近日，美國哈佛大學(xué)的Joost J.Vlassak課題組與麻省理工學(xué)院的Peter J.Foster等人合作，研究了活細胞骨架材料中的耗散和跨尺度能量傳播。相關(guān)成果已于2023年3月31日在國際學(xué)術(shù)期刊《美國科學(xué)院院刊》上發(fā)表。

該課題組使用最新開發(fā)的皮卡瓦級量熱計來實驗測量表現(xiàn)出突現(xiàn)大尺度流動的活性微管凝膠的能量學(xué)。研究發(fā)現(xiàn)，僅約占系統(tǒng)總能耗的十億分之一的能量貢獻于這些突現(xiàn)的流動。研究人員開發(fā)了一個化學(xué)動力學(xué)模型，定量捕捉系統(tǒng)的總熱耗散如何隨著ATP和微管濃度變化而變化，但在高馬達濃度下分解，表明存在馬達之間的干擾。最后，他們還估算了能量損失在不同尺度上如何積累。這些結(jié)果共同強調(diào)了能量效率作為工程活性材料時的一個關(guān)鍵考慮因素，也是向開發(fā)生命系統(tǒng)非平衡熱力學(xué)邁出的重要一步。

研究人員表示，生命系統(tǒng)本質(zhì)上是非平衡的：它們利用代謝產(chǎn)生的化學(xué)能來推動其突現(xiàn)的動力學(xué)和自組織。細胞骨架是這些動力學(xué)的一個關(guān)鍵驅(qū)動因素，是活性物質(zhì)的典型例子，其中分子馬達注入的能量在長度尺度上形成級聯(lián)作用，使材料突破了熱力學(xué)平衡的限制，展示了僅因為不斷注入能量才能出現(xiàn)的新型非平衡動力學(xué)。盡管近年來在使用局部探針量化熵產(chǎn)生和詳細平衡破缺方面取得了實驗進展，但人們對于活性物質(zhì)的能量學(xué)以及能量如何從分子尺度傳播到突現(xiàn)的尺度仍知之甚少。

(相關(guān)資料圖)

附：英文原文

Title: Dissipation and energy propagation across scales in an active cytoskeletal material

Author: Foster, Peter J., Bae, Jinhye, Lemma, Bezia, Zheng, Juanjuan, Ireland, William, Chandrakar, Pooja, Boros, Rémi, Dogic, Zvonimir, Needleman, Daniel J., Vlassak, Joost J.

Issue&Volume: 2023-3-31

Abstract: Living systems are intrinsically nonequilibrium: They use metabolically derived chemical energy to power their emergent dynamics and self-organization. A crucial driver of these dynamics is the cellular cytoskeleton, a defining example of an active material where the energy injected by molecular motors cascades across length scales, allowing the material to break the constraints of thermodynamic equilibrium and display emergent nonequilibrium dynamics only possible due to the constant influx of energy. Notwithstanding recent experimental advances in the use of local probes to quantify entropy production and the breaking of detailed balance, little is known about the energetics of active materials or how energy propagates from the molecular to emergent length scales. Here, we use a recently developed picowatt calorimeter to experimentally measure the energetics of an active microtubule gel that displays emergent large-scale flows. We find that only approximately one-billionth of the system’s total energy consumption contributes to these emergent flows. We develop a chemical kinetics model that quantitatively captures how the system’s total thermal dissipation varies with ATP and microtubule concentrations but that breaks down at high motor concentration, signaling an interference between motors. Finally, we estimate how energy losses accumulate across scales. Taken together, these results highlight energetic efficiency as a key consideration for the engineering of active materials and are a powerful step toward developing a nonequilibrium thermodynamics of living systems.

DOI: 10.1073/pnas.2207662120

Source: https://www.pnas.org/doi/10.1073/pnas.2207662120

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