Peptide Sequence

Definition

A peptide sequence is the ordered arrangement of amino acids in a peptide chain, written from the N-terminus (amino end) to the C-terminus (carboxyl end). It is the primary structure of a peptide and determines its identity and properties.

Overview

The peptide sequence is the most fundamental identifier of a specific peptide. Each sequence is unique and defines the peptide's molecular weight, charge distribution, folding pattern, and biological activity. Sequence verification is a critical quality control step in peptide manufacturing.

Technical Explanation

Sequence Representation: Sequences are written using single-letter or three-letter amino acid codes. For example, the peptide BPC-157 has the sequence: Gly-Glu-Pro-Pro-Pro-Gly-Lys-Pro-Ala-Asp-Asp-Ala-Gly-Leu-Val.

N-Terminus and C-Terminus: - N-Terminus: The start of the peptide chain with a free amino group (-NH₂) - C-Terminus: The end of the peptide chain with a free carboxyl group (-COOH) - The directionality (N→C) is critical for biological activity

Sequence Identification: - Mass spectrometry confirms the molecular weight matches the theoretical value from the sequence - Amino acid analysis verifies composition - Edman degradation or MS/MS sequencing confirms the actual order

Importance in Peptide Documentation

The peptide sequence is the foundation of identity testing. Every COA includes mass spectrometry results that confirm the molecular weight matches the theoretical weight calculated from the sequence. Sequence accuracy is essential for both research reproducibility and regulatory compliance.

Related Terms

• Amino Acid
• Peptide
• Terminal Groups
• Mass Spectrometry
• Identity

Frequently Asked Questions

Q: How is a peptide sequence confirmed? A: Mass spectrometry (MS) provides the experimental molecular weight, which is compared to the theoretical weight from the sequence. Tandem MS (MS/MS) can directly sequence the peptide. Amino acid analysis provides compositional confirmation.

Q: Can two different peptides have the same sequence? A: No — the sequence defines the peptide's identity. Different sequences mean different peptides, even if they share some fragments.