[Nuclease S1 for DNA molecular weight determination in multiplasmid Escherichia coli strains]

DNase treatment used to convert supercoiled DNAs to the open form is suitable for molecular weight determination by electron microscopy or agarose gel electrophoresis. The comparative experiments showed that S1-nuclease has advantages over DNase for molecular weight determination in preparations containing many species of plasmids of significantly differing sizes, isolated from multiplasmid E. coli strains.