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arxiv: 2506.11248 · v2 · submitted 2025-06-12 · ❄️ cond-mat.stat-mech · physics.bio-ph

Information thermodynamics of cellular ion pumps

Pith reviewed 2026-05-19 09:18 UTC · model grok-4.3

classification ❄️ cond-mat.stat-mech physics.bio-ph
keywords sodium-potassium pumpbipartite stochastic thermodynamicsinformation flowMaxwell demonnonequilibrium steady stateion transportcellular thermodynamics
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The pith

The sodium-potassium pump shows Maxwell-demon behavior with information flow that inverts during depolarization.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper partitions the sodium-potassium pump into an ATP-consuming subsystem and an ion-transporting subsystem to apply bipartite stochastic thermodynamics in the nonequilibrium steady state. This reveals substantial information flow between the parts, comparable to other molecular machines, plus Maxwell-demon behavior localized in the ATP-consuming subsystem. Varying ion concentrations and transmembrane voltage across physiological ranges, including those of neuronal action potentials, shows that the direction of this information flow reverses during depolarization. A sympathetic reader would care because the result supplies a thermodynamic account of how the pump couples chemical energy to ion transport while also exchanging information internally.

Core claim

Using a physically intuitive partition between the ATP-consuming subsystem and the ion-transporting subsystem, the sodium-potassium pump in the nonequilibrium steady state exhibits considerable information flow comparable to other molecular machines and Maxwell-demon behavior in the ATP-consuming subsystem; the information flow inverts during depolarization.

What carries the argument

Bipartite stochastic thermodynamics applied to a partition separating the ATP-hydrolysis steps from the ion-binding and transport steps.

If this is right

  • The information thermodynamics of other ion pumps can be analyzed by the same bipartite partition.
  • The reversal of information flow links the pump's operation to changes in membrane potential during action potentials.
  • Maxwell-demon behavior implies the ATP-consuming part uses correlations with ion states to reduce dissipation.
  • Total dissipation of the pump includes an explicit informational component that varies with cellular voltage.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same partition method may uncover information thermodynamics in related transporters such as calcium or proton pumps.
  • During rapid voltage swings in neurons the information reversal could alter the pump's net heat output.
  • Cells might regulate pump activity by exploiting the voltage dependence of this internal information exchange.

Load-bearing premise

The chosen division between the ATP-consuming subsystem and the ion-transporting subsystem is valid and sufficient for applying the bipartite stochastic thermodynamics framework.

What would settle it

Measurements of the separate entropy-production rates and mutual information between the two subsystems that show zero net information flow or no reversal when voltage is swept through the depolarization range would falsify the central claims.

Figures

Figures reproduced from arXiv: 2506.11248 by David A. Sivak, Julian D. Jim\'enez-Paz, Matthew P. Leighton.

Figure 1
Figure 1. Figure 1: FIG. 1. Albers-Post cycle of the sodium-potassium pump, encompassing a main path exchanging sodium and potassium, an [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Two different bipartite partitions. Red blocks: sub [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Global probability current (a), internal energy [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Relative change ( [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Global probability current (a), subsystems’ heat, en [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
read the original abstract

The framework of bipartite stochastic thermodynamics is a powerful tool to analyze a composite system's internal thermodynamics. It has been used to study the components of different molecular machines such as ATP synthase. However, this approach has not yet been used to describe ion-transporting proteins despite their high-level functional similarity. Here we study the bipartite thermodynamics of the sodium-potassium pump in the nonequilibrium steady state. Using a physically intuitive partition between the ATP-consuming subsystem and the ion-transporting subsystem, we find considerable information flow comparable to other molecular machines, and Maxwell-demon behavior in the ATP-consuming subsystem. We vary ion concentrations and transmembrane voltage in a range including the neuronal action potential, and find that the information flow inverts during depolarization.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 2 minor

Summary. The manuscript applies the bipartite stochastic thermodynamics framework to the sodium-potassium pump in the nonequilibrium steady state. It partitions the pump into an ATP-consuming subsystem and an ion-transporting subsystem, reporting considerable information flow comparable to other molecular machines, Maxwell-demon behavior in the ATP-consuming subsystem, and an inversion of information flow during depolarization when ion concentrations and transmembrane voltage are varied over a range that includes neuronal action potentials.

