Alexandre B. Almeida

Validation of Capillarity Theory at the Nanometer Scale by Atomistic Computer Simulations of Water Droplets and Bridges in Contact with Hydrophobic and Hydrophilic Surfaces

Capillarity is the study of interfaces between two immiscible liquids or between a liquid and a vapor. The theory of capillarity was created in the early 1800s, and it is applicable to mesoscopic and macroscopic (>1 μm) systems. In general, macroscopic theories are expected to fail at the <10 nm scales where molecular details may become relevant. In this work, we show that, surprisingly, capillarity theory (CT) provides satisfactory predictions at 2–10 nm scales. Specifically, we perform atomistic molecular dynamics (MD) simulations of water droplets and capillary bridges of different symmetry in contact with various surfaces. The underlying structure of the surfaces corresponds to hydroxilated (crystalline) silica which is modified to cover a wide range of hydrophobicity/hydrophilicity. In agreement with CT, it is found that water contact angle is independent of the droplet/bridge geometry and depends only on the hydrophobicity/hydrophilicity of the surface employed. In addition, CT provides the correct ...

Chemokine Receptors Expression on T Cells and Response to HAART Among Chronic HIV-1-Infected Subjects

Chemokines receptors are used by HIV-1 for entry into CD4(+) T cells. The beta-chemokines are capable of inhibiting HIV replication. This study determined the CCR5 and CXCR4 expression on T cells in HIV-1-infected patients treated with HAART. The successfully treated group (plasma viral load <400 copies/mL), when compared with the failure group (plasma viral load >400 copies/mL), had higher median CD4(+) T cells count (583 and 245 cells/mm(3); respectively, p< 0.0001). The failure patients had higher numbers and intensity of CCR5 and CXCR4-expressing T cells. Successfully treated patients were able to normalize the co-receptors expression-over on T cells. The viremic group showed higher CCR5 expression on CD4(+) T cells and lower number of cells; CCR5 expression was normalized in the aviremic group; the naïve group showed lower CCR5 expression and higher numbers of CD4 T cells; all groups showed normal CXCR4 expression compared to healthy controls. These findings may have clinical implications, since down-regulation of these co-receptors could be an adjuvant strategy for anti-HIV treatment.