H. Nagase et al., TEMPERATURE-CHANGE OF THE LAMELLAR STRUCTURE OF DPPC DISACCHARIDE/WATER SYSTEMS WITH LOW WATER-CONTENT/, Biochimica et biophysica acta. Biomembranes, 1371(2), 1998, pp. 223-231
Temperature change in L-alpha-dipalmitoyl phosphatidylcholine (DPPC)/d
isaccharide systems with low water content (less than 8 wt.%) was inve
stigated using X-ray diffraction within a range of two transition temp
eratures. X-ray diffraction above the higher transition temperature sh
owed a broad symmetric peak, indicating the L alpha phase. Below the h
igher transition temperature, two overlapping diffraction peaks we:re
observed. After peak separation, temperature change in these systems w
as analyzed using peak parameters of the two peaks. Peak parameters of
the lower angle peak changed continuously up to and above the higher
transition temperature, suggesting the systems to be in a liquid cryst
al phase below the higher transition temperature. Fourier-transform in
frared (FT-IR) spectra of the DPPC/trehalose system with 5.5 wt.% wate
r showed the wave number of asymmetric stretching of phosphate groups
to change at the lower transition temperature and that of symmetric st
retching of CH2 groups, to change between the lower and higher transit
ion temperatures. Thus, below the lower transition temperature, the sy
stem is shown to be in a gel phase. Conformational change in phosphate
groups occurred at the lower transition temperature. Within the lower
and higher transition temperatures, two phases were found to coexist
and transition from the gel phase to L alpha phase to occur continuous
ly. Above the higher transition temperature, the system is in the L al
pha phase. (C) 1998 Elsevier Science B.V. All rights reserved.