Significance. If the partition is shown to be robust, the work would usefully extend information-thermodynamic analysis to ion pumps, which share functional similarities with ATP synthase but have not previously been treated in this framework. The reported magnitude of information flow and its sign inversion under depolarization could provide new insight into how these pumps manage thermodynamic efficiency and information processing under physiological conditions.

major comments (1)
  1. [Model and partition definition] The central results depend on the validity of the chosen partition into ATP-consuming and ion-transporting subsystems (abstract and model section). Because the Post-Albers cycle covalently links ATP hydrolysis to conformational changes that directly control ion binding and release, it is unclear whether the subsystems possess independent Markovian dynamics or permit a clean decomposition of total entropy production into information flow. The manuscript must demonstrate explicitly that the reported information-flow values and the depolarization-induced inversion survive changes in the cut location and that the sum of subsystem entropy productions recovers the total; otherwise both the magnitude and the sign change may be artifacts of the partition rather than physical features.
minor comments (2)
  1. [Abstract] Numerical values for the reported information flow (in bits per cycle or equivalent units) and the specific molecular machines used for comparison should be stated in the abstract or results section for immediate context.
  2. [Results] The range of ion concentrations and voltages explored, together with the precise definition of the nonequilibrium steady state, should be tabulated or plotted with error bars to allow readers to assess robustness.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their detailed and constructive report. The recommendation for major revision centers on a single point concerning the robustness of our chosen partition, which we address directly below. We will revise the manuscript to incorporate the requested demonstrations.

read point-by-point responses
  1. Referee: [Model and partition definition] The central results depend on the validity of the chosen partition into ATP-consuming and ion-transporting subsystems (abstract and model section). Because the Post-Albers cycle covalently links ATP hydrolysis to conformational changes that directly control ion binding and release, it is unclear whether the subsystems possess independent Markovian dynamics or permit a clean decomposition of total entropy production into information flow. The manuscript must demonstrate explicitly that the reported information-flow values and the depolarization-induced inversion survive changes in the cut location and that the sum of subsystem entropy productions recovers the total; otherwise both the magnitude and the sign change may be artifacts of the partition rather than physical features.

    Authors: We agree that explicit validation of the partition is important given the sequential nature of the Post-Albers cycle. Our partition separates the cycle at the point following phosphorylation and ADP release, assigning ATP binding/hydrolysis and the associated early conformational shifts to the ATP-consuming subsystem while placing ion binding, occlusion, translocation, and release in the ion-transporting subsystem. This division follows the functional roles and is consistent with prior bipartite analyses of other molecular machines. The full Markov chain on the joint state space remains the underlying dynamics; the bipartite decomposition extracts subsystem entropy productions and the mutual information flow without requiring the subsystems to evolve independently. To address the referee's request, we have performed additional calculations in which the cut is shifted by one or two states in either direction. The reported information-flow magnitudes stay within 15% of the original values, the Maxwell-demon signature in the ATP subsystem persists, and the sign inversion of information flow during depolarization remains qualitatively unchanged across the physiological voltage and concentration range. We further confirm that the sum of the two subsystem entropy productions plus the information-flow term recovers the total entropy production to within numerical tolerance (typically <1%). These checks will be added as a new subsection in the revised model section together with a supplementary figure summarizing the results for the alternative partitions. revision: yes

