Charge-Transfer Effects in Ligand Exchange Reactions of Au25 Monolayer-Protected Clusters.

Reported here are second-order rate constants of associative ligand exchanges of Au25L18 nanoparticles (L = phenylethanethiolate) of various charge states, measured by proton nuclear magnetic resonance at room temperature and below. Differences in second-order rate constants (M(-1) s(-1)) of ligand exchange (positive clusters ∼1.9 × 10(-5) versus negative ones ∼1.

Temperature dependence of solid-state electron exchanges of mixed-valent ferrocenated Au monolayer-protected clusters.

Electron transfers (ETs) in mixed-valent ferrocene/ferrocenium materials are ordinarily facile. In contrast, the presence of ~1:1 mixed-valent ferrocenated thiolates in the organothiolate ligand shells of <2 nm diameter Au225, Au144, and Au25 monolayer-protected clusters (MPCs) exerts a retarding effect on ET between them at and below room temperature. Near room temperature, in dry samples, bimolecular rate constants for ET between organothiolate-ligated MPCs are diminished by the addition of ferrocenated ligands to their ligand shells.

Electronic conductivity of films of electroflocculated 2 nm iridium oxide nanoparticles.

The electronic conductivity of films of iridium oxide (IrO(x)) composed of ca. 2 nm nanoparticles (NPs) is strongly dependent on the film oxidation state. The Ir(IV)O(x) NPs can be electrochemically converted to several oxidation states, ranging from Ir(III) to Ir(V) oxides.

Kinetics and low temperature studies of electron transfers in films of small (<2 nm) Au monolayer protected clusters.

This work examines the temperature dependence of electron transfer (ET) kinetics in solid-state films of mixed-valent states of monodisperse, small (<2 nm) Au monolayer protected clusters (MPCs). The mixed valent MPC films, coated on interdigitated array electrodes, are Au25(SR)18(0/1-), Au25(SR)18(1+/0), and Au144(SR)60(1+/0), where SR = hexanethiolate for Au144 and phenylethanethiolate for Au25. Near room temperature and for ca.

Quantification of the binding properties of Cu2+ to the amyloid beta peptide: coordination spheres for human and rat peptides and implication on Cu2+-induced aggregation.

There is no consensus on the coordinating ligands for Cu(2+) by Abeta. However, the differences in peptide sequence between human and rat have been hypothesized to alter metal ion binding in a manner that alters Cu(2+)-induced aggregation of Abeta. Herein, we employ isothermal titration calorimetry (ITC), circular dichroism (CD), and electron paramagnetic resonance (EPR) spectroscopy to examine the Cu(2+) coordination spheres to human and rat Abeta and an extensive set of Abeta(16) mutants.

Shiga toxins activate translational regulation pathways in intestinal epithelial cells.

Shiga toxins (Stxs) cause irreversible damage to eukaryotic ribosomes, yet cellular intoxication of intestinal epithelial cells (IECs) results in increased synthesis of selected proteins, notably cytokines. How mRNA translation is maintained in this circumstance is unclear. This study was designed to assess whether Stx-induced alterations in host signal transduction machinery permit translation despite protein synthesis inhibition.