Effect of the addition of a nonionic surfactant on the complex poly(asparagine)--cationic surfactant.
Poly(asparagine) (pAsn) at 0.1wt % in the presence of dodecyltrimethylammonium bromide (DTAB) and pentaoxyethylene octyl ether (C(8)E(5)) at 1:1 molar ratio leads to the formation of mixed DTAB/C(8)E(5) micelle-like aggregates onto the polypeptide as a total surfactant critical association concentration (cac) is reached, as revealed by surface tension measurements and NMR chemical shifts. Two-dimensional nuclear Overhauser enhancement spectroscopy (NOESY) capable of revealing spatial relationships among proximal protons has been performed on the pAsn-DTAB-C(8)E(5)-water system to study structural details of the surfactant-polypeptide aggregates. NOESY cross-peaks at sample temperature of 298.15 K indicate that the polypeptide interacts with the DTAB/C(8)E(5) micelle-like aggregates. The NOE intermolecular effects also show direct interactions between surfactant and polypeptide in the pAsn-DTAB-water system, whereas no interaction has been revealed in the pAsn-C(8)E(5)-water system. Furthermore, the experimental evidence suggest that the DTAB-polypeptide complex is mainly driven by the polar attraction between the two molecules.
Roscigno
Paola
P
Dipartimento di Chimica, Università degli Studi di Napoli Federico II, Via Cinthia Monte S. Angelo, 80126 Napoli, Italy.
D'Auria
Gabriella
G
Falcigno
Lucia
L
D'Errico
Gerardino
G
Paduano
Luigi
L
D002412:Cations / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*
D002412:Cations; D007477:Ions; D010455:Peptides; D013501:Surface-Active Agents; C045164:polyasparagine