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A variety of amphiphilic helical peptides have been shown to exhibit a transition from adsorbing parallel to a membrane surface at low concentrations to inserting perpendicularly into the membrane at high concentrations. Furthermore, this transition has been correlated to the peptides' cytolytic activities. X-ray lamellar diffraction of diphytanoyl(More)
A technique of neutron in-plane scattering for studying the structures of peptide pores in membranes is described. Alamethicin in the inserted state was prepared and undeuterated and deuterated dilauroyl phosphatidylcholine (DLPC) hydrated with D2O or H2O. Neutron in-plane scattering showed a strong dependence on deuteration, clearly indicating that water(More)
Magainin 2 is a 23-residue antibiotic peptide found in the skin of Xeonpus laevis (African clawed frog). It belongs to a broad class of alpha-helical peptides which interact directly with the lipid bilayer. Very little is presently known about the nature of this peptide/lipid interaction on the molecular level. We have performed a sequence of lamellar X-ray(More)
Alamethicin adsorbs on the membrane surface at low peptide concentrations. However, above a critical peptide-to-lipid ratio (P/L), a fraction of the peptide molecules insert in the membrane. This critical ratio is lipid dependent. For diphytanoyl phosphatidylcholine it is about 1/40. At even higher concentrations P/L > or = 1/15, all of the alamethicin(More)
Antimicrobial peptides isolated from the host defense systems of animals have been shown to exert their activity directly on the lipid bilayer of cell membranes, but the antimicrobial mechanisms are not clear, due chiefly to the difficulty of discerning the high-order structures formed by these peptides in membranes. Previously we have shown that these(More)
As the motor vehicle population in China continues to increase at an annual rate of approximately 15%, air pollution related to vehicular emissions has become the focus of attention, especially in large cities. There is an urgent need to identify the severity of this pollution in China. Based on an investigation into vehicle service characteristics, this(More)
We demonstrate a technique for measuring x-ray (or neutron) scattering with the momentum transfer confined in the plane of membrane, for the purpose of studying lateral organization of proteins and peptides in membrane. Unlike freeze-fracture electron microscopy or atomic force microscopy which requires the membrane to be frozen or fixed, in-plane x-ray(More)
The bacterial artificial chromosome (BAC) system is widely used in isolation of large genomic fragments of interest. Construction of a routine BAC library requires several months for picking clones and arraying BACs into superpools in order to employ 4D-PCR to screen positive BACs, which might be time-consuming and laborious. The major histocompatibility(More)
Adsorption of amphiphilic peptides to the headgroup region of a lipid bilayer is a common mode of protein-membrane interactions. Previous studies have shown that adsorption causes membrane thinning. The degree of the thinning depends on the degree of the lateral expansion caused by the peptide adsorption. If this simple molecular mechanism is correct, the(More)
Using oriented circular dichroism, we have found that magainin adopts an alpha-helical conformation with two distinct orientations when interacting with a lipid bilayer. At low concentrations, magainin is absorbed parallel to the membrane surface. However, at high concentrations, magainin is inserted into the membrane. This transition occurs at roughly the(More)