Biological Clock and Ultradian Metabolic Oscillation in Saccharomyces cerevisiae

Chong Suk Kwon(권정숙),Ho-Yong Sohn(손호용) 한국생명과학회 2018 생명과학회지 Vol.28 No.8

생물시계(Biological clock)는 생명체에서 나타나는 반복되는 자율적인 리듬을 말하며, 단일세포는 물론 다세포 생명체의 기본적인 대사와 이에 따른 표현형과 행동을 직접적으로 조절하고 있다. 이러한 생물시계는 동면 리듬, 수면 리듬, 심장박동 리듬 및 짝짓기 노래 리듬 등 매우 다양하며, 24시간 이상의 주기를 infradian rhythm, 24시간 주기를 circadian rhythm, 24시간 이내의 짧은 주기를 ultradian rhythm으로 구분한다. 효모 Saccharomyces cerevisiae는 최소 5종 이상의 반복되는 자율적인 리듬이 알려져 있으며, 이중 일부는 생체시계로 인식되고 있다. 본 리뷰에서는 Saccharomyces cerevisiae의 glycolytic oscillation (T= 1~30분), cell cycle-dependent oscillation (T= 2~16 시간), ultradian metabolic oscillation (T= 15~50분), yeast colony oscillation (T= 수 시간) 및 circadian oscillation (T= 24시간)에 대한 연구 결과를 제시하고, 특히 ultradian metabolic oscillation의 특징, 집단 동조인자(population synchronizer), 동조인자의 조절 기작 및 효모 생물시계의 대사공학 분야의 이용성을 제시하여 효모를 이용한 동적 대사조절 및 생물시계 연구가 가능함을 제시하였다. Biological clocks are the basis of temporal control of metabolism and behavior. These clocks are characterized by autonomous free-running oscillation and temperature compensation and are found in animals, plants, and microorganisms. To date, various biological clocks have been reported. These include clocks governing hibernation, sleep/wake, heartbeat, and courtship song. These clocks can be differentiated by the period of rhythms, for example, infradian rhythms (> 24-hr period), circadian rhythms (24-hr period), and ultradian rhythms (< 24-hr period). In yeast (Saccharomyces cerevisiae), at least five different autonomous oscillations have been reported; (1) glycolytic oscillations (T = 1~30 min), (2) cell cycle-dependent oscillations (T = 2~16 hr), (3) ultradian metabolic oscillations (T = 15~50 min), (4) yeast colony oscillations (T = a few hours), and (5) circadian oscillations (T = 24 hr). In this review, we discuss studies on oscillators, pacemakers, and synchronizers, in addition to the application of biological clocks, to demonstrate the nature of autonomous oscillations, especially ultradian metabolic oscillations of S. cerevisiae.

질소로 희석된 부탄 층류부상화염에서 화염진동에 관한 연구

윤성환(Sung Hwan Yoon),박정(Jeong Park),권오붕(Oh Boong Kwon),배대석(Dae Seok Bae) 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.40

Characteristics of lifted butane flames diluted with nitrogen have been investigated experimentally in order to elucidate the individual mechanism of flame oscillations. Flame oscillations are classified into five regimes in laminar free-jet lift-off flames: a stabilized lift-off regime (Ⅰ), a heat-loss-induced oscillation (Ⅱ), a buoyancy-induced oscillation in addition to a heat-loss-induced oscillation (Ⅲ), a combined form of an oscillation prior to blow-out and a heat-loss-induced oscillation (Ⅳ), and that of an oscillation prior to blow-out and a buoyancy-induced oscillation in addition to a heat-loss-induced oscillation (Ⅴ). Characterization of the individual Flame oscillations modes are presented and discussed with Strouhal-numbers and their relevant parameters through the analysis of power spectrum for temporal variation of lift-off height.

Research of the Mechanism of Low Frequency Oscillation Based on Dynamic Damping Effect

Wenying Liu,Rundong Ge,Dandan Zhu,Weizhou Wang,Wei Zheng,Fuchao Liu 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.4

For now, there are some low frequency oscillations in the power system which feature low frequency oscillation with positive damping and cannot be explained by traditional low frequency oscillation mechanisms. Concerning this issue, the dynamic damping effect is put forward on the basis of the power-angle curve and the study of damping torque in this article. That is, in the process of oscillation, damping will dynamically change and will be less than that of the stable operating point especially when the angle of the stable operating point and the oscillation amplitude are large. In a situation with weak damping, the damping may turn negative when the oscillation amplitude increases to a certain extent, which may result in an amplitude-increasing oscillation. Finally, the simulation of the two-machine two-area system verifies the arguments in this paper which may provide new ideas for the analysis and control of some unclear low frequency phenomena.

