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Article

DNA-Templated Formation of a Helical Cyanine Dye J-Aggregate

Miaomiao Wang, Gloria L. Silva,^† and Bruce A. Armitage*

Contribution from the Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213-3890

J. Am. Chem. Soc., 2000, 122 (41), pp 9977–9986

DOI: 10.1021/ja002184n

Publication Date (Web): September 28, 2000

†

Permanent address: Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.

To whom correspondence should be addressed: army@ cyrus.andrew.cmu.edu.

Abstract

UV−vis and CD spectroscopy reveal that a tricationic cyanine dye spontaneously assembles into a helical J-aggregate in the presence of a double-helical DNA template. The stability of the J-aggregate is strongly dependent on the dye concentration and DNA length in a manner that reflects a high degree of cooperativity in formation of the aggregate. Slight changes in environmental conditions such as temperature and ionic strength result in interconversion between J- and H-aggregates. The aggregate likely consists of dimeric units assembled in an offset, face-to-face orientation within the minor groove of the DNA template, analogous to an earlier report of H-aggregation on DNA by a related cyanine dye. A model is proposed that relates the two aggregate structures by translation of one monomer from a given dimer along the floor of the minor groove. This translation requires adjacent monomers to also translate, leading to the observed cooperativity.

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