Surface-enhanced Raman and steady fluorescence study of interaction between antitumoral drug 9-aminoacridine and trypsin-like protease related to metastasis processes, guanidinobenzoatase

Fluorescence spectroscopy and surface-enhanced Raman spectroscopy (SERS) we re applied to study the interaction of the antitumoral drug 9-aminoacridine (9AA) with a trypsin-like protease guanidinobenzoatase (GB) extracted from a mouse Erlich tumor. As a consequence of this interaction, a strong 9AA e xciplex emission was detected in the emission fluorescence spectra at certa in drug and enzyme concentrations. A SERS study was accomplished on silver colloids at several excitation wavelengths in order to obtain more informat ion about the interaction mechanism. The results derived from Raman spectro scopy indicated that 9AA in the amino monomeric form may interact with the enzyme by means of two different bonds: an ionic bond with a negatively cha rged amino acid and a ring stacking interaction with an aromatic residue pl aced in the catalytic site of GB. This interaction mechanism was responsibl e for a strong exciplex emission detected at a longer wavelength than the e xpected value of the normal fluorescence emission. Moreover, the GB concent ration dependence of the interaction suggested that the drug was sensitive to the quaternary structure of the enzyme. (C) 2001 John Wiley & Sons, Inc.