N-terminus
Definition
The amino-terminal end of a peptide or protein chain. Peptide sequences are conventionally written from the N-terminus toward the C-terminus.
By PurePeptideHub Editorial Team · Updated . Educational source review; independent clinical review pending.
Reading sequence direction
The order of residues matters. In the illustrative sequence Gly-Ala-Ser, glycine is at the N-terminal end and serine is at the C-terminal end. Reversing the written order describes a different sequence. A sequence label should also specify modifications when they are present.
References: [1]
Free and modified ends
A peptide’s N-terminal amino group can be chemically modified, so N-terminus does not always mean an unmodified free amino group. Terminal modifications and cyclic structures require additional notation. The name of the end and the chemistry at that end are related but distinct details.
Why this matters in a report
When comparing a certificate of analysis with a research paper, match the sequence and terminal modifications, not only the informal product name. A similar residue count does not establish molecular identity. Analytical confirmation still requires appropriate methods.