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Hanisch DT, Schneider MF. Specific Regulation of Enzymatic Activity by Interface Pulses. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024. [PMID: 38330005 DOI: 10.1021/acs.langmuir.3c02658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2024]
Abstract
The thermodynamic state of the interface in which an enzyme is embedded can regulate the enzymatic activity. Indeed, it has been demonstrated by others and us that close to the maximum in compressibility, the activity of the enzyme is at a maximum as well. Pulses propagating along the interface can modulate the interface state and were demonstrated to be able to modulate the activity of interface-associated acetylcholinesterase (AChE). Here, we demonstrate that enzyme activity modulation by interface pulses depends specifically on the pulse type. Using membrane-embedded enzyme phospholipase A2 (PLA2), enzyme activity can be monitored by detecting the lateral pressure without an additional assay required. We show that pulses that shift the state toward higher pressure and higher lateral density increase the enzymatic activity, while pulses that reduce the pressure induce the opposite effect. These results further support a physical mechanism for enzyme-enzyme communication where compressibility, lateral density, and pressure (thermodynamic state) and not specific molecular modifications regulate enzymatic activity.
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Affiliation(s)
- Daniel T Hanisch
- Medical and Biological Physics, Department of Physics, TU Dortmund University, Otto-Hahn-Str. 4, 44227 Dortmund, Germany
| | - Matthias F Schneider
- Medical and Biological Physics, Department of Physics, TU Dortmund University, Otto-Hahn-Str. 4, 44227 Dortmund, Germany
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2
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Peets T, Tamm K, Engelbrecht J. On mathematical modeling of the propagation of a wave ensemble within an individual axon. Front Cell Neurosci 2023; 17:1222785. [PMID: 37576569 PMCID: PMC10416108 DOI: 10.3389/fncel.2023.1222785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 07/12/2023] [Indexed: 08/15/2023] Open
Abstract
The long history of studying the propagation of an action potential has revealed that an electrical signal is accompanied by mechanical and thermal effects. All these effects together generate an ensemble of waves. The consistent models of such a complex phenomenon can be derived by using properly the fundamental physical principles. In this paper, attention is paid to the analysis of concepts of continuum physics that constitute a basis for deriving the mathematical models which describe the emergence and propagation of a wave ensemble in an axon. Such studies are interdisciplinary and based on biology, physics, mathematics, and chemistry. The governing equations for the action potential together with mechanical and thermal effects are derived starting from basics: Maxwell equations, conservation of momentum, Fourier's law, etc., but modified following experimental studies in electrophysiology. Several ideas from continuum physics like external forces and internal variables can also be used in deriving the corresponding models. Some mathematical concepts used in modeling are also briefly described. A brief overview of several mathematical models is presented that allows us to analyze the present ideas of modeling. Most mathematical models deal with the propagation of signals in a healthy axon. Further analysis is needed for better modeling the pathological situations and the explanation of the influence of the structural details like the myelin sheath or the cytoskeleton in the axoplasm. The future possible trends in improving the models are envisaged.
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Affiliation(s)
- Tanel Peets
- Department of Cybernetics, School of Science, Tallinn University of Technology, Tallinn, Estonia
| | - Kert Tamm
- Department of Cybernetics, School of Science, Tallinn University of Technology, Tallinn, Estonia
| | - Jüri Engelbrecht
- Department of Cybernetics, School of Science, Tallinn University of Technology, Tallinn, Estonia
- Estonian Academy of Sciences, Tallinn, Estonia
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3
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Heimburg T. The excitable fluid mosaic. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184104. [PMID: 36642342 DOI: 10.1016/j.bbamem.2022.184104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 11/23/2022] [Accepted: 12/13/2022] [Indexed: 01/15/2023]
Abstract
The Fluid Mosaic Model by Singer & Nicolson proposes that biological membranes consist of a fluid lipid layer into which integral proteins are embedded. The lipid membrane acts as a two-dimensional liquid in which the proteins can diffuse and interact. Until today, this view seems very reasonable and is the predominant picture in the literature. However, there exist broad melting transitions in biomembranes some 10-20 degrees below physiological temperatures that reach up to body temperature. Since they are found below body temperature, Singer & Nicolson did not pay any further attention to the melting process. But this is a valid view only as long as nothing happens. The transition temperature can be influenced by membrane tension, pH, ionic strength and other variables. Therefore, it is not generally correct that the physiological temperature is above this transition. The control over the membrane state by changing the intensive variables renders the membrane as a whole excitable. One expects phase behavior and domain formation that leads to protein sorting and changes in membrane function. Thus, the lipids become an active ingredient of the biological membrane. The melting transition affects the elastic constants of the membrane. This allows for the generation of propagating pulses in nerves and the formation of ion-channel-like pores in the lipid membranes. Here we show that on top of the fluid mosaic concept there exists a wealth of excitable phenomena that go beyond the original picture of Singer & Nicolson.1.
