Pulse NMR study of the interaction of calcium ion with dipalmitoylphosphatidylcholine lamellae

✍ Scribed by Toshiyuki Shibata

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 431 KB
• Volume: 53
• Category: Article
• ISSN: 0009-3084
• DOI: 10.1016/0009-3084(90)90132-b

✦ Synopsis

Molecular motion of dipalmitoylphosphatidylcholine (DPPC)/CaCI 2 lamellae in a gel phase was studied by pulse NMR. Proton 1/T a for DPPC in a gel phase showed that the rate of reorientation about the long axis of the lipid molecule decreased gradually from 0 to 500 mM CaCl 2. At 10--50 mM CaCl 2 the correlation time reached the value of the inverse Larmor frequency (approx. 2.6 ns). A proton NMR absorption spectrum and a spin-pair-dipolar-echo (SPDE) decay showed that the second moment in the hydrocarbon chain region decreased below about 1 mM CaCi 2 and increased from 1 to 500 mM CaCI 2. The second moment in the polar head group increased gradually with an increase in the CaCI 2 concentration. The increase in the second moment at the high CaCi 2 concentrations was attributed to an increase in the order parameters of the segments both in the polar head group and in the hydrocarbon chain region. At the lower CaCl~ concentrations, however, calcium ion possibly induced disorder in the lamellae which led to a decrease in the order parameter in the hydrocarbon chain region.