Search results for "molecules"
showing 10 items of 1147 documents
HEAT: High accuracy extrapolated ab initio thermochemistry.
2004
A theoretical model chemistry designed to achieve high accuracy for enthalpies of formation of atoms and small molecules is described. This approach is entirely independent of experimental data and contains no empirical scaling factors, and includes a treatment of electron correlation up to the full coupled-cluster singles, doubles, triples and quadruples approach. Energies are further augmented by anharmonic zero-point vibrational energies, a scalar relativistic correction, first-order spin-orbit coupling, and the diagonal Born-Oppenheimer correction. The accuracy of the approach is assessed by several means. Enthalpies of formation (at 0 K) calculated for a test suite of 31 atoms and mole…
Carbon nanotubes as electrodes for dielectrophoresis of DNA
2006
Dielectrophoresis can potentially be used as an efficient trapping tool in the fabrication of molecular devices. For nanoscale objects, however, the Brownian motion poses a challenge. We show that the use of carbon nanotube electrodes makes it possible to apply relatively low trapping voltages and still achieve high enough field gradients for trapping nanoscale objects, e.g., single molecules. We compare the efficiency and other characteristics of dielectrophoresis between carbon nanotube electrodes and lithographically fabricated metallic electrodes, in the case of trapping nanoscale DNA molecules. The results are analyzed using finite element method simulations and reveal information abou…
Monte Carlo simulation of DNA electrophoresis
1989
This paper describes an attempt to study the electrophoresis mobility of a DNA molecule in a gel by means of a Monte Carlo simulation. We find that the electrophoresis mobility mu can be well described by the empirical equation mu v kappa 1/N + kappa 2E2 with N being the number of monomers of the model chain and E being the applied field. For small E the data can merge into the linear response result mu = kappa 1/N. The paper also discusses necessary extensions of the present approach.
Electrophoresis of colloidal dispersions in the low-salt regime
2007
We study the electrophoretic mobility of spherical charged colloids in a low-salt suspension as a function of the colloidal concentration. Using an effective particle charge and a reduced screening parameter, we map the data for systems with different particle charges and sizes, including numerical simulation data with full electrostatics and hydrodynamics and experimental data for latex dispersions, on a single master curve. We observe two different volume fraction-dependent regimes for the electrophoretic mobility that can be explained in terms of the static properties of the ionic double layer.
Endothelin-1 modulates the expression of adhesion molecules on fibroblast-like synovial cells (FLS)
1996
Endothelin-1 is known to possess various biological properties. In the present study we have investigated the effects of Endothelin-1 (Et-1) on the expression of adhesion molecules ICAM-1, VCAM-1 and CD-44 by fibroblast-like synoviocytes. Cultured fibroblast-like synoviocytes were treated with Et-1 in the absence or presence of C1306, a specific endothelin-A-receptor antagonist. Cell surface expression of ICAM-1, VCAM-1 and CD-44 was determined by immunofluorescence studies, Cyto-ELISA and FACS-analysis. ICAM-1, VCAM-1 and CD-44 were constitutively expressed on cultured FLS. After incubation with Et-1 the expression of ICAM-1, VCAM-1 and CD-44 increased. The level of expression of adhesion …
Licofelone, a novel 5-LOX/COX-inhibitor, attenuates leukocyte rolling and adhesion on endothelium under flow
2005
The main mechanism of action of non-steroidal anti-inflammatory drugs (NSAIDs) is the inhibition of cycloxygenases COX-1 and COX-2. During recent years, combined 5-LOX/COX-inhibition, interfering with the biosynthesis of both prostaglandins and leukotrienes (LTs), has emerged as a possibility to avoid side effects related to COX-inhibition. The aim of the present study was to investigate if there is a contribution of mechanisms other than the reduction of inflammatory prostaglandins and leukotrienes to the anti-inflammatory effect of the LOX/COX inhibitor licofelone. In a flow chamber assay, licofelone (10-30 microM) dose-dependently decreased both the rolling and adhesion of leukocytes on …
Abacavir and didanosine induce the interaction between human leukocytes and endothelial cells through Mac-1 upregulation
2010
Objective: Abacavir and didanosine are nucleoside reverse transcriptase inhibitors (NRTI) widely used in therapy for HIV-infection but which have been linked to cardiovascular complications. The objective of this study was to analyze the effects of clinically relevant doses of abacavir and didanosine on human leukocyte―endothelium interactions and to compare them with those of other NRTIs. Design and methods: The interactions between human leukocytes ― specifically peripheral blood polymorphonuclear (PMN) or mononuclear (PBMC) cells ― and human umbilical vein endothelial cells were evaluated in a flow chamber system that reproduces conditions in vivo. The expression of adhesion molecules wa…
Differential regulation of endothelial cell adhesion molecule expression by nitric oxide donors and antioxidants.
1998
Although nitric oxide (NO) and antioxidants inhibit adhesion molecule expression, their inhibitory effects on nuclear factor kappaB (NF-kappaB) activation may differ. The NO donors, but not 8-bromo-cGMP, decreased tumor necrosis factor alpha (TNF-alpha)-induced VCAM-1, ICAM-1, and E-selectin expression by 11-70%. In contrast, NAC completely abolished VCAM-1 and E-selectin expression and decreased ICAM-1 expression by 56%. Gel shift assays demonstrate that NF-kappaB activation was inhibited by both NO and antioxidants. The activation of NF-kappaB involves the phosphorylation and degradation of its cytoplasmic inhibitor IkappaB-alpha by 26S proteasomes. The 26S proteasome inhibitor MG132 prev…
E-selectin modulates the malignant properties of T84 colon carcinoma cells.
2002
The extravasation of metastatic cells is regulated by molecular events involving the initial adhesion of tumor cells to the endothelium and subsequently the migration of cells in the host connective tissue. E-selectin on endothelial cells and sialyl Lewis X carbohydrate component on tumor cells are mainly involved in the adhesion of colon carcinoma cells to the endothelium of target organ. Interaction of T84 colon cancer cells to purified E-selectin in vitro caused an increase in the tyrosine phosphorylation of a number of proteins as well as the modulation of cellular properties correlated to the metastatic phenotype. Specifically, E-selectin-stimulated actin reorganization, increased coll…
Antibodies to proteinase 3 increase adhesion of neutrophils to human endothelial cells
1993
SUMMARY The detection of anti-neutrophil cytoplasmic antibodies (ANCA), especially those with specificity for proteinase 3, is important in the diagnosis and in monitoring disease activity of Wegener's granulomatosis and related vasculitides. An ubiquitous feature of all ANCA-associated acute vascular injury is lytic necrosis. Adhesion of neutrophils to endothelium is a fundamental early step of the inflammatory response. Recently we were able to show that ANCA recognize their target antigen (proteinase 3) translocated into the membrane of human endothelial cells. The aim of this study was to investigate the effect of ANCA on the adhesion of neutrophils to human endothelial cells. Incubatio…