Properties of signal-sequence peptides at an air-water interface.

The surface behaviour of three signal-sequence polypeptides (the pretrypsinogen 2 signal sequence, a synthetic consensus signal sequence and the putative signal sequence of ovalbumin) were studied at an air-water interface. It was found that the surface stabilities of the spread polypeptide films were higher than those of polypeptides and proteins previously investigated (including melittin and membrane proteins), and that the signal peptides had a much lower affinity for the interface than had other peptides and proteins. The observed molecular areas of the signal-sequence peptides indicated that the molecules have a considerable degree of secondary structure at the surface interface.