A synthetic peptide, corresponding to the 110−121 sequence of VP3-HAV (hepatitis A virus) protein, was synthesized, and its interactions with membrane models were analyzed with monomolecular layer models. Surface activity measurements indicate that the peptide is able to modify the surface activity of water forming monomolecular films. Compression isotherms and penetration kinetics determinations suggest that the hydrophobic moiety of the peptide is able to insert into phospholipidic monolayers promoting an expansion. Moreover, as interactions are stronger with stearylamine-containing monolayers, an electrostatic effect cannot be discarded.
The RGD region of the (110-121) peptide sequence (FWRGDLVFDFQV) of VP3 capsid protein of hepatitis A virus, which is described to be responsible for a high immunoresponse, was changed for RGE and RKD amino acids in order to analyze the change effect on the physicochemical properties of the peptide. Peptides were synthesized by solid-phase synthesis and characterized by amino acid analysis, analytical highperformance liquid chromatography, and electrospray mass spectrometry. The peptides had surface activity concentration dependent, formed stable monolayers at the air/water interface, and were able to insert into lipid monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phosphatidylglycerol, phosphatydic acid, L-R-phosphatidyl-L-serine, stearylamine, sphyngomyelin, and liver extract. Differential scanning calorimetry (DSC) was used to investigate the thermotropic phase properties of binary mixtures of DPPC and the three peptides. DSC data showed a complete abolition of DPPC pretransition and significant broadening of the main phase transition with increasing amounts of peptide. These results are indicative of an interfacial location of the peptides and with some penetration of the nonpolar amino acid side chains into the hydrocarbon chain region closer to the polar/nonpolar interface. Finally, fluorescence spectroscopy confirmed the preferential interaction of the peptides with the liquid crystalline state of the bilayer with a contribution of both hydrophobic and electrostatic forces.
Shorter analogues of a continuous epitope of hepatitis A virus, VP3(110–121) peptide, failed to react with convalescent sera, indicating the importance of the entire peptide in the epitope structure. To better understand the influence of the structural properties of this 12‐mer peptide epitope on its biological activity, the interaction of smaller peptide analogues with phospholipid biomembrane models was investigated by a combination of spectroscopic and biophysical techniques. In this article we describe our findings concerning the surface activity and the interaction of peptides with simple mono‐ and bilayer membranes composed of a zwitterionic phospholipid (dipalmitoyl phosphatidylcholine, DPPC), an anionic phospholipid (dipalmitoyl phosphatidylglicerol, DPPG), or a DPPC/DPPG mixture. The results indicate that the net negative charge of the peptide is in some way responsible of the specific interactions between VP3(110–121) and membrane phospholipids, and necessary to induce β‐type conformations upon vesicle interaction. © 2000 John Wiley & Sons, Inc. Biopoly 54: 477–488, 2000
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