Interlamellar waters in dimyristoylphosphatidylethanolamine-water system as studied by calorimetry and X-ray diffraction.
The number of water molecules incorporated into the interlamellar region in a gel phase of dimyristoylphosphatidylethanolamine (DMPE)-water system containing up to about 40 g% water was estimated by techniques of calorimetry and X-ray diffraction. The calorimetric estimation based upon enthalpy changes of deconvoluted ice-melting peaks revealed that bulk water existing outside lipid bilayers begins to appear although the gel phase is not fully hydrated. The gel phase showed a linear depression of its transition temperature proportional to the amount of freezable waters interposed between bilayers. For a fully hydrated gel phase, the numbers of non-freezable and freezable interlamellar waters estimated by calorimetric analysis were about 2.3 and 3.7 molecules per lipid, respectively. The limiting, total number of interlamellar waters, 6 H2O/lipid, agreed with that estimated from both the X-ray diffraction data and the absolute specific volume for a DMPE molecule. Furthermore, the analysis for the lamellar intensity data is also consistent with the result of calorimetric analysis.
Kodama
M
M
Department of Biochemistry, Faculty of Science, Okayama University of Science, Japan.
Aoki
H
H
Takahashi
H
H
Hatta
I
I
D002152:Calorimetry, Differential Scanning; D005615:Freezing; D005782:Gels / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics; D014867:Water / Q000737:chemistry* / Q000378:metabolism; D014961:X-Ray Diffraction
D005782:Gels; D010714:Phosphatidylethanolamines; D014867:Water