Cation
Cation — A positively charged ion, such as the protonated amino groups on lysine and arginine side chains at physiological pH.
What Is a Cation?
A cation is a positively charged ion. In peptide chemistry, cations include protonated N-terminal amines (NH3⁺), protonated Lys side chains (ε-NH3⁺), protonated Arg guanidinium, protonated His imidazolium, and metal cations (Cu²⁺, Zn²⁺) that coordinate with peptide residues.
Significance
- Net charge: Cationic peptides (net positive charge) are attracted to anionic bacterial membranes, driving AMP selectivity
- Cation exchange: Positively charged peptides bind negatively charged CEX resins at pH below pI
- ESI-MS: Peptide ions formed by proton addition [M+zH]²⁺ in positive mode
Frequently Asked Questions
What is Cation?
A positively charged ion, such as the protonated amino groups on lysine and arginine side chains at physiological pH.
Why is Cation important in peptide research?
Cation 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.