Sensing Single Protein Molecules with Solid-State Nanopores - Nanopores: Sensing and Fundamental Biological Interactions - page 129

Chapter 6
Sensing Single Protein Molecules
with Solid-State Nanopores
Bradley Ledden, Daniel Fologea, David S. Talaga, and Jiali Li
Abstract This chapter is focused on the development of experiments and theory of
using solid-state nanopores for sensing single protein molecules in their native and
unfolded states. Proteins serve diverse roles such as transport carriers, catalysts,
molecular motors, cellular structural support, and others that make life possible.
Because of these widely differing roles, proteins have an enormously diverse set of
shapes, sizes, and charge structures as compared to polynucleic acids. Solid-state
nanopores are particularly suitable for characterizing single proteinmolecules because
they can be fabricated with adjustable dimensions and are stable under conditions that
denature proteins. This chapter describes the nanopore experimental setup, signal
recording, data analysis, and basic principles related to the experiments and the theory
connecting the electrical signal with the properties of proteins. Examples of experi-
mental results illustrate the ability of solid-state nanopores to differentiate proteins in
their folded and unfolded states. Native-state protein nanopore translocation follows
biased one-dimensional diffusion of charged particles that is sensitive to size and
electrical charge. Due to the heterogeneous charge sequence of polypeptides, unfolded
proteins obey a coupled electrophoretic and thermally activated process that is
sequence specific. The chapter concludes with a discussion of future directions and
open challenges for single protein characterization using solid-state nanopores.
Keywords Protein capture • Protein shape during translocation • Protein's Charge
variation with pH • Parameters affecting translocation