Construction of Helical J‐Aggregates Self‐Assembled from a Thymidylic Acid Appended Anthracene Dye and DNA as a Template

Abstract

The thymidylic acid appended anthracene dye 2,6-bis[5-(3'-thymidylic acid)pentyloxy]anthracene (1) was synthesized, and the self-assembly of 1 and the binary self-assembly of 1 with a complementary single-stranded 20-meric oligodeoxyadenylic acid (dA(20)) were performed in 0.1 x TE buffer solution (i.e., 1.0 x 10(-3) M Tris-HCl, 1.0 x 10(-4) M ethylenediaminetriacetic acid (EDTA)). The characteristic J-band, small Stokes shift (6 nm), Cotton effect, and helical nanofibers 5.1 nm in diameter are observed in UV/Vis, fluorescence, and circular dichroism (CD) spectroscopies and atomic force microscopy (AFM) measurements for the binary self-assembly of 1 and dA(20) in aqueous solution. These observations revealed that the helical J-aggregates, in which the short-axis transition dipoles of the anthracene moieties are aligned in a head-to-tail fashion, are formed from the binary self-assembly of 1 and dA(20). The UV/Vis absorption and CD band of the anthracene L(a) region were found to be strongly dependent on temperature and showed cooperative changes for the binary self-assembly of 1 and dA(20). The self-assembly of the single-component 1 produced right- and left-handed helical nanofibers with diameters ranging from 4.0 to 10 nm. In contrast, for the binary self-assembly, the UV/Vis and fluorescence spectra showed no J-band and the Stokes shift was at approximately 107 nm for the single-component 1 in aqueous solution. In addition, the binary self-assembly of 1 and noncomplementary single-stranded 20-meric oligothymidylic acid (dT(20)) showed a small J-band and the J-band disappeared at 50 degrees C upon heating. On the basis of these observations, we concluded that thymine-adenine base-pair formation induced supramolecular helical J-aggregates in the binary self-assembly of 1 and dA(20) in aqueous solutions.