Session: Advances in Spectroscopy:

In recent years, many medically promising antibiotics have been discovered in nature, especially in insect-microbe symbioses. One of the better-studied examples of this kind of defensive relationship is that of fungus-growing ants and the antibiotic-producing Actinobacteria. These bacteria produce several defensive chemicals with myriad uses, including one antibiotic that inhibits the growth of several bacterial strains, including other Actinobacteria. This antibiotic (known as nocamycin O) is a promising candidate for medicinal use due to its similarities to bacterial RNA polymerase inhibitors tirandamycin and streptolydigin, which inhibit several human pathogens. The determination of the structure of nocamycin O will be an important first step toward determining its function and its potential utility in the medical field. This can be done efficiently and accurately using nuclear magnetic resonance spectroscopy (NMR). NMR can be used on its own to attempt to solve the structure of a compound, or in tandem with virtual chemical shift calculations that act as a check to correct the experimentally-derived structure. Overall, NMR and chemical shift calculations have become integral components to biochemical and biomedical research because they make structure elucidation much easier. My research sought to confirm the structure of nocamycin O using prior NMR data for the compound, as well as novel 2D NMR data collected in MeOD and DMSO with complementary 13C-NMR spectrum calculations performed using DFT in Spartan ‘18. Comparative analysis of NMR spectra for nocamycin O and nocamycin I revealed key differences in chemical shift values; the carbon with the additional -OH in nocamycin O experienced a shift change of almost 40 ppm, while other carbons in the molecule showed a change of 5-10 ppm. These changes were likely due to a difference in nuclear environment at these positions, which was confirmed via the DFT calculations and ROESY spectrum.

Elisabeth Lawton

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