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Milster S, Darwish A, Göth N, Dzubiella J. Synergistic chemomechanical dynamics of feedback-controlled microreactors. Phys Rev E 2023; 108:L042601. [PMID: 37978612 DOI: 10.1103/physreve.108.l042601] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 09/06/2023] [Indexed: 11/19/2023]
Abstract
The experimental control of synergistic chemomechanical dynamics of catalytically active microgels (microreactors) is a key prerequisite for the design of adaptive and biomimetic materials. Here, we report a minimalistic model of feedback-controlled microreactors based on the coupling between the hysteretic polymer volume phase transition and a volume-controlled permeability for the internal chemical conversion. We categorize regimes of mono- and bistability, excitability, damped oscillations, as well as sustained oscillatory states with tunable amplitude, as indicated by experiments and representable by the FitzHugh-Nagumo dynamics for neurons. We summarize the features of such a "colloidal neuron" in bifurcation diagrams with respect to microgel design parameters, such as permeability and relaxation times, as a guide for experimental synthesis.
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Affiliation(s)
- Sebastian Milster
- Applied Theoretical Physics - Computational Physics, Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany
| | - Abeer Darwish
- Applied Theoretical Physics - Computational Physics, Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany
| | - Nils Göth
- Applied Theoretical Physics - Computational Physics, Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany
| | - Joachim Dzubiella
- Applied Theoretical Physics - Computational Physics, Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany
- Cluster of Excellence livMatS @ FIT - Freiburg Center for Interactive Materials and Bioinspired Technologies, Albert-Ludwigs-Universität Freiburg, D-79110 Freiburg, Germany
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2
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Hu CY, Achari A, Rowe P, Xiao H, Suran S, Li Z, Huang K, Chi C, Cherian CT, Sreepal V, Bentley PD, Pratt A, Zhang N, Novoselov KS, Michaelides A, Nair RR. pH-dependent water permeability switching and its memory in MoS 2 membranes. Nature 2023; 616:719-723. [PMID: 37076621 DOI: 10.1038/s41586-023-05849-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 02/15/2023] [Indexed: 04/21/2023]
Abstract
Intelligent transport of molecular species across different barriers is critical for various biological functions and is achieved through the unique properties of biological membranes1-4. Two essential features of intelligent transport are the ability to (1) adapt to different external and internal conditions and (2) memorize the previous state5. In biological systems, the most common form of such intelligence is expressed as hysteresis6. Despite numerous advances made over previous decades on smart membranes, it remains a challenge to create a synthetic membrane with stable hysteretic behaviour for molecular transport7-11. Here we demonstrate the memory effects and stimuli-regulated transport of molecules through an intelligent, phase-changing MoS2 membrane in response to external pH. We show that water and ion permeation through 1T' MoS2 membranes follows a pH-dependent hysteresis with a permeation rate that switches by a few orders of magnitude. We establish that this phenomenon is unique to the 1T' phase of MoS2, due to the presence of surface charge and exchangeable ions on the surface. We further demonstrate the potential application of this phenomenon in autonomous wound infection monitoring and pH-dependent nanofiltration. Our work deepens understanding of the mechanism of water transport at the nanoscale and opens an avenue for the development of intelligent membranes.
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Affiliation(s)
- C Y Hu
- National Graphene Institute, University of Manchester, Manchester, UK
- Department of Chemical Engineering, University of Manchester, Manchester, UK
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- College of Chemistry and Chemical Engineering, iChEM, Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen, China
| | - A Achari
- National Graphene Institute, University of Manchester, Manchester, UK.
- Department of Chemical Engineering, University of Manchester, Manchester, UK.
| | - P Rowe
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
| | - H Xiao
- National Graphene Institute, University of Manchester, Manchester, UK
- Department of Chemical Engineering, University of Manchester, Manchester, UK
| | - S Suran
- National Graphene Institute, University of Manchester, Manchester, UK
- Department of Chemical Engineering, University of Manchester, Manchester, UK
| | - Z Li
- School of Chemical Engineering, Dalian University of Technology, Panjin, China
| | - K Huang
- National Graphene Institute, University of Manchester, Manchester, UK
- Department of Chemical Engineering, University of Manchester, Manchester, UK
| | - C Chi
- National Graphene Institute, University of Manchester, Manchester, UK
- Department of Chemical Engineering, University of Manchester, Manchester, UK
| | - C T Cherian
- National Graphene Institute, University of Manchester, Manchester, UK
- Department of Chemical Engineering, University of Manchester, Manchester, UK
- Department of Physics and Electronics, Christ University, Bangalore, India
| | - V Sreepal
- National Graphene Institute, University of Manchester, Manchester, UK
- Department of Chemical Engineering, University of Manchester, Manchester, UK
| | - P D Bentley
- School of Physics, Engineering and Technology, University of York, York, UK
| | - A Pratt
- School of Physics, Engineering and Technology, University of York, York, UK
| | - N Zhang
- National Graphene Institute, University of Manchester, Manchester, UK
- Department of Chemical Engineering, University of Manchester, Manchester, UK
- School of Chemical Engineering, Dalian University of Technology, Panjin, China
| | - K S Novoselov
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore, Singapore
| | - A Michaelides
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
| | - R R Nair
- National Graphene Institute, University of Manchester, Manchester, UK.
