Inorganic–organic lead halide perovskite could be efficient when used as the light-harvesting component of solar cells; here incorporation of methylammonium lead bromide into formamidinium lead iodide stabilizes the perovskite and improves the power conversion efficiency of the solar cell up to 17.9 per cent. Inorganic–organic lead halide perovskites are currently attracting considerable interest for solar-cell applications. Most of the best performing perovskite solar cells to date have made use of methylammonium-based perovskites; formamidinium-based perovskites have also shown promise, but are not as stable. Now Nam Joong Jeon and colleagues show that the formamidinium-based perovskites can be stabilized by the addition of some methylammonium-based perovskite, and that solar cells incorporating the resulting compositionally tuned materials can reach new heights of efficiency. Of the many materials and methodologies aimed at producing low-cost, efficient photovoltaic cells, inorganic–organic lead halide perovskite materials1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17 appear particularly promising for next-generation solar devices owing to their high power conversion efficiency. The highest efficiencies reported for perovskite solar cells so far have been obtained mainly with methylammonium lead halide materials1,2,3,4,5,6,7,8,9,10. Here we combine the promising—owing to its comparatively narrow bandgap—but relatively unstable formamidinium lead iodide (FAPbI3) with methylammonium lead bromide (MAPbBr3) as the light-harvesting unit in a bilayer solar-cell architecture13. We investigated phase stability, morphology of the perovskite layer, hysteresis in current–voltage characteristics, and overall performance as a function of chemical composition. Our results show that incorporation of MAPbBr3 into FAPbI3 stabilizes the perovskite phase of FAPbI3 and improves the power conversion efficiency of the solar cell to more than 18 per cent under a standard illumination of 100 milliwatts per square centimetre. These findings further emphasize the versatility and performance potential of inorganic–organic lead halide perovskite materials for photovoltaic applications.

Compositional engineering of perovskite materials for high-performance solar cells

The ionotropic glutamate receptors are ligand-gated ion channels that mediate the vast majority of excitatory neurotransmission in the brain. The cloning of cDNAs encoding glutamate receptor subunits, which occurred mainly between 1989 and 1992 ([Hollmann and Heinemann, 1994][1]), stimulated this

/pdf/the-glutamate-receptor-ion-channels-560mntczdb.pdf

The glutamate receptor ion channels

The application of molecular cloning technology to the study of the glutamate receptor system has led to an explosion of knowledge about the structure, expression, and function of this most important fast excitatory transmitter system in the mammalian brain. The first functional ionotropic glutamate receptor was cloned in 1989 (Hollmann et al 1989) , and the results of this molecular-based approach over the past three years are the focus of this review. We discuss the implications of and the new questions raised by this work-which is probably only a glance at this fascinating and complex signaling system found in brains from the snails to man. Glutamate receptors are found throughout the mammalian brain, where they constitute the major excitatory transmitter system. The longest-known and best-studied glutamate receptors are ligand-gated ion channels, also called ionotropic glutamate receptors , which are permeable to cations. They have traditionally been classified into three broad subtypes based upon pharmaco­ logical and electrophysiological data: a-amino-3-hydroxy-5-methyl-4isoxazole propionate (AMPA) receptors, kainate (KA) receptors , and N-methyl-D-aspartate (NMDA) receptors. Recently, however, a family of G protein-coupled glutamate receptors , which are also called metabotropic glutamate or transl -aminocyclopentanel ,3-dicarboxylate (tACPD) recep­ tors, was identified (Sugiyama et al 1987) . (For reviews of the classification and the pharmacological and electrophysiological properties of glutamate receptors see Mayer & Westbrook 1987, Collingridge & Lester 1989, Honore 1989, Monaghan et al 1989, Wroblewski & Danysz 1 989, Hansen &

Cloned Glutamate Receptors

http://brainmind.umin.jp/public/kojima2003c.pdf

The BDNF val66met polymorphism affects activity-dependent secretion of BDNF and human memory and hippocampal function