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Affiliation(s)
- Thomas Heimburg
- Membrane Biophysics Group, Niels Bohr Institute, University of Copenhagen, Denmark.
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Paeger A, Fillafer C, Schneider MF. Evidence for a transition in the cortical membranes of Paramecium. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184073. [PMID: 36243036 DOI: 10.1016/j.bbamem.2022.184073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 09/02/2022] [Accepted: 10/07/2022] [Indexed: 11/06/2022]
Abstract
Ever since the pioneering studies in the 1960s and 70s, the importance of order transitions for cell membrane functions has remained a matter of debate. Recently, it has been proposed that the nonlinear stimulus-response curve of excitable cells, which manifests in all-or-none pulses (action potentials (AP)), is due to a transition in the cell membrane. Indeed, evidence for transitions has accumulated in plant cells and neurons, but studies with other excitable cells are expedient in order to show if this finding is of a general nature. Herein, we investigated intact, motile specimens of the "swimming neuron" Paramecium. The cellular membranes were labelled with the solvatochromic fluorophores LAURDAN or Di-4-ANEPPDHQ. Subsequently, a cell was trapped in a microfluidic channel and investigated by fluorescence spectroscopy. The generalized polarization (GP) of the fluorescence emission from cell cortical membranes (probably plasma and alveolar membranes) was extracted by an edge-finding algorithm. The thermo-optical state diagram, i.e. the dependence of GP on temperature, exhibited clear indications for a reversible transition. This transition had a width of ~10-15 °C and a midpoint that was located ~4 °C below the growth temperature. The state diagrams with LAURDAN and Di-4-ANEPPDHQ had widely identical characteristics. These results suggested that the cortical membranes of Paramecium reside in an order transition regime under physiological growth conditions. Based on these findings, membrane potential fluctuations, spontaneous depolarizing spikes, and thermal excitation of Paramecium was interpreted.
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Affiliation(s)
- Anne Paeger
- Medical and Biological Physics, Department of Physics, Technical University Dortmund, Otto-Hahn-Str. 4, 44227 Dortmund, Germany.
| | - Christian Fillafer
- Medical and Biological Physics, Department of Physics, Technical University Dortmund, Otto-Hahn-Str. 4, 44227 Dortmund, Germany.
| | - Matthias F Schneider
- Medical and Biological Physics, Department of Physics, Technical University Dortmund, Otto-Hahn-Str. 4, 44227 Dortmund, Germany.
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Lun T, Wang D, Li L, Zhou J, Zhao Y, Chen Y, Yin X, Ou S, Yu J, Song R. Low-dissipation optimization of the prefrontal cortex in the -12° head-down tilt position: A functional near-infrared spectroscopy study. Front Psychol 2022; 13:1051256. [PMID: 36619014 PMCID: PMC9815614 DOI: 10.3389/fpsyg.2022.1051256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 11/23/2022] [Indexed: 12/24/2022] Open
Abstract
Introduction Our present study set out to investigate the instant state of the prefrontal cortex (PFC) in healthy subjects before and after placement in the -12°head-down tilt (HDT) position in order to explore the mechanism behind the low-dissipation optimization state of the PFC. Methods 40 young, right-handed healthy subjects (male: female = 20: 20) were enrolled in this study. Three resting state positions, 0°initial position, -12°HDT position, and 0°rest position were sequentially tested, each for 10 minutes. A continuous-wave functional near-infrared spectroscopy (fNIRS) instrument was used to assess the resting state hemodynamic data of the PFC. After preprocessing the hemodynamics data, we evaluated changes in resting-state functional connectivity (rsFC) level and beta values of PFC. The subjective visual analogue scale (VAS) was applied before and after the experiment. The presence of sleep changes or adverse reactions were also recorded. Results Pairwise comparisons of the concentrations of oxyhemoglobin (HbO), deoxyhemoglobin (HbR), and hemoglobin (HbT) revealed significant differences in the aforementioned positions. Specifically, the average rsFC of PFC showed a gradual increase throughout the whole process. In addition, based on graph theory, the topological properties of brain network, such as small-world network and nodal degree centrality were analyzed. The results show that global efficiency and small-world sigma (σ) value were differences between 0°initial and 0°rest. Discussion In this study, placement in the -12°HDT had a significant effect on PFC function, mainly manifested as self-inhibition, decreased concentration of HbO in the PFC, and improved rsFC, which may provide ideas to the understanding and explanation of neurological diseases.
