Anion
Anion — A negatively charged ion, such as the carboxylate form of aspartic acid or glutamic acid side chains at physiological pH.
What Is an Anion?
An anion is a negatively charged ion. In peptide chemistry, anions are relevant as counterions (TFA⁻, Cl⁻, acetate⁻), as charged side chains (Asp and Glu carboxylates at physiological pH), and as the basis for anion-exchange chromatography separation of negatively charged peptides.
Peptide Context
- Counterions: TFA⁻ (MW 113) contributes significantly to vial weight, reducing net peptide content
- Residue charge: Asp (pKa 3.7) and Glu (pKa 4.1) are anionic at pH > 5
- C-terminus: Free carboxyl group is anionic at pH > 3 (unless amidated)
Frequently Asked Questions
What is Anion?
A negatively charged ion, such as the carboxylate form of aspartic acid or glutamic acid side chains at physiological pH.
Why is Anion important in peptide research?
Anion is a fundamental concept in chemistry 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.