Hyo Gil Choi

Mitochondrial thioredoxin-responding off-on fluorescent probe.

We synthesized a new probe, Mito-Naph, to visualize mitochondrial thioredoxin (Trx) activity in cells. A fluorescence off-on change is induced by disulfide cleavage of the probe, resulting from a reaction with Trx and subsequent intramolecular cyclization by the released thiolate to give a fluorescent product. By measuring the fluorescence at 540 nm, Trx activity can be detected at nanomolar concentrations (down to 50 nM) well below its physiological levels. The in vitro and in vivo Trx preference of Mito-Naph was demonstrated by fluorometric and confocal microscopic experiments. In vitro kinetic analysis of the disulfide bond cleavage revealed that the second-order rate constant for Trx is (4.04 ± 0.26) × 10(3) (M s)(-1), approximately 5000 times faster than that for GSH. The inhibition experiments involving PX-12, a selective inhibitor of Trx, also revealed that the emission from Mito-Naph significantly decreased in PX-12 dose-dependent manners, both in living cells and in cellular protein extracts. The Trx preference was further supported by an observation that the fluorescence intensity of rat liver extract was decreased according to the Trx depletion by immunoprecipitation. On the basis of these results, it is concluded that Mito-Naph preferentially reacts with Trx, compared with other biological thiols containing amino acids in vitro and in vivo.

Effect of EC Level of Irrigation Solution on Tomato Growth and Inorganic Ions of Root Zone in Soilless Culture of Tomato Plant Using Coir Substrate

In hydroponics, the nutrient solution is supplied considering the water and nutrient uptake characteristics of crops. However, as the ionic uptake characteristics are changed as a result of the weather conditions or the growth response of the crops, the root zone can not be maintained in optimal condition. In addition, the coir substrate has been used mainly for the tomato cultivation in place of the inorganic substrate, there are few studies on long-term cultivation using coir substrate. Therefore, this study was conducted to investigate the effect of EC level of irrigation solution on tomato growth and inorganic ions of root zone in soilless culture using coir. Coir substrate mixed with 5 : 5 chip and dust was used. EC level of irrigation solution was 1.0, 1.5, 2.0, and 3.0 dS·m. At the initial stage, NO3N, P, Ca and Mg in the drainage were lower than the irrigation level at 1.0 and 1.5 dS·m. However, EC 2.0 dS·m or higher, all the ions except P were highly concentrated in the drainage. The average fruit weight was not significantly different between 1.0 and 1.5 dS·m until 3th cluster, but from the next cluster, the higher the EC level, the smaller the weight. The number of fruit and yield to 6th cluster was the highest at 1.5dS·m. From the next cluster, The yield was decreased with the higher EC level. At the early stage of growth, BER occurred only in EC 3.0 dS·m, but increased in all treatments with increasing irradiation. The incidence rate of EC 3.0 dS·m was higher than that of the lower EC level treatment. Additional key words : EC, drainage, blossom-end rot(BER), soluble solids content

Optical Characteristics of Two New Functional Films and Their Effect on Leaf Vegetables Growth and Yield

Three leaf vegetables, namely green lettuce, red lettuce (Lactuca sativa) and red-veined chicory (Cichorium intybus) were grown in minigreenhouses covered with two new functional films and conventional polyethylene film (PE). Seedlings of leaf vegetables were transplanted in a plastic troughs filled with soil-perlite mixture. Two functional films were made from polyolefin (PO) material. Measurement of optical characteristics showed that polyolefin films have better transmittance for the photosynthetic active radiation (PAR, 400-700nm) and higher absorptance for the ultraviolet radiation (UV, 300-400nm) in comparison with the conventional PE film. After three months of utilization higher loss in PAR transmittance was observed for conventional PE film. Leaf vegetables growth was enhanced and yield was increased in greenhouses covered by new functional films.