"Bound" = the residue inside the chain (glycosidic water already removed); Table 2 adds the reducing-end group. Permethylated values keep the NIST fixed methyl counts (Hex / HexNAc 3, dHex 2, NeuAc 5), i.e. 1->4 linkages are assumed.
Table 2 · Glycan mass
"Use in Table 3" makes that glycoform the M used for the adduct list. The glycopeptide row = residue sum + peptide mass (the anomeric water and the peptide's condensation cancel out); get the peptide mass from MassCalc on this site.
Table 3 · Monoisotopic m/z of ESI molecular-ion adducts
m/z = (n·M + Σ adduct atom masses − z·m(e)) ÷ |z|; ACN acetonitrile, DMSO dimethyl sulfoxide, FA formic acid, HAc acetic acid, TFA trifluoroacetic acid, IsoProp isopropanol, MeOH methanol.
Monoisotopic = mass of the lightest stable nuclide (electrons included); average = CIAAW standard atomic weight, the same table MassCalc uses. Electron mass 0.00054858 Da.
What this tool is
GlycoCalc is an exact-mass calculator for glycomics: given Hex5HexNAc4dHex1NeuAc1 it tells you the formula and mass of the native glycan, its permethylated derivative, the 2-AB label, the glycopeptide formed with an 1188.5 Da peptide, and which ESI adduct ions you should see. It mirrors the NIST Glyco Mass Calculator - same inputs, same three tables, same add-on groups - so the two can be compared cell by cell.
Everything is computed in your own browser: the atomic mass table, residue definitions and the 52 adducts ship with the page, there is no backend and nothing is uploaded. Your inputs are kept in local storage, and "Copy link" hands the exact same glycan definition to a colleague.
Features
Eight residue typesThe NIST set (NeuAc, Hex, HexNAc, dHex) plus four frequently needed extras: NeuGc, hexuronic acid (HexA), sulfated hexose (HexS) and xylose - each with underivatized and permethylated mass and composition.
Seven glycoforms + custom modifiersNative, reduced (alditol), permethylated, permethylated + reduced, 2-AA, 2-AB and spacer-labelled glycans, plus a glycopeptide row (peptide mass) and two custom modifiers entered as a mass or as C/H/N/O/S/P atom counts.
52 ESI adduct ions37 positive and 15 negative ions covering 1+ to 4+, 2M/3M aggregates and solvent/acid adducts (acetonitrile, methanol, DMSO, isopropanol, formic, acetic and trifluoroacetic acid); select several glycoforms to compare them side by side.
Mass and composition always agreeEvery row's elemental composition comes from the same atomic mass table, so you can recompute the mass by hand; the permethylated end group is included in the composition (the NIST sheet leaves it out) - see the differences section.
Dark mode and three languagesLight/dark theme and Simplified / Traditional Chinese / English interfaces; the chemical notation is universal.
Copy and shareAll three tables copy out as tab-separated text for Excel, and the whole input set is encoded in the page URL.
How to use it
Enter the number of each residue in Table 1 (press Example for an A2G2S2F IgG1 Fc glycan with the EEQYNSTYR peptide).
Table 2 lists every glycoform with monoisotopic / average mass and elemental composition; type a peptide mass into the glycopeptide row when needed.
Click "Use in Table 3" on a row to make it the M; select several and Table 3 adds one column each.
Pick positive, negative or both ion modes, match against your spectrum, then "Copy link" to share.
Differences from the NIST sheet
(1) Adduct m/z is always computed from the atoms added plus the net charge (ion mass = Σ atomic masses − z·m(e)). Several NIST rows are labelled −H but their numbers were computed with +H (M+ACN-H, M+CH3OH-H, M+2ACN-H, M+IsoProp-H, M+ACN-Na, 2M+3H2O-2H); we relabel those to match the number. Three further rows (M+IsoProp-H, M+IsoProp+Na-H, M-H2O-H) miss a proton/electron correction, so we recompute them - differences range from 0.0005 to 2.02 Da.
(2) Permethylated composition: the NIST sheet's CH3s row adds carbon, hydrogen and oxygen only up to the residue sum (the number of methyls depends on the linkage pattern it cannot know), so its end group is missing from the composition. We include it (C2H6O / C2H7O); the masses are identical to NIST.
(3) Average masses use the current CIAAW standard atomic weights (the same table as MassCalc on this site) whereas the NIST tool quotes the 2007 values; for glycans of this size that is about 0.003 Da. Monoisotopic masses match digit for digit - compare those.
FAQ
What is the difference between "bound" and a free reducing end?
Table 1 sums residues as they sit in the chain - every glycosidic bond has already lost a water, so the sum has no terminal water. Table 2 then adds the group matching your sample: +H2O for a free reducing glycan, +H2O+H2 for the alditol, +H2O+C7H8N2 for 2-AB labelling; for a glycopeptide the anomeric water and the peptide's condensation water cancel, leaving residue sum + peptide mass.
How exact is the permethylated mass?
It keeps the NIST convention: a fixed number of methyls per residue (Hex / HexNAc 3, dHex 2, NeuAc 5), which is equivalent to assuming all 1->4 linkages. A non-reducing terminal residue carries one more methylatable hydroxyl, so real permethylated spectra sit a few × 14.0157 Da higher; no calculator can resolve that without the linkage pattern - the NIST sheet has the same limitation.
Where do I get the peptide mass?
MassCalc on this site (peptide section) turns a sequence with modifications into an exact mass; copy the number into the glycopeptide row here.
My peak is 21.982 Da above M+H - what is it?
Sodium: M+Na sits 21.9820 Da above M+H, and M+2Na-H 43.9639 Da above it. M+H, M+Na and M+K are adjacent rows in Table 3, so the check is quick. Sulfated glycans respond better in negative mode - look at that block.
Is anything uploaded?
No. The page is fully static; inputs go to browser local storage and, only when you click it, into the share URL.
