Calculator Inputs
Use the grid below for residue counts, calculation mode, adduct, and charge state. Results appear above this form after submission.
Example Data Table
| Example | Composition | Monoisotopic mass (Da) | Use case |
|---|---|---|---|
| Example N-glycan core extension | Hex5 HexNAc4 | 1640.5922 | Two HexNAc above a pentasaccharide mannose-rich frame. |
| Fucosylated biantennary with two NeuAc | Hex6 HexNAc5 Fuc1 NeuAc2 | 2733.9731 | Common complex composition for screening precursor candidates. |
| NeuAc and NeuGc mixed composition | Hex4 HexNAc5 NeuAc1 NeuGc1 | 2279.8045 | Helpful when comparing acetylated and glycolylated sialic forms. |
| Neutral fucosylated small composition | Hex3 HexNAc2 Fuc1 | 1056.3857 | Simple mass check for compact neutral compositions. |
Formula Used
Neutral composition mass
Neutral mass = Σ(count × residue mass) + optional water mass
Each residue contributes its residue-level mass. The water term is added when you want the full neutral glycan composition mass at the reducing end.
Observed m/z
m/z = (neutral mass + z × adduct mass) / z
This converts the neutral composition into an ion mass for the selected adduct and charge state, which helps compare calculated and observed precursor values.
Count percentage
Count % = residue count / total residues × 100
This shows the composition balance of the glycan by residue count, which is helpful for fast profile comparisons between candidates.
Mass contribution percentage
Mass % = residue subtotal / residue mass sum × 100
This highlights which residue classes dominate the total glycan mass before the optional water term is applied.
How to Use This Calculator
1. Enter residue counts
Fill in the counts for Hex, HexNAc, Fuc, NeuAc, NeuGc, Pent, HexA, and Kdn. Leave any unused residue at zero.
2. Choose calculation settings
Select monoisotopic or average mass, choose the ion adduct, pick a charge state, and decide whether the reducing-end water should be included.
3. Review the outputs
After calculation, inspect the neutral mass, selected m/z, residue percentages, charge-state table, and chart above the form.
4. Export the result
- Use the CSV button for spreadsheet work or batch record keeping.
- Use the PDF button for quick reporting, printing, or lab-book documentation.
- Compare your calculated m/z values with experimental precursor values before deeper structural interpretation.
Residue Reference Table
| Residue code | Residue name | Monoisotopic mass (Da) | Average mass (Da) |
|---|---|---|---|
| Hex | Hexose (Hex) | 162.0528 | 162.1406 |
| HexNAc | N-Acetylhexosamine (HexNAc) | 203.0794 | 203.1925 |
| Fuc | Deoxyhexose / Fucose (Fuc) | 146.0579 | 146.1412 |
| NeuAc | N-Acetylneuraminic acid (NeuAc) | 291.0954 | 291.2559 |
| NeuGc | N-Glycolylneuraminic acid (NeuGc) | 307.0903 | 307.2553 |
| Pent | Pentose (Pent) | 132.0423 | 132.1146 |
| HexA | Hexuronic acid (HexA) | 176.0321 | 176.1241 |
| Kdn | Keto-deoxynononic acid (Kdn) | 250.0689 | 250.2031 |
FAQs
1. What does this calculator estimate?
It sums residue masses from a glycan composition, adds optional reducing-end water, and converts the neutral mass into m/z for a chosen adduct and charge. It works well for quick screening, reporting, and precursor plausibility checks.
2. Should I use monoisotopic or average mass?
Use monoisotopic mass when comparing exact precursor assignments in mass spectrometry. Use average mass for broader composition summaries, teaching, or situations where you prefer isotopic averaging instead of exact monoisotopic values.
3. Why is water included as an option?
Composition calculations often add the reducing-end water to recover the full neutral glycan mass. Leaving it off can help when you specifically want only the summed residue contribution without the terminal water term.
4. Does this tool identify branching or linkage?
No. It is a composition calculator, not a structural interpreter. Two glycans can share the same composition while differing in branching, linkage, stereochemistry, or site-specific arrangement.
5. Why can different glycans have similar masses?
Some residue combinations produce very close or even identical totals. That means mass alone may narrow candidates, but it rarely proves a unique glycan structure without additional fragmentation or orthogonal evidence.
6. How should I enter fucose and sialic acids?
Enter fucose under Fuc. Put N-acetylneuraminic acid under NeuAc, N-glycolylneuraminic acid under NeuGc, and Kdn under Kdn. Keeping these acidic residues separate helps you compare related glycan families correctly.
7. What does the Plotly graph show?
The bar trace displays residue counts. The line trace shows each residue class contribution to the residue mass total. Together they reveal whether a composition is count-heavy, mass-heavy, or balanced across residue types.
8. When do multi-charge ions matter?
Higher charge states become important when larger glycans appear at lower observed m/z values than their neutral masses suggest. Checking 2+, 3+, and 4+ views can quickly explain experimental precursor placement.