Deposition of proteins of aberrant conformation is the hallmark of many neurodegenerative diseases. Misfolding of the normally globular mutant superoxide dismutase-1 (SOD1) is a central, early, but poorly understood event in the pathogenic cascade leading to familial forms of ALS. Here we report that aggregates composed of an ALS-causing SOD1 mutant penetrate inside cells by macropinocytosis and rapidly exit the macropinocytic compartment to nucleate aggregation of the cytosolic, otherwise soluble, mutant SOD1 protein. Once initiated, mutant SOD1 aggregation is selfperpetuating. Mutant SOD1 aggregates transfer from cell to cell with remarkable efficiency, a process that does not require contacts between cells but depends on the extracellular release of aggregates. This study reveals that SOD1 aggregates, propagate in a prion-like manner in neuronal cells and sheds light on the mechanisms underlying aggregate uptake and cell-to-cell transfer.amyotrophic lateral sclerosis | amyloid | transmission | protein folding | endocytosis

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[reaction: see text] The fluorescent photoinduced electron transfer (PET) chemosensors 2 and 3 were designed for the recognition of anions possessing two binding sides such as dicarboxylates and pyrophosphate; the anion recognition in DMSO takes place through the two charge neutral thiourea receptor sites with concomitant PET quenching of the anthracene moiety. The anion binding of acetate, phosphate, and pyrophosphate to 2 and 3 was also evaluated by using 1H NMR in DMSO-d6.

Chiroptically active fluorescent semiconductor nanocrystals, quantum dots (QDs), are of high interest, from a theoretical and technological point of view, because they are promising candidates for a range of potential applications. Optical activity can be induced in QDs by capping them with chiral molecules, resulting in circular dichroism (CD) signals in the range of the QD ultraviolet−visible (UV-vis) absorption. However, the effects of the chiral ligand concentration and binding modes on the chiroptical properties of QDs are still poorly understood. In the present study, we report the strong influence of the concentration of a chiral amino acid (cysteine) on its binding modes upon the surface of CdSe/CdS QDs, resulting in varying QD chiroptical activity and corresponding CD signals. Importantly, we demonstrate that the increase of cysteine concentration is accompanied by the growth of the QD CD intensity, reaching a certain critical point, after which it starts to decrease. The intensity of the CD signal varies by almost an order of magnitude across this range. Nuclear magnetic resonance and Fourier transform infrared data, supported by density functional theory calculations, reveal a change in the binding mode of cysteine molecules from tridentate to bidentate when going from low to high concentrations, which results in a change in the CD intensity. Hence, we conclude that the chiroptical properties of QDs are dependent on the concentration and binding modes of the capping chiral ligands. These findings are very important for understanding chiroptical phenomena at the nanoscale and for the design of advanced optically active nanomaterials.

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The synthesis and photophysical evaluation of two enatiomerially pure dimetallic lanthanide luminescent triple-stranded helicates is described. The two systems, formed from the chiral (R,R) ligand 1 and (S,S) ligand 2, were produced as single species in solution, where the excitation of either the naphthalene antennae or the pyridiyl units gave rise to Eu(III) emission in a variety of solvents. Excitation of the antennae also gave rise to circularly polarized Eu(III) luminescence emissions for Eu(2):1(3) and Eu(2):2(3) that were of equal intensity and opposite sign, confirming their enantiomeric nature in solution providing a basis upon which we were able to assign the absolute configurations of Eu(2):1(3) and Eu(2):2(3).

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The synthesis of the fluorescent photoinduced electron transfer (PET) chemosensors 1-3 for bis-anions such as bis-carboxylates and pyrophosphate in organic solvents is described herein. These sensors are based on the receptor-spacer-fluorophore-spacer-receptor motif where the receptors are charge neutral aromatic thiourea or urea receptors and the fluorophore is anthracene. The anion recognition was evaluated using 1H NMR as well as absorption and fluorescence spectroscopy in DMSO. For simple anions such as acetate or fluoride, the recognition was shown to be through hydrogen bonding of the corresponding anion to the receptors. This gave rise to only minor changes in the absorption spectra, but significant changes in the fluorescence emission spectra, which was substantially (70-95%) quenched. Analysis of these recognition events implied a 1 : 2 (sensor : anion) binding and ideal PET behaviour for ions such as AcO- and H2PO4-. For F-, the luminescent quenching indicated a 1 : 1 binding, but we deduced that this was due more to complete quenching of the excited state after the addition of one equivalent of the anion. For all of the anions, the quenching contributed to enhanced efficiency of PET from the receptors to the excited state of the fluorophore. In the case of the bis-anions (ambient), such as di-carboxylates, similar fluorescence quenching was observed. However, here either a 1 : 1 or a 1 : 2 binding was observed depending on the length of the spacer separating the two carboxylate moieties and the nature of the receptor. Whereas both pyrophosphate and malonate gave rise to a 1 : 1 binding, glutarate gave rise to approximately 1 : 2 binding for the thiourea sensors 1 and 2. However, for the urea based sensor 3, the binding was found to be 1 : 1 for all the bis-anions. For such a 1 : 1 binding we propose that the anion most likely bridges the fluorophore moiety. This was also evident from the 1H NMR (DMSO-d6) spectrum where the anthracene resonances were significantly affected. By simply modifying the electronic structure of the receptor, the sensitivity of the recognition process could also be modified; e.g. compound 1, bearing the trifluoromethyl substituent, showed stronger binding to the bis-anions than 2, which possessed a simple phenyl moiety.