https://scholar.dgist.ac.kr/handle/20.500.11750/345 2026-04-04T13:19:52Z https://scholar.dgist.ac.kr/handle/20.500.11750/59246 Title: 초주일 리듬 기반 식물의 신규 뿌리 재생 촉진 방법 Author(s): 임준현; Vu Thi Quy; 홍성현; 남홍길; 박성진 Abstract: 초주일 리듬(UR)은 24시간 미만의 주기로 순환한다. 그러나 이러한 리듬의 조절과 기능은 명확하지 않다. 본 발명자들은 절제된 애기장대(Arabidopsis) 잎에서 ~3시간 기간 일주기(circadian)-독립적 UR을 확인하였다. 유전자 발현 및 기능적 분석은 UR이 신규 뿌리 재생(de novo root regeneration; DNRR)의 양성 조절인자임을 시사한다. UR을 나타내는 식물호르몬(phytohormone)- 및 DNRR-연결 유전자를 포함하는 4,073개 유전자를 전사체(transcriptomic) 분석으로 밝혀냈다. 본 발명자들은 돌연변이 탐색(forward genetic screen)을 이용하여 rou(regulator of ultradian rhythm) 변이체들을 동정하고, EAR1(Enhancer of ABA co-Receptor 1)이 UR 사이클링에 필수적인 것을 확인하였다. rou1 변이체는 UR의 부족을 나타내었고, 뿌리 재생 및 관련 유전자 발현을 감소시켰다. 호르몬 처리는 전사 및 번역 후 단계에서 EAR1 수준을 변화시켰으며, 이는 EAR1이 절제된 잎에서 동적 호르몬-관련 유전자 발현을 매개하여, UR을 생성하고 DNRR을 촉진한다는 것을 의미한다. 본 발명에 따르면, 잎 절제가 URs을 유발하고, 식물에서 가능한 생존 메커니즘인 호르몬 조절을 통해 DNRR로 이어진다는 것을 확인할 수 있다. https://scholar.dgist.ac.kr/handle/20.500.11750/59003 Title: The Localization of Biological Compounds on the Soft Interface of Microdroplet May Answer the Accelerated Reaction Rates Inside Microdroplet Author(s): Lhee, SangMoon; Kim, Sunhee; Nam, Hong Gil Abstract: Many researchers have reported that microdroplet environment is a good reaction bath providing the remarkably accelerated chemical reaction rates and is directing the reaction path differently from the corresponding bulk-phase reactions. Since the related thermodynamic parameters gave the clues to the uneven distribution of molecules inside the small-compartmentalized space, we have visualized the localization of several biological compounds inside the aqueous microdroplet including proteins, nucleic acids, and carbohydrates with the help of some fluorescence microscopy techniques. Now, we present the localization of molecules on the water-oil interface is common under physiological condition and the charge states of molecules and interface contributes to the variation of the distribution. The observation of the molecules on the interface by means of fluorescence anisotropy gives us some suggestions that the molecular movement on the interface is not only spatially restricted, but is also guided with orientation. We suggest that such the guided movements with some degree of order is another contribution factor to accelerating the unfavorable reaction including enzymatic reactions. 2018-02-19T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/59002 Title: Accelerated biomolecular kinetics revealed by microdroplet fusion mass spectrometry Author(s): Lee, Jae Kyoo; Nam, Hong Gil; Zare, Richard Abstract: We have developed a new time-resolved mass spectrometry using fused microdroplets (PNAS, 2016). This technique enables (1) recording fast chemical reactions on the microsecond timescale which is about two orders of magnitude faster than previously developed time-resolved mass spectrometry, (2) capturing early molecular events occurring within a few microseconds, and (3) studying liquid-phase kinetics in confined environment such as in microdroplets which contrasts against the studies carried out in reactions in bulk solution. The power of this technique to monitor fast kinetics and to detect reaction intermediates was demonstrated through the kinetic studies of protein unfolding, the hydrogen-deuterium exchange in peptides, and protein-ligand interactions. We have found a markedly high acceleration of reaction rates in microdroplets by factors of 103 to 106 compared to bulk solutions regardless of reaction mechanisms, including specific covalent and nonspecific noncovalent bonding (Q Rev Biophys, 2015). To address the mechanism of the reaction acceleration, we examined several factors influencing the acceleration of acid-induced chlorophyll demetallation. The investigation of the effect of charge and the different solvent composition on the reaction rate acceleration revealed that the reaction acceleration was mainly attributed to the micro-confinement effect rather than the introduced charges, solvent composition, and solvent evaporation effect in microdroplet. The behavior of accelerated reaction suggests that the biochemical reactions occurring in confined environments such as in cells would significantly differ from what has been conventionally understood. 2017-04-01T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/59000 Title: Laser desorption/ionization droplet delivery mass spectrometry for live single cell analysis and imaging Author(s): Lee, Jae Kyoo; Nam, Hong Gil; Zare, Richard Abstract: We have developed a new high-resolution ambient ionization mass spectrometry techniques named laser desorption/ionization droplet delivery mass spectrometry (LDIDD-MS) (Anal Chem, 2016). A pulsed UV laser beam (266 nm) is focused on a surface covered with target analytes to induce their desorption and ionization (Fig. 1A). A spray of liquid droplets is simultaneously directed onto the laser-focused surface region to capture the ionized analytes and deliver them to a mass spectrometer. This approach of rapid and effective capturing of molecules after laser desorption/ionization allows the limit of detection for the amino acid lysine to be as low as 2 amol under ambient ionization conditions. A high spatial resolution around 3 µm for mass spectrometric imaging of a mouse brain tissue was achieved. The LDIDD-MS was employed for single-cell analysis of cellular apoptosis. A significant differences in the profiles of fatty acids and lipids between normal healthy cells and apoptosis-induced HEK cells was observed (Fig. 1B). We observed upregulation of phosphatidylcholine lipid with a relatively shorter carbon chain length and downregulation of phosphatidylcholine with a relatively longer carbon chain length, suggesting a possible new mechanism for apoptotic morphological changes. This technique also allows for a direct measurement of liquid-phase samples including amino acids, peptides, and proteins. A real-time detection of exocytosed neurotransmitters from live PC12 cells, which has been a significant challenge for mass spectrometric analysis, was achieved without damaging cells. 2017-04-01T15:00:00Z