Bb. Bonev et Mr. Morrow, HYDROSTATIC PRESSURE-INDUCED CONFORMATIONAL-CHANGES IN PHOSPHATIDYLCHOLINE HEADGROUPS - A H-2 MMR STUDY, Biophysical journal, 69(2), 1995, pp. 518-523
The effects of pressure and temperature on 1,2-dipalmitoyl-sn-glycero-
3-phosphocholine and 1,2-dimyristoyl-sn-glycero-3-phosphocholine headg
roup conformations were examined using deuterium nuclear magnetic reso
nance. Isothermal compression was found to produce a decrease in the c
holine alpha deuteron quadrupole splitting and increases in the cholin
e beta and gamma deuteron quadrupole splittings. A similar counterdire
ctional change, seen in the presence of positive surface charge, has b
een attributed to tilting of the headgroup away from the bilayer surfa
ce in response to the torque exerted on the phosphocholine dipole by p
ositive surface charges. The direction of the change in headgroup deut
eron quadrupole splitting is consistent with the pressure-induced redu
ction in area per lipid in the liquid crystalline phase, which can be
inferred from the ordering of phospholipid acyl chains under comparabl
e conditions. The temperature dependences of the headgroup deuteron qu
adrupole splittings were also examined. It was found that at elevated
pressure, the alpha splitting was insensitive to temperature, whereas
the beta and gamma splittings decreased. The response of the beta deut
eron splitting to temperature was found to be weaker at elevated press
ure than at ambient pressure.