The interfacial and electrochemical behavior of 6-thioguanosine-6-thioguanine riboside (6TGR)-on a hanging mercury drop electrode was studied with ac and cyclic voltarnmetry in a solution of 0.1 M Na2SO4 and 0.01 M sodium acetate buffer at pH 4.3. A self-assembled monolayer (SAM) of chemisorbed 6TGR molecules formed under determined adsorption conditions was characterized. A low-density monolayer of chemisorbed 6TGR molecules and a condensed monolayer of physisorbed ones, which are successively formed by reduction of the SAM, were also studied. (c) 2006 Elsevier Inc. All rights reserved.