DNA Hydrogel as Template for Nanofunctional Materials

Nokyoung PARK,Kyuhyun IM,Jaehyun HUR 한국생물공학회 2013 한국생물공학회 학술대회 Vol.2013 No.10

Fabrication of Self-Healable and Patternable Polypyrrole/Agarose Hybrid Hydrogels for Smart Bioelectrodes

Park, Nokyoung,Chae, Seung Chul,Kim, Il Tae,Hur, Jaehyun American Scientific Publishers 2016 Journal of nanoscience and nanotechnology Vol.16 No.2

<P>We present a new class of electrically conductive, mechanically moldable, and thermally self-healable hybrid hydrogels. The hybrid gels consist of polypyrrole and agarose as the conductive component and self-healable matrix, respectively. By using the appropriate oxidizing agent under conditions of mild temperature, the polymerization of pyrrole occurred along the three-dimensional network of the agarose hydrogel matrix. In contrast to most commercially available hydrogels, the physical crosslinking of agarose gel allows for reversible gelation in the case of our hybrid gel, which could be manipulated by temperature variation, which controls the electrical on/off behavior of the hybrid gel electrode. Exploiting this property, we fabricated a hybrid conductive hydrogel electrode which also self-heals thermally. The novel composite material we report here will be useful for many technological and biological applications, especially in reactive biomimetic functions and devices, artificial muscles, smart membranes, smart full organic batteries, and artificial chemical synapses.</P>

상사와 부하 네트워크 중심성이 직무몰입 및 직무스트레스에 미치는 영향: 업무지시 네트워크를 중심으로

기노경(NoKyoung Ki) 한국인적자원개발학회 2020 인적자원개발연구 Vol.23 No.3

Parallel-processing continuous-flow device for optimization-free polymerase chain reaction

Kim, Hanok,Park, Nokyoung,Hahn, Jong Hoon Springer-Verlag 2016 Analytical and bioanalytical chemistry Vol.408 No.24

<P>A parallel-processing four-station polymerase chain reaction (PCR) device has been developed, which performs continuous-flow PCR without optimization of the annealing temperature. Since the annealing temperature of each station can be controlled independently, the device covers an annealing temperature range of 50-68 A degrees C, which is wide enough to perform PCR for any DNA fragment regardless of its optimum annealing condition. This arrangement lets us continuously obtain an amplified amount of a DNA fragment at least from one of the stations. The device consists of four identical cylindrical stations (diameter 20 mm, height 55 mm). A polytetrafluoroethylene capillary reactor (length 2 m, I.D. 100 mu m, O.D. 400 mu m) is wound helically up around each station. The whole assembly is designed to minimize the number of heating blocks (for providing temperatures of denaturation, annealing, and extension) to be seven and to shape a compact cube (height 55 mm, base 60 mm x 60 mm). The reproducibility for continuous-flow PCR is reasonably high (run-to-run and station-to-station relative standard deviation of their amplification is lower than 6 % and about 4 %, respectively). Performance on the optimization-free DNA amplification has been evaluated with four DNA samples with different annealing conditions and product sizes (323, 608, 828, and 1101 bp), which has demonstrated that in all cases, PCR is successful at least on one station. In addition, three DNA fragments with different lengths (323, 1101, and 2836 bp) have been successfully amplified in a segmented-flow mode without the carry-over contamination between segments. This result suggests that this device could serve as the PCR module of a continuous-flow high-throughput on-line total DNA analysis system integrating all necessary modules from cell lysis/DNA extraction to PCR product analysis.</P>

Electrical Modulation of Graphene by the Self-Assembly of DNA-Functionalized Gold Nanoparticles

Kim, Tae Geun,Park, Nokyoung,Kim, Un Jeong,Hur, Jaehyun American Scientific Publishers 2017 Journal of nanoscience and nanotechnology Vol.17 No.11

