Proton NMR study of the binding of bis(acridines) to d(AT)5.cntdot.d(AT)5. 1. Mode of binding

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Abstract
1H NMR was used to investigate the mode of binding to d(AT)5-d(AT)5 of a series of bis(acridine) derivatives connected by different types of linker chains. The length and character (ionic, aliphatic, rigids and flexible) of the linker chains have a profound effect on the binding of these derivatives to the DNA. Bis(acridine) derivatives with linker chains shorter than 9 .ANG. monointercalate under the conditions used in the NMR study, whereas those bis(acridines) with chains of 9.8 .ANG. or longer bisintercalate. There was no evidence for the violation of the so-called neighbor exclusion principle. Although all of the bis(acridines) contain the same chromophores, their NMR spectra clearly demonstrate that they form complexes with d(AT)5-(AT)5 which have different structures. This emphasizes the important effect that the linker chain has on the structure of the intercalation complex.