• Archives of Pharmacal Research
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• v.10 no.2
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• pp.75-79
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• 1987

Liposomes were studied as a drug delivery system. Multilamellar vesicles, small unilamellar vesicles and large unilamellar vesicles containing cytarabine were prepared using egg yolk lecithin and cholesterol. Large unilamellar vesicles showed the highest encapsulation efficiency of all and their encapsulation efficiency increased as the buffer volume decreased. Cholesterol increased the stability of liposomal drug products as drug carriers and reduced the permeability of drug across the liposomal membrane. The release rate of cytarabine increased with incubation temperature and decreased with cholesterol incorporation in liposomal membrane. The release mechanism of cytarabine from large unilamellar vesicles in vitro was chiefly due to simple diffusion across the liposomal membrane rather than liposomal rupture.

• Journal of the Korean Applied Science and Technology
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• v.25 no.1
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• pp.48-51
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• 2008

Dipalmitoyl phosphatidyl choline and p-nitrophenyl palmitate were directly sonicated in acidic water for 6 minutes to give clear stock solutions. The catalytic hydrolysis of p-nitrophenyl palmitate was studied at $30-50^{\circ}C$ in the presence of unilamellar vesicle and mixture of unilamellar and multilamellar aggregates. The difference of reaction rate between unilamellar and multilamellar was observed. The rate of unilamellar reaction compared to the rate of mixture reaction showed more catalytic effect. The phase transition temperature of vesicle was measured at $37-44^{\circ}C$.

• Proceedings of the Korean Biophysical Society Conference
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• 1996.07a
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• pp.6-6
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• 1996

Gap junction channels were reconstituted into unilamellar liposomes using immunoaffinity purified connexin 32 gap junction protein from rat liver. Vesicles containing open channels and close channels were separated by means of iso-osmolar sucros density gradient sedimentation. The open channels formed in lipid vesicles were permeable to a fluorescent dye molecule, lucifer yellow of which the hydrodynamic size is similar to pore size of gap junctions in vivo. (omitted)

• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.743-748
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• 2013

The temperature dependence of the partition coefficients of a neuropeptide, substance P (SP), in isotropic acidic bicelles was investigated by using a pulsed field gradient nuclear magnetic resonance diffusion technique. The addition of negatively charged dimyristoylphosphatidylserine to the neutral bicelle changed the SP partitioning a little, which implies that the hydrophobic interaction between the hydrophobic residues of SP and the acyl chains of lipid molecules is the major interaction while the electrostatic interaction is minor in SP binding in a lipid membrane. From the temperature dependence of the partition coefficients, thermodynamic functions were calculated. The partitioning of SP into the acidic bicelles is enthalpy-driven, as it is for small unilamellar vesicles and dodecylphosphocholine micelles, while peptide partitioning into a large unilamellar vesicle is entropy-driven. This may mean that the size of lipid membranes is a more important factor for peptide binding than the surface curvature and surface charge density.

• Bulletin of the Korean Chemical Society
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• v.13 no.4
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• pp.381-384
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• 1992

The hydrolytic susceptibility of large unilamellar vesicle (LUV) toward cabbage phospholipase D (PLD) was studied. The activity of PLD was determined by pH stat titration method. Using phosphatidylcholine LUV as substrate a pH optimum of 6.96 was observed. For maximal activity the optimal temperature of $31^{\circ}C$ and 10 mM of Ca2+ were required. The apparent Km value estimated was 2.5 mM. The hydrolytic activity of PLD toward PC LUV was somewhat high despite the absence of activator in assay system and this high susceptibility of PC LUV may be attributed to the structural properties of LUV. The effect of amphiphatic substances such as dicetyl phosphate and phosphatidic acid on the enzyme activity were also examined in mixed LUVs.

• Bulletin of the Korean Chemical Society
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• v.5 no.4
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• pp.154-158
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• 1984

In order to characterize the permeability of small unilamellar vesicles (SUV), efflux of 6-carboxyfluorescein (6-CF) from the vesicles was monitored spectrophotofluorometrically. Since the entrapped highly quenched 6-CF (200 mM) became fluorescent upon release from the vesicles, the 6-CF could be used as an efflux probe. SUV containing entrapped 6-CF was prepared from egg phosphatidylcholine and separated by gel filtration on Sepharose 4B. Observed change of relative fluorescent intensity with time was sigmoidal. From this curve, the parameter of permeability was determined either by half-time or a released amount per unit time from the initial slope. Half-time of efflux of prepared SUV having 302 ng phospholipid/ml in 10 mM Tris-HCl buffer pH 7.4 was 21.0 min at $37{\circ}C$. Various factors which could affect the half-time were examined including temperature, pH, salt, and vesicle concentration. In particular the effect of vesicle concentration on the efflux revealed that the permeability can be a function of the concentration.

