Structure and Pharmacological Effect
Structurally, Gramicidin S differs from Gramicidin D, which is a linear peptide and forms a beta helix in cellular membranes. The mode of action is not entirely agreed upon, but it is generally accepted that it is the disruption of the barrier properties of cellular membranes which causes cell death. Recent research reveals that Gramicidin S interacts more so with anionic membranes (such as those of bacteria) vs. zwitterionic membranes and more fluid membranes. It has a molecular mass of ca. 1,140 and is a solid, usually encapsulated in two-percent sterile spirit solution. In vitro assays show it has a MIC of 5-15 μg/mL.
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