Therefore, if a mutation leads to the replacement of a small side chain by a large one, the folded conformation will tend not to be able to accommodate the new residue. Refer to the pKa values . There is typically 1 ion pair per approximately 30 protein residues. A less specific property concerns the net charge of a protein. Polarity Charged and neutral polar side chains participate in hydrogen bonds, both with each other, with the main chain polar atoms and with solvent.
E bond has a partial double bond character.
Each oxygen can accept a hydrogen in two hydrogen bonds. His has two imidazole nitrogens, either or both of which is protonated. Trp can donate a hydrogen in a single hydrogen bond. A general feature of globular proteins is that such hydrophobic residues are found in the protein interior, while polar residues occur on the surface. In this respect, protein folding may be roughly compared to the formation of lipid micelles in aqueous solution- the chain becomes arranged such that apolar groups are buried, and polar groups exposed.