Scientist mimics African frog’s ability to kill bacteria

By By Julie Jay

By Julie Jay

Annelise Barron, professor of chemical and biological engineering at Northwestern University, hopes her investigation will combat infections caused by bacteria resistant to current antibiotics.

And to bring that information to the U, she presented her lab’s investigation into the development of new antibacterial compounds at the department of bioengineering’s seminar last week.

Barron said being “fascinated by the beauty of natural systems” inspired her development of molecules that mimic a family of peptides termed magainins.

These peptides are secreted from the skin of the African clawed frog Xenopus laevis as part of the frog’s natural protection against bacterial infection.

She said these peptides display both hydrophobic, or greasy, characteristics, as well as positive charges in a helical formation similar to DNA.

She described how the basic antibacterial properties involve preferential interaction of the positive charges with the negatively charged bacterial cell membranes rather than mammalian cell membranes, which display both positive and negative charges, although the exact mechanism is unknown.

Current technologies are not capable of delivering peptides orally because of digestion in the stomach, Barron said.

So her research group chose to mimic these peptides with non-natural molecules, termed peptoids, which are not recognized by mammalian enzymes and could therefore be delivered orally.

Peptoids, Barron said, display similar molecular backbones to peptides. However, the functional side chains, which differentiate the 20 essential amino acids, are attached to the nitrogen atom rather than the adjacent carbon.

Barron said she chose these molecules for a number of reasons, one of which involves the ability to choose any type of side chain rather than just the 20 seen for natural amino acids.

Her lab screened a library of peptoid compounds with modifications in hydrophobicity and the number and placement of positive charges. They discovered one molecule that exhibited similar widespread antibacterial potency and low toxicity to human cells compared with magainins.

Greg Harbers, a post-doctoral student in the department of pharmaceutics and pharmaceutical chemistry, said he feels that Barron “is very enthusiastic about her research. Peptoids have been investigated for various drug applications, and it will be interesting to see their utilization as antibiotics.”

Future work for her lab involves improving the potency of the antibacterial properties and decreasing their toxicity toward mammalian cells. Barron described how her work may be useful in treating tuberculosis and her hope that these molecules that may target cancer cells.