2ND-HARMONIC GENERATION FROM THE AIR-WATER-INTERFACE OF AN AQUEOUS-SOLUTION OF THE DIPEPTIDE BOC-TRP-TRP

The air/water interface of aqueous (t-butyloxycarbonyl)-tryptophan-try ptophan (Boc-Trp-Trp) has been studied by surface second harmonic gene ration (SHG). The SHG signals obtained with a linearly polarised funda mental indicate a Langmuir-like adsorption isotherm. Wavelength-depend ent circularly differential harmonic generation (SHG-CD) was observed together with SHG optical rotation. The SHG signals from the LL and DD enantiomer show equal but opposite dependence on the handedness of th e fundamental radiation and the DL diastereoisomer gave rise to a diff erent spectrum.