The role of the endosomal chloride/proton antiporter ClC-5 in proximal tubule endocytosis and kidney physiology

The chloride channel (CLC) protein family comprises ion channels and proton-coupled anion transporters with fundamental physiological roles in humans. Several properties of CLC proteins defy the rigid dichotomy between ion channels and transporters as these opposite thermodynamic mechanisms of transport are implemented in a very similar structural architecture. All the CLC transporters are expressed in intracellular organelles where they are somehow important for the ionic homeostasis of these compartments. However, their specific physiological role is still unclear. This chapter focuses on the biophysical properties and physiological role of the endosomal Cl−/H+ antiporter ClC-5 mutated in Dent’s disease

Spatial filter and its application in three-dimensional single molecule localization microscopy

Single molecule localization microscopy (SMLM) allows the imaging of cellular structures with resolutions five to ten times below the diffraction limit of optical microscopy. It was originally introduced as a two-dimensional technique based on the localization of single emitters as projection onto the x-y imaging plane. The determination of the axial position of a fluorescent emitter is only possible by additional information. Here we report a method (spatial filter SMLM (SFSMLM)) that allows to determine the axial positions of fluorescent molecules and nanoparticles on the nanometer scale by the usage of two spatial filters, which are placed in two otherwise identical emission detection channels. SFSMLM allows axial localization in a range of ca. 1.5 μm with a localization precision of 15 - 30 nm in axial direction. The technique was utilized for localizing and imaging small cellular structures – e.g. actin filaments, vesicles and mitochondria - in three dimensions

Recombination dynamics of deep defect states in zinc oxide nanowires

The recombination dynamics of defect states in zinc oxide nanowires has been studied by developing a general expression for time-resolved photoluminescence intensity based on a second-order approximation for the radiative and non-radiative recombination rates. The model allows us to determine the parameters that characterize the recombination from deep defect states (defect concentration, unimolecular lifetime and bimolecular coefficient) through multi-fitting analysis of time-resolved photoluminescence measurements. Analyses conducted on zinc oxide nanowires gave deep state concentrations of the order of 10(18) cm(-3) and unimolecular lifetimes and bimolecular recombination coefficient comparable to those typical of interband recombination in direct gap semiconductors. The consistency of a 'two-channel decay' model (double exponential decay) has been tested by means of a similar analysis procedure. The results suggest that double exponential fitting of time-resolved photoluminescence data of zinc oxide nanowires may be just a mere phenomenological tool which does not reflect the real recombination dynamics of the visible emission band

On the mechanism of photoluminescence quenching in tin dioxide nanowires by NO2 adsorption

The recent observation of selective photoluminescence (PL) quenching in tin dioxide (SnO2) nanowires (NWs) upon adsorption of nitrogen dioxide (NO2) molecules triggered much interest on possible applications of SnO2 nanostructures as selective optochemical transducers for gas sensing. Understanding the peculiar gas–nanostructure interaction mechanisms lying behind this phenomenon may be of great interest in order to improve the selectivity of solid-state gas sensing devices. With this aim, we studied the luminescence features of SnO2 NWs in controlled adsorption conditions by means of continuous wave- and time-resolved PL techniques. We show that, under assumption of a Langmuir-like adsorption of gas molecules on the nanostructures surface, the decrease of PL intensity is linearly proportional to surface density of adsorbed molecules, while the recombination rates of excited states are not significantly affected by the interaction with NO2. These findings support a picture in which NO2 molecules act as 'static quenchers', suppressing emitting centres of SnO2 in an amount proportional to the number of adsorbed molecules. A simple model based on the above mechanism and allowing good fitting of the data is described and discussed. The possible indirect or direct role of oxygen vacancy states in SnO2 luminescence is finally discussed

On the mechanism of photoluminescence quenching in tin dioxide nanowires by NO2 adsorption

The recent observation of selective photoluminescence (PL) quenching in tin dioxide (SnO(2)) nanowires (NWs) upon adsorption of nitrogen dioxide (NO(2)) molecules triggered much interest on possible applications of SnO(2) nanostructures as selective optochemical transducers for gas sensing. Understanding the peculiar gas-nanostructure interaction mechanisms lying behind this phenomenon may be of great interest in order to improve the selectivity of solid-state gas sensing devices. With this aim, we studied the luminescence features of SnO(2) NWs in controlled adsorption conditions by means of continuous wave-and time-resolved PL techniques. We show that, under assumption of a Langmuir-like adsorption of gas molecules on the nanostructures surface, the decrease of PL intensity is linearly proportional to surface density of adsorbed molecules, while the recombination rates of excited states are not significantly affected by the interaction with NO(2). These findings support a picture in which NO(2) molecules act as 'static quenchers', suppressing emitting centres of SnO(2) in an amount proportional to the number of adsorbed molecules. A simple model based on the above mechanism and allowing good fitting of the data is described and discussed. The possible indirect or direct role of oxygen vacancy states in SnO(2) luminescence is finally discussed