The voltage dependence of the TMEM16B/anoctamin2 calcium-activated chloride channel is modified by mutations in the first putative intracellular loop

Ca(2+)-activated Cl(-) channels (CaCCs) are involved in several physiological processes. Recently, TMEM16A/anoctamin1 and TMEM16B/anoctamin2 have been shown to function as CaCCs, but very little information is available on the structure-function relations of these channels. TMEM16B is expressed in the cilia of olfactory sensory neurons, in microvilli of vomeronasal sensory neurons, and in the synaptic terminals of retinal photoreceptors. Here, we have performed the first site-directed mutagenesis study on TMEM16B to understand the molecular mechanisms of voltage and Ca(2+) dependence. We have mutated amino acids in the first putative intracellular loop and measured the properties of the wild-type and mutant TMEM16B channels expressed in HEK 293T cells using the whole cell voltage-clamp technique in the presence of various intracellular Ca(2+) concentrations. We mutated E367 into glutamine or deleted the five consecutive glutamates (386)EEEEE(390) and (399)EYE(401). The EYE deletion did not significantly modify the apparent Ca(2+) dependence nor the voltage dependence of channel activation. E367Q and deletion of the five glutamates did not greatly affect the apparent Ca(2+) affinity but modified the voltage dependence, shifting the conductance-voltage relations toward more positive voltages. These findings indicate that glutamates E367 and (386)EEEEE(390) in the first intracellular putative loop play an important role in the voltage dependence of TMEM16B, thus providing an initial structure-function study for this channel. \ua9 2012 Cenedese et al

COVID-19 respiratory support outside the ICU's doors. An observational study for a new operative strategy

During the first wave of the Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) pandemic, we faced a massive clinical and organizational challenge having to manage critically ill patients outside the Intensive Care Unit (ICU). This was due to the significant imbalance between ICU bed availability and the number of patients presenting Acute Hypoxemic Respiratory Failure caused by SARS-CoV-2-related interstitial pneumonia. We therefore needed to perform Non-Invasive Ventilation (NIV) in non-intensive wards to assist these patients and relieve pressure on the ICUs and subsequently implemented a new organizational and clinical model. This study was aimed at evaluating its effectiveness and feasibility

Nanostructured Photoelectrochemical Biosensing Platform for Cancer Biomarker Detection

The innovative photoelectrochemical properties of multifunctional nanomaterials are here investigated for the development of biosensing platforms for rapid and sensitive detection of a class of cancer biomarker candidates, known as microRNAs. Many different transducers have been proposed, so far, for microRNA detection. Recently, with the emergence of novel photoelectrochemically active species and new detection schemes, photoelectrochemistry has received increasing attention. Gold nanostructures have been, here, used to modify TiO2 electrodes. The surface of the nanostructured platform has been modified by nucleic acid capture probes (CPs). Biotinylated target miRNAs have been recognized by the specific CPs. The biosensing platform has been incubated with streptavidin alkaline phosphatase and exposed to a proper substrate. The product of the enzymatic reaction has been photoelectrochemically monitored. A compact and hand-held analytical device has been developed in order to have a final prototype in line with the concept of point of care testing. (C) 2017 The Authors. Published by Elsevier Ltd

Interactions between permeation and gating in the TMEM16B/anoctamin2 calcium-activated chloride channel

