Duckhyun Kim

High Molar Extinction Coefficient Organic Sensitizers for Efficient Dye-Sensitized Solar Cells

We have designed and synthesized highly efficient organic sensitizers with a planar thienothiophene-vinylene-thienothiophene linker. Under standard global AM 1.5 solar conditions, the JK-113-sensitized cell gave a short circuit photocurrent density (J(sc)) of 17.61 mA cm(-2), an open-circuit voltage (V(oc)) of 0.71 V, and a fill factor (FF) of 72%, corresponding to an overall conversion efficiency (eta) of 9.1%. The incident monochromatic photo-to-current conversion efficiency (IPCE) of JK-113 exceeds 80% over the spectral region from 400 to 640 nm, reaching its maximum of 93% at 475 nm. The band tails off toward 770 nm, contributing to the broad spectral light harvesting. Solar-cell devices based on the sensitizer JK-113 in conjunction with a volatile electrolyte and a solvent-free ionic liquid electrolyte gave high conversion efficiencies of 9.1% and 7.9%, respectively. The JK-113-based solar cell fabricated using a solvent-free ionic liquid electrolyte showed excellent stability under light soaking at 60 degrees C for 1000 h.

New type of organic sensitizers with a planar amine unit for efficient dye-sensitized solar cells.

A new type of organic sensitizers incorporating a planar amine unit have been synthesized and demonstrated to be a highly efficient sensitizers, showing evidence of lateral interactions on the TiO(2) surface. Under standard global air mass 1.5 solar conditions, the JK-98 sensitized cell gave a short circuit photocurrent density (J(sc)) of 16.78 mA cm(-2), an open-circuit voltage (V(oc)) of 0.745 V, and a fill factor (ff) of 0.70, corresponding to an overall conversion efficiency (η) of 8.71%.

Selection of 5-methyltryptophan resistant rice mutants from irradiated calli derived from embryos

For increasing the contents of specificfree amino acids in rice (Oryzasativa L.) cultivar, Donganbyeo, mutantcell lines resistant to growth inhibitionby 5-methyltryptophan (5MT) were selectedfrom embryo cultured callus irradiated with50 Gy of gamma rays. Two lines, M2-1and M2-2, were obtained from theregenerated plants by selfing. Thesegregation ratios of resistance andsensitivity in these lines fitted 9:7 and3:1 ratios, respectively. Considering theagronomic traits, M2-1 was about thesame as the original variety in culm lengthand a little longer or higher in paniclelength and number of tillers. However, thefertility of M2-1 significantlyincreased compared to the originalvariety. M2-2 had an extremely highculm length and tillering capacity. Four5MT-resistant homozygous M3lines (MRclasses), M3-1-40 and M3-1-116from M2-1 (MR I),and M3-2-8 and M3-2-12from M2-2 (MR II), were obtained inthe same manner as with the M2generation. Protein contents of brown ricewere increased about 19% and 32% and the total contents of 9 free essentialamino acids were 71% and 34% greater thanthe original variety in the MR I andMR II groups, respectively. However, forthe free essential amino acids of polishedrice, there was no difference from theoriginal variety.

Identification of Kunitz trypsin inhibitor mutations using SNAP markers in soybean mutant lines

The Kunitz trypsin inhibitor (KTi) in soybean has several polymorphic types that are controlled by multiple alleles, which behave in a co-dominant fashion. Of these, Tia and Tib, which differ by nine amino acids, are the predominant types. In order to develop a single nucleotide amplified polymorphism (SNAP) marker for the classification of the predominant KTi types, Tia and Tib, and evaluate KTi activities by differing KTi type total 451 soybean mutant lines (M12–M16 generation) were incorporated in this study. Among 451 soybean mutants, 144 and 13 mutant lines showed decreased and increased trypsin inhibitor activity when compared with the original cultivars, respectively. To identify the KTi type, we designed a SNAP marker. Among 451 mutant lines from 12 soybean cultivars and landraces, 8 mutant lines derived from cvs. Baekwoon, Paldal and Suwon115 showed a change in KTi type when compared with the original cultivars using the SNAP marker. Five mutant lines in Suwon115 changed from Tib to Tia, while two mutant lines derived from cv. Baekwoon and one mutant line derived from cv. Paldal were changed from Tia to Tib. These changes of KTi types were confirmed by sequencing of the KTi genes and non-denaturing polyacrylamide gel electrophoresis of the KTi proteins. To identify the effect of KTi activity based on the change in KTi type, we measured the KTi activity using the three cultivars and eight mutant lines that showed changes in KTi type. Two mutant lines (BW-1 and 7-2) derived from cv. Baekwoon and one mutant line (PD-5-10) from cv. Paldal that changed from Tia to Tib showed lower activity than the original cultivar. In cv. Suwon115, five mutant lines that changed from Tib to Tia showed higher activity than the original cultivar. These results indicate that the designed SNAP marker was capable of identifying the KTi type and that Tia activity was higher than Tib activity in soybean.

Utilization of algal sugars and glycerol for enhanced cephalosporin C production by Acremonium chrysogenum M35

In our previous study, glycerol was utilized as an additional carbon source for the production of cephalosporin C (CPC) by Acremonium chrysogenum M35. In this study, algal sugars extracted from the third‐generation biomass were utilized in the CPC production for the first time. The CPC production improved about twofold when using the algal sugars as the carbon source. The complex medium including algal sugars and glycerol was utilized, and 7·3 g l−1 CPC production was achieved in a 250‐ml shaking flask. To determine the important variables for the CPC production, Plackett–Burman design was carried out and 6·18 g l−1 of CPC was estimated under the numerically optimized conditions. Under the optimized conditions, the CPC production was performed in a 5‐l scale bioreactor, affording CPC production at a rate of 7·1 g l−1. Moreover, 6·7 g l−1 CPC was produced using crude glycerol as the substrate.

Expressed sequence tags from wheat roots under hypoxia

Hypoxia due to waterlogging adversely affects agricultural crops in many parts of the world and severely impacts overall annual production levels. To evaluate the response of wheat roots to a controlled hypoxic environment at the level of transcription, a cDNA library was constructed using hypoxia-stressed wheat. A total of 1274 clones (94.8%) out of 1344 sequences were found to be at least 50 bp long. Phrap assembly using high quality sequences formed 879 sets of non-overlapping sequences. Based on BLASTx analysis against the nonredundant database, a total of 494 unigenes showed a high homology to the registered amino acid sequences of plant (E < e−10). A total of 112 unigenes, which were not matched to any wheat ESTs in the database, were detected. A functional classification of 118 clones whose transcript levels were evaluated under hypoxia was performed according to gene ontology. These results may provide useful information for further investigations to better understand the response of wheat roots to waterlogging.