A comparative study of the interactions of cationic hetarenes with quadruplex-dna forming oligonucleotide sequences of the insulin-linked polymorphic region (ILPR)

Abstract

The interactions of the ILPR sequence (ILPR = "insulin-linked polymorphic region") a2 [d(ACAG 4TGTG4ACAG4TGTG4)] with [2.2.2]heptamethinecyanine derivatives 1a-e and with the already established quadruplex ligands coralyne ( 2 ), 3,3′-[2,6-pyridinediylbis(carbonylimino)]bis[1-methylquinolinium] ( 3 ), 4,4′,4″,4⌄-( 21 H ,23 H - porphine-5,10,15,20-tetrayl)tetrakis[1-methylpyridinium] (4), naphtho[2,1-b:3,4-b′:6,5-b″:7,8-b⌄]tetraquinolizinium (5) and thiazole orange (6) were studied. It is demonstrated with absorption, fluorescence and CD spectroscopy that all investigated ligands bind with relatively high affinity to the ILPR-quadruplex DNA a2 (0.2-5.5 × 106 M-1 ) and that in most cases the binding parameters of ligand-ILPR complexes are different from the ones observed with other native quadruplex-forming DNA sequences.