Glossary

Amino Acid Sequence

Biochemistry

Amino Acid Sequence — The specific linear order of amino acids in a peptide or protein chain, determined by the genetic code and critical to biological function.

What Is an Amino Acid Sequence?

An amino acid sequence is the ordered list of amino acid residues in a peptide chain, read from the N-terminus (amino end) to the C-terminus (carboxyl end). The sequence is the primary determinant of a peptide's three-dimensional structure, biological activity, and physical properties. It is written using either the three-letter code (Gly-His-Lys) or single-letter code (GHK).

Notation Conventions

Standard direction: Always written N-terminus to C-terminus (left to right)
Modifications: N-terminal acetylation noted as "Ac-"; C-terminal amidation as "-NH2"
D-amino acids: Prefixed with "D-" or lowercase single letter (e.g., D-Phe or f)
Disulfide bonds: Indicated by connecting lines or parenthetical notation of bonded cysteine positions

Sequence Verification Methods

Mass spectrometry confirms total molecular weight matches the calculated value. MS/MS fragmentation (tandem MS) determines the actual order of residues by analyzing the b-ion and y-ion series. Edman degradation provides orthogonal confirmation by sequentially removing and identifying N-terminal residues.

Why Sequence Accuracy Matters

A single amino acid substitution can completely alter biological activity, receptor binding specificity, or stability. Vasopressin and oxytocin differ by only 2 of 9 residues yet have dramatically different functions. Always verify the sequence on the Certificate of Analysis matches the intended target.

Frequently Asked Questions

What is Amino Acid Sequence?

The specific linear order of amino acids in a peptide or protein chain, determined by the genetic code and critical to biological function.

Why is Amino Acid Sequence important in peptide research?

Amino Acid Sequence is a fundamental concept in biochemistry as it relates to peptide science. It directly influences experimental design, compound characterization, and the reliability of research outcomes across biochemistry and molecular biology disciplines.

Authority Sources

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