Gramicidin S (Molecule of the Month for May 2010)
Gramicidin S or Gramicidin Soviet is an antibiotic effective against some Gram positive and Gram negative bacteria as well as some fungi. It is a derivative of gramicidin, produced by the Gram positive bacterium Bacillus brevis. Gramicidin S is a cyclodecapeptide, constructed as two identical pentapeptides joined head to tail, formally written as cyclo(-Val-Orn-Leu-D-Phe-Pro-)2. An interesting point is that it utilizes two amino acids uncommon in peptides: ornithine as well as the unnatural stereoisomer of phenylalanine. Gramicidin S has historically been employed as a topical antibiotic for the treatment of infections from superficial wounds. It exhibits strong antibiotic activity against a broad spectrum of Gram negative and Gram-positive bacteria and against several pathogenic fungi. Like Gramicidin D, Gramicidin S causes hemolysis at low concentrations, thus is not an effective drug for the treatment of systemic infections. Additionally, Gramicidin S has been employed as a spermicide and therapeutic for genital ulcers caused by sexually transmitted disease
Gramicidin S was discovered by Russian microbiologist Georgyi Frantsevitch Gause and his wife Maria Brazhnikova in 1942. Within the year Gramicidin S was being used in Soviet military hospitals to treat infection and eventually found usage at the front lines of combat by 1946. Gause was awarded the Stalin Prize for Medicine for his discovery in 1946. In 1944, Gramicidin S was sent by the Ministry of Health of the USSR to Great Britain via the International Red Cross in a collaborative effort to establish the exact structure. English chemist Richard Synge proved that the compound was an original antibiotic and a polypeptide using paper chromatography. He would later go on to receive the Nobel Prize for his work in chromatography.
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
Formal Chemical Name (IUPAC)
Update by Karl Harrison
(Molecule of the Month for May 2010 )