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:
“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)
“As life developed, I faced each problem as it came along. As my activities and work broadened and reached out, I never tried to shirk. I tried never to evade an issue. When I found I had something to do—I just did it.”
—Eleanor Roosevelt (1884–1962)
“There is, I think, no point in the philosophy of progressive education which is sounder than its emphasis upon the importance of the participation of the learner in the formation of the purposes which direct his activities in the learning process, just as there is no defect in traditional education greater than its failure to secure the active cooperation of the pupil in construction of the purposes involved in his studying.”
—John Dewey (1859–1952)