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:
“Love and work are viewed and experienced as totally separate activities motivated by separate needs. Yet, when we think about it, our common sense tells us that our most inspired, creative acts are deeply tied to our need to love and that, when we lack love, we find it difficult to work creatively; that work without love is dead, mechanical, sheer competence without vitality, that love without work grows boring, monotonous, lacks depth and passion.”
—Marta Zahaykevich, Ucranian born-U.S. psychitrist. “Critical Perspectives on Adult Women’s Development,” (1980)
“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)
“Minds do not act together in public; they simply stick together; and when their private activities are resumed, they fly apart again.”
—Frank Moore Colby (1865–1925)