<P>We report on a new approach for controlling the electrical properties of graphene by the introduction of a highly ordered array of DNA-grafted gold nanoparticles. The arrangement of these nanoparticles was highly influenced by the surface wetting properties of graphene. With different graphene UV-irradiation times, the ordered domain size of nanoparticles increased, which, in turn, affected the electrical properties of graphene. Upon measuring the electrical properties using graphene field effect transistors, the ambipolar characteristics of graphene (Dirac point voltage of similar to 20 V) only appeared when a large area of graphene was covered by the monolayer of hexagonal, close-packed gold nanoparticles, resulting in the n-doping of graphene. It is conceivable that a new way of modulating graphene properties can provide beneficial information and can be used for relevant future applications.</P>

Electrical modulation of graphene by the self-assembly of DNA-functionalized gold nanoparticles

Tae Geun KIM,Nokyoung PARK,Un Jeong KIM,Jaehyun HUR 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

Restacking-Inhibited 3D Reduced Graphene Oxide for High Performance Supercapacitor Electrodes

Lee, Ji Hoon,Park, Nokyoung,Kim, Byung Gon,Jung, Dae Soo,Im, Kyuhyun,Hur, Jaehyun,Choi, Jang Wook American Chemical Society 2013 ACS NANO Vol.7 No.10

<P>Graphene has received considerable attention in both scientific and technological areas due to its extraordinary material properties originating from the atomically single- or small number-layered structure. Nevertheless, in most scalable solution-based syntheses, graphene suffers from severe restacking between individual sheets and thus loses its material identity and advantages. In the present study, we have noticed the intercalated water molecules in the dried graphene oxide (GO) as a critical mediator to such restacking and thus eliminated the hydrogen bonding involving the intercalated water by treating GO with melamine resin (MR) monomers. Upon addition of MR monomers, porous restacking-inhibited GO sheets precipitated, leading to the carbonaceous composite with an exceptionally large surface area of 1040 m<SUP>2</SUP>/g after a thermal treatment. Utilizing such high surface area, the final graphene composite exhibited excellent electrochemical performance as a supercapacitor electrode material: specific capacitance of 210 F/g, almost no capacitance loss for 20 000 cycles, and ∼7 s rate capability. The current study delivers a message that various condensation reactions engaging GO sheets can be a general synthetic approach for restacking-inhibited graphene in scalable solution processes.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-10/nn4040734/production/images/medium/nn-2013-040734_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn4040734'>ACS Electronic Supporting Info</A></P>

DNA Hydrogel Based Nanocomplexes for Cancer Specific Therapeutics with Targeted Delivery and Photothermally Activated Anticancer Peptide Drug Release

Mohzibudin QUAZI,Minhyuk LEE,Nokyoung PARK 한국생물공학회 2022 한국생물공학회 학술대회 Vol.2022 No.9

한국 시스템통합 산업의 생태지위(Niche) 구조와 기업간 경쟁역학 : 네트워크 분석을 통한 기업 성과의 설명

한준(Joon Han),신동엽(Dongyoub Shin),기노경(Nokyoung Ki) 한국전략경영학회 2004 한국전략경영학회 학술대회발표논문집 Vol.- No.-

