Fig. 1.

Idealized schematic of d(T_m-A_n) oligos in solution (hairpins) and after adsorption on gold (L-shape model). (Left) The UV absorbance at 260 nm for d(T₂₅-A_n) hairpins was measured in 1 M CaCl₂-TE buffer at 1°C per minute of heating (red lines) or cooling (black lines). (Right) In the L-shape model, the d(A) blocks (red) adsorb flat on the gold surface and the d(T) blocks (green) extend away from the surface. The surface density of dA nucleotides on gold is approximately independent of the d(A) length. Increasing the length of the d(A) block therefore decreases the grafting density of the oligos. Increasing the length of the d(T) block increases the polyelectrolyte effects in the brush layer.