Duplex structure formation between oligo(dA)'s and oligo(dT)'s generated by thymine-specific interaction with netropsin.

The formation of oligomeric duplex molecules in the presence of the antibiotic netropsin in the series p(dA)n-p(dT)n is demonstrated using low-temperature CD measurements. Addition of Netropsin to mixtures of oligomers generates the same type of CD spectra as observed for poly(dA)-poly(dT) and maintains the duplex structure at temperatures at which base pairing of free oligomers is thermodynamically unstable. The shortest chain length forming a netropsin complex by thymine-specific interaction with the oligopeptide is represented by p(dA)4-p(dt)4. Studies with sequence isomers show that adjacent thymine residues strongly favour the complex formation with the oligopeptide.