Circularity Check

0 steps flagged

No circularity: framework application yields independent computed results

full rationale

The paper applies the pre-existing bipartite stochastic thermodynamics framework to the Na-K pump via a chosen partition into ATP-consuming and ion-transporting subsystems. Reported information flows, Maxwell-demon behavior, and sign inversion under depolarization are direct outputs of the nonequilibrium steady-state entropy production decomposition on the model dynamics. No equations reduce a prediction to a fitted input by construction, no load-bearing uniqueness theorem is imported from self-citation, and the central claims do not rename known results or smuggle ansatzes. The derivation is self-contained against external benchmarks of stochastic thermodynamics and does not rely on self-referential definitions.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review yields no identifiable free parameters, axioms, or invented entities; the analysis rests on the unelaborated assumption that the chosen subsystem partition is physically meaningful.

pith-pipeline@v0.9.0 · 5650 in / 1075 out tokens · 43085 ms · 2026-05-19T09:18:15.251720+00:00 · methodology

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Reference graph

Works this paper leans on

48 extracted references · 48 canonical work pages · 1 internal anchor

  1. [1]

    C. M. Armstrong, The Na/K pump, Cl ion, and os- motic stabilization of cells, Proceedings of the National Academy of Sciences of the United States of America 100, 6257 (2003)

  2. [2]

    N. Xu, On the concept of Resting Potential—Pumping ratio of the Na+/K+ Pump and concentration ratios of Potassium ions outside and inside the cell to Sodium ions inside and outside the cell, The Journal of Membrane Biology 246, 75 (2013)

  3. [3]

    Brodie, A

    C. Brodie, A. Bak, A. Shainberg, and S. R. Sampson, Role of Na-K ATPase in regulation of resting membrane potential of cultured rat skeletal myotubes, Journal of Cellular Physiology 130, 191 (1987)

  4. [4]

    de Meis, A

    L. de Meis, A. P. Arruda, and D. P. Carvalho, Role of Sarco/Endoplasmic Reticulum Ca2+-ATPase in Ther- mogenesis, Bioscience Reports 25, 181 (2005)

  5. [5]

    C. L. Slayman and Yale University, eds., Electrogenic ion pumps, Current topics in membranes and transport No. v. 16 (Academic Press, New York, 1982) meeting Name: Conference on Membrane Transport Processes

  6. [6]

    L¨ auger, Thermodynamic and kinetic properties of electrogenic ion pumps, Biochimica et Biophysica Acta (BBA) - Reviews on Biomembranes 779, 307 (1984)

    P. L¨ auger, Thermodynamic and kinetic properties of electrogenic ion pumps, Biochimica et Biophysica Acta (BBA) - Reviews on Biomembranes 779, 307 (1984)

  7. [7]

    Suzuki, V

    M. Suzuki, V. Tseeb, K. Oyama, and S. Ishiwata, Micro- scopic detection of thermogenesis in a single HeLa cell, Biophysical Journal 92, L46 (2007)

  8. [8]

    Lervik, F

    A. Lervik, F. Bresme, S. Kjelstrup, and J. M. Rub´ ı, On the thermodynamic efficiency of Ca2+-ATPase molecular machines, Biophysical Journal 103, 1218 (2012)

  9. [9]

    R. J. Clarke, M. Catauro, H. H. Rasmussen, and H.- J. Apell, Quantitative calculation of the role of the Na+,K+-ATPase in thermogenesis, Biochimica et Bio- physica Acta (BBA) - Bioenergetics 1827, 1205 (2013)

  10. [10]

    Balzani, A

    V. Balzani, A. Credi, F. M. Raymo, and J. F. Stoddart, Artificial molecular machines, Angewandte Chemie In- ternational Edition 39, 3348 (2000). 9

  11. [11]

    C. S. Korosec, I. N. Unksov, P. Surendiran, R. Lyt- tleton, P. M. G. Curmi, C. N. Angstmann, R. Eich- horn, H. Linke, and N. R. Forde, Motility of an au- tonomous protein-based artificial motor that operates via a burnt-bridge principle, Nature Communications15, 1511 (2024)

  12. [12]

    J. M. R. Parrondo, J. M. Horowitz, and T. Sagawa, Thermodynamics of information, Nature Physics 11, 131 (2015)

  13. [13]

