Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal...

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Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers in Non-equilibrium Physics 2015 28 July 2015, YITP, Kyoto

Transcript of Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal...

Page 1: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Maxwell's Demon in Biochemical Signal Transduction

Takahiro Sagawa Department of Applied Physics, University of Tokyo

New Frontiers in Non-equilibrium Physics 2015 28 July 2015, YITP, Kyoto

Page 2: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Collaborators on Information Thermodynamics

• Masahito Ueda (Univ. Tokyo)

• Shoichi Toyabe (Tohoku Univ.)

• Eiro Muneyuki (Chuo Univ.)

• Masaki Sano (Univ. Tokyo)

• Sosuke Ito (Titech)

• Naoto Shiraishi (Univ. Tokyo)

• Sang Wook Kim (Pusan National Univ.)

• Jung Jun Park (National Univ. Singapore)

• Kang-Hwan Kim (KAIST)

• Simone De Liberato (Univ. Paris VII)

• Juan M. R. Parrondo (Univ. Madrid)

• Jordan M. Horowitz (MIT)

• Jukka Pekola (Aalto Univ.)

• Jonne Koski (Aalto Univ.)

• Ville Maisi (Aalto Univ.)

Page 3: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Outline

• Introduction

• Information and entropy

• Information thermodynamics: a general framework

• Paradox of Maxwell’s demon

• Thermodynamics of autonomous information processing

• Application to biochemical signal transduction

• Summary

Review of previous results

Today’s main part!

Page 4: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Outline

• Introduction

• Information and entropy

• Information thermodynamics: a general framework

• Paradox of Maxwell’s demon

• Thermodynamics of autonomous information processing

• Application to biochemical signal transduction

• Summary

Page 5: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Thermodynamics in the Fluctuating World

Thermodynamics of small systems with large heat bath(s)

Second law W F

Nonlinear & nonequilibrium relations

Thermodynamic quantities are fluctuating!

Page 6: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Information Thermodynamics

Information processing at the level of thermal fluctuations

Foundation of the second law of thermodynamics

Application to nanomachines and nanodevices

System Demon

Information

Feedback

Review: J. M. R. Parrondo, J. M. Horowitz, & T. Sagawa, Nature Physics 11, 131-139 (2015).

Page 7: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Szilard Engine (1929)

Heat bath

T

Initial State Which? Partition

Measurement

Left

Right

Feedback

ln 2

F E TS Free energy: Decrease by feedback Increase

Isothermal, quasi-static expansion B ln 2k T

Work

Can control physical entropy by using information

L. Szilard, Z. Phys. 53, 840 (1929)

Page 8: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Information Heat Engine

Memory (Controller)

System (Working engine)

Can increase the system’s free energy even if there is no energy flow between the system and the controller

Information

Feedback

Entropic cost Free energy / work

Page 9: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Experimental Realizations

• With a colloidal particle Toyabe, TS, Ueda, Muneyuki, & Sano, Nature Physics (2010)

Efficiency: 30% Validation of

• With a single electron Koski, Maisi, TS, & Pekola, PRL (2014)

Efficiency: 75% Validation of

( )W Fe

( ) 1W F Ie

Page 10: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Outline

• Introduction

• Information and entropy

• Information thermodynamics: a general framework

• Paradox of Maxwell’s demon

• Thermodynamics of autonomous information processing

• Application to biochemical signal transduction

• Summary

Page 11: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Shannon Information

9

10

1

10

Information content with event : 1

lnkp

k

Shannon information: 1

lnk

k k

H pp

Average

Page 12: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Mutual Information

0 ( )I H M

No information No error

System S Memory M I

( : ) ( ) ( ) ( )I S M H S H M H SM

System S Memory M (measurement device)

Measurement with stochastic errors

0

1

0

1

1

1

Ex. Binary symmetric channel

Correlation between S and M

I

)1ln()1(ln2ln I

Page 13: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Entropy Production

System S

Heat bath B

(inverse temperature β)

Heat Q

Entropy production in the total system: QSS SSB

Change in the Shannon entropy of S

If the initial and the final states are canonical distributions: FWS SB

Free-energy difference

W Work

Averaged heat absorbed by S

Stochastic dynamics of system S (e.g., Langevin system)

