Gramicidin

Gramicidin (Gramicidine) is an antimicrobial peptide. Gramicidin dimers form ion channel-like pores in the cell membranes and organelles of bacterial and animal cells, allowing inorganic monovalent ions, such as potassium and sodium ions, to pass freely through the pores by diffusion, disrupting the important ionic gradient between membranes and thus killing the cells by various actions. Gramicidin is effective against Gram-positive bacteria such as Bacillus subtilis and Staphylococcus aureus, but is not as effective against Gram-negative bacteria such as Escherichia coli.

Gramicidin A is a peptide antibiotic isolated from B. brevis.Gramicidin A is a highly hydrophobic channel-forming ion carrier that forms monovalent cation-permeable channels in artificial membranes.Gramicidin A induces the degradation of hypoxia-inducible factor 1 alpha (HIF-1 alpha) and reduces the growth of a mouse xenograft model of human renal cell carcinoma. Gramicidin A has antibacterial, antimalarial and hemolytic activities.

Gramicidin C, a naturally occurring polypeptide antibiotic, is isolated from B. brevis var. G.B.

(-)-Epicatechin gallate ((-)-Epicatechin 3-O-gallate) is one of the catechin isomers and a potent antioxidant that can modulate a wide range of membrane proteins. Its bilayer-modifying potency was tested using gramicidin A (gA) channels as probes. All the catechins alter gA channel function and modify bilayer properties, with a 500-fold range in potency. The gallate group causes current block, as evident by brief downward current transitions.