Escherichia coli strain B is most widely studied DNA after k-12. The genomes of E coli strain B and k-12 show differences in the IS sequence elements. Strain B have B-islands and express O-specific side-chain LPS. The product is unsheared genomic DNA.

50% GC; T_m = 90.5 °C

The DNAs are particularly useful for genomic analysis, including PCR, library construction in bacteriophage λ, and in heterologous pre-hybridization and hybridization protocols.
Deoxyribonucleic acid sodium salt from Escherichia coli strain B has been used for:

• PCR reactions of genomic DNA of Gardnerella vaginalis
• nick translation and radiolabeling of dNTP
• generating standard curve for 16S rDNA quantification
• transfecting neutrophils
• testing the extraction methods

One unit will yield an A₂₆₀ of 1.0 in 1.0 ml of 1 mM Tris-HCl, pH 7.5, with 1 mM NaCl and 1 mM EDTA (1 cm light path).

Purified by anion exchange chromatography, dialyzed against a solution of 1 mM sodium chloride, 1 mM EDTA and 1 mM Trizma HCl, pH 7.5 and lyophilized at a concentration of approx. 2 units per mL. Approx. 20 A₂₆₀ units per mg DNA. % GC is the percentage of G/C base pairs. T_m is the temperature at the midpoint of the thermal denaturation profile.

Analyzed by gel electrophoresis and visualization after ethidium bromide staining, with single predominant band of 45 kB or greater.

DNA in solution will reanneal on standing at room temperature so it is recommended to boil the solution for 10 minutes and then cool on ice for at least 5 minutes prior to use.