“…Consequently, the likelihood that any molecule detected in a metabolomics experiment is actually in a library (or even close to a molecule that is [ 10 ]) is quite small, and most are not [ 11 , 12 , 13 , 14 , 15 ]. Experimentally, commonly just 10% of molecules can be identified from what are reproducible spectral features in complex matrices such as serum (e.g., [ 16 , 17 , 18 , 19 , 20 ]), despite the existence of many heuristics such as neutral mass loss, isotope patterns, and so on [ 21 , 22 , 23 , 24 ]. Solving the mass spectral molecular identification problem is thus seen widely as the key unsolved problem of metabolomics [ 4 , 11 , 14 , 15 , 19 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ].…”