층류부상화염에서 화염진동에 관한 연구

윤성환(Sung Hwan Yoon),박정(Jeong Park),권오붕(Oh Boong Kwon),김정수(Jeong Soo Kim) 한국연소학회 2009 KOSCOSYMPOSIUM논문집 Vol.- No.39

Characteristics of lift-off propane flames diluted with nitrogen have been investigated experimentally to elucidate flame oscillations. Flame stability maps are compared for the fuel tube diameters of 0.3 and 1.0㎜ to clarify the flame oscillations. Flame oscillation modes are classified into three: a pure self-oscillation, a combined form of self-oscillation and buoyancy-induced oscillation, and a combined form of self-oscillation and diffusive-thermal instability. It is shown that the self-oscillation is not relevant to a diffusive-thermal instability and a hydrodynamic instability caused by buoyancy, and appears at all lifted flame conditions irrespective of fuel Lewis number. These experimental evidences are displayed through the analysis of power spectrum for temporal variation of lift-off height. The possible scenario of the self-excitation mechanism is also addressed.

Arc oscillation을 이용한 가스터빈용 CM247LC 초내열합금 응고균열 민감도 제어 기구

김경민,정예선,이의종,이형수,서성문,천은준 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.11

가스터빈 블레이드 제조 및 재생과정에서 용접 및 적층 공정은 필수적으로 고려되고 있다. 특히 블레이드 국산화 소재로 검토되고 있는 CM247LC 초내열합금은 용접시 응고균열에 취약한 소재로 알려져 있어, 건전한 블레이드 용접 구조를 확보하기 위해서는 용접소재 및 공정 최적화를 통한 응고균열 제어가 필수적이다. 한편, 용접 시 oscillation의 적용은 응고조직 제어를 통해 용접부 성능 향상을 도모할 수 있는 대표적인 공정 변수로써, 다수의 선행연구를 통해 응고균열 발생 억제 효과까지 존재하는 것으로 보고되고 있다. 하지만 대부분의 해당 연구들은 자기 구속(self-restraint) 시험에 기반한 정성 평가결과 만을 제시하고 있으며, 용접소재 및 공정간의 절대 비교가 가능한 응고균열 온도범위(solidification cracking temperature range, SCTR) 평가 등, 정량 평가에 관한 연구는 상당히 부족한 실정이다. 본 연구에서는 oscillation 용접을 적용한 Varestraint 시험 및 평가절차를 고안하였고, 이를 통해 oscillation 조건(0.6~1.2 Hz)에 따른 CM247LC 초내열합금 용접부 SCTR을 체계적으로 평가하였다. Varestraint 시험에 따른 응고균열은, IR 열화상 카메라로 측정한 균열 전파경로 상의 열이력 및 응고성장 방향 등을 종합적으로 고려하여 SCTR로 정량화 하였다. 그 결과 CM247LC 합금 직선 용접 시의 SCTR은 400 K, 0.6 및 1.2 Hz oscillation 용접부는 276, 476 K로 각각 평가되었다. 역확산(back-diffusion)과 용접 응고과정의 냉각속도를 고려한 Scheil 식 계산을 통해 각 조건의 mushy zone 범위는 동등 수준(약 400 K)임을 확인하였으나, oscillation 조건에 따라 SCTR 은 큰 차이를 보이는 결과가 얻어졌다. 특히 0.6 Hz 조건의 SCTR 축소 거동은, EBSD 및 EPMA 분석을 통해 oscillation 경로상의 국부적인 G(온도구배)/R(응고속도)값 저하에 따른 미세한 등축 덴드라이트 조직 형성으로 균열 전파가 억제된 결과로 판단되었다.

강의 연속주조시 Mold Oscillation에 따른 Flux층 내의 동적 압력변화 해석

박태호 ( Park Tae Ho ),김지훈 ( Kim Ji Hun ),최주 ( Choe Ju ),예병준 ( Ye Byeong Jun ) 한국주조공학회 2004 한국주조공학회지 Vol.24 No.1

N/A The pressure of the mold flux acting on the meniscus shell was investigated through the coupling analysis of heat transfer in the mold and fluid flow in the flux caused by the mold oscillation. Finite element method was employed to solve the conservation equation associated with appropriate boundary conditions. As reported by previous workers. the axial pressure is positive on the negative strip time and negative on the positive strip time. A maximum pressure is predicted toward the top of the meniscus shell which has the thin shell arid a maxirnuni value is in proportion to the relative mold oscillation velocity. The relative mold oscillation velocity was changed by the effect of meniscus level fluctuation. Therefore the pressure of the mold flux acting o n the menisctis shell was different each cycle ofthe mold oscillation due to the irregularity of relative mold oscillation velocity

Research of the Mechanism of Low Frequency Oscillation Based on Dynamic Damping Effect

