Effects of Calcium on Membrane Molecular Dynamics Studied by Fast Field-Cycling NMR Relaxometry

• Main Authors: YU, JIA-RU, 余佳儒
• Other Authors: HWANG, DENNIS W.
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/88267465574102336531

碩士 === 國立中正大學 === 化學暨生物化學研究所 === 101 === Biomembranes, mostly composed of phospholipid molecules and proteins, forms a barrier between the intra- and extra-cellular environments and be able to control the material enters and exits the cell. Phospholipids can form bilayer structure (Lamellar phase, Lα phase) and nonbilayer structures (Inverted hexagonal phase, HII phase) in many bio-systems, particularly in regard to membrane fusion and exocytosis. HII phase are involved to destabilize membrane structures and membrane destabilization both in vivo and in vitro usually can be induced by external agents, such as metal ions (Ca2+ and K+ ) and biomolecules (protein and peptide). In this study, the effects of calcium on the lamellar-to-inverted hexagonal (Lα/HII) phase transition and the dynamics for phospholipids on liposome were investigated. The samples of POPC/cholesterol and POPC liposome were prepared with various concentration of Ca2+. The states of Lα/HII phase transition were verified by variable temperature 31P NMR spectroscopy. Zeta potential was also measured to investigate surface potential of liposome. The detailed molecular dynamics on membrane were explored by fast field-cycling nuclear magnetic resonance relaxometry (FFC NMR). The results of R1 relaxation measured by FFC NMR we got some molecular dynamic parameters by molecular dynamic fitting. For POPC liposomes, Ca2+ can reduce bending elastic modulus (κ) and repulsion force. For POPC/cholesterol liposome, although the effects of liposome from Ca2+ just like POPC liposome, cholesterol cause phospholipids tightly packed and make membrane more rigid. Consequently, the Lα/HII phase transition temperature is affected and shifts from 293 K-303 K in POPC liposome system to 303 K-313 K in POPC/cholesterol liposome system.