Figure 2.

Steady-state absorption and circular dichroism of squaraine monomers and dimers tethered to HJ. The spectra were recorded in 1× TBE, 15 mM MgCl₂ at room temperature. The concentrations of squaraine–DNA constructs were 1.5 μM. (a) Absorption profiles of single bis(chloroindolenine)squaraine covalently attached to strand A of HJ (i.e., monomers) do not show dependence on the length of the linker. (b) CD spectra of achiral bis(chloroindolenine)squaraine covalently attached to strand A of HJ (i.e., monomers) do not exhibit an induced CD signal. (c) Absorption profiles of dimers with equal linkers are blue-shifted relative to the monomers, indicative of the presence of excitonic coupling. (d) CD profiles of dimers with equal linkers show exciton-coupled CD signals with low amplitude. (e,g,i) Absorption profiles of dimers with unequal linkers are blue-shifted relative to the monomers, indicative of the presence of excitonic coupling. (f) CD profile of dimers B^medC^long and B^longC^med show exciton-coupled CD signal with low magnitude. (h,j) CD profiles of dimer pairs B^longC^short/B^shortC^long and B^medC^short/B^shortC^med show high-magnitude exciton-coupled CD signals of opposite handedness.