Signaling through Raf-1 in the neovasculature and target validation by nanoparticles. (1/2196)

A recent study demonstrated that vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) activate Raf-1 kinase in an experimental neovasculature system. The study showed that bFGF and VEGF activate p21-activated protein kinase-1 (PAK-1) and Src kinase, respectively. PAK-1 and Src kinases phosphorylate specific serine and tyrosine residues within the activation loop of Raf-1 kinase. Their findings further suggest that phosphorylation at these sites protects endothelial cells from apoptosis induced by both intrinsic and extrinsic factors. The tumor neovasculature provides specific molecular markers or "zip codes". This group of investigators has previously shown that nanosphere-aided targeting of the neovasculature with mutant Raf-1 causes regression of the tumor vasculature. Thus, nanoparticles coated with "zip code"-specific homing biomolecules may be useful for delivering anti-angiogenic molecules that can induce tumor regression.  (+info)

Reducing activity of colloidal platinum nanoparticles for hydrogen peroxide, 2,2-diphenyl-1-picrylhydrazyl radical and 2,6-dichlorophenol indophenol. (2/2196)

Shimizu and Tsuji established a method of preparing colloidal platinum nanoparticles, whose average size is 2 nm, by ethanol reduction of H(2)PtCl(6) in the absence of protective agents for the particles. Platinum nanoparticles have negative surface potential and are stably suspended from an electric repulsion between them. The platinum nanoparticles reduced hydrogen peroxide and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) below 0.1 ppm. It is necessary to use higher concentration of platinum nanoparticles for the reduction of 2,6-dichlorophenol indophenol (DCIP) than that of hydrogen peroxide and 2,2-diphenyl-1-picrylhydrazyl radical, because reoxidation of DCIPH(2) (reduced) by oxygen was not negligible under our experimental conditions. These results indicate that electrons on platinum nanoparticles produced by the method of Shimizu and Tsuji can reduce hydrogen peroxide, DPPH radical or DCIP transferring electrons.  (+info)

Homogeneous detection of unamplified genomic DNA sequences based on colorimetric scatter of gold nanoparticle probes. (3/2196)

Nucleic acid diagnostics is dominated by fluorescence-based assays that use complex and expensive enzyme-based target or signal-amplification procedures. Many clinical diagnostic applications will require simpler, inexpensive assays that can be done in a screening mode. We have developed a 'spot-and-read' colorimetric detection method for identifying nucleic acid sequences based on the distance-dependent optical properties of gold nanoparticles. In this assay, nucleic acid targets are recognized by DNA-modified gold probes, which undergo a color change that is visually detectable when the solutions are spotted onto an illuminated glass waveguide. This scatter-based method enables detection of zeptomole quantities of nucleic acid targets without target or signal amplification when coupled to an improved hybridization method that facilitates probe-target binding in a homogeneous format. In comparison to a previously reported absorbance-based method, this method increases detection sensitivity by over four orders of magnitude. We have applied this method to the rapid detection of mecA in methicillin-resistant Staphylococcus aureus genomic DNA samples.  (+info)

Oligonucleotide-displaced organic monolayer-protected silver nanoparticles and enhanced luminescence of their salted aggregates. (4/2196)

N-(2-mercaptopropionyl)glycine (tiopronin) monolayer-protected silver particles were partially displaced by single-stranded oligonucleotides through ligand exchanges. The oligonucleotide-displaced particles could be hybridized with complementary fluorophore-labeled oligonucleotides. Both the oligonucleotide-displaced and hybridized particles could be aggregated by electrostatic interactions with salt in buffer solution, and the aggregates displayed enhanced luminescence from fluorophores. This result suggests the possible application of surface-enhanced fluorescence from metallic nanoparticle aggregation for DNA detection.  (+info)

Nanostructure of cationic lipid-oligonucleotide complexes. (5/2196)

