We realize the coupling of carbon
nanotubes as a one-dimensional
model system to near-field cavities for plasmon-enhanced Raman scattering.
Directed dielectrophoretic assembly places single-walled carbon nanotubes
precisely into the gap of gold nanodimers. The plasmonic cavities
enhance the Raman signal of a small nanotube bundle by a factor of
103. The enhanced signal arises exclusively from tube segments
within the cavity as we confirm by spatially resolved Raman measurements.
Through the energy and polarization of the excitation we address the
extrinsic plasmonic and the intrinsic nanotube optical response independently.
For all incident light polarizations, the nanotube Raman features
arise from fully symmetric vibrations only. We find strong evidence
that the signal enhancement depends on the orientation of the carbon
nanotube relative to the cavity axis.
Resolution of acute inflammation is an active process coordinated by proresolving lipid mediators (SPMs) such as lipoxins (LXs) and resolvins (Rvs), which are formed by the concerted action of 2 lipoxygenases (LOs). Because the exact molecular mechanisms of SPM biosynthesis are not completely understood, we aimed to investigate LX and D-type Rv formation in human leukocytes and HEK293T cells overexpressing leukotriene (LT) pathway enzymes. Activity assays in precursor (15-hydroxyeicosatetraenoic acids, 17-HDoHE)-treated granulocytes [polymorphonuclear leukocytes (PMNLs)] showed a strict dependence of LXA 4 /RvD 1 biosynthesis on cell integrity, and incubation with recombinant human 5-LO did not lead to LX or Rv formation. Pharmacologic inhibition of 5-LO activating protein (FLAP) by MK-886 inhibited LXA 4 /RvD 1 biosynthesis in precursor-treated PMNLs (drug concentration causing 50% inhibition ∼0.3/0.2 mM), as did knockdown of the enzyme in MM6 cells, and precursor-treated HEK293T overexpressing 5-LO produced high amounts of LXA 4 only in the presence of FLAP. In addition, inhibition of cytosolic phospholipase A 2a (cPLA 2a ) interfered with LXA 4 / RvD 1 formation from exogenous precursors in PMNLs. Furthermore, inhibition of the LT synthases LTA 4 hydrolase and LTC 4 synthase in PMNL/platelet coincubations augmented LXA 4 levels. These findings show that several enzymes known to be involved in the biosynthesis of proinflammatory LTs, such as FLAP and cPLA 2a , also contribute to LX and Rv formation.-
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