Direct observation of native and unfolded glucose oxidase structures by scanning tunnelling microscopy

Abstract

Native and unfolded glucose oxidase (GOD) structures have been directly observed with scanning tunnelling microscopy (STM) for the first time. STM images show an opening butterfly-shaped pattern for the native GOD. When GOD molecules are extended on anodized, highly ordered pyrolytic graphite (HOPG), a helical structure composed of double-stranded chains was obtained under STM. These results are in good agreement with previous description of the GOD molecular structure. A simple model of the unfolding process for GOD molecules was proposed to explain these observations. Electrochemical evidence was provided to support the results obtained with STM and the proposed model.