Observation and analysis of single DNA nano-kinetics by pin-fiber video scope

The nano-kinetic movement of a single DNA molecule was observed and analyzed by a newly developed video-microscope system with an optical fiber, called a pin-fiber video scope. A single lambda-DNA molecule was put in focus using fiber-illumination, and the stretching and shrinking motion was measured. The molecule's kinetics were analyzed by numerical calculations and are discussed. A photocleavage phenomenon of DNA molecules was also visualized by the pin-fiber video scope. The new video-microscope system has the potential to observe and analyze the nano-kinetics of a single molecule.     

A novel synthesis of substituted quinolines using ring-closing metathesis (RCM): its application to the synthesis of key intermediates for anti-malarial agents

A method for synthesizing substituted quinolines using ruthenium-catalyzed ring-closing metathesis as a key step has been developed. Substituted 1,2-dihydroquinolines, 4-silyloxy-1,2-dihydroquinoline and 4-methoxy-1,2-dihydroquinoline, were successfully synthesized in excellent yields via ene-ene metathesis and silyl or alkyl enol ether-ene metathesis, respectively. The synthetic intermediates of the antimalarial agents quinine, chloroquine, and PPMP-quinine hybrid were efficiently synthesized by this methodology.     

Synthesis of 2-[2-(8-hydroxyquinolyl)azo]-1-naphthol and its use in the spectrophotometric determination of calcium in potable water

The synthesis of a novel reagent, 2-[2-(8-hydroxyquinolyl)azo]-1-naphthol (HQAN), is described. The acidity constants of the reagent and its reactions with various metal ions are reported. The HQAN reagent forms a soluble calcium chelate in 50% (v/v) dioxane/ water at pH > 8.5 (? = 24 000 l mol^?1 cm ^t-1 at 570 nm). It also forms chelates with magnesium, other alkaline earth metals, and ivalent Mn, Fe, Ni, Cu, Zn, Cd and Pb. These interferences (except for Mn) can be avaoided by pH adjustment or by adding masking agents, and a very simple procedure for the determination of calcium in potable waters is obtained.     

Uniaxial alignment of the smallest diamagnetic susceptibility axis using time-dependent magnetic fields

A diamagnetic particle with magnetic susceptibilities chi3 < chi2 = chi1 < 0 was subjected to a rotating magnetic field to obtain an alignment of the chi3 axis (the smallest susceptibility axis) in the direction perpendicular to the plane of the rotating magnetic field. A polymer short fiber, whose fiber axis coincides with the chi3 axis, was suspended in a fluid with the same density, and then a rotating magnetic field generated by a rotation of a pair of permanent magnets was applied. The fiber axis, rotating following the applied field, finally ended up with an alignment perpendicular to the plane of the rotating magnetic field. The experimental data on the time course of the alignment was in good agreement with the numerical calculation based on the equation of rotation.     

Theoretical study of photochemical reactions: Electron assignment and the state correlation diagram

A general way for drawing the state correlation diagram and seeking the reaction path is presented. If a high-symmetry reacting system is given, its least-motion path that maintains the symmetry is primarily examined. For a given state, it is judged whether the least-motion path is symmetry allowed or forbidden. If allowed, it is called the direct process. If forbidden, the symmetry imposed on the system should be relaxed, resulting in the mixing of MO 's. Then, the energy barrier of the avoided crossing for some excited states is removed and the possible reaction path is found. After this procedure, the symmetry-allowed paths may be sought by the geometry optimization with a suitable wave function. By the use of such a procedure, the dissociation of diazomethane and (3H-)diazirine is found to proceed via the C_s and C₂ symmetries.     

Mixed-valence state of optically active 1',1'"-bis(2-phenylbutyl)-1,1''-biferrocenium pentaiodide: effects of cation symmetry and intermolecular interaction on trapped-/detrapped-valence states

The effects of cation symmetry and packing on the mixed-valence state of binuclear ferrocene derivatives are discussed separately by using chiral isomers and racemic modification of 1',1' "-bis(2-phenylbutyl)-1,1' '-biferrocenium pentaiodide. The pentaiodide anion has a polymeric structure and is composed of triiodide anion and iodine molecule units. The (R,S) isomer having an inversion center shows a detrapped-valence state even at 78 K. On the other hand, the (R,R) and the (S,S) isomers having no inversion center show a trapped-valence state at room temperature. The racemic modification, however, consisting of the (R,R) and the (S,S) isomers shows a perfect detrapped-valence state at room temperature. This finding shows that the packing effect overcomes the effect of cation asymmetry.     

