Direct Quantification of Damaged Nucleotides in Oligonucleotides Using an Aerolysin Single Molecule Interface

DNA lesions such as metholcytosine­(^mC), 8-OXO-guanine (^OG), inosine (I), etc. could cause genetic diseases. Identification of the varieties of lesion bases are usually beyond the capability of conventional DNA sequencing which is mainly designed to discriminate four bases only. Therefore, lesion detection remains a challenge due to massive varieties and less distinguishable readouts for structural variations at the molecular level. Moreover, standard amplification and labeling hardly work in DNA lesion detection. Herein, we designed a single molecule interface from the mutant aerolysin (K238Q), whose sensing region shows high compatibility to capture and then directly convert a minor lesion into distinguishable electrochemical readouts. Compared with previous single molecule sensing interfaces, the temporal resolution of the K238Q aerolysin nanopore is enhanced by two orders, which has the best sensing performance in all reported aerolysin nanopores. In this work, the novel K238Q could discriminate directly at least three types of lesions (^mC, ^OG, I) without labeling and quantify modification sites under the mixed heterocomposition conditions of the oligonucleotide. Such a nanopore electrochemistry approach could be further applied to diagnose genetic diseases at high sensitivity.