It's like a molecular lock waiting for the right key (a drug like morphine or fentanyl) to unlock or ... Proteins on μ-Opioid Receptor Structure and Ligand Binding, The Journal of Physical ...

Drugs such as heroin or cocaine have fixed formulas, but fentanyl is sneakier. Drug makers can tweak just one tiny part of its chemical structure – like swapping a single Lego piece – to ...