• Proceedings of the Korean Biophysical Society Conference
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• 1999.06a
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• pp.45-45
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• 1999

Cytochrome c (cyt c) binds to acidic membranes at low ionic strength. Replacement of Lys-72 or Lys-87 by Glu reduced the binding affinity of cyt c toward large unilamellar vesicles (LUV) in liquid crystalline phase. The differences were smaller for LUV in gel phase. A fraction of bound cyt c was non-electrostatically associated.(omitted)

• Journal of the Korean Chemical Society
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• v.47 no.5
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• pp.466-471
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• 2003

The effect of polyamines on the cabbage phospholipase D(PLD) activity was investigated. The PLD activity was determined by pH-stat titration of phosphatidic acid, one of the enzymatic reaction product, using phosphatidyl choline small unilamellar vesicles as a substrate. The cabbage PLD was activated approximately 4 fold by spermine at 1 mM concentration. This spermine effect appears to be similar to the previous report on the PLD activation of rat brain mitochondrial fraction. It was also found that cationic polypetides such as polylysine and polyhistidine exerted a marked enhancement effect on the cabbage PLD. Particularly polyhistidine exerted approximately 5.5 fold enhancement effect at 0.062 mM concentration. The polyamine effect on the cabbage PLD was reexamined in the phosphatidylcholine/sodium dodecyl sulfate mixed micellar system. The relevance of polyamine effect on PLD activity is discussed in relation to the active site of PLD.

• Journal of the Korean Applied Science and Technology
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• v.27 no.4
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• pp.391-398
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• 2010

Soybean lecithin liposomes composed phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl inositol and phosphatidic acid were prepared by using the previously developed supercritical reverse phase evaporation method. The effect of phospholipid composition on the formation of liposomes and physicochemical properties were examined by means of trapping efficiency measurements, transmission electron microscopy, dynamic light scattering and zeta potential measurements. The trapping efficiency of liposomes for D-(+)-glucose made of CNA-Ⅰ which contains approximately 95% phosphatidyl choline is higher than that of CNA-II and CNA-O which contain approximately 32% phosphatidyl choline. However there is no any difference between the trapping efficiency of liposomes for D-(+)-glucose made of CNA-II which has saturated hydrocarbons tails and that of liposomes made of CNA-O which has unsaturated hydrocarbon chains. The electron micrographs of liposomes made of CNA-II and CNA-O show small spherical liposomes with diameter of $0.1\sim0.25{\mu}m$, while that of CNA-I shows large unilamellar liposomes with diameter of $0.2\sim1.2{\mu}m$. These results clearly show that phospholipid structure of phosphatidylcholine allows an efficient preparation of large unilamellar liposomes and a high trapping efficiency for water soluble substances. Liposomes made of CNA-II and CNA-O remained well-dispersed for at least 14 days, while liposome suspension made of CNA-I separated in two phase at 14 days due to aggregation and fusion of liposomes. The dispersibility of liposomes made of CNA-I is lower than that of CNA-II and CNA-O due to the smallar zeta potential of CNA-I.

• Archives of Pharmacal Research
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• v.9 no.3
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• pp.119-125
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• 1986

Digitonin is a strong hemolysin and glycyrrhizin has protective activity against the deterring effect of other hemolytic saponins. The interaction of these saponins with liposomes was studied as a function of cholesterol in membrane. In the case of multilamellar vesicles, which act as ideal osmometers, digitonin distrupted the barrier function of liposomes composed of phosphatidyl choline, dicetyl phosphate and cholesterol, however, did not influence on cholesterol-lacking liposomes. Glycyrrhizin had similar effect on liposomes irrespective of cholesterol in membrane. In the test with large unilamellar vesicles, digitonin increased the lysis with increasing cholesterol content in membrane, but glycyrrhizin showed no detectable change in cholesterol-containing liposomes. These results suggest that incorporation of cholesterol into liposomes increases the susceptibility to digitonin, resulting in lysis of liposomes, and that the inhibitory effect of glycyrrhizin against other hemolytic saponins in cholesterol-independent.