Immobilization of DNA through intercalation at self-assembled monolayers on gold

A novel acridine derivative (1) connected with a disulfide bond through a l ong methylene spacer has been synthesized, and its interactions with DNA in solutions and at a self-assembled monolayer surface on gold have been stud ied. Spectroscopic and thermal data indicated that 1 intercalated successfu lly to DNA in buffer solutions. The mixed monolayers of 1 and 2, which has a similar molecular structure to that of 1 except for the lack of the acrid ine moiety, on gold substrates were then prepared. When DNA binding propert ies onto these monolayers were examined by means of a quartz crystal microb alance, there was a monolayer composition (mole fraction of 1 in the mixed monolayer, 0.04) at which the most effective binding of DNA took place. The interaction of this DNA-immobilized monolayer with polylysines (D, L) was examined by comparing circular dichroism spectra before and after binding o f polylysines, and such a two-dimensionally immobilized DNA was found to ha ve an ability to bind poly-L-lysine predominately.