---
title: "Protonated molecule: research glossary | Sable Peptides"
description: "A protonated molecule, written [M+H]⁺, is the ion formed when a neutral molecule gains a proton during positive-mode ionisation. Its m/z equals the molecul"
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publisher: Sable Peptides Limited (UK company 17488610)
note: Research use only. Not for human or veterinary use.
---

Glossary

# Protonated molecule

A protonated molecule, written \[M+H\]⁺, is the ion formed when a neutral molecule gains a proton during positive-mode ionisation. Its m/z equals the molecular mass plus about 1.007 Da. Multiply protonated forms such as \[M+2H\]²⁺ are common for peptides analysed by electrospray ionisation.

Source: [en.wikipedia.org](https://en.wikipedia.org/wiki/Protonation)

## Related terms

-   [Electrospray ionisation](/glossary/electrospray-ionisation)

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