At least two members of the TMEM16/anoctamin family, TMEM16A (also known as anoctamin1) and TMEM16B (also known as anoctamin2), encode Ca2+-activated Cl- channels (CaCCs), which are found in various cell types and mediate numerous physiological functions. Here, we used whole-cell and excised inside-out patch-clamp to investigate the relationship between anion permeation and gating, two processes typically viewed as independent, in TMEM16B expressed in HEK 293T cells. The permeability ratio sequence determined by substituting Cl- with other anions (PX/PCl) was SCN- > I- > NO3 - > Br- > Cl- > F- > gluconate. When external Cl- was substituted with other anions, TMEM16B activation and deactivation kinetics at 0.5 \u3bcM Ca2+ were modified according to the sequence of permeability ratios, with anions more permeant than Cl- slowing both activation and deactivation and anions less permeant than Cl- accelerating them. Moreover, replacement of external Cl- with gluconate, or sucrose, shifted the voltage dependence of steady-state activation (G-V relation) to more positive potentials, whereas substitution of extracellular or intracellular Cl- with SCN- shifted G-V to more negative potentials. Dose-response relationships for Ca2+ in the presence of different extracellular anions indicated that the apparent affinity for Ca2+ at +100 mV increased with increasing permeability ratio. The apparent affinity for Ca2+ in the presence of intracellular SCN- also increased compared with that in Cl-. Our results provide the first evidence that TMEM16B gating is modulated by permeant anions and provide the basis for future studies aimed at identifying the molecular determinants of TMEM16B ion selectivity and gating. \ua9 2014 Betto et al

Assessment of the olfactory function in Italian patients with type 3 von Willebrand disease caused by a homozygous 253 Kb deletion involving VWF and TMEM16B/ANO2.

Type 3 Von Willebrand disease is an autosomal recessive disease caused by the virtual absence of the von Willebrand factor (VWF). A rare 253 kb gene deletion on chromosome 12, identified only in Italian and German families, involves both the VWF gene and the N-terminus of the neighbouring TMEM16B/ANO2 gene, a member of the family named transmembrane 16 (TMEM16) or anoctamin (ANO). TMEM16B is a calcium-activated chloride channel expressed in the olfactory epithelium. As a patient homozygous for the 253 kb deletion has been reported to have an olfactory impairment possibly related to the partial deletion of TMEM16B, we assessed the olfactory function in other patients using the University of Pennsylvania Smell Identification Test (UPSIT). The average UPSIT score of 4 homozygous patients was significantly lower than that of 5 healthy subjects with similar sex, age and education. However, 4 other members of the same family, 3 heterozygous for the deletion and 1 wild type, had a slightly reduced olfactory function indicating that socio-cultural or other factors were likely to be responsible for the observed difference. These results show that the ability to identify odorants of the homozygous patients for the deletion was not significantly different from that of the other members of the family, showing that the 253 kb deletion does not affect the olfactory performance. As other genes may compensate for the lack of TMEM16B, we identified some predicted functional partners from in silico studies of the protein-protein network of TMEM16B. Calculation of diversity for the corresponding genes for individuals of the 1000 Genomes Project showed that TMEM16B has the highest level of diversity among all genes of the network, indicating that TMEM16B may not be under purifying selection and suggesting that other genes in the network could compensate for its function for olfactory ability

ON/OFF switching of silicon wafer electrochemistry by pH-responsive polymer brushes

pH-Switchable electrochemical properties are demonstrated for the first time for native oxide-coated silicon wafer electrodes. Ultrathin and ultrathick pH-responsive poly(methacrylic acid) (PMAA) brushes, obtained by surface-initiated atom transfer radical polymerization, were used to achieve redox gating. PMAA brushes are reversibly switched between their protonated and deprotonated states by alternating acidic and basic pH, which corresponds to a swelling/collapsing behavior. As a result, the electrochemical properties of the PMAA brush-modified silicon electrode are switched “ON” and “OFF” simply by changing pH. The electrochemical properties of the modified electrode were examined by means of cyclic voltammetry and electrochemical impedance spectroscopy both in the absence and presence of ruthenium(III) hexamine, a well-known cationic redox probe.ISSN:2050-7526ISSN:2050-753

Salivary glucose concentration and daily variation in the oral fluid of healthy patients