- Department of Chemical Engineering, University of Manchester, Manchester, UK.
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Milster S, Kim WK, Dzubiella J. Feedback-controlled solute transport through chemo-responsive polymer membranes. J Chem Phys 2023; 158:104903. [PMID: 36922137 DOI: 10.1063/5.0135707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Abstract
Polymer membranes are typically assumed to be inert and nonresponsive to the flux and density of the permeating particles in transport processes. Here, we theoretically study the consequences of membrane responsiveness and feedback on the steady-state force-flux relations and membrane permeability using a nonlinear-feedback solution-diffusion model of transport through a slab-like membrane. Therein, the solute concentration inside the membrane depends on the bulk concentration, c0, the driving force, f, and the polymer volume fraction, ϕ. In our model, the solute accumulation in the membrane causes a sigmoidal volume phase transition of the polymer, changing its permeability, which, in return, affects the membrane's solute uptake. This feedback leads to nonlinear force-flux relations, j(f), which we quantify in terms of the system's differential permeability, Psys Δ∝dj/df. We find that the membrane feedback can increase or decrease the solute flux by orders of magnitude, triggered by a small change in the driving force and largely tunable by attractive vs repulsive solute-membrane interactions. Moreover, controlling the inputs, c0 and f, can lead to the steady-state bistability of ϕ and hysteresis in the force-flux relations. This work advocates that the fine-tuning of the membrane's chemo-responsiveness will enhance the nonlinear transport control features, providing great potential for future (self-)regulating membrane devices.
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Affiliation(s)
- Sebastian Milster
- Applied Theoretical Physics-Computational Physics, Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany
| | - Won Kyu Kim
- Korea Institute for Advanced Study, Seoul 02455, Republic of Korea
| | - Joachim Dzubiella
- Applied Theoretical Physics-Computational Physics, Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany
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Zeltser G, Sukhanov IM, Nevorotin AJ. MMM - The molecular model of memory. J Theor Biol 2022; 549:111219. [PMID: 35810778 DOI: 10.1016/j.jtbi.2022.111219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 07/01/2022] [Accepted: 07/04/2022] [Indexed: 11/17/2022]
Abstract
Identifying mechanisms underlying neurons ability to process information including acquisition, storage, and retrieval plays an important role in the understanding of the different types of memory, pathogenesis of many neurological diseases affecting memory and therapeutic target discovery. However, the traditional understanding of the mechanisms of memory associated with the electrical signals having a unique combination of frequency and amplitude does not answer the question how the memories can survive for life-long periods of time, while exposed to synaptic noise. Recent evidence suggests that, apart from neuronal circuits, a diversity of the molecular memory (MM) carriers, are essential for memory performance. The molecular model of memory (MMM) is proposed, according to which each item of incoming information (the elementary memory item - eMI) is encoded by both circuitries, with the unique for a given MI electrical parameters, and also the MM carriers, unique by its molecular composition. While operating as the carriers of incoming information, the MMs, are functioning within the neuron plasma membrane. Inactive (latent) initially, during acquisition each of the eMIs is activated to become a virtual copy of some real fact or events bygone. This activation is accompanied by the considerable remodeling of the MM molecule associated with the resonance effect.
