DNA binding behavior of peptides carrying acridinyl units: First example of effective poly-intercalation

Bis-, tris-, tetrakis-, and pentakis-acridinyl (Acr) peptides 2-5 were synthesized from Fomc-Lys(Acr)-OH and Fmoc-Lys(Boc)-OH with the peptide synthesizer. The molar absorptivity of these peptides saturated with an increase in the number of the acridinyl unit in the peptide, suggesting intramolecular stacking of the acridinyl units. It was found from Scatchard analysis by means of spectrophotometry that all the peptides can bind to double stranded DNA with very high affinity even under high salt conditions (0.4 M NaCl) and the logarithmic binding constant increased in proportion to the number of the acridinyl unit in the peptide. This result suggested effective poly-intercalation of all the acridinyl units into double stranded DNA.