Activities
The modes of action by which antimicrobial peptides kill bacteria is varied and includes disrupting membranes, interfering with metabolism, and targeting cytoplasmic components. The initial contact between the peptide and the target organism is electrostatic, as most bacterial surfaces are anionic, or hydrophobic, such as in the antimicrobial peptide Piscidin. Their amino acid composition, amphipathicity, cationic charge and size allow them to attach to and insert into membrane bilayers to form pores by ‘barrel-stave’, ‘carpet’ or ‘toroidal-pore’ mechanisms. Alternately, they may penetrate into the cell to bind intracellular molecules which are crucial to cell living. Intracellular binding models includes inhibition of cell wall synthesis, alteration of the cytoplasmic membrane, activation of autolysin, inhibition of DNA, RNA, and protein synthesis, and inhibition of certain enzymes. However, in many cases, the exact mechanism of killing is not known. One emerging technique for the study of such mechanisms is dual polarisation interferometry,. In contrast to many conventional antibiotics these peptides appear to be bacteriocidal (bacteria killer) instead of bacteriostatic (bacteria growth inhibitor). In general the antimicrobial activity of these peptides is determined by measuring the minimal inhibitory concentration (MIC), which is the lowest concentration of drug that inhibits bacterial growth.
Read more about this topic: Antimicrobial Peptides
Famous quotes containing the word activities:
“No culture on earth outside of mid-century suburban America has ever deployed one woman per child without simultaneously assigning her such major productive activities as weaving, farming, gathering, temple maintenance, and tent-building. The reason is that full-time, one-on-one child-raising is not good for women or children.”
—Barbara Ehrenreich (b. 1941)
“Both gossip and joking are intrinsically valuable activities. Both are essentially social activities that strengthen interpersonal bonds—we do not tell jokes and gossip to ourselves. As popular activities that evade social restrictions, they often refer to topics that are inaccessible to serious public discussion. Gossip and joking often appear together: when we gossip we usually tell jokes and when we are joking we often gossip as well.”
—Aaron Ben-Ze’Ev, Israeli philosopher. “The Vindication of Gossip,” Good Gossip, University Press of Kansas (1994)
“When mundane, lowly activities are at stake, too much insight is detrimental—far-sightedness errs in immediate concerns.”
—Franz Grillparzer (1791–1872)