modified L-glutamic acid residue glutamate 5-glycerol ester 203.079376220703125 203.19000244140625 74.03678131103515625 74.0800018310546875 PSI-MOD C 8 H 13 N 1 O 5 artifact modification from DeltaMass none C 3 H 6 O 2 E MOD:00992 From DeltaMass: Average Mass: 74 Average Mass Change: 74 References: Anal. Biochem. 1993 Vol 208 No. 2 382-386, PubMed:8452236. [DeltaMass] This article only suggests this as a possible modification and does no characterization. Isolation and stuctural evidence for artifactual modification are found in PubMed:18767873 [JSG].