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

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 pK_a.

pH	Line width (Δν_1/2-Δν_1/2°) (Hz)	Exchange rate of N(5)-H (s-¹)	pK_a (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

The flavin was 5 mM in 250 mM Tris + 100 mM NaCl. The estimation of the pK_a value is based on the line width of the corresponding ¹⁵N signal as described in the text.

ISSN: 1471-2091