Figure 3.

1D ¹H NMR spectra of CPS preparations from serotypes 2 and 1/2 in 33 mM phosphate pD 8.0 in D₂O. (a,b) Full spectrum. (c–f) Expansion of the methyl region. (a,d) SS2to1/2 mutant, 500 MHz, 77 °C. (b,f) SS1/2to2 mutant, 500 MHz, 75 °C. (c) Serotype 2 field strain, 600 MHz, 50 °C¹⁷. (e) Serotype 1/2 field strain, 700 MHz, 42 °C¹⁹. Specific characteristics of the ¹H NMR spectrum due to the presence of GalNAc in the native serotype 1/2 CPS were also found in the spectrum of the CPS from the corresponding mutant expressing serotype 1/2 CPS. Conversely, the spectrum of the CPS from the mutant expressing serotype 2 CPS, as well as that of the native serotype 2 CPS, lacked the signal attributed to N-acetyl of GalNAc.