Building a Peptide Monoisotopic and Average Mass Calculator in Python

说明与用途

使用Python脚本计算肽段的单同位素和平均质量，采用官方原子质量来源，并与开源包进行验证。

问题

Synthetic peptide users need accurate mass predictions for mass spectrometry, but manual calculations are error‑prone.

结果

The script accurately reproduces peptide masses, demonstrating the difference between monoisotopic and average masses and providing a reliable tool for researchers.

工作流

• Define monoisotopic, average, and proton masses from NIST and IUPAC sources.
• Store each amino acid residue as an elemental formula (C,H,N,O,S) minus H₂O.
• Sum residue formulas for the peptide, add one H₂O for termini.
• Calculate monoisotopic and average masses by multiplying element counts by their masses and summing.
• Divide by charge to obtain m/z.
• Compare results with an external library for validation.

证据

The math is simple: add up the residues, add one water, and divide by the charge.

来源

I used two primary sources and opened both to check the values: Monoisotopic masses: NIST, ... Average masses: IUPAC CIAAW... Proton mass: NIST CODATA...

来源

Rather than hard‑coding residue masses, I store each residue as an elemental formula.

来源