Ung-In Cho

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.

PHOTOACOUSTIC MEASUREMENTS FOR CATALYTIC EFFECTS OF PEROVSKITE ELECTRODES IN A SEALED-OFF CO2 DISCHARGE TUBE

To investigate catalytic activities of perovskite-type electrodes in a sealed-off CO2 laser cavity, we studied the dissociation and reformation reactions of CO2 during electric discharge by monitoring the concentration change of CO2 as a function of time. A photoacoustic spectroscopy detection was introduced to measure the amount of CO2 in a closed discharge system. The catalytic activities in the dissociation of CO2 were demonstrated and compared for both Cu and La0.7Sr0.3CoO3 cathodes. The discharge with the gas mixture of CO2:N2:He=1:1:8 was performed under nine combinations of different conditions at pressures of 10, 20, and 30 Torr and discharge currents of 3, 4, and 5 mA. Within 1 min after the discharge, the concentration of CO2 reduced drastically by as much as 60% for both cathodes. In the case of the Cu cathode, the amounts of CO2 in the tube had not recovered even after 30 min, while with the perovskite cathode the CO2 contents recovered slowly up to 90%–95% within 5 min and then remained almos...

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.

Realization of spiking by an excitable chemical system

It is theoretically demonstrated that an excitable chemical system can function as a spiking neuron and a chemical spiking neuron network can be constructed. The Oregonator is used as a model for a chemical spiking neuron. The chemical spiking neuron modeled by the Oregonator is similar in behavior to the spiking neuron model of Maass even though the Oregonator has a different excitation mechanism from the spiking neuron model. In the spiking neuron network, information is encoded and processed by using the timing of the spikes in spiking neurons. It is shown that chemical spiking neuron networks can be constructed by the unidirectional selective coupling of the spiking chemical neurons. The chemical spiking neuron network can process information encoded temporally like the spiking neuron network with a restriction in the range of the weight of couplings between the chemical neurons.