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Linear and Circular Dichroism Characterization of Thionine Binding Mode with DNA Polynucleotides

Lookup NU author(s): Dr Eimer TuiteORCiD



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


The binding mode of thionine (3,7-diamino-5-phenothiazinium) with alternating and non-alternating DNA polynucleotides at low binding ratios was conclusively determined using linear and circular dichroism spectroscopies. The binding to [poly(dG-dC)]2 and poly(dG).poly(dC) was purely intercalative and was insensitive to ionic strength. Intercalative binding to [poly(dA-dT)]2 is observed at low ionic strength, but a shift of some dye to an non-intercalative mode is observed as the background salt concentration increases. With poly(dA).poly(dT), intercalative binding is unfavourable, although some dye molecules may intercalate at low ionic strength, and groove binding is strongly promoted with increasing concentration of background salt. However, stacking with bases is observed with single-stranded poly(dA) and with triplex poly(dT)*poly(dA).poly(dT) which suggests that the unusual structure of poly(dA).poly(dT) precludes intercalation. Thionine behaves similarly to the related dye methylene blue, and small differences may be attributed either to the ability of thionine to form H-bonds that stabilize intercalation or to its improved stacking interactions in the basepair pocket on steric grounds.

Publication metadata

Author(s): Tuite EM, Norden B

Publication type: Article

Publication status: Published

Journal: Spectrochimica Acta A

Year: 2018

Volume: 189

Pages: 86-92

Print publication date: 15/01/2018

Online publication date: 01/08/2017

Acceptance date: 01/08/2017

Date deposited: 09/08/2017

ISSN (print): 1386-1425

ISSN (electronic): 1873-3557

Publisher: Elsevier


DOI: 10.1016/j.saa.2017.07.064

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Funder referenceFunder name
Engineering and Physical Sciences Research Council UK (EPSRC GR/S23315/01).