Brain-derived neurotrophic factor modulation of Kv1.3 channel is disregulated by adaptor proteins Grb10 and nShc

Background  

Neurotrophins are important regulators of growth and regeneration, and acutely, they can modulate the activity of voltage-gated ion channels. Previously we have shown that acute brain-derived neurotrophic factor (BDNF) activation of neurotrophin receptor tyrosine kinase B (TrkB) suppresses the Shaker voltage-gated potassium channel (Kv1.3) via phosphorylation of multiple tyrosine residues in the N and C terminal aspects of the channel protein. It is not known how adaptor proteins, which lack catalytic activity, but interact with members of the neurotrophic signaling pathway, might scaffold with ion channels or modulate channel activity.     

C-shaped nanoaperture-enhanced germanium photodetector

We present a C-shaped nanoaperture-enhanced Ge photodetector that shows 2-5 times the photocurrent enhancement over that from a square aperture of the same area at 1310 nm wavelength. We demonstrate the polarization dependence of the C-aperture photodetector over a wide wavelength range. Our experimental observation agrees well with finite-difference time-domain simulation results.     

Magnetism and candidate muon-probe sites in RBa2Cu3O y

Key results of zero-field (ZF) and transverse-field (TF) muon-spin-relaxation (μSR) experiments on superconducting and insulating RBa₂Cu₃O _y (R123 _y , with R=Eu, Gd, Pr and Pr/Y:y=6, 7) are examined. The chemical behavior of the positive muon probe is addressed, and muon-oxygen bonding is shown to occur in all these cuprates. To explain magnetic fields at muon-probe sites in Pr _x Y_1−x Ba₂Cu₃O _y (0<=x<0.5,y=7 andx=0,y=6) samples, improvements on the reported magnetic structures from neutron diffraction are necessary. Cu magnetism in Pr123y (y=6,7) is observed belowT _N1, which is near RT. The magnetism seen belowT _N2 can be interpreted assuming an additional ordering in the Cutt-O chain layers. Alternatively, Pr ordering is also considered as the cause of the second phase transition. Considering the specific muon-probe location, a more detailed interpretation can be provided for the μSR parameters, measured in the normal and mixed states of these unconventional superconductors.     

Specific heat studies in a-Se and a-Se<Subscript>90</Subscript>M<Subscript>10</Subscript> (M = In,Sb, Te) alloys

Specific heat measurements have been made in a-Se and a-Se₉₀M₁₀ (M = In, Sb, Te) alloys using differential scanning calorimetry (DSC) technique to see the effect of additives In, Sb and Te on the specific heat in a-Se. An extremely large increase in the specific heat values has been observed at the glass transition temperature. It has also been found that the values of C _p below glass transition temperature (C _pg ) and after glass transition (C _pe ) are highly composition dependent. This indicates that the additives used in the present study influences the structure of the a-Se. Specific heat and atomic mass values of the additive elements are found to be significant for the explanation of present results.     

Phase fluctuations in a strongly disordered s-wave NbN superconductor close to the metal-insulator transition

We explore the role of phase fluctuations in a three-dimensional s-wave superconductor, NbN, as we approach the critical disorder for destruction of the superconducting state. Close to critical disorder, we observe a finite gap in the electronic spectrum which persists at temperatures well above T(c). The superfluid density is strongly suppressed at low temperatures and evolves towards a linear-T variation at higher temperatures. These observations provide strong evidence that phase fluctuations play a central role in the formation of a pseudogap state in a disordered s-wave superconductor.     

Hyperfine interactions in iron — Yttrium oxide systems

Hyperfine interactions of iron — yttrium oxide systems have been investigated by Mössbauer spectroscopy and magnetic measurements. The mixed oxides having varying ratios were prepared by heating the coprecipitated oxyhydroxides to about 1000°C in air. The room temperature Mössbauer spectra are complex in nature and some of them exhibit as may as 10 well resolved peaks consisting of two sets of magnetically split hyperfine six line patterns, indicating existence of two different environments around Fe. The values of specific magnetic susceptibility change with increasing amount of yttrium is maximum for 1:1 (Y:Fe) and then falls continuously. The observed H_n values are less than the reported values for α-Fe₂O₃. From the observed data it appears that a transition for the composition of 1:1 definitely takes place and probably two species are formed. Some of the mixed oxides behave like iron filings in a magnetic field.     

Ligand Modifications Produce Two-Step Magnetic Switching in a Cobalt(dioxolene) Complex

Mononuclear monodioxolene valence tautomeric (VT) cobalt complexes typically exist in their low spin (l.s.) Co^III(cat²⁻) and high spin (h.s.) Co^II(sq⋅⁻) forms (cat²⁻=catecholato, and sq⋅⁻=seminquinonato forms of 3,5−di−^tBu-1,2-dioxolene), which reversibly interconvert via temperature-dependent intramolecular electron transfer. Typically, the remaining four coordination sites on cobalt are supported by a tetradentate ligand whose properties influence the temperature at which VT occurs. We report that replacing one chelating pyridyl arm of tris(2-pyridylmethyl)amine (tpa) with a weaker field ortho-anisole moiety facilitates access to a third magnetic state, and examine a series of related complexes. Variable temperature crystallographic, magnetic, calorimetric, and spectroscopic studies support that this third state is consistent with l.s. Co^II(sq⋅⁻). Thus, our ligand modifications not only provide access to the VT transition from l.s. Co^III(cat²⁻) to l.s. Co^II(sq⋅⁻), but at higher temperatures, the complex undergoes spin crossover from l.s. Co^II(sq⋅⁻) to h.s. Co^II(sq⋅⁻), representing the first example of two-step magnetic switching in a mononuclear monodioxolene cobalt complex. We hypothesize that ligand dynamicity may facilitate access to the rarely observed l.s. Co^II(sq⋅⁻) intermediate state, suggesting a new design criterion in the development of stimulus-responsive multi-state molecular switches.