Crystals of the the MqsA–dsDNA complex contain both DNA and protein. (a) Crystals of the MqsA–dsDNA-2 complex. (b) Crystals from (a) were washed sequentially in two drops of fresh mother liquor and then one drop of water and were finally transferred to 5 µl SDS–PAGE loading buffer. The sample was heated, run on an SDS–PAGE gel and the gel was stained in TAE buffer supplemented with ethidium bromide to stain for DNA. Lane 1, washed crystals; lane 2, the MqsA–dsDNA-2 protein–DNA complex sample used for crystallization trials; lane 3, dsDNA-2 alone. (c) Crystals treated identically as in (b) except that the gel was transferred to Coomassie stain in order to stain for protein. Lane 1, washed crystals; lane 2, MqsA–dsDNA-2 protein–DNA complex sample used for crystallization trials; lane 3, MqsA protein alone.