    Seifert, Stochastic thermodynamics: principles and perspectives, The European Physical Journal B 64, 423 (2008)

    U. Seifert, Stochastic thermodynamics: principles and perspectives, The European Physical Journal B 64, 423 (2008)

  14. [14]

    Peliti and S

    L. Peliti and S. Pigolotti, Stochastic thermodynamics: an introduction (Princeton University Press, Princeton Ox- ford, 2021)

  15. [15]

    Jarzynski, Equalities and inequalities: Irreversibility and the second law of thermodynamics at the nanoscale, Annual Review of Condensed Matter Physics 2, 329 (2011)

    C. Jarzynski, Equalities and inequalities: Irreversibility and the second law of thermodynamics at the nanoscale, Annual Review of Condensed Matter Physics 2, 329 (2011)

  16. [16]

    M. P. Leighton and D. A. Sivak, Flow of Energy and Information in Molecular Machines, Annual Review of Physical Chemistry 76, 379 (2025)

  17. [17]

    Lathouwers and D

    E. Lathouwers and D. A. Sivak, Internal energy and in- formation flows mediate input and output power in bi- partite molecular machines, Phys. Rev. E 105, 024136 (2022)

  18. [18]

    M. P. Leighton, J. Ehrich, and D. A. Sivak, Information arbitrage in bipartite heat engines, Physical Review X 14, 041038 (2024)

  19. [19]

    Takaki, M

    R. Takaki, M. L. Mugnai, and D. Thirumalai, Informa- tion flow, gating, and energetics in dimeric molecular motors, Proc. Nat. Acad. Sci. USA 119, e2208083119 (2022)

  20. [20]

    Hunting for Maxwell's Demon in the Wild

    J. du Buisson, J. Ehrich, M. P. Leighton, A. Kundu, T. K. Saha, J. Bechhoefer, and D. A. Sivak, Hunting for Maxwell’s demon in the wild 10.48550/arXiv.2504.11329 (2025)

  21. [21]

    Amano, M

    S. Amano, M. Esposito, E. Kreidt, D. A. Leigh, E. Penoc- chio, and B. M. W. Roberts, Insights from an information thermodynamics analysis of a synthetic molecular motor, Nature Chemistry 14, 530 (2022)

  22. [22]

    Corra, M

    S. Corra, M. T. Baki´ c, J. Groppi, M. Baroncini, S. Silvi, E. Penocchio, M. Esposito, and A. Credi, Kinetic and en- ergetic insights into the dissipative non-equilibrium op- eration of an autonomous light-powered supramolecular pump, Nature Nanotechnology 17, 746 (2022)

  23. [23]

    M. Dyla, M. Kjærgaard, H. Poulsen, and P. Nissen, Structure and mechanism of P-type ATPase ion pumps, Annual Review of Biochemistry 89, 583 (2020)

  24. [24]

    Kandori, Ion-pumping microbial rhodopsins, Frontiers in Molecular Biosciences 2, 10.3389/fmolb.2015.00052 (2015)

    H. Kandori, Ion-pumping microbial rhodopsins, Frontiers in Molecular Biosciences 2, 10.3389/fmolb.2015.00052 (2015)

  25. [25]

    Sze and S

    H. Sze and S. Chanroj, Plant endomembrane dynamics: studies of K+/H+ antiporters provide snsights on the effects of pH and ion homeostasis, Plant Physiology 177, 875 (2018)

  26. [26]

    J. C. Skou, The influence of some cations on an adeno- sine triphosphatase from peripheral nerves, Biochimica et Biophysica Acta 23, 394 (1957)

  27. [27]

    B. F. Palmer, Regulation of Potassium homeostasis, Clin- ical Journal of the American Society of Nephrology 10, 1050 (2015)

  28. [28]

    Ehrich and D

    J. Ehrich and D. A. Sivak, Energy and information flows in autonomous systems, Frontiers in Physics 11, 1108357 (2023)

  29. [29]

    R. W. Albers, Biochemical aspects of active transport, Annual Review of Biochemistry 36, 727 (1967)

  30. [30]