Liu, Wenying,Ge, Rundong,Zhu, Dandan,Wang, Weizhou,Zheng, Wei,Liu, Fuchao The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.4

For now, there are some low frequency oscillations in the power system which feature low frequency oscillation with positive damping and cannot be explained by traditional low frequency oscillation mechanisms. Concerning this issue, the dynamic damping effect is put forward on the basis of the power-angle curve and the study of damping torque in this article. That is, in the process of oscillation, damping will dynamically change and will be less than that of the stable operating point especially when the angle of the stable operating point and the oscillation amplitude are large. In a situation with weak damping, the damping may turn negative when the oscillation amplitude increases to a certain extent, which may result in an amplitude-increasing oscillation. Finally, the simulation of the two-machine two-area system verifies the arguments in this paper which may provide new ideas for the analysis and control of some unclear low frequency phenomena.

Nonlinear Drop Oscillations by EWOD

오정민(Jung Min Oh),고성희(Sung Hee Ko),강관형(Kwan Hyoung Kang) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

The nonlinear behaviours of the shape oscillations induced by the EWOD are investigated. Experimental observations show that there exists the strong frequency dependence of the drop oscillations. The shape oscillation equations are derived to the first order by using a domain perturbation method to describe the drop oscillations. The boundary condition at the contact line is modelled to simulate a time-periodic oscillation of contact line, which is the driving force of the shape oscillations of a whole drop. The modified shape mode equations are coupled one another, which is a distinctive feature in the first order problems. The numerical simulations agree well qualitatively with the experiments. The frequency dependence of each mode is investigated, which shows that only one of the shape modes is excited at peak excitation frequency. The lowest order-mode is also analyzed in phase portrait to show a nonlinear behaviour of drop oscillation.

RPF 가스화 가스 외부가진 적용 단계적연소 NOx 저감특성

김은혁,전영남 한국폐기물자원순환학회 2015 한국폐기물자원순환학회지 Vol.32 No.5

Nitrogen oxide (NOx) is one of air pollutants generated from the combustion of fuels, causing serious environmental problems. A novel externally oscillated staged combustion for RPF syngas was proposed in this work. The staged combustion could reduce NOx by the fuel-rich state combustion, while the external oscillation could achieve complete burn-out by stabilizing the flame. It also improved combustibility with an acceleration of the mass and heat momentum transfer. Parametric studies were achieved for the NOx reduction characteristics on the air staging and fuel staging in each case of with or without external oscillation. For the case of without oscillation, NOx reduction rate for the fuel staging had higher value as 75% than air staging as 67%. However, an application of external oscillation for both cases gives higher NOx reduction rate of 79%. The optimal condition for the oscillated fuel staging was that the air ratio in main burning zone, reburning zone and burnout zone were 1.1, 0.6 and 1.15, respectively, having 200 Hz of external oscillation.

Regulation of Branched-Chain, and Sulfur-Containing Amino Acid Metabolism by Glutathione during Ultradian Metabolic Oscillation of Saccharomyces cerevisiae

Sohn Ho- Yong,Kum Eun-Joo,Kwon Gi-Seok,Jin Ingnyol,Kuriyama Hiroshi The Microbiological Society of Korea 2005 The journal of microbiology Vol.43 No.4

Autonomous ultradian metabolic oscillation (T$\simeq$50 min) was detected in an aerobic chemostat culture of Saccharomyces cerevisiae. A pulse injection of GSH (a reduced form of glutathione) into the culture induced a perturbation in metabolic oscillation, with respiratory inhibition caused by $H_2S$ burst pro-duction. As the production of $H_2S$ in the culture was controlled by different amino acids, we attempted to characterize the effects of GSH on amino acid metabolism, particularly with regard to branched chain and sulfur-containing amino acids. During stable metabolic oscillation, concentrations of intra-cellular glutamate, aspartate, threonine, valine, leucine, isoleucine, and cysteine were observed to oscil-late with the same periods of dissolved $O_2$ oscillation, although the oscillation amplitudes and maximal phases were shown to differ. The methionine concentration was stably maintained at 0.05 mM. When GSH (100 $\mu$M) was injected into the culture, cellular levels of branched chain amino acids increased dramatically with continuous $H_2S$production, whereas the cysteine and methionine concentrations were noticeably reduced. These results indicate that GSH-dependent perturbation occurs as the result of the promotion of branched chain amino acid synthesis and an attenuation of cysteine and methionine synthesis, both of which activate the generation of $H_2S$. In a low sulfate medium containing 2.5 mM sulfate, the GSH injections did not result in perturbations of dissolved $O_2$ NAD(P)H redox oscillations without burst $H_2S$ production. This suggests that GSH-dependent perturbation is intimately linked with the metabolism of branched-chain amino acids and $H_2S$ generation, rather than with direct GSH-GSSG redox control.