Clear Discrimination of Single-Molecule of a Single-Stranded DNA Homopolymers and Hetero-Homopolymers Through a New Mutant of Mycobacterium smegmatis Porin A, MspA

Recent advances in biological nanopores for nanopore sequencing, sensing and comparison of functional variations in MspA mutants

“…M3MspA shows transient or sometimes permanent (needs voltage polarity) spontaneous blockades beyond ∼± 60 mV. 102 …”

“…This imbalance of ions was appeared to change the membrane's polarity but keep the pore functional up to ∼± 50 mV. Eventually, further increase in applied voltage ≥± 60 mV was found to halt the further flow of ions owing to the accumulation of Cl − ions at the trans side 102 and K + would also hang around trans to perpetuate the overall electrical neutrality of the system. 103 Hence, M3MspA does not exhibit anion-selectivity at higher voltages.…”

“…M3MspA shows transient or sometimes permanent (needs voltage polarity) spontaneous blockades beyond $AE 60 mV. 102 If we compare M3MspA with Wt MspA, we would be able to understand the key role of charge distribution in nanopore sensing. Since, the gating potential of both Wt-MspA and M3MspA is comparable $AE 60 mV, but it is the surface charge distribution inside the nanopore that decides the fate of ssDNA entry.…”

“…Apart from statistical analysis, the difference is quite apparent by just looking at the current trace, another key step towards nanopore DNA sequencing. 102 Recently, MspA has been used in the detection of DNA lesions, 148 identication and discrimination of small analytes (metal ions) up to $10 pA current amplitude. 149 Besides, direct sequencing of xeno-nucleic acid (FANA), 78 direct sequencing of naturally occurring microRNA for the rst time and scrutiny of epigenetic modications in microRNA 150 were made possible by employing Nanopore-Induced Phase-Shi Sequencing (NIPSS).…”

“… 101 This mutant was found to reduce the speed of ssDNA ∼10–30 folds in real-time experiments. Recently, Bhatti, et al , explored this new mutant of MspA, termed as M3MspA through detection of ssDNA homopolymers and hetero–homopolymers with well-resolved signature events up to some milliseconds dwell time and corresponding signature events, 102 as shown in Fig. 5(C) .…”