= Denaturation
{disambiguate=biochemistry}
{wiki}
= Protein denaturation
{synonym}
<Protein denaturation> is the loss of a <protein>'s native spatial organization, often with loss of biological function. Changes in <temperature>, <pH> or surroundings can disrupt <protein secondary structure>, <protein tertiary structure> or <protein quaternary structure>. <Protein denaturation> ordinarily preserves the <peptide bonds> and <protein primary structure>; it is different from cutting the chain. Recovery by <protein folding> is possible in some cases, but removing the denaturing conditions does not guarantee that every <protein> recovers. See https://openstax.org/books/biology-2e/pages/3-4-proteins[Clark, Douglas and Choi: denaturation, environmental conditions and loss of function].
\Image[/protein-folding-and-denaturation.png]
{title=<Protein folding>, <protein denaturation>, chain cleavage and <protein aggregation> are distinct events}
{description=Original toy schematic. Folded and unfolded drawings both preserve all twelve <amino acid residues> in the same order and all eleven <peptide bonds>. Cleavage removes one internal <peptide bond>, leaving two fragments with ten remaining <peptide bonds> in total. The separate <protein aggregation> drawing contains two associated chains with eleven <peptide bonds> each. Refolding is a qualified possibility, not a universal outcome. The drawings are not actual <protein> coordinates.}
In the diagram, unfolding preserves all eleven <peptide bonds>. Cleaving the connection between positions 6 and 7 leaves two six-residue fragments: each contains five <peptide bonds>, so there are $5+5=10$ in total. Simply cooling or otherwise restoring suitable conditions cannot recover the original chain by <protein folding> alone; the missing <covalent bond> would have to be remade. Conversely, <protein aggregation> can impede recovery without breaking any <peptide bond>. These distinctions explain why loss of function does not by itself reveal whether a <protein> unfolded, associated with other chains, or suffered chemical damage.
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