Identifying individual proteins using nanopores and supercomputers
The amount and types of proteins our cells produce tell us important details about our health and how our bodies work. But the methods we have of identifying and quantifying individual proteins are inadequate to the task. Not only is the diversity of proteins unknown, but often, amino acids are changed after synthesis through post-translational modifications.
In recent years, much progress has been made in DNA reading using nanopores — minute membranes large enough to let an unspooled DNA strand through, but just barely. By carefully measuring the ionic voltage of the nanopore as DNA crosses over, biologists have been able to rapidly identify the order of base pairs in the sequence. In fact, this year, nanopores were used to finally sequence the entire human genome — something that was not previously possible with other technologies.
In new research out in Science magazine, researchers from Delft University of Technology in the Netherlands and the University of Illinois at Urbana-Champaign (UIUC) in the U.S. have extended these DNA nanopore successes and provided a proof-of-concept that the same method is possible for single protein identification, characterizing proteins with single-amino-acid resolution and a vanishingly small (10^-6 or 1 in a million) margins of error.
“This nanopore peptide reader provides site-specific information about the peptide’s primary sequence that may find applications in single-molecule protein fingerprinting and variant identification,” the authors wrote.
The workhorses of our cells, proteins are a long peptide strings made of 20 different types of amino acids. The researchers utilized an enzyme called helicase Hel308 that can attach to DNA-peptide hybrids and pull them, in a controlled way, through a biological nanopore known as MspA (mycobacterium smegmatis porin A). They chose the Hel308 DNA helicase because it can pull peptides through the pore in half-nucleotide observable steps, which correspond closely to single amino acids.
Each step through the narrow gate theoretically produces a unique current signal as the amino acid partially blocks an electrical current carried by ions through the nanopore. More

