(A) Dependence of the mobility ratios, μ(A-tract)/μ(random), observed for: (•,○), A4T1in(0); (▲,Δ), A4T1in(6); and (♦,⋄), A4T1in(10) as a function of cation concentration in BGEs containing: TBA+ (solid symbols) or Li+ (open symbols). The error bars correspond to the standard deviation of replicate measurements in each BGE. (B) Fractional change of the mobility ratios observed for A4T1in(0) and A4T1in(6) as a function of cation concentration; the transition midpoint occurs at 150 ± 10 mM cation.