Chemistry of amino acids and protein structure
Amino acid structure and its classification
L and D amino acids
Isoelectric point (pI) of amino acids
Classification of different amino acids
- Hydrophobic amino acids have nonpolar side chains, such as alkyl groups or aromatic groups.
- Hydrophilic—neutral—amino acids contain polar side chains, such as hydroxyl, , and sulfhydryl, , groups.
- Hydrophilic—acidic—amino acids have side chains that contain carboxylic acid, , groups.
- Hydrophilic—basic—amino acids have side chains that contain amine, , groups.
How are amino acids joined together?
Mechanism of peptide bond formation
Step 2: The carbonyl bond reforms with the elimination of hydroxide ion.
Step 3: The hydroxide ion abstracts a proton—elimination of water—and the positive charge on nitrogen is neutralized. This results in the formation of a new bond—a peptide bond between the two amino acids.
The double-bond character of the peptide bond
Forces that keep the different protein structures together
|Level of protein structure||Interactions that stabilize the structure|
|Primary||Covalent bond (amide/peptide bond)|
|Tertiary||Ionic bonds, disulfide bonds, hydrophobic interactions, hydrogen bonding|
|Quaternary||Ionic bonds, disulfide bonds, hydrophobic interactions, hydrogen bonding|