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. Author manuscript; available in PMC: 2013 Dec 17.
Published in final edited form as: J Am Chem Soc. 2012 Sep 10;134(37):10.1021/ja305720w. doi: 10.1021/ja305720w

Figure 3.

Figure 3

In order to simplify switch synthesis (i.e. to avoid the synthesis of a tetra-modified DNA probe), we have designed a modular architecture in which the two antigens are attached via the hybridization of two copies of a 17-base DNA strand (yellow strands) each modified only via the addition of the antigen (here the hapten digoxigenin, Dig). The modular stem-loop scaffold contains a frame inversion near one end to allow for symmetrical labeling of two copies of the same modified recognition strand, reducing fabrication cost and complexity (Figure S1C). The gain and affinity of this modular switch compare closely to those of our non-modular electrochemical sensor (Fig. 2b). As is its specificity: the modular sensor is, as shown, insensitive to the addition of 3 μM of human-mixed antibodies (dashed line). The titrations shown in this figure represent the average of measurements conducted with three independently fabricated sensors, with error bars reflecting standard deviation.