[Paper Review] Do biological molecular machines act as Maxwell's demons?

Michał Kurzyński, Przemysław Chełminiak|arXiv (Cornell University)|Dec 12, 2014

Advanced Thermodynamics and Statistical Mechanics9 references3 citations

TL;DR

This paper investigates whether biological molecular machines, such as enzymes, can act as Maxwell's demons by leveraging information and entropy reduction to transduce free energy. Using a stochastic model of protein dynamics on a critical complex network, the study shows that entropy reduction during transient states enables information creation and organization, suggesting that biological machines may function as Maxwell's demons not by performing work, but by processing information and reducing energy losses.

ABSTRACT

The nanoscopic isothermal machines are not only energy but also information transducers. We show that the generalized fluctuation theorem with information creation and entropy reduction can be fulfilled for the enzymatic molecular machines with the stochastic dynamics, which offers a choice of the work performance in a variety of ways. A model of such dynamics, specified by a critical complex network, is investigated. The main conclusion of the study is that the processing of free energy has to be distinguished from the processing of organization, which we identify with an adequately defined thermodynamic variable. Maxwell's demon utilizes entropy reduction for creation of information, which, from the former point of view, may be used for a reduction of energy losses, hence ultimately, for the performance of work. From the latter point of view, however, it can be used for other purposes, for example molecular recognition. This can be the case of biological molecular machines. From the biological perspective, the ascertainment is important, that the information creation and storage take place in the long lasting transient stages before completing the free energy transduction cycles. From a broader physical perspective, a supposition could be of special importance, that information is a change of organization, the thermodynamic function of state of the system.

Motivation & Objective

• To determine whether biological molecular machines can function as Maxwell's demons by utilizing entropy reduction and information processing.
• To distinguish between free energy transduction and organization transduction in isothermal, non-equilibrium systems.
• To investigate the role of transient, long-lived states in information and organization creation during energy transduction cycles.
• To model stochastic dynamics of protein machines using critical complex networks to assess conditions under which entropy reduction and information gain occur.
• To explore the thermodynamic significance of organization as a state variable distinct from energy and entropy.

Proposed method

• Formalizing the generalized fluctuation theorem with information creation and entropy reduction in isothermal, mesoscopic systems.
• Modeling protein molecular machines as stochastic networks with Markovian dynamics on a critical complex network structure.
• Simulating the system using a computer model of a branching tree network to analyze transient states and entropy-information dynamics.
• Defining organization as a thermodynamic variable linked to entropy reduction and information creation, distinct from free energy and bound energy.
• Analyzing the relationship between coupling degree (ε) and transmission ratio (n) to assess conditions for zero-cost information processing.
• Applying Landauer's principle to account for entropy production during memory erasure in information processing cycles.

Experimental results

Research questions

• RQ1 Can biological molecular machines act as Maxwell's demons by reducing entropy through information processing?
• RQ2 What is the role of transient, long-lived states in the creation of information and organization during free energy transduction?
• RQ3 How does the coupling degree (ε) relate to the transmission ratio (n) in stochastic protein dynamics, and what does this imply for energy efficiency?
• RQ4 In what way is organization a distinct thermodynamic variable from free energy and entropy in isothermal systems?
• RQ5 Under what conditions can information creation lead to a reduction in energy dissipation without performing net work?

Key findings

• The generalized fluctuation theorem with information creation and entropy reduction is fulfilled in stochastic models of enzymatic molecular machines.
• Entropy reduction and information creation occur during long-lasting transient stages before completion of free energy transduction cycles.
• The study identifies organization as a thermodynamic variable distinct from free energy and entropy, with information being equivalent to a change in organization.
• A relationship ε < n is found between the coupling degree and transmission ratio, suggesting conditions under which energy dissipation can be minimized.
• The model shows that information processing can reduce energy losses without necessarily performing work, supporting the idea that biological machines may act as Maxwell's demons in an information-processing sense.
• The results suggest that dimeric or higher-ordered protein structures may be evolutionarily favored to enable total compensation of entropy production by information creation, achieving zero-cost operation.