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Table 1 Line widths of the 15N resonance signal of the reduced FMN N(5) atom as function of pH and estimation of the N(5)-H pKa.

From: Reduced Flavin: NMR investigation of N(5)-H exchange mechanism, estimation of ionisation constants and assessment of properties as biological catalyst

pH Line width (Δν1/2-Δν1/2°) (Hz) Exchange rate of N(5)-H (s-1) pKa (calculated)
6 21 525  
6.7 42 270  
7.15 47 242  
7.8 34 107  
8.95 18 57  
9.05 6 19  
9.7 3 9 20.5
10.25 14 44 20.3
10.5 61 191 20.0
11 33.5 339 20.2
  1. The flavin was 5 mM in 250 mM Tris + 100 mM NaCl. The estimation of the pKa value is based on the line width of the corresponding 15N signal as described in the text.