RESUMO
Synthetic optimization of a biologically labile class of dipeptides that function as efflux pump inhibitors to potentiate the antibacterial agent levofloxacin in Pseudomonas aeruginosa has led to the discovery of a related series of compounds that are completely stable in a variety of biological matrices. Other than the stability profile, the in vitro profile of the new series is essentially identical to that observed with the original one. A prototypical compound from the new series demonstrates potentiation in an in vivo model of infection.
Assuntos
Anti-Infecciosos/farmacologia , Dipeptídeos/síntese química , Levofloxacino , Ofloxacino/farmacologia , Pseudomonas aeruginosa/efeitos dos fármacos , Animais , Anti-Infecciosos/química , Anti-Infecciosos/metabolismo , Transporte Biológico Ativo/efeitos dos fármacos , Dipeptídeos/sangue , Dipeptídeos/química , Dipeptídeos/farmacologia , Desenho de Fármacos , Estabilidade de Medicamentos , Sinergismo Farmacológico , Camundongos , Testes de Sensibilidade Microbiana , Conformação Molecular , Estrutura Molecular , Ofloxacino/química , Ofloxacino/metabolismo , Pseudomonas aeruginosa/fisiologia , Ratos , Relação Estrutura-AtividadeAssuntos
Anti-Infecciosos/farmacologia , Proteínas da Membrana Bacteriana Externa/antagonistas & inibidores , Proteínas de Transporte/antagonistas & inibidores , Dipeptídeos/síntese química , Levofloxacino , Proteínas de Membrana Transportadoras , Ofloxacino/farmacologia , Pseudomonas aeruginosa/efeitos dos fármacos , Proteínas da Membrana Bacteriana Externa/química , Proteínas da Membrana Bacteriana Externa/genética , Proteínas de Transporte/química , Proteínas de Transporte/genética , Dipeptídeos/farmacologia , Resistência Microbiana a Medicamentos , Estabilidade de Medicamentos , Sinergismo Farmacológico , Endopeptidases/metabolismo , Expressão Gênica , Estrutura Molecular , Ornitina/química , Pseudomonas aeruginosa/genética , Pseudomonas aeruginosa/metabolismo , Relação Estrutura-AtividadeRESUMO
A series of 14 residue amphipathic alpha-helical peptides, in which the sidechains of glutamic acid and lysine have been covalently joined, was synthesized in order to determine the effect of spacing, position and orientation of these lactam bridges. It was found that although an (i, i+3) spacing would position the lactam bridge on the same face of the helix, these lactams with 18-member rings were actually helix-destabilizing regardless of position or location. On the other hand, (i, i+4) lactams with 21-member rings were helix-stabilizing but this was dependent on orientation. Glutamic acid-lysine lactams increased the helical content of the peptide when compared with their linear homologue in benign conditions (50 mM KH2PO4, 100 mM KCl, pH 7). Two Glu-Lys (i, i+4) lactams located at the N- and C-termini gave rise to a peptide with greater than 99% helical content in benign conditions. Peptides with Lys-Glu oriented lactams were random structures in benign conditions but in the presence of 50% TFE could be induced into a helical conformation. The stability of the single-stranded alpha-helices, as measured by thermal denaturations in 25% TFE indicated that Glu-Lys oriented lactam bridges stabilized the helical conformation relative to the linear unbridged peptide. One Glu-Lys lactam in the middle of the peptide was more effective at stabilizing helical structure than two Glu-Lys lactams positioned one at each end of the molecule. The lactams with the Lys-Glu orientation were destabilizing relative to the unbridged peptide. This study demonstrates that correct orientation and position of a lactam bridge is critical in order to design peptides with high helical content in aqueous media.
