Chemistry Reference
In-Depth Information
Figure 12.16 Photographs of solutions of (a) polymer 12, (b) 12
þ
single-stranded DNA,
and (c) 12
þ
double-stranded DNA. (d) Schematic description of the formation of polythio-
phene/single-stranded nucleic acid duplex and polythiophene/hybridized nucleic acid
triplex forms. Reprinted from Ho et al. (2002). Copyright 2002 Wiley-VCH Verlag GmbH
and Co. KGaA.
Conversely, cationic polythiophenes have found applications as chromogenic
sensors for a variety of anions, including nucleic acids. The binding of the imidazo-
lium salt functionalized polymer 12 to single-stranded DNA induces a yellow to red
chromatic transition. Addition of the complementary DNA strand to this solution
regenerates the yellow color. The initial color change is believed to arise from
increased linearization of the polythiophene upon binding to DNA. Addition of the
complementary strand generates duplex DNA, which the polythiophene can also
bind to, but only in a nonlinear fashion (Ho et al. 2002; Fig. 12.16).
Polythiophene binding to a sequence of DNA capable of forming a G-quartet
was demonstrated (Ho and Leclerc 2004). Addition of polythiophene 12 to the
single-stranded DNA resulted in a chromatic transition from yellow to pink/red.
Figure 12.17 Detection of potassium mediated G-quartet formation. Reprinted from Ho and
Leclerc (2004). Copyright 2004 American Chemical Society.
