L-selenocysteinyl molybdenum bis(molybdopterin guanine dinucleotide) (Sec) 1572.0400390625 1572.9857177734375 1722.0799560546875 1723.939453125 PSI-MOD U none C 43 H 52 N 21 O 27 P 4 S 4 Se 1 Mo 1 A protein modification that effectively converts an L-selenocysteine residue to L-selenocysteinyl molybdenum bis(molybdopterin guanine dinucleotide). natural MOD:00253 C 40 H 47 N 20 O 26 P 4 S 4 Mo 1 molybdenum pterin containing modification modified L-selenocysteine residue