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Affiliation(s)
- Tingting Lun
- Clinical Medical College of Acupuncture, Moxibustion and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Dexin Wang
- Clinical Medical College of Acupuncture, Moxibustion and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Li Li
- College of TCM health care, Guangdong Food and Drug Vocational College, Guangzhou, China
| | - Junliang Zhou
- Department of Traditional Chinese Medicine, Nanhai District Maternal and Child Health Hospital, Foshan, China
| | - Yunxuan Zhao
- Clinical Medical College of Acupuncture, Moxibustion and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Yuecai Chen
- Clinical Medical College of Acupuncture, Moxibustion and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Xuntao Yin
- Department of Radiology, Guangzhou women and children's Medical Center, Guangzhou Medical University, Guangzhou, China
| | - Shanxing Ou
- Department of Radiology, Southern Theater Command Hospital of PLA, Guangzhou, China
| | - Jin Yu
- Clinical Medical College of Acupuncture, Moxibustion and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China,*Correspondence: Jin Yu, Rong Song
| | - Rong Song
- Guangdong Provincial Key Laboratory of Sensor Technology and Biomedical Instrument, School of Biomedical Engineering, Sun Yat-sen University, Guangzhou, China,*Correspondence: Jin Yu, Rong Song
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Heimburg T. The effect of stretching on nerve excitability. Hum Mov Sci 2022; 86:103000. [DOI: 10.1016/j.humov.2022.103000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 08/11/2022] [Accepted: 08/31/2022] [Indexed: 11/04/2022]
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Tamagawa H, Delalande B. The membrane potential arising from the adsorption of ions at the biological interface. Biol Futur 2022; 73:455-471. [PMID: 36463564 DOI: 10.1007/s42977-022-00139-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 11/19/2022] [Indexed: 12/05/2022]
Abstract
Membrane theory makes it possible to compute the membrane potential of living cells accurately. The principle is that the plasma membrane is selectively permeable to ions and that its permeability to mobile ions determines the characteristics of the membrane potential. However, an artificial experimental cell system with an impermeable membrane can exhibit a nonzero membrane potential, and its characteristics are consistent with the prediction of the Goldman-Hodgkin-Katz eq., which is a noteworthy concept of membrane theory, despite the membrane's impermeability to mobile ions. We noticed this troublesome facet of the membrane theory. We measured the potentials through permeable and impermeable membranes where we used the broad varieties of membranes. Then we concluded that the membrane potential must be primarily, although not wholly, governed by the ion adsorption-desorption process rather than by the passage of ions across the cell membrane. A theory based on the Association-Induction Hypothesis seems to be a more plausible mechanism for the generation of the membrane potential and to explain this unexpected physiological fact. The Association-Induction Hypothesis states that selective ion permeability of the membrane is not a condition for the generation of the membrane potential in living cells, which contradicts the prediction of the membrane theory. Therefore, the Association-Induction Hypothesis is the actual cause of membrane potential. We continued the theoretical analysis by taking into account the Association-Induction Hypothesis and saw that its universality as a cause of potential generation mechanism. We then concluded that the interfacial charge distribution is one of the fundamental causes of the membrane potential.
