Residue
Residue — A single amino acid unit within a peptide or protein chain, named for the molecular remainder after water is lost during peptide bond formation.
What Is a Residue?
A residue is a single amino acid unit within a peptide or protein chain. The term "residue" (rather than "amino acid") is used because each unit has lost a water molecule during peptide bond formation. A peptide's length is described by its residue count: oxytocin has 9 residues, insulin has 51 residues, and growth hormone has 191 residues.
Residue Properties
- Residue weight: Molecular weight of the amino acid minus 18.02 Da (water lost during bond formation)
- Average residue weight: ~111 Da. Used to estimate peptide MW from residue count
- Numbering: Residues numbered from N-terminus (residue 1) to C-terminus. Mutations described as [original][position][replacement], e.g., D-Phe2
Frequently Asked Questions
What is Residue?
A single amino acid unit within a peptide or protein chain, named for the molecular remainder after water is lost during peptide bond formation.
Why is Residue important in peptide research?
Residue 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.