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5.
1.
1.
1 Physical and chemical properties
β-lactam drugs are mostly organic acids, but they are difficult to dissolve in water
.
The free carboxyl groups of PENs and CEPs are quite acidic (pKa 2.
The carboxyl group of PENs β-lactam ring and the unshared electron pair of the N atom cannot be conjugated, so it is easily attacked by electrophiles and nucleophiles
.
The core part (6-APA) has no ultraviolet absorption properties, and the ultraviolet absorption of its molecules usually comes from the benzene ring on the side chain, which lacks characteristic
The chemical properties of β-lactam drugs are unstable
.
The β-lactam ring is the most unstable part of the chemical structure of this type of drug.
5.
1.
1.
2 Purpose
Beta-lactam drugs have strong antibacterial effects and can be used to treat diseases caused by various cocci and gram-positive bacteria
.
The mechanism of action of various β-lactam drugs is similar.
By inhibiting cell wall mucopeptide synthetase, a type of penicillin binding proteins (PBPs), it prevents the synthesis of cell wall mucopeptides and causes bacterial cell wall defects.
Bacteria swell and lyse
.
In addition, it can also trigger the autolysing enzyme activity of bacteria to achieve a lethal effect on bacteria
β-lactam drugs have a narrow antibacterial spectrum, most of which are only effective against gram-positive bacteria and a few gram-negative bacteria, but are ineffective against most gram-negative bacteria
.
This is related to its antibacterial mechanism, because the mucopeptide content of the cell wall of gram-positive bacteria is higher than that of gram-negative bacteria, so they are more sensitive to gram-positive bacteria
After using PENs for a period of time, the antibacterial effect will decrease
.
The main reason is that Staphylococcus aureus or some other bacteria have developed resistance to PENs
