Molecular Weight: 371.39 Molecular Formula: C16H18N3NaO4S CAS No: 69-52-3 Synonym: D(-) α-Aminobenzylpenicillin.Na Ampicillin belongs to the penicillin group of b-lactam antibiotics. It differs from penicillin by the presence of an amino group. It inhibits bacterial cell-wall synthesis (peptidoglycan cross-linking) by inactivating transpeptidases on the inner surface of the bacterial cell membrane. This broad spectrum antibiotic is effective against Gram-positive and Gram-negative bacteria. In cell culture, ampicillin is used as an antibacterial agent and as a selection agent to select transformed bacteria. Many common vectors carry genes encoding resistance to ampicillin and are identified by the ability of the host bacteria to grow in the presence of this antibiotic. Resistance is mediated by cleavage of β-lactam ring of ampicillin by β-lactamase. In cell culture applications ampicillin sodium salt is generally used at a concentration of 100mg/L for antibacterial use. In ampicillin resistance studies, it is used at a concentration of 20-125µg/ml. A022 is sterile filtered solution formulated to contain 10mg ampicillin per ml