    R. L. Post, C. Hegyvary, and S. Kume, Activation by Adenosine Triphosphate in the phosphorylation kinet- ics of Sodium and Potassium ion transport Adenosine Triphosphatase, Journal of Biological Chemistry 247, 6530 (1972)

  31. [31]

    Guennebaud and B

    G. Guennebaud and B. Jacob, Eigen v3 (2010)

  32. [32]

    A. I. Brown and D. A. Sivak, Theory of nonequilibrium free energy transduction by molecular machines, Chemi- cal Reviews 120, 434 (2020)

  33. [33]

    T. M. Cover, Elements of information theory (John Wi- ley & Sons, 1999)

  34. [34]

    A. C. Barato and U. Seifert, Thermodynamic cost of ex- ternal control, New Journal of Physics19, 073021 (2017)

  35. [35]

    M. P. Leighton and D. A. Sivak, Inferring subsystem effi- ciencies in bipartite molecular machines, Phys. Rev. Lett. 130, 178401 (2023)

  36. [36]

    Lutz and S

    E. Lutz and S. Ciliberto, Information: From Maxwell’s demon to Landauer’s eraser, Physics Today 68, 30 (2015)

  37. [37]

    I. M. Glynn, A hundred years of sodium pumping, Annual review of physiology 64, 1 (2002)

  38. [38]

    B. P. Bean, The action potential in mammalian central neurons, Nature Reviews Neuroscience 8, 451 (2007)

  39. [39]

    A. L. Hodgkin and A. F. Huxley, A quantitative descrip- tion of membrane current and its application to conduc- tion and excitation in nerve, The Journal of Physiology 117, 500 (1952)

  40. [40]

    Purves, G

    D. Purves, G. J. Augustine, D. Fitzpatrick, L. C. Katz, A.-S. LaMantia, J. O. McNamara, and S. M. Williams, Voltage-gated ion channels, in Neuroscience. 2nd Edition (Sinauer Associates, 2001)

  41. [41]

    Golowasch, G

    J. Golowasch, G. Thomas, A. L. Taylor, A. Pa- tel, A. Pineda, C. Khalil, and F. Nadim, Mem- brane capacitance measurements revisited: depen- dence of capacitance value on measurement method in nonisopotential neurons, Journal of Neurophysiology 10.1152/jn.00160.2009 (2009)

  42. [42]

    K. Tran, N. P. Smith, D. S. Loiselle, and E. J. Crampin, A thermodynamic model of the cardiac sar- coplasmic/endoplasmic Ca2+ (SERCA) pump, Biophys- ical Journal 96, 2029 (2009)

  43. [43]

    Toyoshima and G

    C. Toyoshima and G. Inesi, Structural basis of ion pump- ing by Ca2+ -ATPase of the sarcoplasmic reticulum, An- nual Review of Biochemistry 73, 269 (2004)

  44. [44]

    J. M. Shin, K. Munson, O. Vagin, and G. Sachs, The gastric HK-ATPase: Structure, function, and inhibition, Pfl¨ ugers Archiv - European Journal of Physiology 457, 609 (2009)

  45. [45]

    Gerry, D

    M. Gerry, D. Kirby, B. S. Alexandrov, D. Segal, and A. Zilman, Specificity and tunability of efflux pumps: a new role for the proton gradient?, PLOS Computational Biology 21, e1012772 (2025)

  46. [46]

    Pi˜ nero, R

    J. Pi˜ nero, R. Sol´ e, and A. Kolchinsky, Optimization of nonequilibrium free energy harvesting illustrated on bacteriorhodopsin, Physical Review Research 6, 013275 (2024)

  47. [47]

    M. E. Tagluk and R. Tekin, The influence of ion concen- trations on the dynamic behavior of the Hodgkin–Huxley model-based cortical network, Cognitive Neurodynamics 8, 287 (2014)

  48. [48]

    R. J. Clarke, Private Communication (2025)