Beta-lactam ring

A four-membered cyclic amide ring in which a carbonyl carbon bonds to a ring nitrogen. Its strained structure enables beta-lactam antibiotics to inhibit bacterial cell-wall synthesis.

Penicillin-binding proteins: Bacterial enzymes that build and remodel peptidoglycan in the cell wall. The ring acylates their active-site serine, blocking cell-wall cross-linking.
Lactam: A cyclic amide whose nitrogen is part of the ring. A beta-lactam is a lactam with its nitrogen adjacent to the carbonyl carbon.
Alexander Fleming: Scottish bacteriologist who discovered penicillin’s antibacterial effect in 1928. His discovery brought a natural beta-lactam antibiotic to scientific attention.
Carbapenem: A broad-spectrum beta-lactam antibiotic class with a carbon atom replacing sulfur in the fused ring. Carbapenems retain the reactive ring while resisting many beta-lactamases.
Antimicrobial resistance: The ability of microorganisms to survive exposure to drugs that once inhibited or killed them. Resistance limits the effectiveness of antibiotics built around this ring.
Peptidoglycan: A mesh-like polymer of sugars and short peptides that gives bacterial cell walls strength. Blocking its cross-linking weakens the wall and can cause bacterial lysis.
Amide: A functional group in which a carbonyl carbon bonds to nitrogen. The ring is defined by this carbonyl–nitrogen linkage.
Dorothy Crowfoot Hodgkin: British chemist who determined molecular structures using X-ray crystallography. Her crystallographic work established penicillin’s strained beta-lactam structure.
Clavulanic acid: A beta-lactam compound used with certain antibiotics to inhibit beta-lactamases. Its ring acts as a sacrificial target for enzymes that would otherwise destroy partner drugs.
Extended-spectrum beta-lactamase: A beta-lactamase capable of hydrolyzing many penicillins and cephalosporins. Its spread challenges the design of ring variants intended to evade hydrolysis.

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