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Affiliation(s)
- Hirohisa Tamagawa
- Department of Mechanical Engineering, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
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Fabiunke S, Fillafer C, Schneider MF. Unitary Response of Solvatochromic Dye to Pulse Excitation in Lipid and Cell Membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:12408-12413. [PMID: 36154016 DOI: 10.1021/acs.langmuir.2c02261] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The existence of acoustic pulse propagation in lipid monolayers at the air-water interface is well known. These pulses are controlled by the thermodynamic state of the lipid membrane. Nevertheless, the role of acoustic pulses for intra- and inter-cellular communication is still a matter of debate. Herein, we used the dye di-4-ANEPPDHQ, which is known to be sensitive to the physical state and transmembrane potential of membranes, in order to gain insights into compression waves in lipid-based membrane interfaces. The dye was incorporated into lipid monolayers made of phosphatidylserine or phosphatidylcholine at the air-water-interface. A significant blue shift of the emission spectrum was detected when the state of the monolayer was changed from the liquid-expanded (LE) to the liquid-condensed (LC) phase. This "transition sensitivity" of di-4-ANEPPDHQ was generalized in experiments with the bulk solvent dimethyl sulfoxide (DMSO). Upon crystallization of solvent, the emission spectrum also underwent a blue shift. During compression pulses in lipid monolayers, a significant fluorescence response was only observed when the main transition is crossed. The optical signature of these waves─in terms of sign and magnitude─was identical to the response of di-4-ANEPPDHQ during action potentials in neurons and excitable plant cells. These findings corroborated the suggestion that action potentials are nonlinear state changes that propagate in the cell membrane.
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Affiliation(s)
- Simon Fabiunke
- Department of Medical and Biological Physics, Technical University Dortmund, 44227 Dortmund, Germany
| | - Christian Fillafer
- Department of Medical and Biological Physics, Technical University Dortmund, 44227 Dortmund, Germany
| | - Matthias F Schneider
- Department of Medical and Biological Physics, Technical University Dortmund, 44227 Dortmund, Germany
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9
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Heimburg T. The thermodynamic soliton theory of the nervous impulse and possible medical implications. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2022; 173:24-35. [PMID: 35640761 DOI: 10.1016/j.pbiomolbio.2022.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 05/05/2022] [Accepted: 05/22/2022] [Indexed: 06/15/2023]
Abstract
The textbook picture of nerve activity is that of a propagating voltage pulse driven by electrical currents through ion channel proteins, which are gated by changes in voltage, temperature, pressure or by drugs. All function is directly attributed to single molecules. We show that this leaves out many important thermodynamic couplings between different variables. A more recent alternative picture for the nerve pulse is of thermodynamic nature. It considers the nerve pulse as a soliton, i.e., a macroscopic excited region with properties that are influenced by thermodynamic variables including voltage, temperature, pressure and chemical potentials of membrane components. All thermodynamic variables are strictly coupled. We discuss the consequences for medical treatment in a view where one can compensate a maladjustment of one variable by adjusting another variable. For instance, one can explain why anesthesia can be counteracted by hydrostatic pressure and decrease in pH, suggest reasons why lithium over-dose may lead to tremor, and how tremor is related to alcohol intoxication. Lithium action as well as the effect of ethanol and the anesthetic ketamine in bipolar patients may fall in similar thermodynamic patterns. Such couplings remain obscure in a purely molecular picture. Other fields of application are the response of nerve activity to muscle stretching and the possibility of neural stimulation by ultrasound.
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Affiliation(s)
- T Heimburg
- Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100, Copenhagen Ø, Denmark.
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10
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Abstract
Phase transitions in materials are accompanied by drastic changes in their properties. Systems abruptly become softer, more conductive, have better heat storage, or support chemical reactions more efficiently. Since changes take place over small variations in external conditions (tension, temperature, pH, calcium), they appear like an on/off switch. Here, we provide experimental evidence that membrane patches of single living cells can go through a reversible phase transition. It is extremely “sharp” (highly nonlinear), and from a thermodynamic point of view we conclude it cannot only be triggered by temperature but also by pH changes (as produced by enzymes). The results strongly support the idea that phase transitions may be a tool for living systems to control their functions even specifically. The origin of nonlinear responses in cells has been suggested to be crucial for various cell functions including the propagation of the nervous impulse. In physics, nonlinear behavior often originates from phase transitions. Evidence for such transitions on the single-cell level, however, has so far not been provided, leaving the field unattended by the biological community. Here, we demonstrate that single cells of a human neuronal cell line display all optical features of a sharp, highly nonlinear phase transition within their membrane. The transition is reversible and does not originate from protein denaturation. Triggered by temperature and modified by pH here, a thermodynamic approach strongly suggests that similar nonlinear state changes can be induced by other variables such as calcium or mechanical stress. At least in lipid membranes, such state changes are accompanied by significant changes in permeability, enzyme activity, elastic, and electrical properties.
