On the selective detection of duplex deoxyribonucleic acids by 2,1,3-benzothiadiazole fluorophores

• Published in: Molecular bioSystems 2010-01, Vol.6 (6), p.967-975
• Main Authors: Neto, Brenno A D, Lapis, Alexandre A M, Mancilha, Fabiana S, Batista, Jr, Eraldo L, Netz, Paulo A, Rominger, Frank, Basso, Luiz A, Santos, Diógenes S, Dupont, Jaïrton
• Format: Article
• Language: English
• Subjects: Actins - chemistry; Actins - genetics; Binding Sites; DNA - chemistry; DNA - genetics; Fluorescent Dyes - chemistry; Humans; Kinetics; Models, Molecular; Molecular Structure; Nucleic Acid Conformation; Polymerase Chain Reaction; Reproducibility of Results; Spectrometry, Fluorescence - methods; Thiadiazoles - chemistry
• ISSN: 1742-206X; 1742-2051
• DOI: 10.1039/b919155k

A series of 4,7-pi-extended 2,1,3-benzothiadiazoles (BTDs) with different molecular architectures, in particular, the organic dyes based on the 4-(arylethynyl)-7-(4-methoxy)-2,1,3-benzothiazole skeleton, can be used at very low concentrations (down to 10 microM) to detect DNA at 1 ppm in phosphate buffer solutions. Upon binding to DNA, these dyes showed an exponential increase in the fluorescence intensity (hyperchromic effect) and a red shift (1-5 nm) in the long-wavelength emission maxima. Pre-steady state kinetic experiments (stopped-flow) demonstrated the fast dye interaction with the biomacromolecules of DNA with an increase in fluorescence, especially with non-symmetrical BTDs containing an ethynyl spacer. An intercalation model could be proposed based on the photophysical properties, X-ray analysis, and theoretical calculations (ab initio). In this model, the intercalation occurs on the ethynyl side of the BTD, and as a consequence, the PhOMe portion is free to perform the ICT process with the BTD core and stabilizes it in the excited state.