2005g-807 aminoacids anti-bacterialagents antibiotics bacteria bacterialcellsurfaces bacterialphysiologicalphenomena beta-lactams betalactamases carrierproteins cellmembrane cellwall chemicalsynthesis chiraldrugs congresses cytology drugeffects enantiomers lactams medical metabolism penicillins pharmaceuticalchemistry pharmacology physiologicaleffect physiology proteinbinding qu60e562005 qw52a62851987 stereoisomerism synthesis