Native MS showing reduced stoichiometry of EthR with the shorter DNA37 and DNA36 sequences. MS spectra of a) EthR and DNA37 in a 6:1 ratio, showing the formation of mainly EthR4-DNA37 complex, some EthR2-DNA37 complex, and a trace of EthR3-DNA37 complex, and b) EthR and DNA36 in a 6:1 ratio, showing formation of mainly EthR2-DNA36 complex and some EthR4-DNA36 complex.