Identical Location Transmission Electron Microscopy Imaging of Site-Selective Pt Nanocatalysts: Electrochemical Activation and Surface Disordering

We have employed identical location transmission electron microscopy (IL-TEM) to study changes in the shape and morphology of faceted Pt nanoparticles as a result of electrochemical cycling; a procedure typically employed for activating platinum surfaces. We find that the shape and morphology of the as-prepared hexagonal nanoparticles are rapidly degraded as a result of potential cycling up to +1.3 V. As few as 25 potential cycles are sufficient to cause significant degradation, and after about 500–1000 cycles the particles are dramatically degraded. We also see clear evidence of particle migration during potential cycling. These finding suggest that great care must be exercised in the use and study of shaped Pt nanoparticles (and related systems) as electrocatlysts, especially for the oxygen reduction reaction where high positive potentials are typically employed.

Expression and cellular localization of the voltage-gated calcium channel α2δ3 in the rodent retina

High-voltage-activated calcium channels are hetero-oligomeric protein complexes that mediate multiple cellular processes, including the influx of extracellular Ca2+, neurotransmitter release, gene transcription, and synaptic plasticity. These channels consist of a primary α1 pore-forming subunit, which is associated with an extracellular α2δ subunit and an intracellular β auxiliary subunit, which alter the gating properties and trafficking of the calcium channel. The cellular localization of the α2δ3 subunit in the mouse and rat retina is unknown. In this study using RT-PCR, a single band at ∼305 bp corresponding to the predicted size of the α2δ3 subunit fragment was found in mouse and rat retina and brain homogenates. Western blotting of rodent retina and brain homogenates showed a single 123-kDa band. Immunohistochemistry with an affinity-purified antibody to the α2δ3 subunit revealed immunoreactive cell bodies in the ganglion cell layer and inner nuclear layer and immunoreactive processes in the inner plexiform layer and the outer plexiform layer. α2δ3 immunoreactivity was localized to multiple cell types, including ganglion, amacrine, and bipolar cells and photoreceptors, but not horizontal cells. The expression of the α2δ3 calcium channel subunit to multiple cell types suggests that this subunit participates widely in Ca-channel-mediated signaling in the retina.