Conformational changes of TcaR in response to ssDNA were monitored using CD spectroscopy [27] . As shown in Figure 3 , the CD spectra of TcaR protein were scanned from 200 to 250 nm in the presence of GC33. With increasing concentrations of GC33 ssDNA, the CD spectrum shows a concomitant decrease in the intensity of the negative peak at 222 and 210 nm, revealing the conformational change of TcaR.