• BMB Reports
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• v.34 no.5
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• pp.446-451
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• 2001

The interaction of cytochrome c with binary phospholipid mixtures was investigated by solid-state $^2H$- and $^{31}P$-NMR. To examine the effect of the interaction on the glycerol backbones, the glycerol moieties of phosphatidylcholine (PC), and cardioliph (CL) were specifically deuterated. On the binding of cytochrome c to the binary mixed bilayers, no changes in the quadrupole splittings of each of the components were observed for the PC/PG, PE/CL and PE/PG liposomes. In contrast, the splittings of CL decreased on binging of protein to the PC/CL liposomes, although those of PC did not change at all. This showed that cytochrome c specifically interacts with CL in PC/CL bilayers, and penetrates into the lipid bilayer to some extent so as to perturb the dynamic structure of the glycerol backbone. This is distinctly different from the mode of interaction of cytochrome c with other binary mixed bilayers. In the $^{31}P$-NMR spectra, line broadening and a decrease of the chemical shift anisotropy were observed on the binding of cytochrome c for all binary mixed bilayers that were examined. These changes were more significant for the PC/CL bilayers. Furthermore, the line broadening is more significant for PC than for CL in PC/CL bilayers. Therefore, it can be concluded that with the polar head groups, not only CL but also PC are involved in the interaction with cytochrome c.

• Journal of Microbiology and Biotechnology
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• v.16 no.6
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• pp.880-888
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• 2006

Pleurocidin, an $\alpha$-helical cationic antimicrobial peptide, was isolated from skin mucosa of winter flounder (Pleuronectes americamus). It had strong antimicrobial activities against Gram-positive and Gram-negative bacteria, but had very weak hemolytic activity. The Gly$^{13,17}\rightarrow$Ala analog (pleurocidin-AA) showed similar antibacterial activities, but had dramatically increased hemolytic activity. The bacterial cell selectivity of pleurocidin was confirmed through the membrane-disrupting and membrane-binding affinities using dye leakage, tryptophan fluorescence blue shift, and tryptophan quenching experiments. However, the non-cell-selective antimicrobial peptide, pleurocidin-AA, interacts strongly with both negatively charged and zwitterionic phospholipid membranes, the latter of which are the major constituents of the outer leaflet of erythrocytes. Circular dihroism spectra showed that pleurocidin-AA has much higher contents of $\alpha$-helical conformation than pleurocidin. The tertiary structure determined by NMR spectroscopy showed that pleurocidin has a flexible. structure between the long helix from $Gly^3$ to $Gly^{17}$ and the short helix from $Gly^{17}$ to $Leu^{25}$. Cell-selective antimicrobial peptide pleurocidin interacts strongly with negatively charged phospholipid membranes, which mimic bacterial membranes. Structural flexibility between the two helices may play a key role in bacterial cell selectivity of pleurocidin.

• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.244-247
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• 2018

Lecithin, a zwitterionic phospholipid, forms spherical reverse micelles in organic solvents such as decane. The addition of multivalent ions like calcium chloride to lecithin organosols induces the transformation of organosols into organogels. A variety of applications of such organogels were found in gelation of fuels, food processing and drug delivery. Here, we investigated the effect of temperature on their rheological properties. In particular, the organogels showed a distinct melting temperature (${\sim}95^{\circ}C$) and their elastic properties decreased with increasing temperature. This is maybe due to the fact that the electrostatic interaction between lecithin and calcium chloride could be weaken with increasing temperature.

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.679-683
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• 2021

Lecithin, a zwitterionic phospholipid, forms spherical reverse micelles in nonpolar organic solvents such as decane. The addition of monovalent ions like lithium chloride (LiCl) to lecithin organosols induces the transformation of organosols into organogels due to the entanglement of reverse cylindrical micelles. In this study, we investigate the effect of pentanol acting as co-surfactant on rheological properties of lecithin/LiCl mixtures. From rheological studies, we find that the viscosity and elastic property of organogels decreased upon the addition of pentanol to organogels. The decrease in viscosity and elastic property can be attributed to the shortening of reverse cylindrical micelles confirmed by small angle X-ray scattering (SAXS).