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Abstract：
The microscopic origins of terahertz (THz) vibrational modes in biological systems are an active and open area of current research. Recent experiments [Phys Rev X. 8, 031061 (2018)] have revealed the presence of a pronounced mode at ∼0.3 THz in fluorophore-decorated bovine serum albumin (BSA) protein in aqueous solution under nonequilibrium conditions induced by optical pumping. This result was heuristically interpreted as a collective elastic fluctuation originating from the activation of a low-frequency phonon mode. In this work, we show that the sub-THz spectroscopic response emerges in a statistically significant manner (>2σ) from such collective behavior, illustrating how photoexcitation can alter specific THz vibrational modes. We revisit the theoretical analysis with proof-of-concept molecular dynamics that introduce optical excitations into the simulations. Using information theory techniques, we show that these excitations can give rise to a multiscale response involving two optically excited chromophores (tryptophans), other amino acids in the protein, ions, and water. Our results motivate new experiments and fully nonequilibrium simulations to probe these phenomena, as well as the refinement of atomistic models of Fröhlich condensates that are fundamentally determined by nonlinear interactions in biology.
摘要：
太赫兹（THz）振动模式在生物系统中的微观起源是当前研究的活跃和开放领域。最近的实验[PhysRevX.8，031061（2018）]揭示了在光泵浦诱导的非平衡条件下，荧光团修饰的牛血清白蛋白（BSA）蛋白在水溶液中存在〜0.3THz的明显模式。该结果被启发式地解释为源于低频声子模式激活的集体弹性波动。在这项工作中,我们表明，亚太赫兹光谱响应出现在统计上显著的方式（>2σ）从这样的集体行为，说明光激发如何改变特定的THz振动模式。我们通过概念验证分子动力学重新审视理论分析，将光学激发引入模拟。利用信息论技术，我们表明，这些激发可以引起涉及两个光激发发色团（色氨酸）的多尺度响应，蛋白质中的其他氨基酸，离子,和水。我们的结果激发了新的实验和完全非平衡模拟来探测这些现象，以及Fröhlich凝析油原子模型的完善，这些模型基本上由生物学中的非线性相互作用决定。
