SELF-ASSEMBLY OF ALPHA-HELIX PEPTIDE CROWN-ETHER CONJUGATE UPON COMPLEXATION WITH AMMONIUM-TERMINATED ALKANETHIOLATE

Hydrophobic helical crowned peptides were synthesized and investigated on formation of an oriented thin layer of the helix peptides. The hel ix peptides in ethanol were incubated with a self-assembled monolayer (SAM) of ammonium-terminated alkanethiolate on a gold surface. The thi ckness of the peptide thin layer formed on the gold surface was determ ined by the surface plasmon resonance method. Complexation of the crow ned peptide with the ammonium-terminated alkanethiolate facilitated fo rmation of a peptide monolayer or multilayers on gold depending on the peptide concentration. The orientation of the helix peptide on the go ld surface was investigated by FT-IR reflection-absorption spectroscop y. The tilt angle of the helix axis from the normal of the gold surfac e was estimated to be 28 degrees, when the crowned peptide complexed w ith the SAM of N-(epsilon-aminocaproyl)aminoethyl disulfide. This degr ee of orientation is more vertical to the surface than that of the com plexed peptide with a SAM of 2-aminoethanethiol hydrochloride. Since t he helix peptide without the crown ether unit was oriented in parallel to the surface, the crown ether/ammonium complexation should promote the vertical orientation of the helix peptides on the gold surface.