Which amino acids have basic side chains?

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Why our bodies need proteins — Amino acid The structure and function of amino acids.

The amino acids that possess basic side chains are arginine, histidine, and lysine.1

These amino acids are characterized by side chains that can accept a proton. At physiological pH, lysine and arginine typically carry a positive charge of +1. Arginine’s side chain contains a guanidino group, which is the most basic of all amino acid side chains. Histidine features an imidazole side chain, allowing it to participate in acid and base catalysis near physiological pH, a property that makes it a frequent component of the active sites in protein enzymes.1

Due to their positive charges, these side chains are also capable of forming ionic bonds, often referred to as salt bridges, with the negatively charged side chains of aspartic or glutamic acid.2