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Affiliation(s)
| | - Ilya M Sukhanov
- Lab. Behavioral Pharmacology, Dept. Psychopharmacology, Valdman Institute of Pharmacology, I.P. Pavlov Medical University, Leo Tolstoi Street 6/8, St. Petersburg 197022, The Russian Federation
| | - Alexey J Nevorotin
- Laboratory of Electron Microscopy, I.P. Pavlov Medical University, Leo Tolstoi Street 6/8, St. Petersburg 197022, The Russian Federation
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Shigeno M, Kushida Y, Yamaguchi M. Molecular switching involving metastable states: molecular thermal hysteresis and sensing of environmental changes by chiral helicene oligomeric foldamers. Chem Commun (Camb) 2016; 52:4955-70. [PMID: 26974494 DOI: 10.1039/c5cc10379g] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Molecular switching is a phenomenon in which the molecular structure reversibly changes in response to external stimulation. It is crucial in biology and is used in various biological sensing applications and responses. In contrast to the well-studied molecular switching involving two or more thermodynamically stable states, switching involving metastable states exhibits notable non-equilibrium thermodynamic properties. Synthetic chiral helicene oligomeric foldamers that exhibit molecular thermal hysteresis in dilute solution are examples. Molecular switching can be used for sensing environmental changes, including temperature threshold, temperature decrease/increase, rate of temperature decrease, counting the numbers 1 and 2, and concentration increase.
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Affiliation(s)
- Masanori Shigeno
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Sendai, 980-8578, Japan.
| | - Yo Kushida
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Sendai, 980-8578, Japan.
| | - Masahiko Yamaguchi
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Sendai, 980-8578, Japan.
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Shigeno M. Nonequilibrium Molecular Switching of Chiral Helicene Oligomers in Double-Helix Formation. YAKUGAKU ZASSHI 2016; 136:1591-1600. [PMID: 27904093 DOI: 10.1248/yakushi.16-00203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Molecular switching is the phenomenon in which a molecular structural change occurs reversibly in response to an external stimulus or energy. It plays an important role in biology, in which it is used for sensing environmental changes. In contrast to well-studied equilibrium molecular switching involving thermodynamically stable states, nonequilibrium molecular switching involving a metastable state is a notable chemical phenomenon and is the theme of this study. Sulfonamido- and aminomethylenehelicene oligomers show a reversible structural change from a double helix to a random coil in dilute solution. A metastable state consisting of random coils can be generated by heating, which shows various nonequilibrium thermodynamic properties. Molecular phenomena including molecular thermal hysteresis, molecular memory effect, and one-directional three-state molecular structural change occur, none of which is observed in an equilibrium molecular switching system. They can be applied to sensing environmental changes such as temperature increases/decreases, temperature change rates, and concentration increases, and for counting the numbers 1 and 2.
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Affiliation(s)
- Masanori Shigeno
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University
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Yamaguchi M, Arisawa M, Shigeno M, Saito N. Equilibrum and Nonequilibrium Chemical Reactions of Helicene Oligomers in the Noncovalent Bond Formation. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2016. [DOI: 10.1246/bcsj.20160133] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Shigeno M, Kushida Y, Yamaguchi M. Energy Aspects of Thermal Molecular Switching: Molecular Thermal Hysteresis of Helicene Oligomers. Chemphyschem 2015; 16:2076-83. [PMID: 25990788 DOI: 10.1002/cphc.201500210] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 04/13/2015] [Indexed: 12/18/2022]
Abstract
Molecular switching is a phenomenon by which a molecule reversibly changes its structure and state in response to external stimuli or energy. Herein, molecular switching is discussed from thermodynamic and kinetic aspects in terms of energy supply with an emphasis on the thermal switching exhibited by helicene oligomers. It includes the inversion of relative thermodynamic stability induced by temperature changes and molecular thermal hysteresis in a closed system. The thermal phenomenon associated with the oligomers involves population/concentration changes between metastable states under nonequilibrium thermodynamic control.
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Affiliation(s)
- Masanori Shigeno
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Sendai 980-8578 (Japan), Fax: (+81) 22-795-6811
| | - Yo Kushida
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Sendai 980-8578 (Japan), Fax: (+81) 22-795-6811
| | - Masahiko Yamaguchi
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Sendai 980-8578 (Japan), Fax: (+81) 22-795-6811.
