title: Search for the optimal linker in tandem hairpin polyamides.
abstract: In order to target specific DNA sequences >or=10 base pairs in size by minor groove binding ligands, a search for the optimal linker in dimers of hairpin polyamides was initiated. Two series of tandem polyamides ImPyIm-(R)[ImPyIm-(R)(H2N)gamma-PyPyPy-L](HN)gamma-PyPyPy-beta-Dp (1a-e), where L represents a series of 4-8 carbon long aliphatic amino acid linkers, and ImPyIm-(R)[ImPyIm-(R)(H2N)gamma-PyPyPyIm-L](HN)gamma-PyPyPy-beta-Dp (2a-e), where L represents a series of 2-6 carbon long aliphatic amino acid linkers, were synthesized and characterized by quantitative DNase I footprinting. beta, gamma and Dp represents beta-alanine, gamma-aminobutyric acid, and 3-(dimethylamino)propylamine, respectively. It was found that the five-carbon 5-aminovaleric acid (delta), is suitable to span one base-pair (bp) of DNA when incorporated into a tandem polyamide. ImPyIm-(R)[ImPyIm-(R)(H2N)gamma-PyPyPy-delta](HN)gamma-PyPyPy-beta-Dp (1b) binds the 10 bp binding-site 5'-AGTGAAGTGA-3' with equilibrium association constant K(a)=3.2 x 10(10) M(-1) and ImPyIm-(R)[ImPyIm-(R)(H2N)gamma-PyPyPyIm-delta](HN)gamma-PyPyPy-beta-Dp (2d) binds the 11 bp binding-site 5'-AGTGATAGTGA-3' with K(a)=9.7 x 10(9) M(-1). Tandem 1b also bind the 11 bp site but with lower affinity affording a 15-fold specificity for the shorter binding site. Replacing a methylene group in the amino acid linker with an oxygen atom to form tandem polyamide ImPyIm-(R)[ImPyIm-(R)(H2N)gamma-PyPyPy-E](HN)gamma-PyPyPy-beta-Dp (4) where E represents the ether linker, resulted in that an 80-fold specificity for the 10 bp binding site over the 11 bp site.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Inger
authors.initials: I
authors.lastname: Kers
authors.forename: Peter B
authors.initials: PB
authors.lastname: Dervan
mesh_terms: D021542:Amino Acids, Neutral; D001483:Base Sequence; D001665:Binding Sites; D003432:Cross-Linking Reagents / Q000138:chemical synthesis* / Q000737:chemistry; D004247:DNA / Q000378:metabolism*; D018983:DNA Footprinting; D007093:Imidazoles; D009757:Nylons / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics; D010957:Plasmids / Q000378:metabolism; D017433:Protein Structure, Secondary; D017186:Titrimetry
chemical_list: D021542:Amino Acids, Neutral; D003432:Cross-Linking Reagents; D007093:Imidazoles; D009757:Nylons; C013809:5-aminovaleric acid; D004247:DNA