Figure 2.

Mono- and divalent cations are detrimental to the peptide’s annealing activity. FRET-based annealing assays with 21R RNA were carried out in the absence or presence of 300 nM Tat(44–61), and at different MgCl₂ and NaCl concentrations. The reaction constants (k_obs) of the reaction in the presence of peptide were divided by the k_obs of the ‘RNA only’ reaction, yielding k_acc. Acceleration of annealing by the peptide was strongly impaired at MgCl₂ concentrations above 2 mM and NaCl concentrations >60 mM.