Mesoscopic Simulations of Adsorption and Association of PEO-PPO-PEO Triblock Copolymers on a Hydrophobic Surface: From Mushroom Hemisphere to Rectangle Brush

The dissipative particle dynamics (DPD) method is used to investigate the adsorption behavior of PEO-PPO-PEO triblock copolymers at the liquid/solid interface. The effect of molecular architecture on the self-assembled monolayer adsorption of PEO-PPO-PEO triblock copolymers on hydrophobic surfaces is elucidated by the adsorption process, film properties, and adsorption morphologies. The adsorption thicknesses on hydrophobic surfaces and the diffusion coefficient as well as the aggregation number of Pluronic copolymers in aqueous solution observed in our simulations agree well with previous experimental and numerical observations. The radial distribution function revealed that the ability of self-assembly on hydrophobic surfaces is P123 > P84 > L64 > P105 > F127, which increased with the EO ratio of the Pluronic copolymers. Moreover, the shape parameter and the degree of anisotropy increase with increasing molecular weight and mole ratio of PO of the Pluronic copolymers. Depending on the conformation of different Pluronic copolymers, the morphology transition of three regimes on hydrophobic surfaces is present: mushroom or hemisphere, progressively semiellipsoid, and rectangle brush regimes induced by decreasing molecular weight and mole ratio of EO of Pluronic copolymers

Mesoscopic Simulations of Adsorption and Association of PEO-PPO-PEO Triblock Copolymers on a Hydrophobic Surface: From Mushroom Hemisphere to Rectangle Brush

The dissipative particle dynamics (DPD) method is used to investigate the adsorption behavior of PEO-PPO-PEO triblock copolymers at the liquid/solid interface. The effect of molecular architecture on the self-assembled monolayer adsorption of PEO-PPO-PEO triblock copolymers on hydrophobic surfaces is elucidated by the adsorption process, film properties, and adsorption morphologies. The adsorption thicknesses on hydrophobic surfaces and the diffusion coefficient as well as the aggregation number of Pluronic copolymers in aqueous solution observed in our simulations agree well with previous experimental and numerical observations. The radial distribution function revealed that the ability of self-assembly on hydrophobic surfaces is P123 > P84 > L64 > P105 > F127, which increased with the EO ratio of the Pluronic copolymers. Moreover, the shape parameter and the degree of anisotropy increase with increasing molecular weight and mole ratio of PO of the Pluronic copolymers. Depending on the conformation of different Pluronic copolymers, the morphology transition of three regimes on hydrophobic surfaces is present: mushroom or hemisphere, progressively semiellipsoid, and rectangle brush regimes induced by decreasing molecular weight and mole ratio of EO of Pluronic copolymers

Mesoscopic Simulations of Adsorption and Association of PEO-PPO-PEO Triblock Copolymers on a Hydrophobic Surface: From Mushroom Hemisphere to Rectangle Brush

The dissipative particle dynamics (DPD) method is used to investigate the adsorption behavior of PEO-PPO-PEO triblock copolymers at the liquid/solid interface. The effect of molecular architecture on the self-assembled monolayer adsorption of PEO-PPO-PEO triblock copolymers on hydrophobic surfaces is elucidated by the adsorption process, film properties, and adsorption morphologies. The adsorption thicknesses on hydrophobic surfaces and the diffusion coefficient as well as the aggregation number of Pluronic copolymers in aqueous solution observed in our simulations agree well with previous experimental and numerical observations. The radial distribution function revealed that the ability of self-assembly on hydrophobic surfaces is P123 > P84 > L64 > P105 > F127, which increased with the EO ratio of the Pluronic copolymers. Moreover, the shape parameter and the degree of anisotropy increase with increasing molecular weight and mole ratio of PO of the Pluronic copolymers. Depending on the conformation of different Pluronic copolymers, the morphology transition of three regimes on hydrophobic surfaces is present: mushroom or hemisphere, progressively semiellipsoid, and rectangle brush regimes induced by decreasing molecular weight and mole ratio of EO of Pluronic copolymers

Dissipative Particle Dynamics Study on the Aggregation Behavior of Asphaltenes under Shear Fields

In the present work, the effects of shear fields on the aggregation of asphaltene molecules in heptane were investigated by means of dissipative particle dynamics simulations. The geometries of asphaltene aggregates without shear fields were studied, and the simulation results provide an interpretation of the experimental results on the microscopic level. The effects of shear fields on asphaltene aggregates were also investigated by accessing the radial distribution functions, spatial orientation correlation functions, and the radii of gyrations. We show that the shear fields can destroy the conformational order of the aggregates by damaging the organized structure and isolating the asphaltenes. As the radius of gyration results show, the asphaltene molecules are elongated to be alike-polymers by shear fields. Moreover, the reason why the viscosity decreases under shear fields is that the shear fields lead to the increase of dimerization free energies

Tat-mediated suppression of miR-221/-222 is NF-κB-dependent.

