• Proceedings of the Korean Biophysical Society Conference
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• 1998.06a
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• pp.16-16
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• 1998

The role of phospholipids in the membrane binding and subsequent insertion of the microsomal protein rabbit cytochrome P450 (P450) lA2 into phospholipid bilayers was investigated. The insertion of P450 lA2 into phospholipid bilayers was determined by the amount of quenching of Trp fluorescence of P450 lA2 by pyrene and brominated and doxyl-labeled phospholipids.(omitted)

• Journal of Nutrition and Health
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• v.30 no.6
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• pp.658-668
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• 1997

Path of a small hydrophobic molecule through the aqueous cytoplasma is not linear. Partition may favor membrane binding by several orders of magnitude : thus significant membrane association will markedly decrease the cytosolic transport rate. The presence of high concentration of soluble binding proteins for these hydrophobic molecules would compete with membrane association and thereby increase transport rate. For long chain fatty acid molecules, a family of cytosolic binding proteins collectively known as the fatty acid binding proteins(FABP), are thought to act as intracellular transport proteins. This paper examines the mechanism of transfer of fluorescent antyroyloxy-labeled fatty acids(AOFA) from purified FABPs to phosholipid membranes. With the exception of the liver FABP, AOFA is transferred from FABP by collisional interaction of the protein with a acceptor membrane. The rate of transfer increased markedly when membranes contain anionic phospholipids. This suggests that positively charged residues on the surface of the FABP may interact with the membranes. Neutralization of the surface lysine residues of adipocyte FABP decreased fatty acid transfer rate, and transfer was found to proceed via aqueous diffusion rather than collisional interaction. Site specific mutagenesis has further shown that the helix-turn-helix domain of the FABP is critical for interaction with anionic acceptor membranes. Thus cytosolic FABP may function in intracellular transport of fatty acid to decrease their membranes association as well as to target fatty acid to specific subcellular sites of utilization.

• Proceedings of the Korean Biophysical Society Conference
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• 1999.06a
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• pp.46-46
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• 1999

Positively charged cytochrome c interacts with the negatively charged mitochondrial inner membrane. This interaction induces conformational changes in bound cytochrome c. In order to estimate the effect of cytochrome c-membrane interaction on the mitochondrial electron transfer, we have investigated oxidation of ferrocytochrom c in the presence of anionic phospholipids.(omitted)

• The Korean Journal of Pharmacology
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• v.26 no.1
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• pp.77-82
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• 1990

The effects of phenothiazine derivatives and calcium on the thermotropic phase transition of bilayers in dipalmitoyl phosphatidylcholine (DPPC) and dipalmitoyl phosphatidic acid (DPPA) liposomes were investigated with differential scanning calorimeter (DSC). Bilayers underwent an abrupt organizational changes at a characteristic temperature when heated. Such temperature-dependent transition was particularly striking and sharp in the bilayers prepared from pure phospholipids. The ability of phenothiazine derivatives to modify the phase transition of phospholipids liposomes was measured by a broadening of the phase transition profile, that transition began to appear at lower temperature than which occurs in untreated liposomes. Calcium ion caused a large upward shift in the transition temperature of DPPC:DPPA (34:66mol%) liposomes. When the liposomes were first incubated with calcium ion followed by phenothiazine derivatives, disappearance of the broad curve centering at $73^{\circ}C$ indicated displacement of calcium ion by phenothiazine derivatives at the anionic site. It is supposed that calcium ion and phenothiazine derivatives might compete with each other on the head group of acidic phospholipid.

• Journal of the Korean Chemical Society
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• v.43 no.2
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• pp.193-198
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• 1999

The transfection efficiency of plasmid DNA was inspected using multi-cationic polymer, 5, 10, 25 and 50KD polyethylenimine (PEI). The optimal neutralization ratio of PEI/DNA complexes by agarose assay was 1.5-2.0 (nmol/nmol) without much difference in molecular weight of PEI.In vitro transfection assay, most of PEI-mediated plasmid delivery was better compared to the naked DNA. Especially, 25KD PEI at optimal condition gave higher transfection rather than the standard assay of DEAE-dextran or Lipofectin. To enhance the cell targeting delivery, the liposome formulations were introduced using phospholipids. As a result, PC/PE liposomes increased 2-2.5 times of the transfection efficiency of PEI single or PC/PE single delivery, but not the case of 25KD PEI. Moreover, the DOTAP/PE-introduced PEI delivery reduced the transfection of DOTAP/PE single delivery. All these results proved that the PEI can be used not only good transfectants and but also good DNA condensing agents in neutral/anionic liposome for cell targeting delivery.