A molecular NAND gate based on Watson-Crick base pairing

[GRAPHICS] A DNA-binding dye, 4',6-diamidino-2-phenylindole (DAPI) signals AT base pai ring with a shift in the fluorescence emission spectrum. The signaling foll ows W-C base-pairing rules, and both dAMP and dTMP are required for the lar gest spectral shift. Thus, the dye with its two phosphate receptor sites fu nctions as a molecular NAND gate accepting nucleotides as inputs. Moreover, when the observation wavelength is changed from 470 to 411.5 nm, the gate functions in TRANSFER logic.