The thermal behaviour of phosphatidylcholine-glycophorin monolayers in relation to monolayer and bilayer internal pressure.
A thermodynamic relationship which allows calculation of the internal pressure (Pi) of a monolayer has been derived, viz: Pi = T(delta pi/delta T)A-pi. Surface pressure (pi)-area (A) isotherms were determined for dioleoylphosphatidylcholine (DOPC), dipalmitoylphosphatidylcholine (DPPC) and a mixture of the latter with 0.28 mol% glycophorin, an intrinsic membrane protein. The isotherms (10 degrees C-42 degrees C) were used to obtain values of (delta pi/delta T)A. Under conditions in which a monolayer is believed to most closely model a bilayer membrane (i.e. 37 degrees C and A = 0.6 nm2/molecule) internal pressures were: DOPC = 0.32 N m-1; DPPC = 0.13 N m-1 and glycophorin/DPPC = 0.36 N m-1. The results do not support some measurements on amphiphile solubility in natural membranes which had been interpreted as evidence of a large increase in internal pressure, due to the intrinsic membrane proteins.
Davies
R J
RJ
Fisons Applied Sensor Technology, Trumpington, Cambridge, UK.
Jones
M N
MN
D004910:Erythrocyte Membrane / Q000502:physiology; D006021:Glycophorins; D006801:Humans; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D013816:Thermodynamics
D006021:Glycophorins; D008051:Lipid Bilayers; D010713:Phosphatidylcholines