In solid-phase peptide synthesis each amino acid carries a temporary group on its amino end, removed before every coupling, and permanent groups on reactive side chains, removed only when the finished peptide is cleaved from the resin. In Fmoc chemistry the temporary group is Fmoc, taken off by a mild base, and the side chains carry acid-labile groups such as tert-butyl, Boc, trityl and Pbf.
A protecting group that survives cleavage stays on the peptide and adds its mass, for example 252.082 Da for Pbf on arginine or 56.063 Da for tert-butyl, which is how such impurities are recognized by mass spectrometry.
See also
Cite this page
Text
Cosmic Peptides. (2026, October 25). Protecting group: glossary entry. Cosmic Peptides Research Library. Retrieved October 26, 2026, from https://cosmicpeptides.com/research/glossary/protecting-group
BibTeX
@misc{cosmicpeptides_research_glossary_protecting_group,
author = {{Cosmic Peptides}},
title = {Protecting group: glossary entry},
howpublished = {Cosmic Peptides Research Library},
year = {2026},
month = oct,
url = {https://cosmicpeptides.com/research/glossary/protecting-group},
urldate = {2026-10-26},
note = {Last reviewed 2026-10-25}
} RIS
TY - ELEC AU - Cosmic Peptides TI - Protecting group: glossary entry T2 - Cosmic Peptides Research Library PB - Cosmic Peptides PY - 2026 DA - 2026/10/25 UR - https://cosmicpeptides.com/research/glossary/protecting-group Y2 - 2026/10/26 LA - en ER -
Cite the date the page was last reviewed, October 25, 2026, as its version. Reference managers such as Zotero can save this page directly.
For in vitro laboratory research only. Not for human or veterinary use. This library describes chemistry, analytical methods and published laboratory research; it gives no guidance on use in people or animals.