FIGURE 2.

Temperature and pH dependence of the ¹⁵N NMR spectrum of the free base form of paromomycin. The resonances corresponding to the five amino nitrogens are indicated, with the pH- and temperature-induced shifts of these resonances being denoted by the dashed lines. The ¹⁵N chemical shifts (δ) are reported relative to NH₃ using 1 M [¹⁵N]urea in DMSO as an external standard, with the ¹⁵N chemical shift of the reference set to 77.0 ppm. (A) ¹⁵N NMR spectra of the free base form of paromomycin at 25°C and pH values of 3.19 (top), 7.70 (middle), and 11.75 (bottom). (B) ¹⁵N NMR spectra of the free base form of paromomycin at pH 7.70 and temperatures of 25°C (top) and 45°C (bottom).