Hydrogen bonding interaction between aminopurinethiol-monolayers and oligonucleotides by QCM and XPS measurements

Selective detection of oligonucleotides on the gold surface modified with a monomolecular layer of aminopurinethiols was demonstrated. A quartz crystal microbalance (QCM) measurement is suitable to detect interactions between the complementary nucleic acid base in solution and the aminopurinethiolate monolayer on gold. 6-Amino-8-purinethiol monolayer had specific interactions with polythymidylic acid (Poly(T)) in solution, whereas it had very weak interaction with polycytidylic acid (Poly(C)). Poly(T) (thymine species) in solution created hydrogen bonding interaction with the 6-amino-8-purinethiol monolayer, because 6-amino-8-purinethiol showed adenine-like conformation on the gold surface. In the case of 2-amino-6-purinethiol monolayer, niether Poly(T) nor Poly(C) were recognized on the substrate. Since 2-amino-6-purinethiol monolayer adsorbed on the gold surface in the parallel direction of the long axis of molecules, the recognition sites of the molecules were blocked. Hydrogen bonding interactions of the 6-amino-8-prinethiol monolayer-base species were identified by X-ray photoelectron spectroscopic (XPS) measurements.