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.     

Odorless substitutes for foul-smelling thiols: syntheses and applications

Several alkanethiols and p-alkylphenylmethanethiols were synthesized, and their odors were compared with those of ethanethiol and benzyl mercaptan by human and instrumental sensors. Among the various thiols analyzed, 1-dodecanethiol (1) and p-heptylphenylmethanethiol (3) were revealed to be odorless. 1-Dodecanethiol (1) has been used instead of ethanethiol for dealkylation of ethers, and p-heptylphenylmethanethiol (3) can replace benzyl mercaptan in the preparation of a 1,3-mercapto alcohol from an ,β-unsaturated ketone. These odorless thiols will greatly improve the physical environment of the researcher working with these foul-smelling compounds.     

Kinetic and ESR studies on radical polymerization of methyl methacrylate in the presence of fullerene

The effect of fullerene (C₆₀) on the radical polymerization of methyl methacrylate (MMA) in benzene was studied kinetically and by means of ESR, where dimethyl 2,2′-azobis(isobutyrate) (MAIB) was used as initiator. The polymerization rate (R_p) and the molecular weight of resulting poly(MMA) decreased with increasing C₆₀ concentration ((0–2.11) × 10⁻⁴ mol/L). The molecular weight of polymer tended to increase with time at higher C₆₀ concentrations. R_p at 50°C in the presence of C₆₀ (7.0 × 10⁻⁵ mol/L) was expressed by R_p = k[MAIB]^0.5[MMA]^1.25. The overall activation energy of polymerization at 7.0 × 10⁻⁵ mol/L of C₆₀ concentration was calculated to be 23.2 kcal/mol. Persistent fullerene radicals were observed by ESR in the polymerization system. The concentration of fullerene radicals was found to increase linearly with time and then be saturated. The rate of fullerene radical formation increased with MAIB concentration. Thermal polymerization of styrene (St) in the presence of resulting poly(MMA) seemed to yield a starlike copolymer carrying poly(MMA) and poly(St) arms. The results (r₁ = 0.53, r₂ = 0.56) of copolymerization of MMA and St with MAIB at 60°C in the presence of C₆₀ (7.15 × 10⁻⁵ mol/L) were similar to those (r₁ = 0.46, r₂ = 0.52) in the absence of C₆₀. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2905–2912, 1998     

Acceleration of Reverse Intersystem Crossing using Different Types of Charge Transfer States

There is a need to boost the rate constant of reverse intersystem crossing (k_RISC) in thermally activated delayed fluorescence (TADF) materials for applications to organic light-emitting diodes. Recently, energy level matching of the locally excited state (LE) and charge transfer state (CT) has been reported to enhance k_RISC. In this study, we conceptually demonstrate that k_RISC can be improved even between CT states without LE states, through the use of different types of CT states. On the basis of this concept, we design a new compound, named DMAC-bPmT, where two phenyl groups of a well-known TADF material DMAC-TRZ are substituted by pyrimidine groups. Theoretical calculations indicated that the energy levels of the different CT states of DMAC-bPmT are very close and enhanced spin orbit coupling may be expected between them. As predicted, DMAC-bPmT experimentally exhibited a k_RISC three times as high as that of DMAC-TRZ.     

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.