microscopy (SEM) studies on human erythrocytes induced shape changes at a 10μM concentration; b) in isolated unsealed human erythrocyte membranes (IUM) a concentration as low as 1μM induced sharp DPH fluorescence anisotropy decrease whereas increasing concentrations produced a monotonically decrease of DPH fluorescence lifetime at 37°C; c) X-ray diffraction studies showed that 200μM induced a complete structural perturbation of dimyristoylphosphatidylcholine (DMPC) bilayers whereas no significant effects were detected in dimyristoylphosphatidylethanolamine (DMPE) bilayers, classes of lipids present in the outer and inner monolayers of the human erythrocyte membrane, respectively; d) fluorescence spectroscopy data showed that increasing concentrations of the complex interacted with the deep hydrophobic core of DMPC large unilamellar vesicles (LUV) at 18°C. All these experiments are consistent with the insertion of M4/HPβCD in the outer monolayer of the human erythrocyte membrane; thus, it can be considered a promising and novel antimalarial agent.
-
effects of phenylpropanolamine ppa on in vitro human erythrocyte membranes and Molecular Models
Biochemical and Biophysical Research Communications, 2011Co-Authors: Mario Suwalsky, Carlos P Sotomayor, Luis F Aguilar, Fernando Villena, Pablo Zambrano, Sigrid Mennickent, Silvia BologninAbstract:Research highlights: {yields} PPA is a common ingredient in cough-cold medication and appetite suppressants. {yields} Reports on its effects on human erythrocytes are very scarce. {yields} We found that PPA induced in vitro morphological changes to human erythrocytes. {yields} PPA interacted with isolated unsealed human erythrocyte membranes. {yields} PPA interacted with class of lipid present in the erythrocyte membrane outer monolayer. -- Abstract: Norephedrine, also called phenylpropanolamine (PPA), is a synthetic form of the ephedrine alkaloid. After reports of the occurrence of intracranial hemorrhage and other adverse effects, including several deaths, PPA is no longer sold in USA and Canada. Despite the extensive information about PPA toxicity, reports on its effects on cell membranes are scarce. With the aim to better understand the Molecular mechanisms of the interaction of PPA with cell membranes, ranges of concentrations were incubated with intact human erythrocytes, isolated unsealed human erythrocyte membranes (IUM), and Molecular Models of cell membranes. The latter consisted in bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), phospholipid classes present in the outer and inner monolayers of most plasmatic cell membranes, respectively. The capacity of PPA to perturb the bilayer structures of DMPC and DMPE was assessed by X-ray diffraction, DMPCmore » large unilamellar vesicles (LUV) and IUM were studied by fluorescence spectroscopy, and intact human erythrocytes were observed by scanning electron microscopy (SEM). This study presents evidence that PPA affects human red cell membranes as follows: (a) in SEM studies on human erythrocytes it was observed that 0.5 mM PPA induced shape changes; (b) in IUM PPA induced a sharp decrease in the fluorescence anisotropy in the lipid bilayer acyl chains in a concentration range lower than 100 {mu}M; (c) X-ray diffraction studies showed that PPA in the 0.1-0.5 mM range induced increasing structural perturbation to DMPC, but no effects on DMPE multibilayers were detected.« less
Fernando Villena - One of the best experts on this subject based on the ideXlab platform.
