Figure 2. Cluster Synthesis.

(A) Absorption spectra of 45 µM S1-S2_12a with varying amounts of Ag⁺. In relation to the oligonucleotide concentration, the relative concentrations are 2 Ag⁺, 4 Ag⁺, 6 Ag⁺, 8 Ag⁺, 10 Ag⁺, and 12 Ag⁺. Up to 8 Ag⁺, absorption increases at 400 nm, which supports population of a specific cluster binding site. Beyond 8Ag⁺, new species with longer wavelength absorbances develop. (B) Absorption spectra of 30 µM S1-S2_12a with 8 Ag⁺ and 4 BH4- acquired with exposure to oxygen (solid line) and to air (dashed line). Oxygen eliminates alternate species and favors the violet absorbing species.