Mutations in the enzyme cytosolic isocitrate dehydrogenase 1 (IDH1) are a common feature of a major subset of primary human brain cancers. These mutations occur at a single amino acid residue of the IDH1 active site, resulting in loss of the enzyme's ability to catalyse conversion of isocitrate to alpha-ketoglutarate. However, only a single copy of the gene is mutated in tumours, raising the possibility that the mutations do not result in a simple loss of function. Here we show that cancer-associated IDH1 mutations result in a new ability of the enzyme to catalyse the NADPH-dependent reduction of alpha-ketoglutarate to R(-)-2-hydroxyglutarate (2HG). Structural studies demonstrate that when arginine 132 is mutated to histidine, residues in the active site are shifted to produce structural changes consistent with reduced oxidative decarboxylation of isocitrate and acquisition of the ability to convert alpha-ketoglutarate to 2HG. Excess accumulation of 2HG has been shown to lead to an elevated risk of malignant brain tumours in patients with inborn errors of 2HG metabolism. Similarly, in human malignant gliomas harbouring IDH1 mutations, we find markedly elevated levels of 2HG. These data demonstrate that the IDH1 mutations result in production of the onco-metabolite 2HG, and indicate that the excess 2HG which accumulates in vivo contributes to the formation and malignant progression of gliomas.

/pdf/cancer-associated-idh1-mutations-produce-2-hydroxyglutarate-3hnshr7hh1.pdf

Cancer-associated IDH1 mutations produce 2-hydroxyglutarate

Recently, GBR1, a seven-transmembrane domain protein with high affinity for γ-aminobutyric acid (GABA) B receptor antagonists, was identified. Here, a GBR1-related protein, GBR2, was shown to be coexpressed with GBR1 in many brain regions and to interact with it through a short domain in the carboxyl-terminal cytoplasmic tail. Heterologously expressed GBR2 mediated inhibition of adenylyl cyclase; however, inwardly rectifying potassium channels were activated by GABA B receptor agonists only upon coexpression with GBR1 and GBR2. Thus, the interaction of these receptors appears to be crucial for important physiological effects of GABA and provides a mechanism in receptor signaling pathways that involve a heterotrimeric GTP-binding protein.

https://science.sciencemag.org/content/sci/283/5398/74.full.pdf

Role of heteromer formation in GABAB receptor function.

Norepinephrine (NE) is widely distributed throughout the brain It modulates intrinsic currents, as well as amplitude and frequency of synaptic transmission affecting the ‘signal-to-noise ratio’ of sensory responses In the visual cortex, α1- and β-adrenergic receptors (AR) gate opposing effects on long-term plasticity of excitatory transmission Whether and how NE recruits these plastic mechanisms is not clear Here, we show that NE modulates glutamatergic inputs with different efficacies for α1- and β-AR As a consequence, the priming of synapses with different NE concentrations produces dose-dependent competing effects that determine the temporal window of spike-timing dependent plasticity (STDP) While a low NE concentration leads to long-term depression (LTD) over broad positive and negative delays, a high NE concentration results in bidirectional STDP restricted to very narrow intervals These results indicate that the local availability of NE, released during emotional arousal, determines the compound modulatory effect and the output of STDP

/pdf/noradrenergic-tone-determines-dichotomous-control-of-2j9hidr5rn.pdf

Noradrenergic ‘Tone’ Determines Dichotomous Control of Cortical Spike-Timing-Dependent Plasticity

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2893%2981186-4

The rat delta-1 and delta-2 subunits extend the excitatory amino acid receptor family.

NMDA receptors (NMDARs) play a pivotal role in the regulation of neuronal communication and synaptic function in the central nervous system. The subunit composition and compartmental localization of NMDARs in neurons affect channel activity and downstream signaling. This review discusses the distinct NMDAR subtypes and their function at synaptic, perisynaptic, and extrasynaptic sites of excitatory and inhibitory neurons. Many neurons express more than one of the modulatory NR2 subunits that participate in the formation of di- and/or triheteromeric channel assemblies (e.g., NR1/NR2A, NR1/NR2B, and/or NR1/NR2A/NR2B). Depending on the subunit composition and presence or absence of intracellular binding partners along the postsynaptic membrane, these NMDAR subtypes are allocated to distinct synaptic inputs converging onto a neuron or are distributed differentially among synaptic or extrasynaptic sites. These sites can carry NR2A and NR2B subunits, supporting the hypothesis that the spatial distribution of scaffolding and signaling complexes critically determines the full spectrum of NMDAR signaling.

NMDA receptor function: subunit composition versus spatial distribution.

https://www.cell.com/neuron/pdf/S0896-6273(00)00039-8.pdf

Georg Köhr

Papers

Role of heteromer formation in GABAB receptor function.

Noradrenergic ‘Tone’ Determines Dichotomous Control of Cortical Spike-Timing-Dependent Plasticity

The rat delta-1 and delta-2 subunits extend the excitatory amino acid receptor family.

NMDA receptor function: subunit composition versus spatial distribution.

Mutagenesis reveals a role for ABP/GRIP binding to GluR2 in synaptic surface accumulation of the AMPA receptor.