title: Single-molecule protein unfolding in solid state nanopores.
abstract: We use single silicon nitride nanopores to study folded, partially folded, and unfolded single proteins by measuring their excluded volumes. The DNA-calibrated translocation signals of beta-lactoglobulin and histidine-containing phosphocarrier protein match quantitatively with that predicted by a simple sum of the partial volumes of the amino acids in the polypeptide segment inside the pore when translocation stalls due to the primary charge sequence. Our analysis suggests that the majority of the protein molecules were linear or looped during translocation and that the electrical forces present under physiologically relevant potentials can unfold proteins. Our results show that the nanopore translocation signals are sensitive enough to distinguish the folding state of a protein and distinguish between proteins based on the excluded volume of a local segment of the polypeptide chain that transiently stalls in the nanopore due to the primary sequence of charges.
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA. talaga@rutgers.edu
authors.forename: David S
authors.initials: DS
authors.lastname: Talaga
authors.forename: Jiali
authors.initials: J
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D002417:Cattle; D004247:DNA / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007782:Lactoglobulins / Q000737:chemistry*; D008969:Molecular Sequence Data; D049329:Nanostructures / Q000737:chemistry*; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000737:chemistry*; D017510:Protein Folding; D017655:Silicon Compounds / Q000737:chemistry*; D014508:Urea / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D007782:Lactoglobulins; D017655:Silicon Compounds; D014508:Urea; D004247:DNA; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C030182:phosphocarrier protein HPr; C032734:silicon nitride