title: Mode of interaction of amphiphilic alpha-helical peptide with phosphatidylcholines at the air-water interface.
abstract: Surface pressure (pi)-, surface potential (deltaV)-, and dipole moment (mu(perpendicular))-area (A) isotherms and morphological behavior were examined for monolayers of a newly designed 18-mer amphiphilic alpha-helical peptide (Hel 13-5), DPPC, and DPPC/egg-PC (1:1) and their combinations by the Wilhelmy method, ionizing electrode method, fluorescence microscopy (FM), and atomic force microscopy (AFM). The newly designed Hel 13-5 showed rapid adsorption into the air-liquid interface to form interfacial films such as a SP-B function. Regardless of the composition and constituents in their multicomponent system of DPPC/egg-PC, the collapse pressure (pi(c); approximately 42 mN m(-1)) was constant, implying that Hel 13-5 with the fluid composition of egg-PC is squeezed out of Hel 13-5/DPPC/egg-PC monolayers accompanying a two- to three-dimensional phase transformation. FM showed that adding a small amount of Hel 13-5 to DPPC induced a dispersed pattern of ordered domains with a "moth-eaten" appearance, whereas shrinkage of ordered domains in size occurred for the DPPC/egg-PC mixture with Hel 13-5. Furthermore, AFM indicated that (i) the intermediate phase was formed in pure Hel 13-5 systems between monolayer states and excluded nanoparticles, (ii) protrusions necessarily located on DPPC monolayers, and (iii) beyond the collapse pressure of Hel 13-5, Hel 13-5 was squeezed out of the system into the aqueous subphase. Furthermore, hysteresis curves of these systems nicely resemble those of the DPPC/SP-B and DPPC/SP-C mixtures reported before.
authors.affiliation: Division of Biointerfacial Science, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Nakahara
authors.forename: Shohei
authors.initials: S
authors.lastname: Nakamura
authors.forename: Takato
authors.initials: T
authors.lastname: Hiranita
authors.forename: Hideya
authors.initials: H
authors.lastname: Kawasaki
authors.forename: Sannamu
authors.initials: S
authors.lastname: Lee
authors.forename: Gohsuke
authors.initials: G
authors.lastname: Sugihara
authors.forename: Osamu
authors.initials: O
authors.lastname: Shibata
mesh_terms: D000327:Adsorption; D000388:Air; D000595:Amino Acid Sequence; D018625:Microscopy, Atomic Force; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D010455:Peptides; D010713:Phosphatidylcholines; D014867:Water