Ampicillin is used to select for mutated or transformed cells that are ampicillin resistant (Amp or AmpR) [i.e., carry the ß-lactamase (bla) gene]. Typically, low-copy-number plasmids require less ampicillin than high-copy-number plasmids.
In some situations (e.g., if extracellular lactamase secretion permits growth of non-transformed bacteria), you may consider replacing ampicillin with carbenicillin, a semi-synthetic ampicillin analog that is often more stable than ampicillin.
100 µg/mL ampicillin is the most commonly used concentration.
Contains 100% ampicillin, sodium salt, USP Grade.