Scientists tweak 80-year-old antibiotic for new medical uses

"Gramicidin A" was originally found in soil bacteria and was the first commercially produced

antibiotic in the early 1940s. Today, doctors continue to prescribe it as a topical cream or drop for certain skin, eye, and throat infections. However, it cannot be used as a tablet or injection.

Recently, a team from the Department of Pharmaceutical Sciences of the University of Tokyo developed and analyzed over 4,000 artificial analogues of Gramicidin A.

"Gramicidin A" is a spiral of 15amino acids. The researchers strategically selected six of those amino acids that could be altered without losing key aspects of the normal structure of gramicidin A. Each of these six amino acids could be replaced with four different amino acids to alter the way peptides bind, resulting in 4,096 variations.

Researchers started testing their newversion of "Gramicidin A" for activity against streptococcus, a common bacterial infection. The strongest participants were then evaluated for their potential ability not to indiscriminately kill human cells by testing their reactions with rabbit blood cells and mouse leukemia cells.

These tests revealed about 10 varieties"Gramicidin A" as promising antibacterial drugs of the future. The results also allowed the researchers to determine how specific structural changes in amino acids affect the overall function of the molecule. This basic information about structure and function is critical to understanding why and how pharmaceuticals work.

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