My friend, who is allergic to gluten, was eating a gluten-free brownie. I was curious about the purpose of gluten in baking, and after a bit of research, found that gluten is actually a protein complex! While the exact structure of gluten is not well characterized, it consists of mostly of gliadin, which is a globular protein molecule, and the more linear glutenin. The main cause of these different structures is actually that gliadin disulfide linkages are primarily intra-molecular, causing them to become more compact, while glutenin proteins interact through both intra- and inter-molecular disulfide linkages! These differences in tertiary structures of course must trace back to their primary structures.
The most interesting part about this is that flour is actually made up of gliadin and glutenin, but they don’t interact until water is added – just another reason it’s so important to consider the environment when considering non-covalent interactions.