Molecular Formula: C16H18N3NaO4S Molecular Weight: 371.4 CAS No: 69-52-3 Ampicillin (D-(-)-#-Aminobenzylpenicillin sodium salt) is a beta-lactam antibiotic with an amino group attached to the penicillin structure. Ampicillin is effective against Gram positive and some Gram negative bacteria. The presence of amino group helps the antibiotic to penetrate the outer membrane of the Gram negative bacteria. Ampicillin inhibits the enzyme transpeptidase which is required for cell wall synthesis. It binds to the penicillin binding proteins and acts as an analogue of acyl-Dalanyl-D-alanine, acylating the transpeptidase enzyme. Eventually inhibiting the cross-linking of peptidoglycan of the cell wall, the final stage of cell wall formation, and ultimately resulting in the lysis of the cell. Ampicillin is used in cell culture as selective agent. A023 is a sterile filtered solution formulated to contain 10 mg ampicillin per ml.