Molecular amphipathicity impacts on peptide surface behaviour

ERNESTO AMBROGGIO; GERARDO FIDELIO

Carlos Paz

Congreso; XLII reunión anual de la Sociedad Argentina de Biofísica; 2013

Protein primary structure has all the information for a specific protein/peptide folding. This sequence can define specific amphiphilic regions in the molecules important for the interaction with interfaces. In order to shed light how amphipathicity has a role in the surface properties of proteins, we designed three pairs of peptides where all six type of molecules have the same hydrophobic residues but different hydrophilic amino acids: positively, negatively and non-charged. The sequence of the peptides is inverted in comparison to their pair. This inversion provokes that one kind of peptide has the N-terminal region hydrophilic and the C-terminus hydrophobic and the other kind of peptide, with the same type of amino acids, the opposite distribution. We evaluated how amphiphilicity has a role in peptide lateral stability at the air-water interface by using the Langmuir monolayer technique. We also performed peptide/peptide mixtures to understand whether there is a coupling within opposed charges and if amphipathicity may contribute to the global lateral stability of the peptide film. In addition we measured membrane destabilization (leakage of a fluorescent solution trapped inside liposomes) and membrane association of these molecules. Finally we analyzed the peptide secondary structure by ATR-FTIR. Our results show a distinctive surface behaviour for each kind of molecule whereas all presented the same secondary structure.