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Super-resolution Imaging of Complex Biological Systems via Chemical Expansion Microscopy
Jae-Byum Chang(장재범) 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
Visualization of the molecular structures inside biological systems is essential to understand the molecular mechanisms of biological phenomena occurring inside these systems. In 2015, a new super-resolution fluorescence imaging technique, called expansion microscopy (ExM), was demonstrated. ExM can achieve sub-60-nm resolution with diffraction-limited microscopy by physically expanding target specimens with a swellable hydrogel. Here, we demonstrate a new ExM technique, which we termed chemical ExM, which can visualize almost all biological structures. In chemical ExM, all biological structures are directly labeled with fluorophores. As the molecular weight of fluorophores is around 1,000 Da, specimens with a thickness of several millimeters can be stained and imaged with a sub-60-nm resolution after expansion. Chemical ExM would be an attractive tool to study various biological systems, as it enables the super-resolution imaging of thick specimens without antibodies.
박재준(Park-Jae Jun),이창훈(Lee-Chang Hoon),최태진(Choi-Tae Jin),최태일(Choi-Tae il),박용범(Park-Yong Byum),이성일(Lee Sung il) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.7
PD의 저항성은 에폭시원형을 포함한 3종류 즉, 에폭시 마이크로 콤포지트를 실란처리 및 미처리한 경우 그리고 나노-마이크로입자가 혼합된 콤포지트의 부분방전저항성을 연구하였다. 이들 재료들은 rod - gap - plane 전극 하에서 PD가 적용 되었다. 원형에폭시수지보다 마이크로 콤포지트가 부분방전저항성이 우월하였다. 더욱이 SiO₂ 나노입자-마이크로 혼합된 콤포지트가 더욱더 큰 저항성을 얻었다. 이는 마이크로 입자사이로 나노입자가 치밀한 조직을 갖고 있기에 이러 우월한 특성을 나타낸 것으로 판단된다.
Stability Studies of Biodegradable Polymersomes Prepared by Emulsion Solvent Evaporation Method
Lee Yu-Han,Chang Jae-Byum,Kim Hong-Kee,Park Tae-Gwan The Polymer Society of Korea 2006 Macromolecular Research Vol.14 No.3
Di-block copolymers composed of two biocompatible polymers, poly(ethylene glycol) and poly(D,L-lactide), were synthesized by ring-opening polymerization for preparing polymer vesicles (polymersomes). Emulsion solvent evaporation method was used to fabricate the polymersomes. Scanning electron microscope (SEM) images confirmed that polymersomes have a hollow structure inside. Confocal laser microscope and optical microscope were also used to verify the hollow structure of polymersomes. Polymersomes having various sizes from several hundred nanometers to a few micrometers were fabricated. The size of the polymersomes could be readily controlled by altering the relative hydrodynamic volume fraction ratio between hydrophilic and hydrophobic blocks in the copolymer structure, and by varying the fabrication methods. They showed greatly enhanced stability with increased molecular weight of PEG. They maintained their physical and chemical structural integrities after repeated cycles of centrifugation/re-dispersion, and even after treatment with surfactants.
Two-Dimensional Nanoparticle Supracrystals: A Model System for Two-Dimensional Melting
Kim, Jin Young,Kwon, S. Joon,Chang, Jae-Byum,Ross, Caroline A.,Hatton, T. Alan,Stellacci, Francesco American Chemical Society 2016 Nano letters Vol.16 No.2
<P>In a Langmuir trough, successive compression cycles can drive a two-dimensional (2D) nanoparticle supracrystal (NPSC) closer to its equilibrium structure. Here, we show a series of equilibrated 2D NPSCs consisting of gold NPs of uniform size, varying solely in the length of their alkanethiol ligands. The ordering of the NPSC is governed by the ligand length, thus providing a model system to investigate the nature of 2D melting in a system of NPs. As the ligand length increases the supracrystal transitions from a crystalline to a liquid-like phase with evidence of a hexatic phase at an intermediate ligand length. The phase change is interpreted as an entropy-driven phenomenon associated with steric constraints between ligand shells. The density of topological defects scales with ligand length, suggesting an equivalence between ligand length and temperature in terms of melting behavior. On the basis of this equivalence, the experimental evidence indicates a two-stage 2D melting of NPSCs.</P>
Directed self-assembly of a two-state block copolymer system
Do Hyung Wan,Choi Hong Kyoon,Gadelrab Karim R.,Chang Jae-Byum,Alexander-Katz Alfredo,Ross Caroline A.,Berggren Karl K. 나노기술연구협의회 2018 Nano Convergence Vol.5 No.25
In this work, ladder-shaped block copolymer structures consisting of parallel bars, bends, and T-junctions are formed inside square confinement. We define binary states by the two degenerate alignment orientations, and study properties of the two-state system. We control the binary states by creating openings around the confinement, changing the confinement geometry, or placing lithographic guiding patterns inside the confinement. Self-consistent field theory simulations show templating effect from the wall openings and reproduce the experimental results. We demonstrate scaling of a single binary state into a larger binary state array with individual binary state control.