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Modeling the tetraphenylalanine-PEG hybrid amphiphile: from DFT calculations on the peptide to molecular dynamics simulations on the conjugate
Zanuy Gomara, David; Hamley, I. W.; Alemán Llansó, Carlos
Universitat Politècnica de Catalunya. Departament d'Enginyeria Química
The conformational properties of the hybrid amphiphile formed by the conjugation of a hydrophobic peptide with four phenylalanine (Phe)residues and hydrophilic poly(ethylene glycol), have been investigated using quantum mechanical calculations and atomistic molecular dynamics simulations. The intrinsic conformational preferences ofthe peptide were examined using the building-up search procedure combined with B3LYP/6- 1G(d) geometry optimizations, which led to the identification of 78, 78, and 92 minimum energy structures for the peptides containing one, two, and four Phe residues. These peptidestend to adopt regular organizations involving turn-like motifs that define ribbon or helicallike arrangements. Furthermore, calculations indicate that backbone ··· side chain interactionsinvolving the N-H of the amide groups and the π clouds of the aromatic rings play acrucial role in Phe-containing peptides. On the other hand,MD simulations on the completeamphiphile in aqueous solution showed that the polymer fragment rapidly unfoldsmaximizing the contacts with the polar solvent, even though the hydrophobic peptidereduce the number of waters of hydration with respect to an individual polymer chain of equivalent molecular weight. In spite of the small effect of the peptide in the hydrodynamic properties of the polymer, we conclude that the two counterparts of the amphiphile tend to organize as independent modules.
2012-05-11
Àrees temàtiques de la UPC::Enginyeria química::Química física::Estructura molecular
Amphiphilic compounds
Molècules amfipàtiques
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