α-Methylation Enables the X-ray Crystallographic Observation of Oligomeric Assemblies Formed by a β-Hairpin Peptide Derived from Aβ.

The assembly of the β-amyloid peptide Aβ into toxic oligomers plays a significant role in the neurodegeneration associated with the pathogenesis of Alzheimer's disease. Our laboratory has developed -methylation as a tool to enable X-ray crystallographic studies of oligomers formed by macrocyclic β-hairpin peptides derived from Aβ. In this investigation, we set out to determine whether α-methylation could be used as an alternative to -methylation in studying the oligomerization of a β-hairpin peptide derived from Aβ.

Different effects of smooth pursuit eye movements on motion-based stimulus response congruency.

In the motion-based stimulus-response compatibility (SRC) effect, responses are faster when the task-irrelevant stimulus motion is congruent with the response movement performance. In the present study, we tested whether smooth pursuit eye movements, related to tracking a moving object, influence motion-based SRC when present on their own or when combined with position-based SRC. We examined the motion-based SRC effect during both the response selection and response execution stages.

A β-barrel-like tetramer formed by a β-hairpin derived from Aβ.

β-Hairpins formed by the β-amyloid peptide Aβ are building blocks of Aβ oligomers. Three different alignments of β-hairpins have been observed in the structures of Aβ oligomers or fibrils. Differences in β-hairpin alignment likely contribute to the heterogeneity of Aβ oligomers and thus impede their study at high-resolution.

Chiral NHC Ligands for Enantioselective Gold(I) Catalysis Under Aerobic Conditions: the Importance of Conformational Flexibility and Steric Hindrance of NHC Ligand on Reactivity.

Gold(I) catalysis has been recognized as a valuable tool for the unique transformation of multiple carbon-carbon bonds. Enantioselective π-catalysis based on gold(I) complexes is, however, still underdeveloped due to lack of privileged ligands. Herein, we present an accessible method to a new family of stable yet catalytically active chiral NHC-Au(I)-Cl complexes.

Comparing highly trained handball players' and non-athletes' performance in a multi-object tracking task.

Highly trained team sports players possess highly developed visual attentional skills, compared with non-athletes. These athletes also have much better motor control than non-athletes. This study compared the performance of intensively trained handball players with non-athletes in a modified version of the multiple object tracking (MOT) task, in which participants were instructed to point at the moving targets with their fingers.

Electronic Structure of de Novo Peptide ACC-Hex from First Principles.

Proteins are promising components for bioelectronic devices due in part to their biocompatibility, flexibility, and chemical diversity, which enable tuning of material properties. Indeed, an increasingly broad range of conductive protein supramolecular materials have been reported. However, due to their structural and environmental complexity, the electronic structure, and hence conductivity, of protein assemblies is not well-understood.

An Improved Turn Structure for Inducing β-Hairpin Formation in Peptides.

Although β-hairpins are widespread in proteins, there is no tool to coax any small peptide to adopt a β-hairpin conformation, regardless of sequence. Here, we report that δ-linked γ(R)-methyl-ornithine ( MeOrn) provides an improved β-turn template for inducing a β-hairpin conformation in peptides. We developed a synthesis of protected MeOrn as a building block suitable for use in Fmoc-based solid-phase peptide synthesis.

Interpenetrating Cubes in the X-ray Crystallographic Structure of a Peptide Derived from Medin.

Amyloidogenic peptides and proteins are rich sources of supramolecular assemblies. Sequences derived from well-known amyloids, including Aβ, human islet amyloid polypeptide, and tau have been found to assemble as fibrils, nanosheets, ribbons, and nanotubes. The supramolecular assembly of medin, a 50-amino acid peptide that forms fibrillary deposits in aging human vasculature, has not been heavily investigated.

Change in Conductive-Radiative Heat Transfer Mechanism Forced by Graphite Microfiller in Expanded Polystyrene Thermal Insulation-Experimental and Simulated Investigations.

This article introduces an innovative approach to the investigation of the conductive-radiative heat transfer mechanism in expanded polystyrene (EPS) thermal insulation at negligible convection. Closed-cell EPS foam (bulk density 14-17 kg·m) in the form of panels (of thickness 0.02-0.

Effects of N-Terminal Residues on the Assembly of Constrained β-Hairpin Peptides Derived from Aβ.

This paper describes the synthesis, solution-phase biophysical studies, and X-ray crystallographic structures of hexamers formed by macrocyclic β-hairpin peptides derived from the central and C-terminal regions of Aβ, which bear "tails" derived from the N-terminus of Aβ. Soluble oligomers of the β-amyloid peptide, Aβ, are thought to be the synaptotoxic species responsible for neurodegeneration in Alzheimer's disease. Over the last 20 years, evidence has accumulated that implicates the N-terminus of Aβ as a region that may initiate the formation of damaging oligomeric species.