Page 14: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Stochastic Entropy Production

Qss SSB

Stochastic entropy production along a trajectory of the system from time 0 to τ

System (phase-space point x)

Heat bath (inverse temperature β)

Q

If the initial and the final states are canonical distributions: FWs SB

W Work

SS Ss

],[ln],[S txPtxs ]0),0([]),([ SSS xsxss

],[ txP : probability distribution at time t

Page 15: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Integral Fluctuation Theorem and Jarzynski Equality

1SB s

e

Integral fluctuation theorem

for any initial and final distributions

0SB s

The second law of thermodynamics (Clausius inequality)

QS S

FW

Seifert, PRL (2005), …

Second law can be expressed by an equality with full cumulants

FWs SBFW ee

Jarzynski equality Jarzynski, PRL (1997)

Page 16: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Outline

• Introduction

• Information and entropy

• Information thermodynamics: a general framework

• Paradox of Maxwell’s demon

• Thermodynamics of autonomous information processing

• Application to biochemical signal transduction

• Summary

Page 17: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Setup

System Y Heat bath B System X Heat bath B

Time evolution of X under the influence of Y with initial and final correlations

Page 18: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Special Cases: Measurement and Feedback

Measurement Feedback

X: Engine Y: Memory

X: Memory Y: Engine

Page 19: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Stochastic Entropy and Mutual Information

XXXB Qss

Entropy increase in XB

][]'[

],'[ln],'[''

yPxP

yxPyxdyPdxI f

yx

][][

],[ln],[

yPxP

yxPyxdxdyPI i

xy][][

],[ln

yPxP

yxPI i

xy

Initial correlation

][]'[

],'[ln'

yPxP

yxPI f

yx

Final correlation

Page 20: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Decomposition of Entropy Production

Iss XBXYB

Total entropy production in XYB

XXXB Qss i

xy

f

yx III '

XXYXYB Qss

Is

Isss

X

YXXY

Page 21: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Fluctuation Theorem

1XYB s

e

Integral fluctuation theorem

TS and M. Ueda, Phys. Rev. Lett. 109, 180602 (2012).

1XB Is

e

Second law 0XYB s

Is XB

Iss XBXYB

Page 22: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Special Case 1: Feedback Control

III rem

1)( remXB

IIse

Feedback: Control protocol depends on the measurement outcome

X: Engine Y: Memory

remXB IIs

ITkFW Bext F : equilibrium free energy

Page 23: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Special Case 2: Measurement

II

1XB Is

e

X: Memory Y: Engine

Is XB

Page 24: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Minimal Energy Cost for Measurement

Is XB

Change in the nonequilibrium free energy of only X

TS and M. Ueda, Phys. Rev. Lett. 109, 180602 (2012).

IsEW XXX

Engine Y

Heat bath B

Memory X

Heat bath B

Work XW

XEEnergy change

Information is not free

Additional energy cost to obtain information

Page 25: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

General Principle of Information Thermodynamics

1XB Is

e

Is XB

1XB Is

e

Is XB

Measurement:

Unified formulation of measurement and feedback

TS and M. Ueda, PRL 109, 180602 (2012).

1)( remXB

IIse

remXB IIs

Feedback:

Page 26: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Outline

• Introduction

• Information and entropy

• Information thermodynamics: a general framework

• Paradox of Maxwell’s demon

• Thermodynamics of autonomous information processing

• Application to biochemical signal transduction

• Summary

Page 27: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

What compensates for the entropy decrease here?

Problem

Memory Heat bath System Heat bath

2lnSB sFor Szilard engine,

Page 28: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Conventional Arguments

Erasure process (From Landauer principle) Bennett

& Landauer

Measurement process

Brillouin

Widely accepted since 1980’s

Page 29: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Total Entropy Production

Is XB0XYB s

Is

Qss

XB

XXYXYB

If the mutual information is taken into account, the total entropy production is always nonnegative for each process of measurement or feedback.

Total entropy production in XYB

Equality: thermodynamically reversible

Page 30: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

What compensates for the entropy decrease here?

