Interfacial properties of gramicidin and gramicidin-lipid mixtures measured with static and dynamic monolayer techniques.
Gramicidin films at the air/water interface are shown to exhibit a phase transition at 225 A2/molecule which might be caused by either cluster formation, reorientation of molecules, conformational changes or multilayer formation. It is further shown that coupling of a charged group on either NH2- or COOH-terminus or elongation of the peptide by two amino acids, only slightly affects the surface area characteristics whereas modification of the tryptophans or even replacement of a single tryptophan by phenylalanine leads to drastic alterations in the surface-area characteristics and a (partial) loss of the phase transition demonstrating that the tryptophans play an important role in the interfacial behavior of gramicidin. The lack of a solvent history effect on the interfacial behavior indicates a rapid conformational interconversion of the peptide at the air/water interface. Gramicidin in mixtures with dioleoylphosphatidylcholine and lysopalmitoylphosphatidylcholine shows a condensing effect whereas gramicidin shows ideal mixing with dioleoylphosphatidylethanolamine. The condensing effect most likely is related to the aggregational state of the peptides which is different in phosphatidylcholines and phosphatidylethanolamines.
Tournois
H
H
Centre of Biomembranes and Lipid Enzymology, University of Utrecht, The Netherlands.
Gieles
P
P
Demel
R
R
de Gier
J
J
de Kruijff
B
B
D000595:Amino Acid Sequence; D006096:Gramicidin; D008051:Lipid Bilayers; D008954:Models, Biological; D008969:Molecular Sequence Data; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D011312:Pressure; D013329:Structure-Activity Relationship; D013499:Surface Properties
D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D006096:Gramicidin; C020888:1,2-dielaidoylphosphatidylethanolamine