Kwang-Yon Kim

The properties of electrochemically prepared Polyindole Perchlorate (PIP)

Abstract Polyindole perchlorate (PIP) was obtained by electro-polymerization, supplying a potential of 0.68 eV. Cyclic voltammetry measurements suggested that the electrode reaction was irreversible. Structural analysis of PIP was performed by various spectroscopic measurements and the results suggested the 1,3-polymerization mechanism of indole. A thermogravimetric analysis (TGA) was performed on the polyindole-based systems, and the results were compared with the polyaniline-based ones. From a comparison of thermal reaction rates in polyindole- and polyaniline-based systems, their thermal characteristics were studied. The electrical conductivity for the PIP pellet was performed in the temperature range from −150 to 25°C. From the result, the values of log Σ at 25°C and the Ea calculated from the Arrhenius plot were −1.67Scm−1 and 0.508 eV, respectively. The PIP pellet experiment suggested that hopping conduction was a possible conduction mechanism and that polarons were the charge carriers. Also, the perchlorate anions placed along the polymer chains acted as electron acceptors. ESR measurement on the PIP powder was performed at 25°C, which provided the various ESR-parameters.

Di-oxanipecotic acids as more stable turn motifs than di-nipecotic acids

The folded structures of peptidomimetics containing dimers of oxanipecotic acid (Oxa) in loop segments were characterized and compared with those of the corresponding nipecotic acid (Nip)-based ones. According to structural studies using FT-IR and NMR spectroscopies, di-oxanipecotic acid adopted more stable turn conformations than di-nipecotic acid, and for tetramers, L,(S)-Oxa,(S)-Oxa,L and L,(S)-Oxa,(R)-Oxa,L formed hairpin-like structures but only L,(R)-Nip,(S)-Nip,L promoted the stable folded conformations.

Assessment of quantitative structure-activity relationship of toxicity prediction models for Korean chemical substance control legislation

Objectives For successful adoption of legislation controlling registration and assessment of chemical substances, it is important to obtain sufficient toxicological experimental evidence and other related information. It is also essential to obtain a sufficient number of predicted risk and toxicity results. Particularly, methods used in predicting toxicities of chemical substances during acquisition of required data, ultimately become an economic method for future dealings with new substances. Although the need for such methods is gradually increasing, the-required information about reliability and applicability range has not been systematically provided. Methods There are various representative environmental and human toxicity models based on quantitative structure-activity relationships (QSAR). Here, we secured the 10 representative QSAR-based prediction models and its information that can make predictions about substances that are expected to be regulated. We used models that predict and confirm usability of the information expected to be collected and submitted according to the legislation. After collecting and evaluating each predictive model and relevant data, we prepared methods quantifying the scientific validity and reliability, which are essential conditions for using predictive models. Results We calculated predicted values for the models. Furthermore, we deduced and compared adequacies of the models using the Alternative non-testing method assessed for Registration, Evaluation, Authorization, and Restriction of Chemicals Substances scoring system, and deduced the applicability domains for each model. Additionally, we calculated and compared inclusion rates of substances expected to be regulated, to confirm the applicability. Conclusions We evaluated and compared the data, adequacy, and applicability of our selected QSAR-based toxicity prediction models, and included them in a database. Based on this data, we aimed to construct a system that can be used with predicted toxicity results. Furthermore, by presenting the suitability of individual predicted results, we aimed to provide a foundation that could be used in actual assessments and regulations.

A novel scheme for probing mode-specific proton transfer in proton-bound homodimers: vibrational predissociation and ab initio study on CH5+·CH4

Abstract A novel experimental scheme for probing mode-specific proton transfer in proton-bound homodimers based on the vibrational predissociation spectroscopy combined with the techniques of mass-selected detection and isotope substitution is described. Its application to CH 5 + ·CH 4 suggests that rapid, non-mode specific proton transfer occurs when three C–H stretch modes are excited. To explain the experimental result, the transition state and the minimum energy path (MEP) for proton transfer in CH 5 + ·CH 4 are further characterized by ab initio method.

De novo design of non-hydrogen-bonded helical pseudopeptides composed of oxanipecotic acid oligomers

Ab initio calculation and circular dichroism experiments reveal that Oxa-oligomers adopted pronounced non-hydrogen-bonded helical structures.