Side chain: General Structure Of Penicillin Ampicillin B Cloxacillin CH Phenoxymethyl- Ticarcillin H B-lactam drugs β actamase(penicillinase) Peptide- glycan matrⅸx Penicillin-binding protein Rigid cell wall of Gram-positive bacteria 口B- lactam drugs Lipopolysacch aride layer Th in matrⅸ Penicillin-bindin g protein Gram-negative bacterial wall KMc 1717