The coordination behaviour and reactivity of partially silicon based crown ethers towards beryllium chloride.

Through reactions of 1,2-disila[12]crown-4 or 1,2-disila-benzo[12]crown-4 ethers with BeCl2 eight-membered Be-O-heterocycles, which are annulated by two six-membered Be-O-cycles were obtained and characterised. The reactions leading to these unusual ring systems have been investigated by NMR and IR spectroscopy as well as reactions with further ligand derivatives.

Alkali and Alkaline Earth Metal Derivatives of Disila-Bridged Podands: Coordination Chemistry and Structural Diversity.

Within this study, the synthesis and coordination chemistry of open-chain ligands bearing disila-units is presented. Instead of basic 1:1 complexes, structural diversity was discovered in the variety of ligand and salt. Stable complexes of alkali and alkaline earth metal complexes were obtained by equimolar reactions of different salts with the disila-bridged podands 8,9-disila-EO5 (1) and 11,12-disila-EO7 (2) (EO5 = pentaethylene glycol; EO7 = heptaethylene glycol).

Crown Ether Complexes of Alkali-Metal Chlorides from SO.

The structures of alkali-metal chloride SO solvates (Li-Cs) in conjunction with 12-crown-4 or 1,2-disila-12-crown-4 show strong discrepancies, despite the structural similarity of the ligands. Both types of crown ethers form 1:1 complexes with LiCl to give [Li(1,2-disila-12-crown-4)(SO Cl)] (1) and [Li(12-crown-4)Cl]⋅4 SO (2). However, 1,2-disila-12-crown-4 proved unable to coordinate cations too large for the cavity diameter, for example, by the formation of sandwich-type complexes.

A structural study of alkaline earth metal complexes with hybrid disila-crown ethers.

Compounds consisting of [M(1,2-disila-[3n]crown-n)] (M = Mg, Ca, Sr, Ba; n = 5, 6) and [Ba(1,2-disila-benzo[18]crown-6)] cations and different anions were obtained by equimolar reaction of the hybrid disila-crown ethers 1,2-disila[15]crown-5 (1), 1,2-disila[18]crown-6 (2) and 1,2-disila-benzo[18]crown-6 (7) with alkaline earth metal salts. Even with strongly coordinating anions such as Br or I stable complexes could be obtained, showing the good coordination ability of these ligands. The structures of all coordination compounds were determined via single crystal X-ray diffraction (XRD).

Synthesis and coordination ability of a partially silicon based crown ether.

The first hybrid crown ether with two adjacent disilane fragments was synthesized through reaction of O(SiMeCl) (3) with O(CHOH). By means of DFT calculations, the complexation ability of 1,2,4,5-tetrasila[12]crown-4 (7) towards Li was determined to be considerably higher compared to [12]crown-4.

Stable Alkali-Metal Complexes of Hybrid Disila-Crown Ethers.

The complexation ability of hybrid disilane and ethylene containing crown ether ring systems was analyzed using 1,2-disila[12]crown-4 (1), 1,2-disila[15]crown-5 (2), 1,2-disila[18]crown-6 (3), and 1,2,7,8-tetrasila[12]crown-4 (7). Alkali-metal complexes (Li(+), Na(+), K(+)) were obtained and analyzed via X-ray diffraction. The complex stability of [Li(1,2-disila[12]crown-4)](+) and [Li(1,2,7,8-tetrasila[12]crown-4)](+) was determined, in relation to the lithium complex of [12]crown-4, by density functional theory (DFT) calculations employing the BP86/def2-TZVP level of theory.

Stepwise synthesis of a stable diphosphasilirane and its unexpected dimerization.

The synthesis of the thermally stable bicyclic diphosphasilirane O(SiiPr2P)2SiiPr2 (4) was achieved via oxidation of the alkaline earth metal substituted cyclic diphosphanide 3 with 1,2-dibromoethane. Nonetheless, during extended storage at low temperature, impurity induced rearrangement in favour of the dimeric species [O(SiiPr2P)2SiiPr2]2 (5) is observed.

Optogenetic stimulation of the auditory pathway.

Auditory prostheses can partially restore speech comprehension when hearing fails. Sound coding with current prostheses is based on electrical stimulation of auditory neurons and has limited frequency resolution due to broad current spread within the cochlea. In contrast, optical stimulation can be spatially confined, which may improve frequency resolution.

Modes and regulation of endocytic membrane retrieval in mouse auditory hair cells.

Synaptic vesicle recycling sustains high rates of neurotransmission at the ribbon-type active zones (AZs) of mouse auditory inner hair cells (IHCs), but its modes and molecular regulation are poorly understood. Electron microscopy indicated the presence of clathrin-mediated endocytosis (CME) and bulk endocytosis. The endocytic proteins dynamin, clathrin, and amphiphysin are expressed and broadly distributed in IHCs.

Probing the functional equivalence of otoferlin and synaptotagmin 1 in exocytosis.

Cochlear inner hair cells (IHCs) use Ca(2+)-dependent exocytosis of glutamate to signal sound information. Otoferlin (Otof), a C(2) domain protein essential for IHC exocytosis and hearing, may serve as a Ca(2+) sensor in vesicle fusion in IHCs that seem to lack the classical neuronal Ca(2+) sensors synaptotagmin 1 (Syt1) and Syt2. Support for the Ca(2+) sensor of fusion hypothesis for otoferlin function comes from biochemical experiments, but additional roles in late exocytosis upstream of fusion have been indicated by physiological studies.

Hearing requires otoferlin-dependent efficient replenishment of synaptic vesicles in hair cells.

Inner hair cell ribbon synapses indefatigably transmit acoustic information. The proteins mediating their fast vesicle replenishment (hundreds of vesicles per s) are unknown. We found that an aspartate to glycine substitution in the C(2)F domain of the synaptic vesicle protein otoferlin impaired hearing by reducing vesicle replenishment in the pachanga mouse model of human deafness DFNB9.

Delineation of large deletions of the MECP2 gene in Rett syndrome patients, including a familial case with a male proband.

Comprehensive genetic screening programs have led to the identification of pathogenic methyl-CpG-binding protein 2 (MECP2) mutations in up to 95% of classical Rett syndrome (RTT) patients. This high rate of mutation detection can partly be attributed to specialised techniques that have enabled the detection of large deletions in a substantial fraction of otherwise mutation-negative patients. These cases would normally be missed by the routine PCR-based screening strategies.