title: The effect of the 4-amino functionality on the photophysical and DNA binding properties of alkyl-pyridinium derived 1,8-naphthalimides.
abstract: The synthesis and characterisation of two cationic pyridinium based 4-amino-1,8-naphthalimide derivatives (2 and 3) are described and compared to those of compound 1. The photophysical properties of 2 and 3 are shown to vary greatly with the solvent polarity and H-bonding ability. The dimethylamino substitution in 3 results in a weak quantum yield of fluorescence emission due to faster non-radiative deactivation of the excited singlet state than that seen for 2. As with 1, the fluorescence of 2 was found to be enhanced in its 1 : 1 complex with 5'-adenosine-monophosphate (5'-AMP) while it was partially quenched in its complex with 5'-guanosine-monophosphate (5'-GMP). In contrast, the fluorescence of 3 was enhanced ('switched on') in the presence of both adenine and guanine rich sequences. Linear and circular dichroism studies showed that each of 1, 2 and 3 binds to double-stranded DNA by intercalation. However, 2 and 3 do not show the preference for AT-rich DNA observed for 1. Comparative fluorescence studies with double stranded DNA show that the emission of was 16 times enhanced in its DNA bound form, suggesting potential use of this structure as a spectroscopic probe for studying nucleic acid structure.
authors.affiliation: School of Chemistry, Centre of Synthesis and Chemical Biology, and Trinity Biomedical Science Institute, University of Dublin, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Swagata
authors.initials: S
authors.lastname: Banerjee
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Kitchen
authors.forename: Thorfinnur
authors.initials: T
authors.lastname: Gunnlaugsson
authors.forename: John M
authors.initials: JM
authors.lastname: Kelly
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D053644:Naphthalimides / Q000138:chemical synthesis / Q000737:chemistry*; D055668:Photochemical Processes; D011726:Pyridinium Compounds / Q000737:chemistry*
chemical_list: D053644:Naphthalimides; D011726:Pyridinium Compounds; D004247:DNA