Discrimination of peptides containing a mixture of positively and negatively charged amino acids. (a–l) The profiles of current trace, blockage histogram, scatter plot of R12 (RRR RRR RRR RRR; a-c), RE3 (RRE RRR RRR RRR; d-f), RD3 (RRD RRR RRR RRR; g-i) and RMM (RRR RRR RKE RDR; j-l). (m) Full current trace before and after the addition of RD3 (Left) and RMM (Right). The blockage histogram is fitted by single Gaussian distribution. Buffer: 0.15 M KCl, 5 mM HEPES, pH7.4. Voltage: −50 mV.