Activating a Silver Lipoate Nanocluster with a Penicillin Backbone Induces a Synergistic Effect against Biofilm.

Many antibiotic resistances to penicillin have been reported, making them obsolete against multiresistant bacteria. Because penicillins act by inhibiting cell wall production while silver particles disrupt the cell wall directly, a synergetic effect is anticipated when both modes of action are incorporated into a cluster. To test this hypothesis, the lipoate ligands (LA) of a silver cluster (Ag) of known composition (AgLA) were covalently conjugated to 6-aminopenicillanic acid, a molecule with a β-lactam backbone.

Electrostatic effects on the reactions of cyclohexanone oxocarbenium ions.

Nucleophilic substitution reactions of 4-substituted cyclohexanone acetals display different selectivities depending upon the electronic nature of the substituent. Alkyl groups favor equatorial positions in the oxocarbenium ions, but alkoxy groups prefer axial conformers. The reactions of acetals with alkoxy groups constrained to either equatorial or axial positions suggest that the presence of an axial alkoxy group distorts the oxocarbenium ion, changing its inherent preferences for facial attack.