title: Comparison of the helix-coil transition of a titrating polypeptide in aqueous solutions and at the air-water interface.
abstract: The transition from alpha-helix to random coil of the titrating polyamino acid co-poly-L-(lysine, phenylalanine), (p-(Lys,Phe)), has been investigated as a function of pH and ionic strength in aqueous solution and at the air-water interface by means of circular dichroism (CD) spectroscopy and the Langmuir surface film balance technique. The results strongly suggest that the helix-coil transition for peptides at the air-water interface can be determined by using the two-dimensional Flory exponent, nu, to express the pH dependent peptide surface conformation. The helix-coil titration curve of p-(Lys,Phe) shifts approximately 2.5 pH units towards lower pH at the air-water interface, as compared with the bulk solution. This finding is of relevance for the understanding of conformation and conformational changes of membrane-transporting and membrane penetrating peptides as well as for the use of peptides in molecular devices.
authors.affiliation: Physical Chemistry 1, Lund University, P.O. Box 124, 221 00 Lund, Sweden. Helen.Sjogren@fkem1.lu.se
authors.forename: Helen
authors.initials: H
authors.lastname: Sjögren
authors.forename: Stefan
authors.initials: S
authors.lastname: Ulvenlund
mesh_terms: D000388:Air; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D036341:Intercellular Signaling Peptides and Proteins; D018625:Microscopy, Atomic Force; D009994:Osmolar Concentration; D010455:Peptides / Q000737:chemistry*; D044367:Phase Transition; D011487:Protein Conformation; D012996:Solutions / Q000737:chemistry; D017186:Titrimetry; D014867:Water / Q000737:chemistry*
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D012996:Solutions; D014867:Water; C028310:poly-L-lysylphenylalanine