NANDv2b has not passed the X-gal assay on plates, so no ONPG data has been measured. This is caused by the weakest hybrid operator downstream. The affinity of this operator (O27) is too weak for repressor to bind to the DNA and repress the promoter.

Figure 1 X-gal plates of NANDv2b. From left to right: R2+R4, R2, R4. Blue colonies show that the weakest hybrid operator is not suitable for NAND gate.