Wow, your first sentence sounded like you knew something or other. But you blew it off with the second.
Big molecules are not small molecules. Let me ask you: Just how close, package-size wise, is the Hib B protein to peanut protein?
How do the two proteins mesh up in filter chromatography?
Dude the whole protein doesn’t pack and interact - it’s the little protrusions and pockets that interact, very small parts of the whole.
Small molecule example was just to make things very simple - anyone can add to 28.
Oxytocin and vasopressin - closely related - close in size and weight, fairly similar in shape - different effects in the body.