AssayIndex
Mass spectrometry

Monoisotopic mass

The mass of the isotopologue in which every atom is its most abundant isotope. All theoretical masses on this site are monoisotopic.

Related terms

Average mass
The abundance-weighted mean mass over the whole natural isotope distribution. What a low-resolution instrument reports. About 600 ppm above the monoisotopic mass for a peptide.
Isotope pattern
The set of peaks arising from natural isotopic variants of a molecule. Its spacing gives the charge state directly: 1/z daltons.

Where this term appears

The glossary exists to make record pages readable without a chemistry degree. Every technical term on a report resolves here.