Dynamic kinetic resolution of amino acid amide catalyzed by D-aminopeptidase and alpha-amino-epsilon-caprolactam racemase

Amino acid amide racemizing activity was discovered in alpha-amino-epsilon-caprolactam (ACL) racemase (EC 5. 1. 1. 15) from Achromobacter obae. The enzymatic synthesis of d-alanine from l-alanine amide has been demonstrated by use of d-aminopeptidase (DAP; EC 3. 4. 11. 19) from Ochrobactrum anthropi C1-38 and ACL racemase. The conversion of 45 mM l-alanine amide was carried out at 30 degrees C for 7 h; l-alanine amide was completely converted to d-alanine, and no l-alanine was detected. The result of successive enzymatic reaction shows that the combination of ACL racemase and DAP can be applied for dynamic kinetic resolution of dl-amino acid amides to yield d-amino acids.     

Specific heat and neutron diffraction study on quaternary sulfides BaNd2CoS5 and BaNd2ZnS5

Magnetic and electrical properties are investigated for quaternary neodymium sulfides BaNd₂TS₅ (T=Co, Zn) through the specific heat, neutron diffraction, and electrical conductivity measurements. Their electrical conductivities show semiconductive behavior, which follows the Arrhenius temperature dependence with the activation energy of E_a=1.46 eV for BaNd₂ZnS₅ and E_a=1.19 eV for BaNd₂CoS₅. The specific heat of BaNd₂ZnS₅ has a λ-type anomaly at 2.8 K due to the antiferromagnetic ordering of the Nd³⁺ moments and a Schottky-type anomaly at around 60 K, which results from the crystal field splitting of the ⁴I_9/2 ground state of the Nd³⁺ ion. The specific heat of BaNd₂CoS₅ shows two λ-type anomalies at 5.7 K due to the antiferromagnetic ordering of Nd³⁺ and at 58 K due to the antiferromagnetic ordering of Co²⁺. The latter overlaps with the Schottky-type anomaly due to the crystal field splitting of the Nd³⁺ ion. Neutron diffraction measurements for BaNd₂CoS₅ show that a magnetic arrangement of the Co²⁺ moments has a collinear antiferromagnetic structure, while that of the Nd³⁺ moments has a noncollinear one.     

Study on multimers and their structures in molecular association mixture

Self-association system of(R)-1,3-butanediol in dilute carbon tetrachloride(CCl4)solution is studied as a model of molecular association mixture.Analysis methods including FSMWEFA(fixed-size moving window evolving factor analysis)combined with PCA(principal component analysis),SIMPLISMA (simple-to-use interactive self-modeling mixture analysis),and ITTFA(iterative target transformation factor analysis)are adopted to resolve infrared spectra of(R)-1,3-butanediol solution.Association number and equilibrium constant are computed.(R)-1,3-butanediol in dilute inert solution is determined as a monomer-trimer equilibrium system.Theoretical investigation of trimer structures is carried out with DFT(density functional theory),and structural factors are analyzed.     

New Proof of the Fukui Conjecture by the Functional Asymptotic Linearity Theorem

The present article provides a new proof of the Fukui conjecture concerning the additivity problem of the zero-point vibrational energies of hydrocarbons. This conjecture played a prominent role in the initial development of the repeat space theory (RST), and continues to be of vital significance in the recent development of the theory of the generalized repeat space X _r (q,d). The new proof of the Fukui conjecture has been given here by establishing the functional version of the Asymptotic Linearity Theorem (ALT), the Functional ALT. This enhanced version of the ALT directly implies the validity of the Fukui conjecture; it easily unifies, in a broad perspective, a variety of additivity phenomena in physico-chemical network systems having many identical moieties, and efficiently solves some interpretational problems of the empirical additivity formulae from experimental chemistry. The proof of the functional version of the ALT is based on a new method transferable to the extended theoretical framework of the generalized repeat space X _r (q,d).     

Estimation of biotinylated lectin by isoelectric focusing

Concanavalin A (Con A) was biotinylated to various degrees using N-biotinyl-omega-aminocaproic-acid-N-hydroxy succinimide ester as the biotinylation reagent, and then analyzed by isoelectric focusing using PhastGel IEF 3-9. The isoelectric points of biotinylated ConAs were found to decrease with increasing concentration of the biotinylation reagent. Analysis by isoelectric focusing followed by dot blotting clearly indicated that the biotinylated ConA with an isoelectric point lower than that of the original ConA by 2.2 +/- 0.6 had the strongest binding activity for ovalbumin.     

