The invention provides a DNA molecule comprising a promoter sequence operably linked to a DNA sequence encoding first and second proteins linked by a hinge region wherein in that the promoter sequence can be one having activity which is induced in response to a change in the surrounding environment and the first protein can be Tetanus toxin C fragment or one or more epitopes thereof. A transformer circuit may be coupled to the fuel pump for increasing the driving speed of the fuel pump when required. Additionally, the system further comprises at least one extra surface parallel to the second lens surface, wherein at least one extra surface has a length L and is parallel to each other.