<p>Pre-treatment of HUVECs with the IKK2/NF-κB inhibitor SC514 (10 µM) abrogated Tat-mediated down-regulation of miR-221/-222 expression. Total RNA was isolated, and the expression of miR-221/-222 was quantified by real-time RT-PCR. RNU6B (U6) was used as the control. All the data are presented as mean ± SD of three independent experiments. **p<0.01 vs control; ^##p<0.01 vs Tat-treated group.</p

Tat-mediated induction of ICAM-1 expression in HUVECs.

<p>(<b>A</b>) Flow cytometric analysis indicating Tat (14.4 nM)-mediated changes in ALCAM, ICAM & VCAM in HUVECs. (<b>B</b>) Exposure of HUVECs to Tat induced time-dependent induction of ICAM-1 mRNA expression by real-time RT-PCR. (<b>C</b>) Effect of Tat, mutant- or heated-Tat on the ICAM-1 mRNA expression by real-time RT-PCR. (<b>D</b>) Western blot analysis demonstrated time-dependent induction of ICAM-1 by Tat (14.4 nM) in HUVECs. (<b>E</b>) Exposure of HUVECs to varying concentrations of Tat induced monocyte adhesion. (<b>F</b>) Effect of Tat, mutant- or heated-Tat on the monocyte adhesion. (<b>G</b>) Neutralizing antibody of ICAM-1 abrogated monocyte adhesion induced by Tat. HUVECs were exposed to Tat for 12 h (14.4 nM) followed by cell adhesion assay. All the data are presented as mean ± SD of three independent experiments. *p<0.05; **p<0.01; ***p<0.001 vs control; ^###p<0.001 vs Tat-treated group.</p

Overexpression of miR-221 or miR-222 inhibits monocyte adhesion induced by Tat in HUVECs.

<p>Transfection of HUVECs with miR-221 or miR-222 precursor abrogated Tat-induced monocyte adhesion. HUVECs were transfected with miR-221 or miR-222 (50 nM) precursors for 24 h, then exposed to Tat (14.4 nM) for 12 h followed by monocyte adhesion assay. All the data are presented as mean ± SD of three independent experiments. **p<0.01 vs control; ^##p<0.01 vs tat-treated group.</p

Tat-mediated induction of ICAM-1 expression involves MAPK signaling pathways.

<p>(<b>A</b>) Western blot analysis demonstrated time-dependent activation of ERK, JNK and p38 by Tat in HUVECs. (<b>B</b>) Inhibition of the ERK, JNK and p38 MAPK pathways by MEK1/2 (U0126, 20 µM), JNK (SP600125, 20 µM) and p38 (SB203580, 20 µM) inhibitors resulted in amelioration of Tat-mediated induction of ICAM-1 expression. (<b>C</b>) Pharmacological inhibition of MAPK pathways by MEK1/2 (U0126, 20 µM), JNK (SP600125, 20 µM) and p38 (SB203580, 20 µM) resulted in amelioration of Tat-mediated induction of monocyte adhesion. All the data are presented as mean ± SD of three independent experiments. **p<0.01 vs control; ^##p<0.01 vs Tat-treated group.</p

Expression of ICAM-1 in HIV Tg and F344 control rats.

<p>(<b>A</b>) Expression in HIV Tg and F344 control rat in the aorta and heart by real time RT-PCR; (<b>B</b>) ICAM-1 protein expression in the aorta and heart by western blot analysis. Representative immunoblot of ICAM-1 was presented in the upper panel. Densitometric analysis of ICAM-1/β-actin. N = 3. *p<0.05 vs F344 control; (<b>C</b>) ICAM-1 immunofluorescence in the aorta and heart. ICAM-1 expression is indicated by red fluorescence, blue fluorescence is nuclei staining (DAPI), and arrows indicate increased ICAM-1 fluorescence. (<b>D</b>) miR-221/-222 mRNA expressions in HIV Tg vs. F344 control (WT) aortas. *p<0.05 compared to F344 controls.</p

Tat-induced expression of ICAM-1 in HUVECs involves miR-221/-222 suppression.

<p>(<b>A</b>) Effect of Tat on the miR-221/-222 by real-time RT-PCR in HUVECs after 6 h exposure to Tat. RNU6B (U6) was used as the control. (<b>B</b>) Functional overexpression of miR-221/-222 (50 nM) decreased ICAM-1 protein expression. HUVECs transfected with miR-221 or miR-222 precursor or a precursor control for 24 h were exposed to Tat (14.4 nM) for 12 h followed by western blot analysis for ICAM-1. All the data are presented as mean ± SD of three independent experiments. **p<0.01 vs control; ^#p<0.05, ^##p<0.01 vs Tat-treated group.</p