A Langmuir Monolayer Study of the Interaction of E1(145−162) Hepatitis G Virus Peptide with Phospholipid Membranes

E1(145−162), a peptide corresponding to the structural protein E1 of the GB virus C, has been shown earlier to bind at pH 7.4 to vesicles containing 1,2-dimyiristoyl-sn-glycero-3-phospho-rac-(1-glycerol)] (DMPG) and 1,2-dimyiristoyl-sn-glycero-3-phosphocholine (DMPC) phospholipids. To deepen the understanding of the interaction of E1(145−162) with the lipid membrane, in this paper, we report a detailed study of the surface properties of peptide, miscibility properties, and behavior of mixed monomolecular films of it and three phospholipids DMPG, DMPC, and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPG). These studies were performed using the Langmuir balance by means of surface adsorption studies, surface pressure−mean molecular area compression isotherms, and penetration kinetics. The Brewster angle microscopy (BAM) was used to study the morphological properties of pure peptide and the mixed monolayers. The results show us that the peptide showed surface activity concentration dependent when injected beneath a buffered solution (HEPES/NaCl, pH 7.4). This tendency to accumulate into the air/water interface confirms its potential capacity to interact with membranes; the higher penetration of peptide into phospholipids is attained when the monolayers are in the liquid expanded state and the lipids are charged negatively maybe due to its negative electric charge that interacts with the positive global charge of the peptide sequence. The area per molecule values obtained suggested that the main arrangement structure for E1(145−162) peptide is the α-helical at the air−water interface that agreed with computational prediction calculations. Miscibility studies indicated that mixtures become thermodynamically favored at low peptide molar fraction.This work is supported by project CTQ2006-15396-C02-02/01-BQU from Secretarı´a de Estado de Investigacio´n, Ministerio de Ciencia e Innovacio´n, Direccio´n General de Programas y transferencia de conocimiento, Subdireccio ´n General de Proyectos de Investigacio´n (Spain). M.J.S.- M. is a recipient of a FPI program predoctoral grant. The authors are members of the consolidated research group by the Generalitat de Catalunya: Peptides and Proteins: physicochemical studies (2005SGR00278). The authors are grateful to Peter Schmidtke, Ph.D. Student at the Molecular Modeling and Bioinformatics Group of the department of Physical Chemistry (Faculty of Pharmacy, University of Barcelona), for his inestimable help on the computational prediction of the peptide structure.Peer reviewe