-
an in vitro study on the antioxidant capacity of usnic acid on human erythrocytes and Molecular Models of its membrane
Biochimica et Biophysica Acta, 2015Co-Authors: Mario Suwalsky, Fernando Villena, Malgorzata Jemiolarzeminska, C Astudillo, Maria Jose Gallardo, Juan Pablo Staforelli, Kazimierz StrzalkaAbstract:Usnic acid (UA) has been associated with chronic diseases through its antioxidant action. Its main target is the cell membrane; however, its effect on that of human erythrocytes has been scarcely investigated. To gain insight into the Molecular mechanisms of the interaction between UA and cell membranes human erythrocytes and Molecular Models of its membrane have been utilized. Dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were chosen as representative of phospholipid classes located in the outer and inner monolayers of the erythrocyte membrane, respectively. Results by X-ray diffraction showed that UA produced structural perturbations on DMPC and DMPE bilayers. DSC studies have indicated that thermotropic behavior of DMPE was most strongly distorted by UA than DMPC, whereas the latter is mainly affected on the pretransition. Scanning electron (SEM) and defocusing microscopy (DM) showed that UA induced alterations to erythrocytes from the normal discoid shape to echinocytes. These results imply that UA molecules were located in the outer monolayer of the erythrocyte membrane. Results of its antioxidant properties showed that UA neutralized the oxidative capacity of HClO on DMPC and DMPE bilayers; SEM, DM and hemolysis assays demonstrated the protective effect of UA against the deleterious oxidant effects of HClO upon human erythrocytes.
-
structural effects of the solanum steroids solasodine diosgenin and solanine on human erythrocytes and Molecular Models of eukaryotic membranes
Biochimica et Biophysica Acta, 2014Co-Authors: Marcela Manriquemoreno, Fernando Villena, Julian Londonolondono, Malgorzata Jemiolarzeminska, Kazimierz Strzalka, Marcia Avello, Mario SuwalskyAbstract:Abstract This report presents evidence that the following Solanum steroids: solasodine, diosgenin and solanine interact with human erythrocytes and Molecular Models of their membranes as follows: a) X-ray diffraction studies showed that the compounds at low molar ratios (0.1–10.0 mol%) induced increasing structural perturbation to dimyristoylphosphatidylcholine bilayers and to a considerable lower extent to those of dimyristoylphosphatidylethanolamine; b) differential scanning calorimetry data showed that the compounds were able to alter the cooperativity of dimyristoylphosphatidylcholine, dimyristoylphosphatidylethanolamine and dimyristoylphosphatidylserine phase transitions in a concentration-dependent manner; c) in the presence of steroids, the fluorescence of Merocyanine 540 incorporated to the membranes decreased suggesting a fluidization of the lipid system; d) scanning electron microscopy observations showed that all steroids altered the normal shape of human erythrocytes inducing mainly echinocytosis, characterized by the formation of blebs in their surfaces, an indication that their molecules are located into the outer monolayer of the erythrocyte membrane.
-
effects of an antimalarial quinazoline derivative on human erythrocytes and on cell membrane Molecular Models
Biochimica et Biophysica Acta, 2012Co-Authors: Yareli Rojasaguirre, Francisco Hernandezluis, Cesar Mendozamartinez, Carlos P Sotomayor, Luis F Aguilar, Fernando Villena, Ivan Castillo, David J Hernandez, Mario SuwalskyAbstract:Plasmodium, the parasite which causes malaria in humans multiplies in the liver and then infects circulating erythrocytes. Thus, the role of the erythrocyte cell membrane in antimalarial drug activity and resistance has key importance. The effects of the antiplasmodial N(6)-(4-methoxybenzyl)quinazoline-2,4,6-triamine (M4), and its inclusion complex (M4/HPβCD) with 2-hydroxypropyl-β-cyclodextrin (HPβCD) on human erythrocytes and on cell membrane Molecular Models are herein reported. This work evidences that M4/HPβCD interacts with red cells as follows: a) in scanning electron microscopy (SEM) studies on human erythrocytes induced shape changes at a 10μM concentration; b) in isolated unsealed human erythrocyte membranes (IUM) a concentration as low as 1μM induced sharp DPH fluorescence anisotropy decrease whereas increasing concentrations produced a monotonically decrease of DPH fluorescence lifetime at 37°C; c) X-ray diffraction studies showed that 200μM induced a complete structural perturbation of dimyristoylphosphatidylcholine (DMPC) bilayers whereas no significant effects were detected in dimyristoylphosphatidylethanolamine (DMPE) bilayers, classes of lipids present in the outer and inner monolayers of the human erythrocyte membrane, respectively; d) fluorescence spectroscopy data showed that increasing concentrations of the complex interacted with the deep hydrophobic core of DMPC large unilamellar vesicles (LUV) at 18°C. All these experiments are consistent with the insertion of M4/HPβCD in the outer monolayer of the human erythrocyte membrane; thus, it can be considered a promising and novel antimalarial agent.
