• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.252-260
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• 1996

In this article, we investigate into the structural changes of liposome to design its functional membranes by the synthesis of two types of liposomes, DPPC liposome and DTAB of hydrocarbon substance/DPPC liposome. The changes of membrane structures are evaluated by the CF fluorescent intensity measured above and below the phase transition temperature of the membrane, $t_c=41^{\circ}C$. CF fluorescent intensities are enhanced by the CF leakage from DPPC liposome at $45^{\circ}C$, while no changes are observed at $20^{\circ}C$. Under the same conditions, it is observed that the intensity enhanced by CF leakage from DPPC/DTAB liposome is larger than that of DPPC liposome alone, which suggests that DPPC/DTAB liposome has irregular arrangement. Under the presence of $Ca^{2+}$, Quin 2 fluorescent intensity in either DPPC liposome or DPPC/DTAB liposome is significantly increasing at $45^{\circ}C$, while almost none of the changes are observed at $20^{\circ}C$. The fluorescent intensity of DPPC liposome turns out to be larger than that of DPPC/DTAB liposome, which suggests that the DPPC/DTAB liposome is structurally more stable than the DPPC liposome. Additionally, when the analysis is done to observe changes in the shapes of membrane surfaces with ANS fluorescent, ANS fluorescent under DPPC or DPPC/DTAB liposome shows each of different appearances at $45^{\circ}C$ and $20^{\circ}C$ respectively. This result indicates that its respective membrane fluidity is changing above and below of the designated temperatures in phase transition. As to the magnitude of change of its membrane fluidity, DPPC liposome is much larger than DPPC/DTAB liposome. As far as the temperature in phase transition measured by DSC are concerned, it is $41^{\circ}C$ and $32^{\circ}C$ for DPPC and DPPC/DTAB liposome respectively, which suggests that DPPC/DTAB liposome has an irregular molecular arrangement in its structure. That is, it is summed up that DPPC/DTAB turns out to be structurally stable, even so, its structure is irregularly arranged.

• KSBB Journal
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• v.15 no.1
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• pp.96-99
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• 2000

Liposome-amino acid conjugates were prepared using phopholipid (dipalmitoylphosphatidylcholine (DPPC) or distearoylph-osphatidylcholine(DSPC)) and hydrophobically modified amino acids (glutamic acid(glu), glutamine(gln) or asparagine(asn)). The size of liposomes was about 100 nm. According to the glucose-induced turbidity changes, liposomes composed of DPPC and glutamic acid have higher glucose binding affinity than liposomes of DPPC-glutamine or DPPC-asparagine. Also, the liposomes were more stable in terms of aggregation or fusion than the others (DPPC-glutamine, DPPC-asparagine and DSPC-amino acids). As a rdsult, stable liposomes with an affinity for glucose could be prepared with DPPC and glutamic acid.

• KSBB Journal
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• v.16 no.2
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• pp.170-173
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• 2001

Liposome-amino acid conjugates were prepared using dipalmitolyphosphatidylcholine(DPPC) and hydrophobically modified asparagine. A microdialyzer was used to measure glucose diffusion. The glucose binding affinity of DPPC-ODA-asparagine liposomes higher than that of DPPC liposomes and distilled water. The size of DPPC-ODA-asparagine was approximately 75-150 nm. Cholesterol increased the stability of liposomes, and reduced the size of liposome particles.

