specification extension to InChi to better support isotopologue reporting
Develop enhanced specifications within the regular InChI standard for representing isotopologues and isotopomers. More specifically, augment the isotopic layer specifications of the regular InChI standard so that specific isotopologues, isotopomers, partial isotopomers, and isotopologue fragments can be represented by a single InChI string and used to identify isotope-informative analytical features.
While the InChI standard has an isotopic layer for representing exact isotopomers, there is not a specification for representing a range (set) of isotopomers. The fundamental issue is that an ambiguous location of specific isotopes of certain atoms cannot be represented in the current standard. This is needed to represent a set of isotopomers that correspond to a specific isotopologue. Currently, an InChI string can represent a specific isotopomer, but not a set of mass-equivalent isotopomers.
InChI=1S/C6H12O6/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2-,3-,4+,5-,6+/m1/s1
C([C@@H]1[C@H]([C@@H]([C@H]([C@@H](O)O1)O)O)O)O
InChI=1S/C6H12O6/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2-,3-,4+,5-,6+/m1/s1/i1+0,2+0,3+0,4+1,5+0,6+0
[12CH2]([12C@@H]1[12C@H]([13C@@H]([12C@H]([12C@@H](O)O1)O)O)O)O
However, there is no way to create a single valid InChI string that represents the isotopologue of alpha-D-glucopyranose containing one 13C atom at an undefined atomic location, which is the signal that would be observed in mass spectrometry experiments. The use of multiple InChI strings to represent this is impractical for many isotopologues.
The full proposal can be found here.
We are actively seeking feedback on this proposal from the broader scientific community.
There are three ways to provide this feedback.