-
effects of phenylpropanolamine ppa on in vitro human erythrocyte membranes and Molecular Models
Biochemical and Biophysical Research Communications, 2011Co-Authors: Mario Suwalsky, Carlos P Sotomayor, Luis F Aguilar, Fernando Villena, Pablo Zambrano, Sigrid Mennickent, Silvia BologninAbstract:Research highlights: {yields} PPA is a common ingredient in cough-cold medication and appetite suppressants. {yields} Reports on its effects on human erythrocytes are very scarce. {yields} We found that PPA induced in vitro morphological changes to human erythrocytes. {yields} PPA interacted with isolated unsealed human erythrocyte membranes. {yields} PPA interacted with class of lipid present in the erythrocyte membrane outer monolayer. -- Abstract: Norephedrine, also called phenylpropanolamine (PPA), is a synthetic form of the ephedrine alkaloid. After reports of the occurrence of intracranial hemorrhage and other adverse effects, including several deaths, PPA is no longer sold in USA and Canada. Despite the extensive information about PPA toxicity, reports on its effects on cell membranes are scarce. With the aim to better understand the Molecular mechanisms of the interaction of PPA with cell membranes, ranges of concentrations were incubated with intact human erythrocytes, isolated unsealed human erythrocyte membranes (IUM), and Molecular Models of cell membranes. The latter consisted in bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), phospholipid classes present in the outer and inner monolayers of most plasmatic cell membranes, respectively. The capacity of PPA to perturb the bilayer structures of DMPC and DMPE was assessed by X-ray diffraction, DMPCmore » large unilamellar vesicles (LUV) and IUM were studied by fluorescence spectroscopy, and intact human erythrocytes were observed by scanning electron microscopy (SEM). This study presents evidence that PPA affects human red cell membranes as follows: (a) in SEM studies on human erythrocytes it was observed that 0.5 mM PPA induced shape changes; (b) in IUM PPA induced a sharp decrease in the fluorescence anisotropy in the lipid bilayer acyl chains in a concentration range lower than 100 {mu}M; (c) X-ray diffraction studies showed that PPA in the 0.1-0.5 mM range induced increasing structural perturbation to DMPC, but no effects on DMPE multibilayers were detected.« less
David A Kofke - One of the best experts on this subject based on the ideXlab platform.
-
cluster integrals and virial coefficients for realistic Molecular Models
Physical Review E, 2020Co-Authors: Richard J Wheatley, Andrew J Schultz, Navneeth Gokul, David A KofkeAbstract:We present a concise, general, and efficient procedure for calculating the cluster integrals that relate thermodynamic virial coefficients to Molecular interactions. The approach encompasses nonpairwise interMolecular potentials generated from quantum chemistry or other sources; a simple extension permits efficient evaluation of temperature and other derivatives of the virial coefficients. We demonstrate with a polarizable model of water. We argue that cluster-integral methods are a potent yet underutilized instrument for the development and application of first-principles Molecular Models and methods.