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Tanford C. Formation of the native structure of proteins: inferences from the kinetics of denaturation and renaturation. CIBA FOUNDATION SYMPOSIUM 2008; 7:125-46. [PMID: 4353755 DOI: 10.1002/9780470719909.ch8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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10
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11
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Boucher M, Chassaing C, Chapuy E, Lorente P. Effects of quinidine, verapamil, nifedipine and ouabain on hysteresis in atrial refractoriness in the conscious dog: an approach to ionic mechanisms. GENERAL PHARMACOLOGY 1999; 32:47-50. [PMID: 9888253 DOI: 10.1016/s0306-3623(98)00056-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
1. This work determines the effects of quinidine, verapamil, nifedipine and ouabain on the hysteresis of the atrial effective refractory period (AERP) in the conscious dog. 2. AERP was always longer in the increasing phase than in the decreasing phase of the extrastimulus method, thus demonstrating the existence of AERP hysteresis. Calculated as the difference between the two values, hysteresis was between 8+/-0.8 and 11+/-1.0 msec. 3. Quinidine increased hysteresis from 9+/-0.7 to 13+/-0.7 msec, whereas verapamil decreased it from 10+/-0.9 to 5+/-0.5 msec and nifedipine did not affect it. Ouabain also lengthened hysteresis from 8+/-0.8 to 11+/-1.2 msec. 4. Thus, these results confirm the existence of a hysteresis phenomenon in the AERP in the conscious dog and are evidence that the fast sodium and slow calcium specific membrane currents participate in this phenomenon.
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Affiliation(s)
- M Boucher
- Department of Physiology, Faculty of Pharmacy, Clermont-Ferrand, France.
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Boucher M, Chassaing C, Chapuy E, Lorente P. Hysteresis in atrial refractoriness in the conscious dog: influence of stimulation parameters and control by the autonomic nervous system. J Cardiovasc Pharmacol 1996; 28:842-7. [PMID: 8961083 DOI: 10.1097/00005344-199612000-00015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This work (a) provides evidence for hysteresis in the atrial effective refractory period (AERP) in the conscious dog; (b) studies the main stimulation parameters that may affect this phenomenon; and (c) evaluates the influence of the autonomic nervous system. AERP was measured by the extrastimulus method in the conscious dog with chronic atrioventricular block (n = 6) during the increasing and decreasing phases of an S1S2 fixed protocol. AERP was longer during the increasing phase than during the decreasing phase, thus demonstrating hysteresis, calculated as the difference between the two values. Hysteresis was greater with an S1S1 basic cycle length of 300 ms than with a basic cycle length of 400 ms, 9 +/- 0.9, and 7 +/- 0.9 ms, respectively. It was also greater with trains of six basic cycles before each extrastimulus S2 than with trains of 12 basic cycles, 9 +/- 0.9 and 7 +/- 1.0 ms, respectively. Suppression of vagal tone with atropine reduced hysteresis from 8 +/- 0.6 to 4 +/- 0.6 ms, whereas suppression of cardioaccelerator tone with propranolol increased it from 9 +/- 0.9 to 14 +/- 1.2 ms. These data were confirmed by the neostigmine-induced increase in hysteresis from 8 +/- 0.8 to 11 +/- 0.8 ms and the isoproterenol-induced decrease in hysteresis from 9 +/- 0.6 to 4 +/- 0.4 ms. Overall, these results provide evidence for a hysteresis effect in the AERP in the conscious dog that is stimulation frequency-dependent and modulated by the autonomic nervous system with permanent increase by vagal tone and decrease by cardioaccelerator tone.
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Affiliation(s)
- M Boucher
- INSERM U. 195, Faculty of Medicine, Clermont-Ferrand, France
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Lorente P, Delgado C, Delmar M, Henzel D, Jalife J. Hysteresis in the excitability of isolated guinea pig ventricular myocytes. Circ Res 1991; 69:1301-15. [PMID: 1718624 DOI: 10.1161/01.res.69.5.1301] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Hysteresis phenomena were demonstrated in the excitability of single, enzymatically dissociated guinea pig ventricular myocytes. Membrane potentials were recorded with patch pipettes in the whole-cell current-clamp configuration. Repetitive stimulation with depolarizing current pulses of constant cycle length and duration but varying strength led to predictable excitation (1:1) and nonexcitation (1:0) patterns depending on current strength. However, transition between patterns depended on the direction of current strength change, and stable hysteresis loops were obtained in stimulus-response pattern versus current strength plots in 31 cells. Increase of pulse duration and decrease of stimulation rate contributed to a reduction in hysteresis loop areas. In addition, at the abrupt transitions from 1:0 to 1:1 patterns, a latency adaptation phenomenon was consistently observed. Bath application of tetrodotoxin (30 microM) produced no change of hysteresis, whereas hysteresis was substantially decreased in cobalt (2 mM) superfusion experiments. Analysis of the changes in amplitude and shape of the subthreshold responses during the transitions from one stable pattern to the other suggested that activity led to an increase in membrane resistance, particularly in the voltage domain between resting and threshold potentials. We therefore modeled the dynamic behavior of the single cells, using an analytical solution aimed at calculating the recovery of activation latency as a function of diastolic membrane resistance. Numerical iteration of the analytical model equations closely reproduced the experimental hysteresis loops in both qualitative and quantitative ways. The effect of stimulation frequency on the model was similar to the experimental findings. The overall study suggests that the excitability pattern of guinea pig ventricular myocytes is responsible for hysteresis and bistabilities when current intensity is allowed to fluctuate around threshold levels.
