Ampicillin is a semi-synthetic derivative of penicillin used to select for ampicillin resistance in mutated and transformed cells. 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.Soluble 1 part in 150 parts H2O as well as in diluted acids and bases. Insoluble in alcohol. Ampicillin is a semi-synthetic derivative of penicillin used to select for ampicillin resistance in mutated and transformed cells. 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.Soluble 1 part in 150 parts H2O as well as in diluted acids and bases. Insoluble in alcohol.