From 2007.igem.org

Conductance Adjusting

As we mentioned above, the noninterference Repressor/Operator pairs can play good roles as “wires”. Of course different pairs have different strength of bond, so these wires will transfer different intensity of signals from upstream components to downstream ones, even though conducting the same two components. In qualitative or semiquantitative experiments this will not be a serious problem, but we must solve it for preciser experiments. We all know that differenet promoters can initialize transcription strongly or weakly ([http://partsregistry.org/Part:BBa_J23100 Parts:BBa_J23100 and its family]). On the other hand, various RBS may lead to various efficiency of translation ([http://partsregistry.org/Part:BBa_J61100 Parts:BBa_J61100 and its family] and [http://partsregistry.org/JCA_Arkin_RBSFamilyPart2 JCA_Arkin_RBS Family]). Naturally we will think of these two approaches: using different promoters or using different RBS. But according to the idea of “modularization”, we don’t want to modify promoters casually because these promoters are the kernel elements of our logic components. Anyway, we can modify the other elements around this kernel, i.e. the RBS and operators. Let’s imagine the wires--every wire have two ends, and each of our Repressor/Operator pairs is a monodirectional wire. The beginning end is just the RBS which activates the translation of this repressor protein, and the tail end is the operator which accesses the repression of this protein.