The aim of this study was to determine the concentration and the variations of salivary glucose in healthy patients who were sampled at five different intervals during the day. Samples of un-stimulated saliva have been collected from 21 healthy patients using the drooling technique and they were divided into two categories. In the first category, patients were asked not to toothbrush their teeth in the 8 hours prior to collection of the salivary sample. Patients in the second category were instead asked to toothbrush 90 minutes before the collection of the first sample of saliva. The glucose concentration was measured in all patients via an enzymatic spectrophotometry. Patients have been selected following a strict inclusion criteria, which included <5% of plaque presence e according to the plaque Index and a total absence of oral disease that could possibly interfere with sample taking or oral fluid analysis. The average age of patients was 22,4±2,6 years old of which 45% were female and 55% were male. Samples were collected five times between 8 am and 12 pm, before and after break-fast. Data was statistically analyzed using the Skewness/Kurtosis Test, Shapiro-Wilk Test, Kruskal Wallis Test and Linear Regression Model, considering values of p0,078) which could however be due to the little number of patients assessed, nonetheless there is a trend, recalling a “pseudo-glycemic curve” not referable to changes in flow rates, probably due to glucose catabolism and shunt

Au Nanoparticles Decorated Graphene-Based Hybrid Nanocomposite for As(III) Electroanalytical Detection

Electrochemical sensors integrating hybrid nanostructured platforms are a promising alternative to conventional detection techniques for addressing highly relevant challenges of heavy metal determination in the environment. Hybrid nanocomposites based on graphene derivatives and inorganic nanoparticles (NPs) are ideal candidates as active materials for detecting heavy metals, as they merge the relevant physico-chemical properties of both the components, finally leading to a rapid and sensitive current response. In this work, a hybrid nanocomposite formed of reduced graphene oxide (RGO) sheets, surface functionalized by &pi;-&pi; interactions with 1-pyrene carboxylic acid (PCA), and decorated in situ by Au NPs, was synthesized by using a colloidal route. The hybrid nanocomposite was characterized by cyclic voltammetry and electrochemical impedance spectroscopy with respect to the corresponding single components, both bare and deposited as a layer-by-layer junction onto the electrode. The results demonstrated the high electrochemical activity of the hybrid nanocomposite with respect to the single components, highlighting the crucial role of the nanostructured surface morphology of the electrode and the PCA coupling agent at the NPs-RGO interphase in enhancing the nanocomposite electroactivity. Finally, the Au NP-decorated PCA-RGO sheets were tested by anodic stripping voltammetry of As(III) ion&mdash;a particularly relevant analyte among heavy metal ions&mdash;in order to assess the sensing ability of the nanocomposite material with respect to its single components. The nanocomposite has been found to present a sensitivity higher than that characterizing the bare components, with LODs complying with the directives established by the U.S. EPA and in line with those reported for state-of-the-art electrochemical sensors based on other Au-graphene nanocomposites

Multi-Walled Carbon Nanotubes (MWCNTs) modified electrodes: Effect of purification and functionalization on the electroanalytical performances

Different modified electrodes were prepared using multi-walled carbon nanotubes (MWCNTs) prepared and purified according to different procedures. Since MWCNTs purification and functionalization is a key point for the electroanalytical performance of the final devices, MWCNTs were previously characterized from the morphological, surface and electrochemical point of view. Different parameters, such as surface area, pore volume, mesoporosity (responsible of thin layer diffusion mechanism), covalent acidity, charge transfer resistance, amorphous impurities contribute to the final performances in terms of higher currents and more reversible behaviour. The best purification method consists in a treatment in sulphonitric mixture for 24 h with the removal of amorphous carbon. The new modified electrodes were successfully employed in the detection of o-toluidine, a hazardous and toxic water pollutant, reaching a sensitivity of 9.2 μA cm−2 ppm−1, a limit of detection of 0.16 ppm and apparent recovery factors very close to 100%. Their application in a complex matrix to monitor o-toluidine, during its photocatalytic removal by ZnO nanopowders, was also investigated.This work was supported by INSTM and Regione Lombardia (agreement signed on 13/11/2012).Peer Reviewe