covalent modification of lysine by omega-maleimido alkanoyl N-hydroxysuccinimido esters 253.0950164794921875 253.25 381.189971923828125 381.42999267578125 C 12 H 15 N 1 O 5 C 18 H 27 N 3 O 6 J. Prot. Chem. 2, 263-277, 1983 K MOD:00593 OBSOLETE because removed from Unimod. modification from Unimod Chemical derivative PSI-MOD Unimod:273 Xlink:SSD artifact covalent modification of lysine by cross-linking reagent true