The Driving Force for the Acylation of β-Lactam Antibiotics by L,D-Transpeptidase 2: Quantum Mechanics/Molecular Mechanics (QM/MM) Study.

08:00 EDT 10th April 2019 | BioPortfolio

Summary of "The Driving Force for the Acylation of β-Lactam Antibiotics by L,D-Transpeptidase 2: Quantum Mechanics/Molecular Mechanics (QM/MM) Study."

β-lactam antibiotics, which are used to treat infectious diseases, are currently the most widely used class of antibiotics. This study focused on the chemical reactivity of five- and six-membered ring systems attached to the β-lactam ring. The ring strain energy (RSE), force constant (FC) of amide (C-N), acylation transition states and second-order perturbation stabilization energies of 13 basic structural units of β-lactam derivatives were computed using the M06-2X and G3/B3LYP multistep method. In the ring strain calculations, an isodesmic reaction scheme was used to obtain the total energies. RSE is relatively greater in the five-(1a-2c) compared to the six-membered ring systems except for 4b, which gives a RSE that is comparable to five-membered ring lactams. These variations were also observed in the calculated inter-atomic amide bond distances (C-N), which is why the six-membered ring lactams C-N bond are more rigid than those with five-membered ring lactams. The calculated ΔG values from the acylation reaction of the lactams (involving the S-H group of the cysteine active residue from L,D transpeptidase 2) revealed a faster rate of C-N cleavage in the five-membered ring lactams especially in the 1-2 derivatives (17.58 kcal mol ). This observation is also reflected in the calculated amide bond force constant (1.26 mDyn/A) indicating a weaker bond strength, suggesting that electronic factors (electron delocalization) play more of a role on reactivity of the β-lactam ring, than ring strain.


Journal Details

This article was published in the following journal.

Name: Chemphyschem : a European journal of chemical physics and physical chemistry
ISSN: 1439-7641


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