Conventional nanopore sequencing technology relies on electrical signals (ionic current). Although it has achieved remarkable success on DNA sequencing, one can imagine how challenging it could be to to realize similar achievements for proteins. The fundamental units that construct the primary structure of a protein is the amino acids, the size of which are only one tenth of nucleotide acids. Moreover, there are only 4 nucleotide acids while there are 20 proteomic amino acids. Even though some studies have already revealed certain preliminary success with conventional nanopore sequencing technology for proteins, we are already next to inevitable limits. Therefore, the involvement of optical signal, which is promising to possess unique specificity to individual amino acids, can be a milestone in the field.

Figure 1. SMRT fluorescence DNA sequencing technology from PacBio received $1.2 billion merger agreement from Illumina in 2018.