Near‐Infrared Optogenetic Genome Engineering Based on Photon‐Upconversion Hydrogels

Photon upconversion (UC) from near‐infrared (NIR) light to visible light has enabled optogenetic manipulations in deep tissues. However, materials for NIR optogenetics have been limited to inorganic UC nanoparticles. Herein, NIR‐light‐triggered optogenetics using biocompatible, organic TTA‐UC hydrogels is reported. To achieve triplet sensitization even in highly viscous hydrogel matrices, a NIR‐absorbing complex is covalently linked with energy‐pooling acceptor chromophores, which significantly elongates the donor triplet lifetime. The donor and acceptor are solubilized in hydrogels formed from biocompatible Pluronic F127 micelles, and heat treatment endows the excited triplets in the hydrogel with remarkable oxygen tolerance. Combined with photoactivatable Cre recombinase technology, NIR‐light stimulation successfully performs genome engineering resulting in the formation of dendritic‐spine‐like structures of hippocampal neurons.     

Size-specific catalytic activity of polymer-stabilized gold nanoclusters for aerobic alcohol oxidation in water

Gold nanoclusters (phi = 1.3 nm) stabilized by poly(N-vinyl-2-pyrrolidone) (Au:PVP NCs) readily oxidize benzylic alcohols to the corresponding aldehydes and/or carboxylic acids under ambient temperature in water. Kinetic measurement revealed that smaller Au:PVP NCs exhibit higher catalytic activity than larger (9.5 nm) homologues and, more surprisingly, than Pd:PVP NCs of comparable size (1.5 and 2.2 nm). On the basis of the marked difference in the kinetic isotope effect and activation energy between Au:PVP and Pd:PVP NCs, a reaction mechanism for alcohol oxidation catalyzed by Au:PVP NCs is proposed in which a superoxo-like molecular oxygen species adsorbed on the surface of the small Au NCs abstracts a hydrogen atom from the alkoxide.     

Thermodynamics of the N2/N3- redox couple in a LiBr-KBr-CsBr melt

Nitrogen electrode reaction has been investigated in a LiBr-KBr-CsBr melt containing Li3N. The reaction N3- --> 1/2N2 + 3e- is confirmed by quantitative analysis of anodically evolved gas. The Nernst relation holds for the rest potential of Ni electrodes at a nitrogen gas pressure, pN2, of 0.05-1.0 atm and an anion fraction of the N3- ions, xN3-, of 0.003-0.010 (anion fraction). Then, the standard formal potential of the N2/N3- couple, , is evaluated to be 0.251 +/- 0.009 V versus Li+/Li (pN2 = 1 atm, xN3- = 1) at 673 K. The dependence of on the temperature (570-730 K) gives a linear relation, whose slope is (-0.930 +/- 0.117) x 10(-3) V K(-1). Thermodynamic quantities for the formation of Li3N in the melt are also estimated.     

Catch and Release of DNA in Coacervate‐Dispersed Gels

Summary: We have synthesized novel coacervate‐droplet gels, which were applied to controlling the transportation of DNA in electrophoresis. Coacervate droplets are colloidal particles and they are usually composed of positive and negative polyelectrolytes. However, the polyzwitterion (polyampholyte) PDMAPS can form coacervate droplets in water by itself, since PDMAPS has both positive and negative charges in each side group of main chain. Coacervate droplets have a unique nature and can catch charged macromolecules such as DNA. In order to utilize the nature of the PDMAPS coacervate droplets for the catch and release of DNA, we stabilized PDMAPS droplets in gels. The droplets catch the DNA in electrophoresis and the release of DNA can be controlled by temperature and salt addition.

Electrophoresis of DNA, using coacervate‐dispersed PAAm gels, prepared at various PDMAPS concentrations. The circles indicate the PAAm gels embedded in agarose gels.     

