Example sentences for: penicillins

How can you use “penicillins” in a sentence? Here are some example sentences to help you improve your vocabulary:

  • As a first approximation of substrate binding, we examined the steady-state kinetics of 4 cephalosporins, 2 penicillins, and 3 carbapenems (Tables 3, 4, 5) and compared the K m values of the mutants with those of wild-type L1.

  • As with the I164A mutant, the changes in K m and k cat for the penicillins and carbapenems were relatively small, as compared with the values obtained with the cephalosporins (Table 4).

  • When penicillins were used as substrates, the Tyr228 mutants exhibited 3- to 13-fold increased K m values and < 2-fold changes in k cat , as compared to the values ascertained using wild-type L1 (Table 4).

  • These bacteria become resistant by a number of mechanisms, such as producing enzymes that hydrolyze or inactivate the antibiotics, producing efflux pumps that transport the antibiotic out of the cell, or modifying their cell wall components so they no longer bind effectively to the antibiotics [ 1 2 3 ] . The most common, least expensive, and effective antibiotics are the β-lactam containing antibiotics, such as the penicillins, cephalosporins, and carbapenems [ 2 4 5 ] . These antibiotics are mechanism-based inhibitors of transpeptidase, a bacterial enzyme required for the production of a strong viable cell wall [ 6 7 ] . In response to the widespread use of β-lactam containing antibiotics, bacteria have acquired the ability to produce β-lactamases, which are enzymes that hydrolyze and inactivate β-lactam containing antibiotics.

  • All crystallographically characterized metallo-β-lactamases have a flexible amino acid chain that extends over the active site [ 37 42 44 45 46 47 48 49 ] . Previous NMR studies on CcrA have shown that this loop "clamps down" on substrate or inhibitor upon binding, and there is speculation that the distortion of substrate upon clamping down of the loop may drive catalysis [ 50 ] . The crystal structure of L1 showed that there is a large loop that extends over the active site, and modeling studies have predicted that two residues, Ile164 and Phe158, make significant contacts with large, hydrophobic substituents at the 2' or 6' positions on penicillins, cephalosporins, or carbapenems [ 37 ] . To test this prediction, Ile 164 and Phe158 were changed from large, hydrophobic residues to alanines to afford the I164A and F158A mutants.

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