Table 1.

Extent of modification by nonenzymatic succinylation and nonenzymatic acetylation as measured by NMR

Construct	Peak	Volume	15N ppm	1H ppm	% Modified
Acetyl-K18	N ε-peak	19.5	127.5	8.0	1.4
	K311 peak	68.8	126.4	8.2
Succinyl-K18	N ε-peak	356.5	125.7	7.9	39.7
	K311 peak	44.9	126.3	8.2

The number of modified lysines was obtained by integrating the shifted lysine epsilon amino resonance and normalizing its volume by that of the backbone lysine NH resonance for a well-resolved lysine residue, K311, as previously reported (71) and was normalized by the total number of lysines (20) in K18. Peak volumes and positions of the corresponding modified epsilon amino resonance and the unmodified K311 peak are shown based on ¹H,¹⁵N HSQC NMR spectra taken at the end of each reaction (nonenzymatic acetylation or succinylation).