Spectrofluorometric determination of kynurenic acid with horseradish peroxidase in the presence of hydrogen peroxide.

The catalytic activity of horseradish peroxidase (HRP) in the presence of hydrogen peroxide has been investigated for the fluorescent derivatization of kynurenic acid under conditions with no exposure to light. Non-fluorescent kynurenic acid was converted into a fluorescent compound (Ex: 367 nm, Em: 470 nm) with HRP in the presence of hydrogen peroxide, and the optimum conditions of this fluorescent derivatization were investigated. Moreover, this fluorescent derivatization was developed for a spectrofluorometric determination of trace amounts of kynurenic acid by measuring the fluorescence intensity of the fluorescent compound. The calibration curve obtained was linear from 1.0 to 10.0 nmol of kynurenic acid in a 1.0 mL sample solution. The relative standard deviation at 5.0 nmol of kynurenic acid was 5.71% (n=5). By adjusting the bandwidths for both the excitation and emission to 15 nm, the calibration curve was also linear in the range between 0.1 to 1.0 nmol of kynurenic acid in a 1.0 mL sample solution. This method was applied to the fluorometric determination of trace amounts of kynurenic acid in the control sera.     

Central Elements in the Universal Enveloping Algebras for the Split Realization of the Orthogonal Lie Algebras

We construct central elements in the universal enveloping algebra using column-determinants for the split realization of the orthogonal Lie algebra. Our central elements are quite new and simple, though they are closely related to what Howe and Umeda gave for the orthogonal Lie algebra under the different realization as the alternating matrices.     

Development of a simultaneous measurement system of x‐ray diffraction and raman spectra: Application to structural study of crystalline‐phase transitions of chain molecules

The development of a bench‐top‐type system for simultaneous measurement of X‐ray diffraction and Raman spectra has been made to investigate structural changes in the phase transitions of chain molecules such as polyethylene, n‐alkane, and so forth from various viewpoints. For the X‐ray diffraction measurement an imaging plate or a charge‐coupled device camera was used as a two‐dimensional detector. For the Raman spectral measurement a miniature Raman spectrometer was used with optical fibers for the irradiation of incident laser beams and collection of scattered signals. For example, in the heating process of the n‐C₃₀H₆₂ sample, the phase transition from orthorhombic‐to‐hexagonal lattices could be detected clearly by the X‐ray and Raman measurements. By comparing these two different types of data in detail, an intimate relationship between conformational disordering and rotational motion of molecular chains is detected more clearly than before. Also, similar discussion can be made for the orthorhombic‐to‐hexagonal phase transition of the geometrically constrained polyethylene sample occurring immediately below the melting point. Another example concerns the structural change in the photoinduced solid‐state polymerization of cis,cis‐diethylmuconate single crystal. From the shifts in the X‐ray reflection position and Raman frequency characteristic of the produced polymer, it was found that the molecular deformation of the polymer chains and lattice strain was induced in the early stage of the polymerization reaction. For the ferroelectric‐phase transition of vinylidene fluoride copolymer, the simultaneous measurement was made for collecting triple information of small‐angle and wide‐angle X‐ray scatterings and Raman spectra to know the relationship between the structural change in the crystal lattice and the morphological change in the lamellar stacking mode. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 495–506, 2002; DOI 10.1002/polb.10112     

An efficient chemical fixation of nitric oxide: convenient and practical synthesis of 1,2,3-oxadiazole 3-oxides

Nitric oxide reacts efficiently with alkynyllithium at low temperature producing 1,2,3-oxadiazole 3-oxides in good yields.     

Communication: A concerted mechanism between proton transfer of Zundel anion and displacement of counter cation

Ab initio path integral molecular dynamics simulation of M(+)(H(3)O(2)(-)) (M = Li, Na, and K) has been carried out to analyze how the structure and dynamics of a low-barrier hydrogen-bonded Zundel anion, H(3)O(2)(-), can be affected by the counter alkali metal cation, M(+). Our simulation predicts that the quantum proton transfer in Zundel anion can be strongly coupled to the motion of counter cation located nearby. A smaller cation can induce larger structural distortion of the Zundel anion fragment making the proton transfer barrier higher, and hence, lower the vibrational excitation energy. It is also argued that a large H∕D isotope effect is present.     

A Light‐Controlled Release System Based on Molecular Recognition of Cyclodextrins

This Communication describes a new light‐controlled release system based on molecular recognition of cyclodextrins. Azobenzene (Azo) residue is employed as a photoresponsive guest residue because it can switch the partner from α‐cyclodextrin (αCD) to β‐cyclodextrin (βCD) by irradiation with UV light. Poly(sodium acrylate)s possessing αCD, βCD, and Azo residues (pAαCD, pAβCD, and pAAzo, respectively) are mixed in aqueous solutions to form aggregates through the formation of inclusion complexes of Azo with αCD and/or βCD. A chemical cargo, 1‐pyrenemethylammonium chloride (PyMA), is contained in the aggregates, and its release behavior is investigated by dialysis experiments under UV irradiation. These data indicate that the amount of PyMA released for the pAαCD/pAβCD/pAAzo ternary mixture is approximately three times as high as those for the pAαCD/pAAzo and pAβCD/pAAzo binary mixtures because of the light‐controlled rearrangement of inclusion complexes.

     

Macroscopic observations of molecular recognition: discrimination of the substituted position on the naphthyl group by polyacrylamide gel modified with β-cyclodextrin

Macroscopic molecular recognition observations were realized using polyacrylamide-based gels modified with α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), 1-naphthylmethyl (1Np), and 2-naphthylmethyl (2Np) moieties, which are denoted as αCD(x)-gel, βCD(x)-gel, 1Np(y)-gel, and 2Np(y)-gel, where x and y indicate the mol % of CD and Np moieties, respectively. The αCD(5)-gel did not adhere to either the 1Np(5)-gel or 2Np(5)-gel, whereas the βCD(5)-gel interacted with both to form alternating or checkered assemblies. Although the difference in the association constants of β-CD for the model polymers was small, the βCD(x)-gel successfully discriminated between 1Np(y)-gel and 2Np(y)-gel at the appropriate x and y.     

Solvent‐Free Synthesis of Benzothiazolines in the Presence of Alumina

o‐Aminothiophenol reacted with ketones and β‐keto esters in the presence of alumina under mild and solvent‐free conditions to afford the corresponding benzothiazolines in high yields. Alumina can be reused for subsequent reactions without any loss of the activity.     

Total synthesis and determination of the absolute configuration of paralemnolin C and biological studies of eremophilane derivatives

The first asymmetric total synthesis of paralemnolin C was achieved. The absolute configuration at C11 of this natural product was determined from the X-ray crystallographic analysis of the epoxide derivative. In addition, biological studies of eremophilane derivatives including paralemnolin C and sagittacin E were carried out.