Abstract
Signal transduction in living cells is vital to maintain life itself, where information transfer in noisy environment plays a significant role. In a rather different context, the recent intensive research on ‘Maxwell's demon'—a feedback controller that utilizes information of individual molecules—have led to a unified theory of information and thermodynamics. Here we combine these two streams of research, and show that the second law of thermodynamics with information reveals the fundamental limit of the robustness of signal transduction against environmental fluctuations. Especially, we find that the degree of robustness is quantitatively characterized by an informational quantity called transfer entropy. Our information-thermodynamic approach is applicable to biological communication inside cells, in which there is no explicit channel coding in contrast to artificial communication. Our result could open up a novel biophysical approach to understand information processing in living systems on the basis of the fundamental information–thermodynamics link.
Highlights
Signal transduction in living cells is vital to maintain life itself, where information transfer in noisy environment plays a significant role
The information transmission inside the feedback loop can be quantified by the transfer entropy, which was originally introduced in the context of time series analysis[17], and has been studied in electrophysiological systems[18], chemical processes[19] and artificial sensorimotors[20]
Information thermodynamics reveals a generalization of the second law of thermodynamics, which implies that the entropy production of a target system is bounded by the transfer entropy from the target system to the outside world[24]
Summary
Signal transduction in living cells is vital to maintain life itself, where information transfer in noisy environment plays a significant role. In a rather different context, the recent intensive research on ‘Maxwell’s demon’—a feedback controller that utilizes information of individual molecules—have led to a unified theory of information and thermodynamics. We combine these two streams of research, and show that the second law of thermodynamics with information reveals the fundamental limit of the robustness of signal transduction against environmental fluctuations. The transfer entropy is the conditional mutual information representing the directed information flow, and gives an upper bound of the redundancy of the channel coding in an artificial communication channel with a feedback loop[21]; this is a fundamental consequence of Shannon’s second theorem[22,23]. We numerically studied the information-thermodynamics efficiency of the signal transduction of E. coli chemotaxis, and found that the signal transduction of E. coli chemotaxis is efficient as an information-thermodynamic device, even when it is highly dissipative as a conventional heat engine
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