Molecular AND gate

Figure 12.14 Schematic diagram for the operation of a two-input molecular AND gate. Ri and R2 are receptors for chemical species X and Y, respectively...

Fig. 2. A molecular AND gate in the shape of compound 1. Fluorescence of the anthracene unit can be quenched by PET from the tertiary amine (depicted as the circle-receptor), and the benzo-crown ether (the square-receptor). In the absence of a both stimuli or b, c only one stimulus, fluorescence is quenched by PET. d Presence of both stimuli removes the possibility of PET, and so the system fluoresces...

Fig. 17. A A molecular AND gate with chemical inputs (H+ and Na+) and a fluorescence output. B Fluorescence spectra of the AND gate (a) in the presence of H+ and Na+, (b) in the presence of H+ and the absence of Na+, (c) in the presence of Na+ and the absence of H+, and (d) in the absence of both H+ and Na+. The fluorescence spectra are adapted from [72] with permission...

The analogy drawn between -stacked solids and duplex DNA has provided a useful starting point for experiments to probe and understand DNA-medi-ated CT. As with the -stacked solids, the DNA base pair array can provide an effective medium for long range CT. Mechanistically, however, the differences between DNA and these solid state materials may be even more important to consider. Duplex DNA, as a molecular -stacked structure, undergoes dynamical motion in solution. The time-dependent and sequence-dependent structures that arise serve to modulate and gate CT. Indeed in probing DNA CT as a function of sequence and sequence-dependent structure, we may better understand mechanistically how CT proceeds and how DNA CT may be utilized. 

Magri DC, Brown GJ, McClean GD, de Silva AP (2006) Communicating chemical congregation a molecular and logic gate with three chemical inputs as a lab-on-a-molecule prototype. J Am Chem Soc 128 4950-4951... 

Rousseau E, Smith JS, Meissner G 1987 Ryanodine modifies conductance and gating behavior of single Ca2+ release channel. Am J Physiol 253 C364—C368 Wallner M, Meera P, Toro L 1999 Molecular basis of fast inactivation in voltage and Ca2+-activated K+ channels a transmembrane /) subunit homolog. Proc Natl Acad Sci USA 96 4137-4142... 

Figure 13. A three-terminal molecular junction (left), molecular switch (center) and four-terminal molecular logic gate (right).

A molecular-level two-input AND gate can be made from two covalently-linked receptors, Ri and R2, that are able to quench the luminescence of a fluorophore, F. When one of the receptors acts as host to a suitable species, it can no longer quench the luminescence of F, but the luminescence can be quenched by the other free receptor. The output signal (luminescence from F) can only be observed when both receptors are bound to chemical species (Figure 12.14). 

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