• Journal of Life Science
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• v.12 no.2
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• pp.121-128
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• 2002

The object of this study was to investigate the effect of membrane fluidity of bellflower(Platycodon grandiflorum A. DC, ; PG) fractions in phosphatidylcholine(PC) liposomes, measured with high-sensitivity differential scanning calorimetry(DSC). We used dipalmitoylphosphatidylcholine(DPPC) bilayers which slake most stable liposomes among the other phosphatidylcholine. The sample PG was extracted and fractionated to five different types : butanol(PGMB), ethylacetate(PGMEA), ethylether(PGMEE), hexane (PGMH) and methanol(PGMM). Among five different solvent fractions, the PGMEE, PGMEA, PGMH and PGMM fractions markedly affected the thermotropic properties of DPPC liposomes, broadened and shifted the thermograms, and reduced the cooperative unit. It might be said that the incorporation of PGMEE, PGMEA and PGMH in DPPC liposomes were located in the hydrophobic core of DPPC bilayers and, PGMM and PGMB in the hydrophilic core of DPPC bilayers. These results suggest that certain substances in the PGMEE, PGMEA and PGMH fractions might have biologically significant effect on the membrane fluidity.

• Journal of Ginseng Research
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• v.20 no.1
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• pp.23-29
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• 1996

The effect of ginseng glycosides and their aglycones on the thermodynamic characteristics of membranes from dipalmitoylphosphatidylcholine (DPPC) was investigated. Total saponins (TS) from Korean red ginseng, Panax ginseng C.A. Meyer, interacted with the Eel Phase of lipid in the Polar region and did not penetrate the deeper glycerol backbone of lipid molecule. From the all investigated components of TS (aglycons and ginsenosides), only 20-(S)-panaxadiol (PD) had an effect similar to TS. High concentration of TS penetrated in hydrophobic Cl-C8 region. The presence of cholesterol did not influence the interaction of TS with DPPC. An elimination of transition, however, took place at 10~100 $\mu\textrm{g}$/ml of TS. DPPC had a low ability to interact with cholesterol (CHL) as compared with other lecithins except ethanolamine. From our results, only TS and PD, at high concentrations (100 mol%), influenced the phase transition of mixture of DPPC:CHL.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.457-461
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• 1998

The vesicle system of DPPC(dipalmitoylphosphaticylcholine)/Chol(Cholesterol) has been modified by incorporating various mole fractions of flourinated surfactant($C_8F_{17}(CH_2)_2OCO-CH_2CH(SO_3Na)COO(CH_2)_2C_8F_{17}$. Sodium bis(1H,1H,2H,2H-heptadecaflurododecyl)-2-sulfosuccinate, FS)/fluorinated fatty acid salt ($C_7F_{15}COONH_4$, ammoniumpentadecaflurooctyrate, FFS), and their physicochemical properties have been investigated in an attempt to enhance the stability of phospholipid vesicle system. The ${\zeta}$-potential measurement by use of Zetamaster sub-micron Particle Electrophoresis Analyzer (Malvern Co.) showed that a charged homogeneous DPPC/Chol/FS vesicle has been formed owing to the incorporated FFS effect on the membrane, playing a role as a cosurfactant in the bilayer between DPPC and FS components. With increase in the concentration of FFS, it was found that the particle size and also surface charge of the DPPC/Chol/FS vesicle decreased. The stability of DPPC/Chol/FS/FFS liposome was found to be enhanced significantly compared to that of DPPC/Chol/FS according to the dispersity change as a function of time. The release rate of dye molecule of Methylene Blue from the DPPC/Chol/FS/FFS vesicle was determined to be slower than that of DPPC/Chol/FS system, and it may be attributed to the increase in microviscosity of the hydrophobic region in the bilayer. The affinfinity of DPPC/Chol/FS/FFS vesicles to albumin was found to be slightly lowered compared to that of DPPC/Chol/FS. Based on these findings, it was confirmed that a more stable and homogeneous vesicle system of DPPC/Chol/FS could be prepared by addition of FFS, acting as a cosurfactant in the aggregate formation.