Revisit the Problem

Memory Heat bath System Heat bath

2lnSB sFor Szilard engine,

Mutual-information change compensates for it.

02ln2lnSBSMB Iss

Page 31: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Key to Resoluve the Paradox

• Maxwell’s demon is consistent with the second law for measurement and feedback processes individually

– The mutual information is the key

• We don’t need the Landauer principle to understanding the consistency

Page 32: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Outline

• Introduction

• Information and entropy

• Information thermodynamics: a general framework

• Paradox of Maxwell’s demon

• Thermodynamics of autonomous information processing

• Application to biochemical signal transduction

• Summary

Page 33: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

• Second law & fluctuation theorem Allahverdyan, Dominik & Guenter, J. Stat. Mech. (2009) Hartich, Barato, & Seifert, J. Stat. Mech. (2014) Horowitz & Esposito, Phys. Rev. X (2014) Horowitz & Sandberg, New J. Phys. (2014) Shiraishi & Sagawa, Phys. Rev. E (2015) Ito & Sagawa, Phys. Rev. Lett. (2013)

• Models of autonomous Maxwell’s demons Mandal & Jarzynski, PNAS (2012) Mandal, Quan, & Jarzynski, Phys. Rev. Lett. (2013) Strasberg, Schaller, Brandes, & Esposito Phys. Rev. Lett. (2013) Horowitz, Sagawa, & Parrondo, Phys. Rev. Lett. (2013) Shiraishi, Ito, Kawaguchi & Sagawa, New J. Phys. (2015)

Thermodynamics of Autonomous Information Processing

Toward deeper understanding of information nanomachines

Page 34: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Two Approaches

• “Transfer entropy” approach

Applicable to non-Markovian dynamics

Second law is weaker in Markovian dynamics

• “Information flow” approach

Not applicable to non-Markovian dynamics

Second law is stronger in Markovian dynamics

But we derived a stronger version! (Poster by Ito)

Ito & Sagawa, Phys. Rev. Lett. (2013)

Second law: Allahverdyan, Dominik & Guenter, J. Stat. Mech. (2009) Hartich, Barato, & Seifert, J. Stat. Mech. (2014) Horowitz & Esposito, Phys. Rev. X (2014) Horowitz & Sandberg, New J. Phys. (2014) Fluctuation theorem: Shiraishi & Sagawa, PRE (2015) Poster by Shiraishi

Page 35: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Transfer Entropy

),( 00 YX

),( 11 nn YX

・・・

),( nn YXTime Transfer entropy:

Directional information flow from X to Y during time n and n+1

nn yyx nnnn

nnnnn

yyypyyxp

yyyxpyyxp

,, 10101

10101

01),|(),|(

),|,(ln),,(

0111 |:)( YYYXIYXT nnnnn

Conditional mutual information

T. Schreiber, PRL 85, 461 (2000)

Directional information transfer between two systems

Page 36: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Many-body Systems with Complex Information Flow

Sosuke Ito & TS, PRL 111, 180603 (2013).

Characterize the dynamics by Bayesian networks

Time

Node: Event Arrow: Causal relationship

Page 37: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Second Law on Bayesian Networks

S. Ito & T. Sagawa, PRL 111, 180603 (2013)

l

lIII trinifin

Iini : Initial mutual information between X and other systems

Ifin : Final mutual information between X and other systems

Itrl : Transfer entropy from X to other systems

: Entropy production in X and the bath

XBS

XBS

Time

Page 38: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Information Flow VS Transfer Entropy

Infinitesimal transition of coupled Langevin system

)(' dttxx

)(txx

)(' dttyy

)(tyy

):():'()()'( yxIyxIQxsxs Stronger:

Information flow

)|':():()':'()()'( yyxIyxIyxIQxsxs Weaker:

)|':()|()'|'( yyxIQyxsyxs

Transfer entropy

)())(),(()( ttytxftx x

)())(),(()( ttytxgty y

0)()( tt yx : independent noise

Page 39: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Outline

• Introduction

• Information and entropy

• Information thermodynamics: a general framework

• Paradox of Maxwell’s demon

• Thermodynamics of autonomous information processing

• Application to biochemical signal transduction

• Summary

Page 40: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Toward Biological Information Processing

Mutual information is experimentally accessible ex. Apoptosis path: Cheong et al. Science (2011).