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The activity of the intrinsically water-soluble enzyme ADAMTS13 correlates with the membrane state when bound to a phospholipid bilayer. Sci Rep 2021; 11:24476. [PMID: 34963692 PMCID: PMC8714821 DOI: 10.1038/s41598-021-04083-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 12/08/2021] [Indexed: 11/15/2022] Open
Abstract
Membrane-associated enzymes have been found to behave differently qualitatively and quantitatively in terms of activity. These findings were highly debated in the 1970s and many general correlations and reaction specific models have been proposed, reviewed, and discarded. However, new biological applications brought up the need for clarification and elucidation. To address literature shortcomings, we chose the intrinsically water-soluble enzyme a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) and large unilamellar vesicles with a relative broad phase transition. We here present activity measurements of ADAMTS13 in the freely dissolved state and the membrane associated state for phosphocholine lipids with different acyl-chain lengths (13:0, 14:0 and 15:0) and thus main phase transition temperatures. While the freely dissolved enzyme shows a simple Arrhenius behavior, the activity of membrane associated ADAMTS13 in addition shows a peak. This peak temperature correlates with the main phase transition temperature of the used lipids. These findings support an alternative theory of catalysis. This theory predicts a correlation of the membrane associated activity and the heat capacity, as both are susceptibilities of the same surface Gibb's free energy, since the enzyme is attached to the membrane.
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Fillafer C, Koll YS, Schneider MF. Lipid Membrane State Change by Catalytic Protonation and the Implications for Synaptic Transmission. MEMBRANES 2021; 12:5. [PMID: 35054529 PMCID: PMC8781637 DOI: 10.3390/membranes12010005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 12/09/2021] [Accepted: 12/14/2021] [Indexed: 06/14/2023]
Abstract
In cholinergic synapses, the neurotransmitter acetylcholine (ACh) is rapidly hydrolyzed by esterases to choline and acetic acid (AH). It is believed that this reaction serves the purpose of deactivating ACh once it has exerted its effect on a receptor protein (AChR). The protons liberated in this reaction, however, may by themselves excite the postsynaptic membrane. Herein, we investigated the response of cell membrane models made from phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatidic acid (PA) to ACh in the presence and absence of acetylcholinesterase (AChE). Without a catalyst, there were no significant effects of ACh on the membrane state (lateral pressure change ≤0.5 mN/m). In contrast, strong responses were observed in membranes made from PS and PA when ACh was applied in presence of AChE (>5 mN/m). Control experiments demonstrated that this effect was due to the protonation of lipid headgroups, which is maximal at the pK (for PS: pKCOOH≈5.0; for PA: pKHPO4-≈8.5). These findings are physiologically relevant, because both of these lipids are present in postsynaptic membranes. Furthermore, we discussed evidence which suggests that AChR assembles a lipid-protein interface that is proton-sensitive in the vicinity of pH 7.5. Such a membrane could be excited by hydrolysis of micromolar amounts of ACh. Based on these results, we proposed that cholinergic transmission is due to postsynaptic membrane protonation. Our model will be falsified if cholinergic membranes do not respond to acidification.