• Journal of Life Science
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• v.10 no.2
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• pp.27-32
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• 2000

To understand the effects of the fraction from Chrysanthemum coronarium L. (CC), we prepared five different types of samples, denoted here as CCMM, CCMH, CCMEA, CCMB and CCMA. We studied the effects of these samples on the phase transition of liposomal membranes by high-sensitivity differential scanning calorimetry (nano-DSC). We used dipalmitoylphosphatidylcholine (DPPC) bilayers which make most stable liposomes among the other phosphatidylcholines. When the samples were added to the bilayers, the phase transition temperatures of DPPC liposomes incorporated with CCMH and CCMEA were decreased by 1.5 and 2^{\circ}C$, while the other three fractions showed less tendencies. The CCMH and CCMEA fractions markedly affected the thermotropic properties of DPPC liposomes, broadened and shifted the thermograms of DSC. It also significantly reduced the size of cooperative unit of the transition. In all cases, there was no change in enthalpy of transition within the concentration range of the CC fractions studied. We concluded that the incorporation of the CCMH and CCMEA into DPPC liposomes was preferentially located in the hydrophobic core of DPPC bilayers compared to the other three fractions CCMM, CCMB and CCMA. These results suggest that certain substances in CCMH and CCMEA fractions might have biologically significant effects on the fluidity of biological membrane.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.4
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• pp.646-650
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• 2001

In this study, we investigated the thermotropic behavior of Daucus carota L. (DCS) extracts in phosphatidylcholine(PC) liposomes using high-sensitivity differential scanning calorimetry (nano-DSC). We used dipalmitoylphosphatidylcholine (DPPC) bilayers which made most stable liposomes among the other phosphatidylcholine. The sample DCS was extracted and fractionated to four different types, hexane(DCSMH), ethylacetate (DCSMEA), butanol (DCSMB) and aqueous(DCSMA) fractions. Compared to the other fractions of Daucus carota L., the DCSMH and DCSMEA fractions markedly affected the thermotropic properties of DPPC liposomes, broadened and shifted the thermograms of transition to lower temperatures. The incorporation of DCSMH and DCSMEA in DPPC liposomes were preferentially located in the hydrophobic core of DPPC bilayers, where it reduced the lipid packing orderness (cooperative unit) in the gel state compared to it in the liquid-crystalline state. These results suggest that the activities of the Daucus carota L. extracts to enhance the fluidity of the liposomal membrane have implication in their biological activities.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.3
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• pp.518-524
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• 1998

Liposomes have been widely employed as biomembrane-mimetic system and drug-delivery system. In these applications, the low stability of liposomes has been the most serious problem. They have relatively short half-lives and easily lysed through interactions with biological components. This study was performed to investigate the effects of godulbaegi extracts on the fludity of phospholipid liposomes. We used dipalmitoyl phosphatidylcholine(DPPC) liposomes which make most stable liposomes among the other phosphatidylcholines. The thermograms of the DPPC liposomal bilayers incorporated with the hexane extract of godulbaegi(Ixeris sonchifolia H.) were obtained, and the enthalpy changes and the sizes of cooperative unit of the transition were calculated. The incorporation of the Ixeris sonchifolia H. into the liposomal bilayers effectively reduced the transition temperature at which the transition from gel state to liquid-crystalline state occurs, broadened the thermogram peaks, and reduced the ratio of van't Hoff to calorimetric enthalpies. These results indicate indicate that the godulbaegi extracts (Ixeris sonchifolia H.) have significant effects on the fluidity of biological membrance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.491-494
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• 2000

Conductive Langmuir-Blodgett(LB) films have recently attracted much interest from the viewpoint of ultrathin film conductors at the molecular level. The result shows that the Maxwell-displacement-current(MDC) measuring technique is useful in the detection of phase-transition over the entire range of molecule areas. At the liquid-solid phase transition, a striking feature in the present current measurement was observed; the I-A isotherm for a DPPC monolayer has sharp bend. Dynamic behavior of monolayers in the presence of an external field was also investigated using the current-measuring technique. Dynamic behavier of DPPC monolayer was measured by displacement current when the molecules are stimulated by pressure velocity. As result, it is known that current is generated of higher current pe마 as compression velocity become faster. Also, in order to clarify the reorganization of the lipid monolayers, it is instructive to plot the relationship between I and 1/$A^2$.