3-(2-Pyridyl)-2-pyrazoline derivatives: novel fluorescent probes for Zn ion

Spectroscopic studies revealed that 3-(2-pyridyl)-2-pyrazoline derivatives have rather strong affinity toward divalent transition metal ions, but have almost no interaction with alkali and alkaline-earth metal ions. In the case of the 5-(4-cyanophenyl) derivative, enhancement of the fluorescence intensity was observed upon addition of the Zn²⁺ ion, while most of other transition metal ions caused complete quenching.     

High-Field and Multifrequency ESR in the Two-Dimensional Triangular Lattice Antiferromagnet NiGa2S4

We report the experimental results of electron spin resonance in high magnetic fields up to about 53 T on the quasi-two-dimensional triangular lattice antiferromagnet NiGa₂S₄. The temperature dependence of the resonance field at 584.8 GHz shows a steep change below about 30 K, indicating a development of the short-range correlation. The frequency dependence of the resonance field at the lowest temperature for H∥c is explained by one of the helical resonance modes. These experimental results suggest that the short-range order is well developed at low temperatures, and the resonance mode is described by a conventional spin wave theory.     

Protonation of Pyridyl‐Substituted TTF Derivatives: Substituent Effects in Solution and in the Proton–Electron Correlated Charge‐Transfer Complexes

Protonated pyridyl‐substituted tetrathiafulvalene electron‐donor molecules (PyH⁺‐TTF) showed significant changes in the electron‐donating ability and HOMO–LUMO energy gap compared to the neutral analogues and gave a unique N⁺?H???N hydrogen‐bonded (H‐bonded) dimer unit in the proton–electron correlated charge‐transfer (CT) complex crystals. We have evaluated these features from the viewpoint of the molecular structure of the PyH⁺‐TTF derivatives, that is, the substitution position of the Py group and/or the presence or absence of the ethylenedithio (EDT) group. Among 2‐PyH⁺‐TTF ( 1 o H⁺ ), 3‐PyH⁺‐TTF ( 1 m H⁺ ), 4‐PyH⁺‐TTF ( 1 p H⁺ ), and 4‐PyH⁺‐EDT‐TTF ( 2 p H⁺ ) systems, the para‐pyridyl‐substituted donors 1 p H⁺ and 2 p H⁺ exhibit more marked changes upon protonation in solution; a larger redshift in the intramolecular CT absorption band and a larger decrease in the electron‐donating ability. Furthermore, the EDT system 2 p H⁺ has the smallest intramolecular Coulombic repulsion energy. These differences are reasonably interpreted by considering the energy levels and distributions of the HOMO and LUMO obtained by quantum chemical calculations. Such substituent effects related to protonation were also examined by comparing the structure and properties of a new H‐bonded CT complex crystal based on 2 p H⁺ with those of its 1 p H⁺ analogue recently prepared by us: Both of them form a similar type of H‐bonded dimer unit, however, its charge distribution as well as the overall molecular arrangement, electronic structure, and conductivity were significantly modulated by the introduction of the EDT group. These results provide a new insight into the structural and electronic features of the PyH⁺‐TTF‐based proton–electron correlated molecular conductors.     

Preparation of O-1∼C-6 and O-7∼C-14 fragments of colletodiol

(5S,2E)-5-Tetrahydropyranyloxy-2-hexenoic acid and p-toluenesulfonylethyl (4R,5R,7R,2E)-7-hydroxy-4,5-dimethylmethylenedioxy-2-octenoate were prepared from ethyl acetoacetate and D-glucose, respectively.     

Preparation of 1,6‐naphthyridine‐2,5(1H,6H)‐diones

Novel method for the synthesis of 3‐acyl‐1,6‐dialkyl‐7‐methyl‐1,6‐naphthyridine‐2,5(1H,6H)‐diones (2) was developed. The reaction of 2‐acyl‐1‐alkylamino‐1‐ethoxyethylenes (1) with acetyl chloride or β‐keto amide 3 with acetyl chloride in the presence of p‐toluenesulfonic acid gave 2 in moderate yield (14‐59% yield).