Spectroscopic study on direction and inclination of helical peptides in monolayers formed at the air/water interface and on a gold substrate

Monolayers at the air/water interface and self-assembled monolayers (SAMs) on a gold substrate were prepared from helical peptide derivatives carrying a 9-ethyl-3-carbazolyl group and a disulfide group. pi-A Isotherms and circular dichroism spectra of Langmuir-Blodgett monolayers on a quartz substrate showed that the helical peptides were lying at the air/water interface. The molecular arrangement in the monolayer was analyzed by fluorescence quenching using in situ fluorescence spectroscopy. Computer simulations for the: quenching experiment under the assumption of the mixed arrangement of parallel and antiparallel orientations explain the experimental data. On the other hand, the helical peptides in the SAMs were found to take standing orientation and a parallel arrangement by Fourier transform infrared reflection-absorption spectroscopy and fluorescence spectroscopy.