Complexes (lipoplexes) between cationic liposomes and single-strand oligodeoxynucleotides (ODN) are potential delivery systems for antisense therapy. The nanometer-scale morphology of these assemblies is relevant to their transfection efficiency. In this work the monocationic lipid dioleoyloxytrimethylammoniumpropane, the neutral "helper" lipid cholesterol, and an 18-mer anti-bcl2 ODN were combined at different ratios. The lipoplexes formed were characterized for the quantity of ODN bound, for the degree of lipid mixing, and for their size. The nanostructure of the system was examined by cryogenic-temperature transmission electron microscopy, augmented by small-angle x-ray scattering. Addition of ODN to cationic liposomes induced both liposome aggregation and the formation of a novel condensed lamellar phase. This phase is proposed to be stabilized by anionic single-strand ODN molecules intercalated between cationic bilayers. The proportion of cholesterol present apparently did not affect the nature of lipoplex microstructure, but changed the interlamellar spacing.  (+info)

A nanosensor for transmembrane capture and identification of single nucleic Acid molecules. (6/2196)

We have engineered a nanosensor for sequence-specific detection of single nucleic acid molecules across a lipid bilayer. The sensor is composed of a protein channel nanopore (alpha-hemolysin) housing a DNA probe with an avidin anchor at the 5' end and a nucleotide sequence designed to noncovalently bind a specific single-stranded oligonucleotide at the 3' end. The 3' end of the DNA probe is driven to the opposite side of the pore by an applied electric potential, where it can specifically bind to oligonucleotides. Reversal of the applied potential withdraws the probe from the pore, dissociating it from a bound oligonucleotide. The time required for dissociation of the probe-oligonucleotide duplex under this force yields identifying characteristics of the oligonucleotide. We demonstrate transmembrane detection of individual oligonucleotides, discriminate between molecules differing by a single nucleotide, and investigate the relationship between dissociation time and hybridization energy of the probe and analyte molecules. The detection method presented in this article is a candidate for in vivo single-molecule detection and, through parallelization in a synthetic device, for genotyping and global transcription profiling from small samples.  (+info)

Rapid double 8-nm steps by a kinesin mutant. (7/2196)

The mechanism by which conventional kinesin walks along microtubules is poorly understood, but may involve alternate binding to the microtubule and hydrolysis of ATP by the two heads. Here we report a single amino-acid change that affects stepping by the motor. Under low force or low ATP concentration, the motor moves by successive 8-nm steps in single-motor laser-trap assays, indicating that the mutation does not alter the basic mechanism of kinesin walking. Remarkably, under high force, the mutant motor takes successive 16-nm displacements that can be resolved into rapid double 8-nm steps with a short dwell between steps, followed by a longer dwell. The alternating short and long dwells under high force demonstrate that the motor stepping mechanism is inherently asymmetric, revealing an asymmetric phase in the kinesin walking cycle. Our findings support an asymmetric two-headed walking model for kinesin, with cooperative interactions between the two heads. The sensitivity of the 16-nm displacements to nucleotide and load raises the possibility that ADP release is a force-producing event of the kinesin cycle.  (+info)

Nanometer size diesel exhaust particles are selectively toxic to dopaminergic neurons: the role of microglia, phagocytosis, and NADPH oxidase. (8/2196)

The contributing role of environmental factors to the development of Parkinson's disease has become increasingly evident. We report that mesencephalic neuron-glia cultures treated with diesel exhaust particles (DEP; 0.22 microM) (5-50 microg/ml) resulted in a dose-dependent decrease in dopaminergic (DA) neurons, as determined by DA-uptake assay and tyrosine-hydroxylase immunocytochemistry (ICC). The selective toxicity of DEP for DA neurons was demonstrated by the lack of DEP effect on both GABA uptake and Neu-N immunoreactive cell number. The critical role of microglia was demonstrated by the failure of neuron-enriched cultures to exhibit DEP-induced DA neurotoxicity, where DEP-induced DA neuron death was reinstated with the addition of microglia to neuron-enriched cultures. OX-42 ICC staining of DEP treated neuron-glia cultures revealed changes in microglia morphology indicative of activation. Intracellular reactive oxygen species and superoxide were produced from enriched-microglia cultures in response to DEP. Neuron-glia cultures from NADPH oxidase deficient (PHOX-/-) mice were insensitive to DEP neurotoxicity when compared with control mice (PHOX+/+). Cytochalasin D inhibited DEP-induced superoxide production in enriched-microglia cultures, implying that DEP must be phagocytized by microglia to produce superoxide. Together, these in vitro data indicate that DEP selectively damages DA neurons through the phagocytic activation of microglial NADPH oxidase and consequent oxidative insult.  (+info)