. 2020 Aug 11;5(33):21094–21103. doi: 10.1021/acsomega.0c02744

Table 1. pK_a Values of Individual Nitrogen Atoms of Tobramycin Determined Using ¹H, ¹³C, and ¹⁵N HMBC NMR Spectroscopy in This Work and Then Compared With the Published Data, as Indicated.

	individual nitrogen atoms pK_a
method	N-1	N-3	N-2′	N-6′	N-3″
¹⁵N NMR^a	7.40	6.20	7.60	8.60	7.40
¹H NMR^b	7.30	6.60	7.50	8.40	7.30
¹⁵N NMR^b	7.40	6.40	7.70	8.50	7.40
¹H NMR^c	7.51 ± 0.03	6.60 ± 0.05	7.80 ± 0.05	9.07 ± 0.10^d	7.62 ± 0.08
¹³C NMR^c	7.61 ± 0.07	6.80 ± 0.15	7.71 ± 0.07	9.15 ± 0.05	7.71 ± 0.03
¹⁵N HMBC NMR^c	7.55 ± 0.05	6.70 ± 0.05	7.75 ± 0.05	9.10 ± 0.05	7.70 ± 0.05

pK_a values of individual nitrogen atoms of tobramycin determined using ¹⁵N NMR spectroscopy in H₂O/D₂O (90:10 v/v) relative to ¹⁵NH₄Cl at 25 °C.¹¹

pK_a values of individual nitrogen atoms of tobramycin determined using ¹H NMR spectroscopy and ¹⁵N NMR spectroscopy in D₂O relative to TMS at 25 °C.¹⁴

This work.

The pK_a value of N-6′ of tobramycin determined using ¹H NMR spectroscopy (in this work) is the average pK_a of the values of N-6′ obtained using ¹H NMR spectroscopic data for 6′a (9.05) and 6′b (9.10).

Table 1. pKa Values of Individual Nitrogen Atoms of Tobramycin Determined Using 1H, 13C, and 15N HMBC NMR Spectroscopy in This Work and Then Compared With the Published Data, as Indicated.

Table 1. pK_a Values of Individual Nitrogen Atoms of Tobramycin Determined Using ¹H, ¹³C, and ¹⁵N HMBC NMR Spectroscopy in This Work and Then Compared With the Published Data, as Indicated.