DNA binding of a proflavine derivative bearing a platinum hanging residue |
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Authors: | Biagini Silvia Bianchi Antonio Biver Tarita Boggioni Alessia Nikolayenko Igor V Secco Fernando Venturini Marcella |
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Institution: | a Dipartimento di Chimica “Ugo Schiff”, Università di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italyb Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa, Italyc School of Chemistry, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, Pietermaritzburg, South Africa |
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Abstract: | New platinum(II) complex of 3,6-diamine-9-6,6-bis(2-aminohethyl)-1,6-diaminohexyl]acridine, AzaPt, has been synthesised and characterised. Behaviour of AzaPt in solution (protonation and possible self-aggregation phenomena) has been investigated by spectral methods (absorbance and fluorescence) at I = 0.1 M and 25 °C, and the equilibrium parameters of binding to calf thymus DNA have been established. Two different modes of DNA binding by the complex were detected, which depend on the polymer to dye molar ratio (P/D). At relatively low P/D values the mode was interpreted as binding by the polyamine residue external to the base pairs, while at high P/D values the binding corresponds to intercalation of the proflavine residue. Such interpretation is supported by the observed salt effect on binding and the temperature variation of the binding constants, which allowed estimating the ΔH and ΔS values contributions. Spectrophotometric analysis of the long time range binding revealed that AzaPt is involved in a slow reaction, interpreted as an attack by the platinum ion on the nucleobases. The time constant for such interaction was calculated and found to be the same order of magnitude as for processes responsible for the action of anti-tumour drugs that do covalently bind to polynucleotides. |
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Keywords: | DNA Proflavine derivatives Platinum complex Covalent binding Intercalation External binding |
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