Ampicillin sodium salt is a semi-synthetic derivative of penicillin used to select for ampicillin resistance in mutated and transformed cells. Ampicillin is a ß-lactam antibiotic that inhibits bacterial cell wall synthesis by inactivating transpeptidases on the inner surface of the bacterial cell membrane. The antimicrobial spectrum includes gram-positive and gram-negative bacteria.
Recommended for antibacterial use in cell culture media at 100 µg/ml and in ampicillin-resistance studies at 20 - 125 μg/ml.
Solubility in water: 1 part in 2 parts H₂O. A stock solution should not be autoclaved but sterilized through filtration and stored frozen where it will be stable for months. Stability of ampicillin in solution is a function of pH, temperature and the identity of the buffer. Optimal storage conditions are 2 - 8 °C and pH 3.8 - 5 where its activity is retained at >90 % for a week.

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