Electrical scanning probe microscopy of biomolecules on surfaces and at interfaces

Abstract

Electrostatic properties play an important role in the interactions and functions of biomolecules. Electrical scanning probe microscopy (SPM) is a unique tool for the study individual biomolecules. Variations of the electrostatic probe technique such as Kelvin probe force microscopy (KFM), scanning surface potential microscopy (SSPM), and scanning Maxwell stress microscopy (SMM), have been developed. These instruments obtain similar electrostatic images but with a different theoretical basis and electronic instrumentation. The experimental technique and substrate preparation are similar to those of other kinds of SPM but with more stringent measurement requirements, which are needed to avoid static charges in air and on the substrate. Detailed experimental techniques and specific examples using Photosystem I (PSI) reaction centers, DNA, protein microarrays on surfaces, and PSI at the air-liquid interface are discussed. The electrical SPM techniques provide a method to study biomolecules in a label-free fashion with nanometer resolution. In the future, with improved resolution, it will be possible to image the charge distribution and polarization of individual biomolecular reaction sites, which will provide insights into biological function at the molecular level. © 2007 Springer Science+Business Media, LLC.