Fig. 2. DNA circuits can be used to control membrane fusion. (a) The addition of blocking strands (dashed) to each of the tendrils delays the interaction between them, as tendril zipping requires the prior displacement of the blocking motifs. (b) Time evolution and (c) values recorded at time = 3 hours of the FRET efficiency Emixing for increasing lengths (Ln) of the blocker overhangs. (d) Blocking a single tendril enables the creation of a band-pass filter. The addition of a trigger strand (ub − TL) which preferentially binds the blocking motif b − TL frees the blocked tendril, thus enabling membrane fusion. However, if excess ub − TL is added, it will bind the non-blocked tendril, resulting in an overall reduction of the fusion efficiency. (e) Kinetic and (f) values at time = 3 hours for Emixing at increasing concentrations of ub − TL, demonstrating optimal fusion efficiencies at intermediate values and thus the sought band-pass filtering effect. See Tables S1 and S2 (ESI†) for ssDNA sequences and strands used for each DNA construct.