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Drukarch B, Wilhelmus MMM, Shrivastava S. The thermodynamic theory of action potential propagation: a sound basis for unification of the physics of nerve impulses. Rev Neurosci 2021; 33:285-302. [PMID: 34913622 DOI: 10.1515/revneuro-2021-0094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 11/12/2021] [Indexed: 11/15/2022]
Abstract
The thermodynamic theory of action potential propagation challenges the conventional understanding of the nerve signal as an exclusively electrical phenomenon. Often misunderstood as to its basic tenets and predictions, the thermodynamic theory is virtually ignored in mainstream neuroscience. Addressing a broad audience of neuroscientists, we here attempt to stimulate interest in the theory. We do this by providing a concise overview of its background, discussion of its intimate connection to Albert Einstein's treatment of the thermodynamics of interfaces and outlining its potential contribution to the building of a physical brain theory firmly grounded in first principles and the biophysical reality of individual nerve cells. As such, the paper does not attempt to advocate the superiority of the thermodynamic theory over any other approach to model the nerve impulse, but is meant as an open invitation to the neuroscience community to experimentally test the assumptions and predictions of the theory on their validity.
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Affiliation(s)
- Benjamin Drukarch
- Department of Anatomy and Neurosciences, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
| | - Micha M M Wilhelmus
- Department of Anatomy and Neurosciences, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
| | - Shamit Shrivastava
- Institute for Biomedical Engineering, University of Oxford, Oxford OX3 7DQ, UK
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Bagatolli LA, Stock RP. Lipids, membranes, colloids and cells: A long view. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183684. [PMID: 34166642 DOI: 10.1016/j.bbamem.2021.183684] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 06/01/2021] [Accepted: 06/16/2021] [Indexed: 12/13/2022]
Abstract
This paper revisits long-standing ideas about biological membranes in the context of an equally long-standing, but hitherto largely unappreciated, perspective of the cell based on concepts derived from the physics and chemistry of colloids. Specifically, we discuss important biophysical aspects of lipid supramolecular structure to understand how the intracellular milieu may constrain lipid self-assembly. To this end we will develop four lines of thought: first, we will look at the historical development of the current view of cellular structure and physiology, considering also the plurality of approaches that influenced its formative period. Second, we will review recent basic research on the structural and dynamical properties of lipid aggregates as well as the role of phase transitions in biophysical chemistry and cell biology. Third, we will present a general overview of contemporary studies into cellular compartmentalization in the context of a very rich and mostly forgotten general theory of cell physiology called the Association-Induction Hypothesis, which was developed around the time that the current view of cells congealed into its present form. Fourth, we will examine some recent developments in cellular studies, mostly from our laboratory, that raise interesting issues about the dynamical aspects of cell structure and compartmentalization. We will conclude by suggesting what we consider are relevant questions about the nature of cellular processes as emergent phenomena.
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Affiliation(s)
- Luis A Bagatolli
- Instituto de Investigación Médica Mercedes y Martín Ferreyra - INIMEC (CONICET)-Universidad Nacional de Córdoba, Friuli 2434, 5016 Córdoba, Argentina; Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina; MEMPHYS - International and Interdisciplinary research network, Denmark.
| | - Roberto P Stock
- MEMPHYS - International and Interdisciplinary research network, Denmark
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Shrivastava S. Shock and detonation waves at an interface and the collision of action potentials. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 162:111-121. [PMID: 33516823 DOI: 10.1016/j.pbiomolbio.2020.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 11/24/2020] [Accepted: 12/13/2020] [Indexed: 10/22/2022]
Abstract
Action potentials in neurons are known to annihilate each other upon collision, while there are cases where they might penetrate each other. The fate of two waves upon collision is critically dependent on the underlying mechanism of propagation and therefore an understanding of possible outcomes of collision under different conditions is important. Previously, compression waves that travel within the plasma membrane of a neuron have been proposed as a thermodynamic basis for the propagation of action potentials. In this context, it was recently shown that two-dimensional compressive shock waves in the model system of lipid monolayers behave strikingly similar to action potentials in neurons and can even annihilate each other upon head-on collision. However, even a qualitative mechanism remained unclear. To this end, we summarise the fundamentals of shock physics as applied to an interface and recap how it explained the observation of threshold and saturation of shockwaves in the lipid monolayer (all - or - none). We then compare the theory with the soliton model that has the same fundamental premise, i.e. the conservation laws and thermodynamics, and was previously proposed as a model for the nerve pulse propagation. We elaborate on how the two approaches make different predictions with regards to collisions and the detailed structure of the wave-front. As a case study and a new qualitative result, we finally show that previously unexplained annihilation of shock waves in the lipid monolayer is a direct consequence of the nature of state changes, i.e. jump conditions, within these shockwaves.
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