-
Virial Coefficients of Helium‑4 from Ab Initio-Based Molecular Models
2019Co-Authors: Andrew J. Schultz, David A KofkeAbstract:We examine the accuracy of virial coefficients Bn(T) for 4He for n = 2–7 and temperatures T from 20 to 1000 K while reporting new values from semiclassical and (for n = 5) path-integral Monte Carlo (PIMC) calculations. All coefficients are based on first-principles two- and three-body Molecular Models from the literature and have estimated stochastic and systematic uncertainty between 0.005 and 20%, depending on n and T (almost all of this due to estimated inaccuracy in the three-body model). The calculated Bn(T) are used to examine the virial equation of state (VEOS) against experimental data from the literature, from 223.15 to 500 K and pressures up to 38 MPa. First, the VEOS is used to calibrate the data, providing adjustments not exceeding the data’s estimated systematic uncertainty. Then, findings from the comparison include the following: (1) the VEOS based on the ab initio Bn(T) is fully consistent with the experimental data; (2) the series requires coefficients up to n = 5 in order to agree with experiment within all relevant uncertainties; (3) individual values Bk(T) can be regressed accurately from the experimental data if other coefficients Bn(T), n ≠ k, are given from the ab initio calculations; however, the uncertainty of these values is less than the coefficient magnitude only for k ≤ 5
-
evaluation of second and third dielectric virial coefficients for non polarisable Molecular Models
Molecular Physics, 2017Co-Authors: Shu Yang, Andrew J Schultz, David A KofkeAbstract:ABSTRACTThe dielectric constant, e, of a dilute vapour can be estimated from the dielectric virial equation of state (VEOS), but the long-ranged nature of the electrostatic interactions complicates the evaluation of coefficients of this series. We propose a formulation of the second and third dielectric coefficients of a general non-polarisable Molecular model that permits their reliable calculation using Mayer sampling Monte Carlo. We demonstrate for three Models: dipolar hard spheres, dipolar Lennard–Jones, and TIP4P water. The coefficients are used to compute e for each model as a function of density, which are compared to Molecular-simulation data. The form of the VEOS relating e to density depends on the dielectric constant e′ of the embedding medium. Three choices are examined: vacuum (e′ = 1), self-consistent (e′ = e) and tin foil (e′ = ∞). The vacuum-boundary form is found to be unreliable, losing accuracy at low density and yielding divergent results for e at moderate densities. In contrast, the ...
-
interpreting gas saturation vapor pressure measurements using virial coefficients derived from Molecular Models
Journal of Chemical & Engineering Data, 2014Co-Authors: Shu Yang, David A Kofke, Andrew J Schultz, Allan H HarveyAbstract:We calculate virial coefficients of gas mixtures to demonstrate their use for interpreting gas-saturation measurements of the vapor pressure of low-volatility compounds. We obtain coefficients from Molecular Models, via calculation of Mayer integrals that rigorously connect the Models and the coefficients. We examine He, CO2, N2, and SF6 as carrier gases, and n-C14H30 and n-C20H42 as prototype low-volatility compounds, considering both united-atom (UA) and explicit-hydrogen (EH) alkane Models for them. Both the pure virial coefficients of every species and the cross-coefficients of each gas with n-C20H42 are calculated up to third order; cross-coefficients of SF6 with n-C14H30 and all EH-based coefficients are given only to second order. Using these coefficients, we calculate corrections to the vapor pressure of n-C20H42 at 323.15 K for all four carrier gases. With the corrections, the derived vapor pressures in He, CO2, and N2 carrier gases are in excellent agreement, resolving most of the variation obse...
Kazimierz Strzalka - One of the best experts on this subject based on the ideXlab platform.
-
an in vitro study on the antioxidant capacity of usnic acid on human erythrocytes and Molecular Models of its membrane
Biochimica et Biophysica Acta, 2015Co-Authors: Mario Suwalsky, Fernando Villena, Malgorzata Jemiolarzeminska, C Astudillo, Maria Jose Gallardo, Juan Pablo Staforelli, Kazimierz StrzalkaAbstract:Usnic acid (UA) has been associated with chronic diseases through its antioxidant action. Its main target is the cell membrane; however, its effect on that of human erythrocytes has been scarcely investigated. To gain insight into the Molecular mechanisms of the interaction between UA and cell membranes human erythrocytes and Molecular Models of its membrane have been utilized. Dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were chosen as representative of phospholipid classes located in the outer and inner monolayers of the erythrocyte membrane, respectively. Results by X-ray diffraction showed that UA produced structural perturbations on DMPC and DMPE bilayers. DSC studies have indicated that thermotropic behavior of DMPE was most strongly distorted by UA than DMPC, whereas the latter is mainly affected on the pretransition. Scanning electron (SEM) and defocusing microscopy (DM) showed that UA induced alterations to erythrocytes from the normal discoid shape to echinocytes. These results imply that UA molecules were located in the outer monolayer of the erythrocyte membrane. Results of its antioxidant properties showed that UA neutralized the oxidative capacity of HClO on DMPC and DMPE bilayers; SEM, DM and hemolysis assays demonstrated the protective effect of UA against the deleterious oxidant effects of HClO upon human erythrocytes.
