Table 1. Self-aggregation and DNA condensation of E.coli Dps and its deletion mutants DpsΔ8 and DpsΔ18 as a function of pH assessed in gel retardation and AFM experiments.

pH	Dps		DpsΔ8		DpsΔ18
	Self-aggregationa	DNA condensationb	Self-aggregationa	DNA condensationb	Self-aggregationa	DNA condensationb
6.3	Yes	Yes	Yes	Yes	No	Noc
7.3	Yes	Yes	Yes	Yes	No	No
7.7	Yes	Yes	No	Noc	No	No
8.2	Yes	Yes	No	No	No	No
8.7	No	No	No	No	No	No

^aDps self-aggregation is defined as the capacity of dodecamers to form oligomers of variable size. The oligomers reach dimensions up to hundreds of nanometers as indicated by AFM imaging. They remain confined to the electrophoresis well and no migration is observed.

^bDps-driven DNA condensation is defined as the capacity of the protein to form large Dps–DNA complexes containing many Dps molecules and one or more DNA plasmids. In the AFM images, the complexes appear as large protein aggregates surrounded by DNA loops from the condensed plasmids. The Dps–DNA condensates remain confined into the well during electrophoresis.

^cDNA condensation as defined above is not observed under these specific conditions. However, the AFM images show that single Dps dodecamers bind to DNA as ‘beads on a string’. Migration of these small Dps–DNA complexes in agarose gels is retarded relative to free plasmid DNA.