The lac repressor and its N-terminal headpiece can bind a mini-operator containing a hairpin loop made of a hexaethylene glycol chain.

The binding of the lac repressor and the lac repressor N-terminal headpiece to a mini-operator with a hairpin loop made of a hexaethylene glycol chain was investigated using circular dichroism spectroscopy. The lac repressor's headpiece binds to the modified mini-operator with the same affinity as to a mini-operator of the same sequence without the hexaethylene glycol loop. The conformational effect due to the binding is not affected by the presence of the hexaethylene loop. It is also shown that the entire lac repressor binds to this modified mini-operator inducing a conformational change.