Porous Molecular Capsules as Non-Polymeric Transducers of Mechanical Forces to Mechanophores.

Mechanical grinding/milling can be regarded as historically the first technology for changing the properties of matter. Mechanically activated molecular units (mechanophores) can be present in various structures: polymers, macromolecules, or small molecules. However, only polymers have been reported to effectively transduce energy to mechanophores, which induces breakage of covalent bonds.

Raman scattering studies on very thin layers of gallium sulfide (GaS) as a function of sample thickness and temperature.

Gallium sulfide is a semiconducting material with a layered structure and a characteristic low interlayer interaction. Because of weak van der Waals forces, GaS crystals are relatively easy to exfoliate to very thin layers. In this work nanometric-GaS layers were obtained by a micro-mechanical exfoliation process and were transferred to Si/SiO substrate.

X-ray Crystallographic Structure of a Teixobactin Derivative Reveals Amyloid-like Assembly.

This paper describes the X-ray crystallographic structure of a derivative of the antibiotic teixobactin and shows that its supramolecular assembly through the formation of antiparallel β-sheets creates binding sites for oxyanions. An active derivative of teixobactin containing lysine in place of allo-enduracididine assembles to form amyloid-like fibrils, which are observed through a thioflavin T fluorescence assay and by transmission electron microscopy. A homologue, bearing an N-methyl substituent, to attenuate fibril formation, and an iodine atom, to facilitate X-ray crystallographic phase determination, crystallizes as double helices of β-sheets that bind sulfate anions.

The Inverse Demand Oxa-Diels-Alder Reaction of Resorcinarenes: An Experimental and Theoretical Analysis of Regioselectivity and Diastereoselectivity.

The Diels-Alder reaction enables introduction of new functionalities onto the resorcinarene skeleton with simultaneous generation of new stereogenic centers and expansion of the internal cavity. We present highly regio- and diastereoselective inverse electron demand oxa-Diels-Alder reactions of resorcinarene ortho-quinone methide with benzofuran and indene, each generating 12 new stereogenic centers. The mechanism and reasons for regioselectivity and diastereoselectivity were analyzed using theoretical calculations (NBO charges, Fukui functions, transition state energies, and thermodynamic stability of the products).

Mechanochemical Encapsulation of Fullerenes in Peptidic Containers Prepared by Dynamic Chiral Self-Sorting and Self-Assembly.

Molecular capsules composed of amino acid or peptide derivatives connected to resorcin[4]arene scaffolds through acylhydrazone linkers have been synthesized using dynamic covalent chemistry (DCC) and hydrogen-bond-based self-assembly. The dynamic character of the linkers and the preference of the peptides towards self-assembly into β-barrel-type motifs lead to the spontaneous amplification of formation of homochiral capsules from mixtures of different substrates. The capsules have cavities of around 800 Å(3) and exhibit good kinetic stability.

Zigzag nanoribbons of two-dimensional silicene-like crystals: magnetic, topological and thermoelectric properties.

The effects of electron-electron and spin-orbit interactions on the ground-state magnetic configuration and on the corresponding thermoelectric and spin thermoelectric properties in zigzag nanoribbons of two-dimensional hexagonal crystals are analysed theoretically. The thermoelectric properties of quasi-stable magnetic states are also considered. Of particular interest is the influence of Coulomb and spin-orbit interactions on the topological edge states and on the transition between the topological insulator and conventional gap insulator states.

Dynamic formation of hybrid peptidic capsules by chiral self-sorting and self-assembly.

Owing to their versatility and biocompatibility, peptide-based self-assembled structures constitute valuable targets for complex functional designs. It is now shown that artificial capsules based on β-barrel binding motifs can be obtained by means of dynamic covalent chemistry (DCC) and self-assembly. Short peptides (up to tetrapeptides) are reversibly attached to resorcinarene scaffolds.

Inherently chiral iminoresorcinarenes through regioselective unidirectional tautomerization.

Tetraformylresorcin[4]arene is obtained in 48% yield via a chromatography-free Duff reaction. The formylated resorcinarene reacts easily with primary aliphatic and aromatic amines. The resulting imines exist exclusively in keto-enamine forms.

Assembly-driven synthesis of hybrid molecular capsules controlled by chiral sorting.

Chiral capsules with polar interiors (reversed capsules) undergo heterochiral sorting and exhibit positive mutalism - both hemispheres mutually benefit from the association. This feature can be coupled with partial reversibility of the formation reaction and utilized to amplify synthesis of hybrid capsules made of hemispheres that cannot be formed independently.