publications by David Needham.

Papers Published

1. Simon, S.A. and McIntosh, T.J. and Magid, A.D. and Needham, D., Modulation of the interbilayer hydration pressure by the addition of dipoles at the hydrocarbon/water interface, Biophys. J. (USA), vol. 61 no. 3 (1992), pp. 786 - 99 .
   (last updated on 2007/04/06)

   Abstract:
   The effects of the cholesterol analog 5α-cholestan-3β-ol-6-one (6-ketocholestanol) on bilayer structure, bilayer cohesive properties, and interbilayer repulsive pressures have been studied by a combination of X-ray diffraction, pipette aspiration, and dipole potential experiments. It is found that 6-ketocholestanol, which has a similar structure to cholesterol except with a keto moiety at the 6 position of the B ring, has quite different effects than cholesterol on bilayer organization and cohesive properties. Unlike cholesterol, 6-ketocholestanol does not appreciably modify the thickness of liquid-crystalline egg phosphatidylcholine (EPC) bilayers, and causes a much smaller increase in bilayer compressibility modulus than does cholesterol. These data imply that 6-ketocholestanol has both its hydroxyl and keto moieties situated near the water-hydrocarbon interface, thus making its orientation in the bilayer different from cholesterol's

   Keywords:
   bioelectric potentials;biomechanics;lipid bilayers;molecular biophysics;X-ray diffraction examination of molecular structure;