-
structural effects of the solanum steroids solasodine diosgenin and solanine on human erythrocytes and Molecular Models of eukaryotic membranes
Biochimica et Biophysica Acta, 2014Co-Authors: Marcela Manriquemoreno, Fernando Villena, Julian Londonolondono, Malgorzata Jemiolarzeminska, Kazimierz Strzalka, Marcia Avello, Mario SuwalskyAbstract:Abstract This report presents evidence that the following Solanum steroids: solasodine, diosgenin and solanine interact with human erythrocytes and Molecular Models of their membranes as follows: a) X-ray diffraction studies showed that the compounds at low molar ratios (0.1–10.0 mol%) induced increasing structural perturbation to dimyristoylphosphatidylcholine bilayers and to a considerable lower extent to those of dimyristoylphosphatidylethanolamine; b) differential scanning calorimetry data showed that the compounds were able to alter the cooperativity of dimyristoylphosphatidylcholine, dimyristoylphosphatidylethanolamine and dimyristoylphosphatidylserine phase transitions in a concentration-dependent manner; c) in the presence of steroids, the fluorescence of Merocyanine 540 incorporated to the membranes decreased suggesting a fluidization of the lipid system; d) scanning electron microscopy observations showed that all steroids altered the normal shape of human erythrocytes inducing mainly echinocytosis, characterized by the formation of blebs in their surfaces, an indication that their molecules are located into the outer monolayer of the erythrocyte membrane.
Silvia Bolognin - One of the best experts on this subject based on the ideXlab platform.
-
effects of phenylpropanolamine ppa on in vitro human erythrocyte membranes and Molecular Models
Biochemical and Biophysical Research Communications, 2011Co-Authors: Mario Suwalsky, Carlos P Sotomayor, Luis F Aguilar, Fernando Villena, Pablo Zambrano, Sigrid Mennickent, Silvia BologninAbstract:Research highlights: {yields} PPA is a common ingredient in cough-cold medication and appetite suppressants. {yields} Reports on its effects on human erythrocytes are very scarce. {yields} We found that PPA induced in vitro morphological changes to human erythrocytes. {yields} PPA interacted with isolated unsealed human erythrocyte membranes. {yields} PPA interacted with class of lipid present in the erythrocyte membrane outer monolayer. -- Abstract: Norephedrine, also called phenylpropanolamine (PPA), is a synthetic form of the ephedrine alkaloid. After reports of the occurrence of intracranial hemorrhage and other adverse effects, including several deaths, PPA is no longer sold in USA and Canada. Despite the extensive information about PPA toxicity, reports on its effects on cell membranes are scarce. With the aim to better understand the Molecular mechanisms of the interaction of PPA with cell membranes, ranges of concentrations were incubated with intact human erythrocytes, isolated unsealed human erythrocyte membranes (IUM), and Molecular Models of cell membranes. The latter consisted in bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), phospholipid classes present in the outer and inner monolayers of most plasmatic cell membranes, respectively. The capacity of PPA to perturb the bilayer structures of DMPC and DMPE was assessed by X-ray diffraction, DMPCmore » large unilamellar vesicles (LUV) and IUM were studied by fluorescence spectroscopy, and intact human erythrocytes were observed by scanning electron microscopy (SEM). This study presents evidence that PPA affects human red cell membranes as follows: (a) in SEM studies on human erythrocytes it was observed that 0.5 mM PPA induced shape changes; (b) in IUM PPA induced a sharp decrease in the fluorescence anisotropy in the lipid bilayer acyl chains in a concentration range lower than 100 {mu}M; (c) X-ray diffraction studies showed that PPA in the 0.1-0.5 mM range induced increasing structural perturbation to DMPC, but no effects on DMPE multibilayers were detected.« less