Copolymerization of 2-methylene-4-phenyl-1,3-dioxolane with electrophilic vinyl monomers through zwitterionic mechanism

Spontaneous copolymerization of cyclic ketene acetal, 2-methylene-4-phenyl-1,3-dioxolane ( I ) with common electrophilic vinyl monomers, such as methyl α-cyanoacrylate (MCA), acrylonitrile (AN), and methyl methacrylate (MMA) were investigated to further explore zwitterion polymerization method with cyclic ketene acetals. In the reaction of I with MCA and AN, spontaneous copolymerization took place at ambient temperature. The copolymers of I with MCA gave low molecular weight polymers, but copolymers obtained with I and AN were high molecular weight polymers. In the reaction of I and MMA, high molecular weight copolymer was obtained only at temperatures above 80°C. Thus, obtained polymers were not the alternating copolymers and possessed high I content in all the cases. From the above results, macrozwitterionic mechanism was suggested as discussed.     

Preparation and separation of all possible rotamers of a stereochemical analog of meso-tartaric acid: optically inactive and optically active isomers of (R,S)-2,2′-bis(methoxycarbonyl)-6,6′-dimethyl-9,9′-bitriptycyl

All the three possible rotamers of the title compound were separated by chromatography, and unambiguously identified by NMR and X-ray analysis. One of the isomers was optically inactive C_i conformation. The other optical active forms were resolved to give a pair of enantiomers, which were characterized by optical rotation and CD spectra. Thus the optical inactivity of a compound such as meso-tartaric acid that can take C_i conformation in solution, is now ascribed to that the molecule has an optically inactive C_i conformer and equal amounts of optically active conformers, that are enantiomers, in solution.     

Physicochemical properties and stability in the acidic solution of a new macrolide antibiotic, clarithromycin, in comparison with erythromycin.

Clarithromycin (6-O-methylerythromycin), a new 14-membered macrolide antibiotic, has been studied to clarify its physicochemical properties and stability in acidic solution, as compared with erythromycin (EM). The solubility of clarithromycin (CAM) in distilled water was lower than that of EM and decreased with increasing temperature. The solubilities of CAM and EM in the phosphate buffer solution at 37 degrees C decreased with an increasing pH and kept constant above pH 9. From pH-solubility profiles, the dissociation constants of CAM and EM were determined to be 8.76 and 8.36, respectively. The partition coefficient of CAM took a higher value than that of EM and increased with an increasing pH. In the acidic solution, the decomposition of CAM and EM obeyed the pseudo-first order kinetics. From the decomposition rate constants, the half life (T1/2) of CAM and EM were determined. In pH 1.39, CAM degraded with a T1/2 of 17 min while EM kinetics corresponded to a T1/2 of 3 s. Therefore, CAM was 340-fold more stable in pH 1.39 and markedly more stable in the acidic solution than EM.     

Cationic polymerization of formaldehyde in liquid carbon dioxide. Part II: A kinetic study of the polymerization

The kinetic behavior on the polymerization of formaldehyde with and without acidic catalyst, in liquid carbon dioxide, in the temperature range of 30 to 50°C. was investigated. In the polymerization without catalyst both the polymer yield and the degree of polymerization increased with reaction time and also with rising temperature. With acidic catalyst, such as acetic acid and dichloroacetic acid, both the polymer yield and the degree of polymerization increased more than that in the polymerization without catalyst. The overall rate of polymerization with and without acidic catalyst was expressed by the first-order rate equation with respect to monomer concentration. From the results it was concluded that the polymerizations belonged to a type of successive polymerization with rapid initiation and no termination. The rate constant and the activation energy of each elementary process of polymerization were estimated on the basis of the results.