Controlled kinetics of non-enzymatic chemiluminescence reactions for simple imaging of DNA and protein

A robust and sensitive non-enzymatic chemiluminescence (CL) imaging method is presented. In the method a fast-emitting CL reaction is tuned to furnish a slower-emitting reaction suitable for simple CL imaging. Typically, non-enzymatic CL reactions between luminol or fluorescein and oxygen species generated by KCN as catalyst, were rather fast and unsuitable for CL imaging; the speed of the reactions could, however, be reduced substantially by changing KCN for CH(3)CN or benzonitrile. Light emission from the tuned CL reaction was intense and long-lived, and even with a simple arrangement high sensitivity could be achieved. The maximum CL peak was reached after approximately 1.5 min in the presence of 25% acetonitrile, and as little as 16 fmol commercial isoluminol-labeled streptavidin was detected and visualized on either microplate or membrane. The approach was further illustrated by imaging of DNA on a membrane and of antibody on a microplate by use of biotin-streptavidin chemistry. Overall, this simple, economical, and sensitive CL imaging system is expected to be very useful in biochemical analysis, and greatly complements currently used enzyme-based CL imaging methods, especially in routine applications.     

Optically active copolyamides by melt and solution condensation polymerization

The melt and solution condensation copolymerization of nylon salts which were prepared from d-camphoric acid and adipic acid with hexamethylenediamine were carried out, and optically active copolyamides were obtained. The copolyamides obtained had a positive specific rotation. The specific rotations for the copolyamides increased with increasing content of d-camphoryl units in the copolymers. The optical rotatory dispersion of the copolyamides had positive curves and were found to fit the simple Drude equation. The λ_c values of the polymers obtained by the melt and solution condensation polymerization were 241 mμ and 245 mμ, respectively.     

Electrochemical synthesis of a polypyrrole thin film with supercritical carbon dioxide as a solvent

A conductive polypyrrole (PPy) film was successfully synthesized in a homogeneous supercritical carbon dioxide (scCO2)/acetonitrile (AN) system. The occurrence of a homogeneous supercritical state was confirmed by observations of the phase behavior of the system through a high-pressure cell with a viewing window. The concentration of a supporting electrolyte, tetrabutylammonium hexafluorophosphate (TBAPF6), significantly changed the phase behavior of the scCO2/AN system. The polymerization rate of the film in that system decreased with further addition of CO2. This result suggested that the low viscosity of scCO2 did not play an important role in improving the growth rate of the PPy film. The low polymerization rate might have been due to the electron-transfer resistance arising from the low dielectric constant of scCO2/AN mixture. The roughness of the film prepared in the homogeneous scCO2/AN system was 1/10 that synthesized in AN itself as a solvent. The slow growth of film and the high diffusion rate of the monomer seemed to account for the smooth flat film formation.     

Donor–acceptor–acceptor-type near-infrared fluorophores that contain dithienophosphole oxide and boryl groups: effect of the boryl group on the nonradiative decay

The use of donor–π–acceptor (D–π–A) skeletons is an effective strategy for the design of fluorophores with red-shifted emission. In particular, the use of amino and boryl moieties as the electron-donating and -accepting groups, respectively, can produce dyes that exhibit high fluorescence and solvatochromism. Herein, we introduce a dithienophosphole P-oxide scaffold as an acceptor–spacer to produce a boryl- and amino-substituted donor–acceptor–acceptor (D–A–A) π-system. The thus obtained fluorophores exhibit emission in the near-infrared (NIR) region, while maintaining high fluorescence quantum yields even in polar solvents (e.g. λ_em = 704 nm and Φ_F = 0.69 in CH₃CN). A comparison of these compounds with their formyl- or cyano-substituted counterparts demonstrated the importance of the boryl group for generating intense emission. The differences among these electron-accepting substituents were examined in detail using theoretical calculations, which revealed the crucial role of the boryl group in lowering the nonradiative decay rate constant by decreasing the non-adiabatic coupling in the internal conversion process. The D–A–A framework was further fine-tuned to improve the photostability. One of these D–A–A dyes was successfully used in bioimaging to visualize the blood vessels of Japanese medaka larvae and mouse brain.

Combination of electron-accepting diarylboryl terminal groups and dithienophosphole oxide spacers with electron-donating triarylamine moieties produces donor–acceptor–acceptor type π-systems, which exhibit emissions in the near-infrared region.