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X-WR-CALNAME:Biomedical Mathematics Group
X-ORIGINAL-URL:https://www.ibs.re.kr/bimag
X-WR-CALDESC:Events for Biomedical Mathematics Group
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TZID:Asia/Seoul
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DTSTART:20210101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20220107T130000
DTEND;TZID=Asia/Seoul:20220107T140000
DTSTAMP:20260427T033132
CREATED:20220106T190000Z
LAST-MODIFIED:20211224T001535Z
UID:5363-1641560400-1641564000@www.ibs.re.kr
SUMMARY:Fundamental limits on the suppression of molecular fluctuations
DESCRIPTION:We will discuss about “Fundamental limits on the suppression of molecular fluctuations”\, Lestas et al\, Nature\, 2010 \nAbstract: Negative feedback is common in biological processes and can increase a system’s stability to internal and external perturbations. But at the molecular level\, control loops always involve signalling steps with finite rates for random births and deaths of individual molecules. Here we show\, by developing mathematical tools that merge control and information theory with physical chemistry\, that seemingly mild constraints on these rates place severe limits on the ability to suppress molecular fluctuations. Specifically\, the minimum standard deviation in abundances decreases with the quartic root of the number of signalling events\, making it extremely expensive to increase accuracy. Our results are formulated in terms of experimental observables\, and existing data show that cells use brute force when noise suppression is essential; for example\, regulatory genes are transcribed tens of thousands of times per cell cycle. The theory challenges conventional beliefs about biochemical accuracy and presents an approach to the rigorous analysis of poorly characterized biological systems.
URL:https://www.ibs.re.kr/bimag/event/2022-01-07/
LOCATION:B378 Seminar room\, IBS\, 55 Expo-ro Yuseong-gu\, Daejeon\, 34126\, Korea\, Republic of
CATEGORIES:Journal Club
ORGANIZER;CN="Jae Kyoung Kim":MAILTO:jaekkim@kaist.ac.kr
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20220113T130000
DTEND;TZID=Asia/Seoul:20220113T140000
DTSTAMP:20260427T033132
CREATED:20220112T190000Z
LAST-MODIFIED:20220112T070151Z
UID:5395-1642078800-1642082400@www.ibs.re.kr
SUMMARY:Quasi-Entropy Closure: A Fast and Reliable Approach to Close the Moment Equations of the Chemical Master Equation
DESCRIPTION:We will discuss about “Quasi-Entropy Closure: A Fast and Reliable Approach to Close the Moment Equations of the Chemical Master Equation”\, Wagner et al\, bioRxiv\, 2021 \nMotivation: The Chemical Master Equation is the most comprehensive stochastic approach to describe the evolution of a (bio-)chemical reaction system. Its solution is a time-dependent probability distribution on all possible configurations of the system. As the number of possible configurations is typically very large\, the Master Equation is often practically unsolvable. The Method of Moments reduces the system to the evolution of a few moments of this distribution\, which are described by a system of ordinary differential equations. Those equations are not closed\, since lower order moments generally depend on higher order moments. Various closure schemes have been suggested to solve this problem\, with different advantages and limitations. Two major problems with these approaches are first that they are open loop systems\, which can diverge from the true solution\, and second\, some of them are computationally expensive. \nResults: Here we introduce Quasi-Entropy Closure\, a moment closure scheme for the Method of Moments which estimates higher order moments by reconstructing the distribution that minimizes the distance to a uniform distribution subject to lower order moment constraints. Quasi-Entropy closure is similar to Zero-Information closure\, which maximizes the information entropy. Results show that both approaches outperform truncation schemes. Moreover\, Quasi-Entropy Closure is computationally much faster than Zero-Information Closure. Finally\, our scheme includes a plausibility check for the existence of a distribution satisfying a given set of moments on the feasible set of configurations. Results are evaluated on different benchmark problems.
URL:https://www.ibs.re.kr/bimag/event/2022-01-13/
LOCATION:B378 Seminar room\, IBS\, 55 Expo-ro Yuseong-gu\, Daejeon\, 34126\, Korea\, Republic of
CATEGORIES:Journal Club
ORGANIZER;CN="Jae Kyoung Kim":MAILTO:jaekkim@kaist.ac.kr
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20220119T110000
DTEND;TZID=Asia/Seoul:20220119T120000
DTSTAMP:20260427T033132
CREATED:20220118T170000Z
LAST-MODIFIED:20220115T115214Z
UID:5400-1642590000-1642593600@www.ibs.re.kr
SUMMARY:Network design principle for robust oscillatory behaviors with respect to biological noise
DESCRIPTION:We will discuss about “Network design principle for robust oscillatory behaviors with respect to biological noise”\, Qiao et al\, bioRxiv\, 2021 \nOscillatory behaviors\, which are ubiquitous in transcriptional regulatory networks\, are often subject to inevitable biological noise. Thus a natural question is how transcriptional regulatory networks can robustly achieve accurate oscillation in the presence of biological noise. Here\, we search all two- and three-node transcriptional regulatory network topologies for those robustly capable of accurate oscillation against the parameter variability (extrinsic noise) or stochasticity of chemical reactions (intrinsic noise). We find that\, no matter what source of the noise is applied\, the topologies containing the repressilator with positive auto-regulation show higher robustness of accurate oscillation than those containing the activator-inhibitor oscillator\, and additional positive auto-regulation enhances the robustness against noise. Nevertheless\, the attenuation of different sources of noise is governed by distinct mechanisms: the parameter variability is buffered by the long period\, while the stochasticity of chemical reactions is filtered by the high amplitude. Furthermore\, we analyze the noise of a synthetic human nuclear factor κB (NF-κB) signaling network by varying three different topologies\, and verify that the addition of a repressilator to the activator-inhibitor oscillator\, which leads to the emergence of high-robustness motif—the repressilator with positive auto-regulation\, improves the oscillation accuracy in comparison to the topology with only an activator-inhibitor oscillator. These design principles may be applicable to other oscillatory circuits.
URL:https://www.ibs.re.kr/bimag/event/2022-01-19/
LOCATION:B378 Seminar room\, IBS\, 55 Expo-ro Yuseong-gu\, Daejeon\, 34126\, Korea\, Republic of
CATEGORIES:Journal Club
ORGANIZER;CN="Jae Kyoung Kim":MAILTO:jaekkim@kaist.ac.kr
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