Table 2.

Comparison of MA-SML versus Higher Nucleophile Loading in the Absence of Ni²⁺.^a

Equivalents GGK-DEAC	Ni2+	% Ligation (4)	% Hydrolysis (5)
1	+	94	3
1	−	65	<1
2	−	78	<1
3	−	84	<1
5	−	88	<1
20	−	91	ndb

^aConditions: 50 μM DARP-LPETGGHH₅, 1-20 equivalents GGK-DEAC nucleophile, 10 μM SrtA_staph, 0/200 μM NiSO₄, sortase reaction buffer (pH 7.5), glycerol (0.2% v/v), residual DMSO (0.2-3% v/v) from GGK-DEAC stock solution, 12 h at room temperature. Reactions were analyzed by LC-ESI-MS and % ligation (4) and % hydrolysis (5) were estimated from peak areas derived from the corresponding deconvoluted mass spectra.

^bnd = hydrolysis by-product not detected.