Folded and Unfolded Single Proteins Analyzed by Their Solid State Nanopore Translocation Dynamics
Jiali Li, David S. Talaga
Abstract The translocation of biological polymers through individual nanometer-scale pores is vital to cellular function and has great potential for technological applications in protein or nucleic acid measurements and identification. Research into this area has been focussed on characterizing the physics of translocation through voltage-biased nanopores and exploiting it to identify or sequence biological polymers. Here we show that the DNA-calibrated translocation signals of ß-lactoglobulin and histidine-containing phosphocarrier protein match quantitatively with that predicted by a simple sum of the partial volumes of the amino acids present in the pore when it stalls due to its primary charge. Our analysis suggests that the majority of the protein molecules were linear or looped during translocation suggesting that physiologically relevant potentials can unfold proteins. Our results suggest that the nanopore translocation physics and signals are sensitive enough to distinguish between proteins based on the excluded volume of a local segment of the polypeptide chain and the primary sequence of charges.