Selectivity of Natural Isoquinoline Alkaloid Assembler in Programming Poly(da) into Parallel Duplex by Polyvalent Synergy.

Ligand-induced assembly of disordered DNAs attracts much attention due to its potential action in transcription regulation and molecular switches-based sensors. Among natural isoquinoline alkaloids (NIAs), we screened out nitidine (NIT) as polyvalent-binding assembler to program poly(dA) into a parallel duplex assembly at neutral pH. The molecule planarity of NIAs was believed to be a determinant factor in programming the parallel poly(dA) assembly. Poly(dA) with more than six adenines can initiate the synergistic binding of NIT to generate the parallel assembly. It is expected that one A-A pair in duplex can bind one NIT molecule provided that poly(dA) is long enough, suggesting the pivotal role of the polyvalent synergy of NIT in programming the parallel poly(dA) assembly. A gold nanoparticles-based colorimetric method was also developed to screen NIT out of NIAs having the potential to construct the poly(dA) assembly. Our work will inspire more interest in developing polyadenine-based switches and sensors by concentrating NIT within the polyadenine parallel assembly.