Ampicillin sodium salt from Xenometrix, supplied as a 200 mg/mL stock solution in sterile water, for selective maintenance of the pKM101 plasmid in Salmonella typhimurium tester strains TA98 and TA100 during overnight culture prior to Ames assay use.
The pKM101 plasmid confers ampicillin resistance to TA98 and TA100 and enhances the SOS error-prone repair response, increasing the sensitivity of these strains to frameshift and base substitution mutagens respectively.
Selective pressure with ampicillin during culture is required to prevent plasmid loss — cultures grown without ampicillin selection will accumulate plasmid-cured derivatives that give reduced spontaneous and induced reversion counts, compromising assay sensitivity and OECD TG 471 acceptance criteria.
Xenometrix ampicillin sodium salt is supplied as a ready-to-use 200 mg/mL solution (sterile, 0.22 μm filtered), genotoxicity-tested at standard working concentration in the Ames MPF assay system to confirm absence of mutagenic activity. Used at a final working concentration of 25 μg/mL in liquid LB culture medium.
Compatible with MacroAmes1 plate incorporation, Ames MPF 384-well, and Ames II 48-well assay formats. For Research Use Only. Not for use in diagnostic procedures.