Publications [#64946] of Sidney A Simon

Papers Published

1. Simon, S.A. and Advani, S. and McIntosh, T.J., Temperature dependence of the repulsive pressure between phosphatidylcholine bilayers, Biophys. J. (USA), vol. 69 no. 4 (1995), pp. 1473 - 83
   (last updated on 2007/04/15)

   Abstract:
   Bilayer structure and interbilayer repulsive pressure were measured from 5 to 50°C by the osmotic stress/X-ray diffraction method for both gel and liquid crystalline phase lipid bilayers. For gel phase dibehenoylphosphatidylcholine (DBPC) the bilayer thickness and pressure-distance relations were nearly temperature-independent, and at full hydration the equilibrium fluid spacing increased ~1 Å, from 10 Å at 5°C to 11 Å at 50°C. In contrast, for liquid crystalline phase egg phosphatidylcholine (EPC), the bilayer thickness, equilibrium fluid spacing, and pressure-distance relation were all markedly temperature-dependent. As the temperature was increased from 5 to 50°C the EPC bilayer thickness decreased ~4 Å, and the equilibrium fluid spacing increased from 14 to 21 Å. Over this temperature range there was little change in the pressure-distance relation for fluid spacings less than ~10 Å, but a substantial increase in the total pressure for fluid spacings greater than 10 Å. These data show that for both gel and liquid crystalline bilayers there is a short-range repulsive pressure that is nearly temperature-independent, whereas for liquid crystalline bilayers there is also a longer-range pressure that increases with temperature. From analysis of the energetics of dehydration we argue that the temperature-independent short-range pressure is consistent with a hydration pressure due to polarization or electrostriction of water molecules by the phosphorylcholine moiety. For the liquid crystalline phase, the 7 Å increase in equilibrium fluid spacing with increasing temperature can be predicted by an increase in the undulation pressure as a consequence of a temperature-dependent decrease in bilayer bending modulus

   Keywords:
   bioelectric phenomena;biomechanics;biothermics;dielectric polarisation;electrostriction;lipid bilayers;liquid crystals;solvation;X-ray diffraction;