본 연구는 한국 시스템통합(Systems Integration) 기업들의 성과를 네트워크 분석을 통해 파악한 생태지위(niche)의 특성에 기반하여 설명한다. 이를 위해 조직생태학 전략경영이론 등에서 자주 사용되어 왔으나 체계적으로 측정된 적이 드물었던 생태지위의 구조를 동일 사업분야에서 경쟁하는 기업들의 공동참여 네트워크(joint involvement networks)에 대한 네트워크 분석을 통해 측정하고, 그 결과 도출된 각 기업 생태지위의 구조적 특성이 성과에 미치는 영향을 분석한다. 이를 위해 본 연구에서는 동일한 사업분야에 참여하는 기업들간에 경쟁이라는 연결관계가 있는 것으로 보고 이에 대한 네트워크 분석을 통해 각 기업의 사이 중앙성, 위세 중앙성, 네트워크 효율성, 네트워크 제약성 등 네 가지 생태지위 특성을 분석하였고, 이 네 가지 독립변수들이 각각 성과변수로 사용된 순이익에 영향을 미칠 것이라는 가설을 검증하였다. 가설검증 결과, 이 네 가지 변수들 중 사이 중앙성, 위세 중앙성, 네트워크 효율성 등 세 변수가 가설에서 예측했던 방향과 같이 통계적으로 유의한 효과를 가지는 것으로 밝혀졌다. The current study empirically examines the effects of niche structures on firm performance in the Korean systems integration industry using the methods of social network analysis. Although the concept of niche has been frequently used in the literatures of organizational ecology and strategic management, it has been seldom empirically measured in a systematic manner. The concept of niche has been just referred to without being clearly defined in the strategic management literature, while it has been discussed primarily at the theoretical level without an elaboration of methods for measurement in the literature of organizational ecology that has taken this concept seriously in its theory developments.<br/> In the organizational ecology literature, the concept of niche has occupied the very central stage of its theoretical formulations since the early years of this influential paradigm. For instance, many of its theoretical arguments, such as competitive exclusion, niche overlap, and resource partitioning, cannot be sustained without presuming the dynamics of niche. Although the concept of niche has been rigorously articulated at the theoretical level in the organizational ecology literature for these reasons, this otherwise methodologically sophisticated paradigm has been uncharacteristically lenient in the empirical measurement of niche. Niche has been measured usually by a priori categories in product markets in most empirical studies of the organizational ecology literature.<br/> To overcome these limits of existing literatures that have not been able to provide a generally acceptable measure of niche, the current paper employs the methods of social network analysis in the empirical configuration of niche structures. Relying on methods for the analysis of joint-involvement networks, we measured structural characteristics of niches by constructing a network data-set in which firms participating in a same business area were regarded to have a tie of competition. By applying the theoretical implications of network properties to our case of joint involvement in same business areas, we erect the following four hypotheses.<br/> First, we hypothesize that betweenness centrality as a measure of the firm's adoption of generalist strategy will positively affect performance. Second, we hypothesize that network efficiency as a measure of the firm's structural hole strategy will positively affect performance. Third, we hypothesize that network constraint as a measure of the firm's compounding competition with a particular set of other firms will negatively affect performance. Fourth, prestige centrality as a measure of the firm's competition with powerful other firms will negatively affect performance.<br/> We empirically tested the four hypotheses for the sample of Korean systems integration firms. According to the results of hypothesis-testing, three out of the four independent variables measuring structural characteristics of niche - betweenness centrality, prestige centrality, and network efficiency - turned out to have statistically significant effects on firm performance measured by net profit. The findings of this study may contribute significantly to the literatures of organizational ecology, social network analysis, and strategic management by providing a generally acceptable measure of niche and also by suggesting a way to integrate these three important areas of management studies. Moreover, the findings of this study may practically contribute to business practitioners by suggesting effective strategies for building the firm's niche structures.

Branched DNA-based Synthesis of Fluorescent Silver Nanocluster

Park, Juwon,Song, Jaejung,Park, Joonhyuck,Park, Nokyoung,Kim, Sungjee Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.4

While single strand DNAs have been widely used for the scaffold of brightly fluorescent silver nanoclusters (Ag NCs), double strand DNAs have not been as successful. Herein, we report a novel synthetic approach for bright Ag NCs using branched double strand DNAs as the scaffolds for synthesis. X-shaped DNA (X-DNA) and Y-shaped DNA (Y-DNA) effectively stabilized Ag NCs, and both X-DNA and Y-DNA resulted in brightly fluorescent Ag NCs. The concentration and molar ratio of silver and DNA were found important for the fluorescence efficiency. The brightest Ag NC with the photoluminescence quantum efficiency of 19.8% was obtained for the reaction condition of 10 ${\mu}M$ X-DNA, 70 ${\mu}M$ silver, and the reaction time of 48 h. The fluorescence lifetime was about 2 ns for the Ag NCs and was also slightly dependent on the synthetic condition. Addition of Cu ions at the Ag NC preparations resulted in the quenching of Ag NC fluorescence, which was different to the brightening cases of single strand DNA stabilized Ag NCs.