Abstract
The surface distribution and emzyme activity of horseradish peroxidase (HRP) selectively immobilized on binary self-assembled monolayers (SAMs) of dithiobis-N-succinimidyl propionate (DTSP) and 1-tetradecanethiol (TDT) have been studied. Scanning tunneling microscopic images of the phase-separated binary SAMs formed by coadsorption on Au (111) substrates show nanometer-scale domains which are 10∼40 nm in diameter and 0.3∼0.7 nm in height. HRP was covalently immobilized on the DTSP domains by immersing the SAM-modified substrate into an HRP solution, followed by washing with a 1 M KCl solution. A tapping-mode atomic force microscopic image of the HRP-immobilized substrate shows holes having a similar diameter to those of the binary SAMs and a depth of 3.6±1.9 nm, indicating the selective immobilization of HRP molecules on the DTSP domains. The enzymatic activity of the immobilized HRP has been confirmed using cyclic voltammetry in the presence of ferrocenecarboxylic acid as an electron-transfer mediator.
