acrolein addition +56 56.026214599609375 56.060001373291015625 Acrolein addition +56 C 3 H 4 O 1 Delta:H(4)C(3)O(1) MOD:00557 OBSOLETE because this modification not supported by the papers listed or any other that I can find[PMT] PSI-MOD Unimod:206 X artifact true