What is the role of information in living systems?

Our finding: Relationship between information and the robustness of adaptation

There is no explicit channel coding inside living cells; Shannon’s second theorem is not straightforwardly applicable

Application of information thermodynamics

Barato, Hartich & Seifert, New J. Phys. 16, 103024 (2014). Sartori, Granger, Lee & Horowitz, PLoS Compt. Biol. 10, e1003974 (2014). Ito & Sagawa, Nat. Commu. 6, 7498 (2015).

Page 41: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

E. Coli moves toward food (ligand)

The information about ligand density is transferred to the methylation level of the receptor, and used for the feedback to the kinase activity.

Signal Transduction of E. Coli Chemotaxis

Page 42: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

: stationary value of at

: kinase activity : methylation level : average ligand density

: time constants

Y. Tu et al., Proc. Natl. Acad. Sci. USA 105, 14855 (2008). F. Tostevin and P. R. ten Wolde, Phys. Rev. Lett. 102, 218101 (2009). F. G. Lan et al., Nature Physics 8, 422 (2012).

Adaptation Dynamics

2D Langevin model

Instantaneous change of at in response to l

t

Memorize lt by m

t

at goes back to the initial value

Negative feedback loop:

Page 43: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

: Change in the conditional Shannon entropy

: Transfer entropy

Second Law of Information Thermodynamics

: Robustness against the environmental noise

Upper bound of the robustness is given by the transfer entropy

S. Ito & T. Sagawa, Nature Communications 6, 7498 (2015).

(Weaker version with transfer entropy)

Page 44: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Without feedback:

Stationary State

Fluctuation (inaccuracy of information transmission) induced by environmental noise

Transfer entropy

Page 45: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

If the Langevin equation is linear:

: noise of m

: power of the signal from a to m

Exact Expression of Transfer Entropy

Analogous to the Shannon–Hartley theorem

Signal-to-noise ratio

Page 46: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Input ligand signal: a, step function. b, sinusoidal function. c, linear function.

Red: robustness of adaptation Green: information-thermodynamic bound

Blue: conventional thermodynamic bound

Numerical simulation:

Information-Thermodynamic Efficiency

Information thermodynamics gives a stronger bound! The adaptation dynamics is inefficient (dissipative) as a conventional

thermodynamic engine, but efficient as an information-thermodynamic engine.

Page 47: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Information-Thermodynamic Figure of Merit

Page 48: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Second law of information thermodynamics

Information dItrt

gives the bound of robustness Jat

Comparison with Shannon’s Information Theory

Information (channel capacity) C gives the bound of achievable rate R

Shannon’s second theorem

Well-defined in living cells

How to define in living cells??

Page 49: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Outline

• Introduction

• Information and entropy

• Information thermodynamics: a general framework

• Paradox of Maxwell’s demon

• Thermodynamics of autonomous information processing

• Application to biochemical signal transduction

• Summary

Page 50: Maxwell's Demon in Biochemical Signal Transduction...Maxwell's Demon in Biochemical Signal Transduction Takahiro Sagawa Department of Applied Physics, University of Tokyo New Frontiers

Summary • Unified framework of information thermodynamics

• Fluctuation theorem for autonomous information processing

• Information thermodynamics of biochemical signal transduction

Thank you for your attention!

S. Ito & T. Sagawa, Phys. Rev. Lett. 111, 180603 (2013). Review: S. Ito & T. Sagawa, arXiv:1506.08519 (2015). N. Shiraishi & T. Sagawa, Phys. Rev. E 91, 012130 (2015).

T. Sagawa & M. Ueda, Phys. Rev. Lett. 109, 180602 (2012). T. Sagawa & M. Ueda, New J. Phys. 15, 125012 (2013).

Review: J. M. R. Parrondo, J. M. Horowitz, & T. Sagawa, Nature Physics 11, 131-139 (2015).

S. Ito & T. Sagawa, Nature Communications 6, 7498 (2015).