TY - JOUR

T1 - The excitable fluid mosaic

AU - Heimburg, Thomas

PY - 2023/3/1

Y1 - 2023/3/1

N2 - 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

AB - 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

KW - Thermodynamics

KW - Domains

KW - Rafts

KW - Elastic constants

KW - Ion channels

KW - Nerves

KW - MONTE-CARLO-SIMULATION

KW - LIPID-MEMBRANES

KW - PHASE-TRANSITION

KW - ERYTHROCYTE-MEMBRANE

KW - MELTING TRANSITION

KW - MODEL MEMBRANES

KW - HEAT-PRODUCTION

KW - ION CHANNELS

KW - NERVE

KW - THERMODYNAMICS

U2 - 10.1016/j.bbamem.2022.184104

DO - 10.1016/j.bbamem.2022.184104

M3 - Journal article

C2 - 36642342

VL - 1865

JO - B B A - Biomembranes

JF - B B A - Biomembranes

SN - 0005-2736

IS - 3

M1 - 184104

ER -