To change something so it doesn't work the way it should anymore, like making a protein or DNA not do its job.
High heat can denature the proteins in our food.
高熱は私たちの食べ物内のタンパク質を変性させることができます。
To take the alcohol out of a drink, usually by adding something that makes the alcohol go away.
They denatured the alcohol to make it undrinkable and avoid paying taxes.
彼らはアルコールを変性させ、飲むことができなくして税金を支払うことを避けました。