Kelvin Physics of Protein Layers Printed in Microarray Format

The electrical properties of protein molecules adsorbed onto a gold substrate are studied using a scanning Kelvin nanoprobe in a microarray format. The results demonstrate that this instrument can provide information on protein orientation, polarization, dimension and molecular interaction. Changes in the work function for absorbed neutravidin, bovine serum albumin and a complex of the two proteins on gold were measured. Also, the analogous changes with respect to the surface concentration of neutravidin were examined and the results indicate a saturation of work function values at a specific surface population. The results are discussed in terms of the Schottky model modified for protein semiconductive properties, such as depletion width, charge carrier density, band bending and permittivity.