Showing papers by "Manfred Lindau published in 2009"
TL;DR: The difference between pKabulk and pKasurf suggests that acid groups further from the substrate surface are easier to ionize and have smaller pKa values, which is first experimental evidence of this behavior of weak polyelectrolyte brushes.
Abstract: Poly(acrylic acid) (PAA) brushes and poly(methacrylic acid) (PMAA) brushes on gold substrates were synthesized by surface-initiated atom-transfer radical polymerization of sodium acrylate and sodium methacrylate in water media at room temperature. Fourier transform infrared spectroscopy (FTIR) titration and contact angle titration methods were used in combination to investigate the dissociation behavior of these two brushes. Whereas FTIR titration gives effective bulk pKa values of the polyacid brushes (pKabulk of PAA brushes is 6.5−6.6 and pKabulk of PMAA brushes is 6.9−7.0), contact angle titration provides effective surface pKa of the brushes (pKasurf of PAA brushes is 4.4 ± 0.01 and pKasurf of PMAA brushes is ∼4.6 ± 0.1). The difference between pKabulk and pKasurf suggests that acid groups further from the substrate surface are easier to ionize and have smaller pKa values. Although such behavior of weak polyelectrolyte brushes has been predicted by theoretical simulation, here we provide the first exp...
162 citations
TL;DR: The results suggest that actin and myosin II facilitate release from individual chromaffin granules by accelerating dissociation of catecholamines from the intragranular matrix possibly through generation of mechanical forces.
Abstract: The roles of nonmuscle myosin II and cortical actin filaments in chromaffin granule exocytosis were studied by confocal fluorescence microscopy, amperometry, and cell-attached capacitance measurements Fluorescence imaging indicated decreased mobility of granules near the plasma membrane following inhibition of myosin II function with blebbistatin Slower fusion pore expansion rates and longer fusion pore lifetimes were observed after inhibition of actin polymerization using cytochalasin D Amperometric recordings revealed increased amperometric spike half-widths without change in quantal size after either myosin II inhibition or actin disruption These results suggest that actin and myosin II facilitate release from individual chromaffin granules by accelerating dissociation of catecholamines from the intragranular matrix possibly through generation of mechanical forces
100 citations
TL;DR: Platinum electrodes fabricated using contact photolithography are able to record single exocytotic events with high resolution and should be suitable for highly parallel electrode arrays allowing simultaneous measurements of single events from multiple cells.
Abstract: Surface patterned platinum microelectrodes (PtEs) insulated with 300 nm thick fused silica were fabricated using contact photolithography. These electrodes exhibit low noise and were used for monitoring single vesicle exocytosis from chromaffin cells by constant potential amperometry as well as fast scan cyclic voltammetry. Amperometric spike parameters were consistent with those obtained with conventional carbon fiber electrodes (CFEs). Catecholamine voltammograms acquired with PtEs exhibited redox peaks with full width at half maximum of ~45 mV, much sharper than those of CFE recordings. The time course of voltammetrically measured release events was similar for PtEs and CFEs. The fused silica insulated PtEs allowed incorporation of micrometer precision surface patterned poly-D-lysine (PDL). PDL-functionalized devices were applied to stimulate mast cells and record single release events without serotonin pre-loading. Microfabricated PtEs are thus able to record single exocytotic events with high resolution and should be suitable for highly parallel electrode arrays allowing simultaneous measurements of single events from multiple cells.
60 citations