Diffusion of XXXX antibiotics through oligomeric or monomeric porin channels of some gram-negative bacteria.

@entity1522 @entity3405 @entity535 @entity7660 @entity29704 @entity36642 @entity3064 @entity2624 @entity526
The penetration of anionic @entity3405 antibiotics through porins was evaluated as a mechanism of drug resistance. The major proteins with porin activity were purified from the outer membranes of six bacteria. Three of the six porins were oligomeric porins. The molecular weights of their monomers were 37 kDa from @entity36642 , 42 kDa from Serratia liquefaciens, and 36 kDa from @entity526 B. The other three porins were heat-modifiable monomeric porins with molecular weights of 43 kDa from @entity29704 and @entity3064 , and 37 kDa from @entity2624 . Comparison of the six porin proteins revealed that, independent of their aggregation state, their @entity535 content is similar but not identical. All have double the amount of negatively charged @entity1522 compared with positively charged @entity1522 . They have a similar polarity and polarity index. Two of the six tested bacteria do not produce beta-lactamase. These two bacteria were sensitive to the different @entity7660 tested. The other four bacteria were resistant to all or to several @entity7660 .A modified liposome swelling method was used for determining the rate of penetration of charged @entity3405 antibiotics. Zwitterionic @entity7660 were found to penetrate into liposomes at a rate that more or less fits their molecular weight, whether the porins are monomeric or oligomeric. The penetration rates of negatively charged @entity7660 are different for oligomeric and monomeric porins. Negatively charged @entity7660 penetrate through oligomeric porins better than estimated by their molecular weight, whereas monomeric porins are less penetrable to negatively charged @entity7660 than estimated by their molecular weight. The contribution of all types of porins to the susceptibility of bacteria to @entity3405 antibiotics (zwitterionic or negatively charged) is apparently doubtful. The porins may decrease or increase bacterial penetration rates to @entity7660 , and only the existence of a potential beta-lactamase that can destroy the penetrating drug will cause resistance.
