Effects of poly(L-lysine) on the structural and thermotropic properties of dipalmitoylphosphatidylglycerol bilayers.
The effects of poly(L-lysine) on the structural and thermotropic properties of dipalmitoylphosphatidylglycerol (DPPG) bilayers were studied with differential scanning calorimetry (DSC), X-ray diffraction and freeze-fracture electron microscopy. For thermal behavior, in the DPPG/poly(L-lysine) system the main transition temperature rises to 45.7 degrees C and the pretransition disappears in opposition to pure DPPG vesicles. An additional transition appears approximately at 36 degrees C for the DPPG/poly(L-lysine) system after incubation at 4 degrees C for two months. The incubated sample gives a X-ray diffraction pattern having several additional reflections in the range of 0.2-0.9 nm at 15 degrees C. These results suggest that even in the presence of poly(L-lysine) the DPPG bilayers form the subgel (Lc) phase after the long incubation at a low temperature. The X-ray diffraction measurements indicate that the structure of the Lc phase for DPPG/poly(L-lysine) system is different from that of pure DPPG bilayers. On the other hand, in the gel (L beta') phase, the wide-angle X-ray diffraction pattern suggests that the presence of poly(L-lysine) hardly affects the packing of hydrocarbon chains in the DPPG bilayers. The small-angle X-ray diffraction and freeze-fracture electron microscopy exhibit that the DPPG/poly(L-lysine) system forms a tightly packed multilamellar structure in which the poly(L-lysine) is intercalated between the subsequent DPPG bilayers.
Takahashi
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H
Department of Applied Physics, School of Engineering, Nagoya University, Japan.
Matuoka
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Kato
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Ohki
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K
Hatta
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I
D002152:Calorimetry, Differential Scanning; D005614:Freeze Fracturing; D008051:Lipid Bilayers / Q000737:chemistry*; D008854:Microscopy, Electron; D008968:Molecular Conformation; D010715:Phosphatidylglycerols / Q000737:chemistry*; D011107:Polylysine / Q000737:chemistry*; D014961:X-Ray Diffraction
D008051:Lipid Bilayers; D010715:Phosphatidylglycerols; D011107:Polylysine; C030345:1,2-dipalmitoylphosphatidylglycerol