EFFECT OF WATER ON LAMELLAR STRUCTURE OF DPPC SUGAR SYSTEMS/

The ability of two monosaccharides, four disaccharides and one trisacc haride, to lower the transition temperature of L-a-dipalmitoyl phospha tidylcholine (DPPC) was investigated using differential scanning calor imetry (DSC) and the ability of these sugars to change the lateral pac king of the acyl chains of DPPC was investigated using wide-angle X-ra y diffraction. The sugars affected the gel-liquid crystal transition t emperature (T-c) of DPPC when the water content of the DPPC/sugar syst ems was less than 20 wt.%. Specifically, T-c of the DPPC without sugar increased to approximately 106 degrees C, the T-c of the DPPC/monosac charide system remained almost constant at 43 degrees C and of the DPP C/disaccharide or trisaccharide systems decreased to approximately 24 degrees C. In the dehydrated state, di-and trisaccharides caused loose r packing of the DPPC hydrocarbon chains than the monosaccharides did, and the sugars affected the packing mode in different ways. The addit ion of water caused this difference in the sugars' effects on the pack ing mode to disappear and further addition of water caused the effect of sugar to almost disappear. Thus, the addition of water to a DPPC/su gar system weakens the interaction between the sugar and lipid and str engthens the DPPC chain packing. (C) 1997 Elsevier Science B.V.