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Affiliation(s)
- P Lorente
- U 195 Institut National de la Santé et de la Recherche Médicale, Clermont-Ferrand, France
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Affiliation(s)
- P Lorente
- U 195 INSERM, Faculté de Médecine, Place Henri Dunant, Clermont-Ferrand, France
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Neumann E, Boldt E, Rauer B, Wolf H, Chang HW. Scanning curves and kinetics of the acetylcholine / acetylcholine receptor hysteresis. J Electroanal Chem (Lausanne) 1988. [DOI: 10.1016/0022-0728(80)80333-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Negendank W, Shaller C. A critical temperature transition of K+-Na+ exchange in human lymphocytes. J Cell Physiol 1980; 103:87-95. [PMID: 7430260 DOI: 10.1002/jcp.1041030113] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Human lymphocytes were equilibrated for 48 hours at 5-6 mM K+ ex over a range of temperatures between 0 and 37 degrees C, and at 5 degrees C over a range of external K+ levels between 0 and 32 mM. Cell K+ and Na+ contents are normal between 37 and 10 decrees. Below 10 degrees there is a critical thermal transition in ion content centering around 3 degrees C. This and the steep sigmoidal isotherms of K+ and Na+ at 5 degrees C confirm the cooperative nature of ion exchange. At 0 degrees, cell K+ is maintained at a concentration that is seven to eight times that of the external medium. Isotopic K+ influx shows smaller, rapidly-exchanging, and larger, slowly-exchanging fractions. The latter, which correspond to the saturable, sigmoidal components of cell K+, are slowed by decreasing temperature. Although there is a critical temperature transition of K+-Na+ exchange, there is no corresponding transition for isotopic K+ exchange, which has an activation energy of 11.6 kcal/mole. The combined ion content and flux data are readily understood by reference to two major concepts of the association-induction hypothesis: that of rapid solute exclusion from cell water existing in a state of polarized multilayers, and that of solute accumulation limited by adsorption onto and desorption from fixed anionic sites that interact with one another in a critical, cooperative fashion.
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Are there any analogies between electrosorption layers of organic compounds and signal-transmitting biomembranes? ACTA ACUST UNITED AC 1979. [DOI: 10.1016/s0022-0728(79)80147-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Barrett TW. Polyelectrolyte hysteresis interpreted as singularities in the Poisson--Boltzmann description. J Theor Biol 1979; 77:523-36. [PMID: 491696 DOI: 10.1016/0022-5193(79)90025-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Kinetic Hysteresis in Enzyme and Fermentation Systems. ACTA ACUST UNITED AC 1978. [DOI: 10.1016/b978-0-12-040302-8.50008-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Hahn HS, Nitzan A, Ortoleva P, Ross J. Threshold excitations, relaxation oscillations, and effect of noise in an enzyme reaction. Proc Natl Acad Sci U S A 1974; 71:4067-71. [PMID: 4530285 PMCID: PMC434329 DOI: 10.1073/pnas.71.10.4067] [Citation(s) in RCA: 45] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
We study a deprotonation reaction by an enzyme with activity dependent on pH. The rate and transport equations are simplified with a number of assumptions, are analyzed according to the presence of different time scales, and are solved numerically to show relaxation oscillation and threshold excitation, for different choices of parameters. The imposition of fluctuations (noise) on the deterministic equations for threshold excitation conditions leads to random occurrence of an excitation and return to steady state at low noise level and to large, random variations in concentrations at high noise level. At intermediate noise levels (of the order of the threshold excitation), however, we find quasi-periodic concentration oscillations. Thus, critical values of external constraints necessary for oscillations are altered by the presence of noise.
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Revzin A, Neumann E, Katchalsky A. Metastable secondary structures in ribosomal RNA molecular hysteresis in the acid-base titration of Escherichia coli ribosomal RNA. J Mol Biol 1973; 79:95-114. [PMID: 4200930 DOI: 10.1016/0022-2836(73)90272-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Weisbuch G, Neumann E. Molecular field theory of hysteresis in helix-coil transitions of polynucleotides. Biopolymers 1973; 12:1479-91. [PMID: 4741154 DOI: 10.1002/bip.1973.360120704] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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