LNCS 2950 - Aspects of Molecular Computing (Frontmatter Pages)

AND Gate
Realizing Switching Functions Using Peptide-Antibody Interactions 357
In the same manner as above we can implement the AND gate. The details are
the following.
1. The antibody Cinit denotes the bit 1.
2. The antibody Cf (labeled antibody) denotes the bit 0.
3. epitope(B1) = {y}, epitope(B2) = {z},
4. epitope(A1) = {yx1}, epitope(A2) = {x2z},
5. epitope(Cinit) = {x1xx2}, epitope(Cf) = {x}.
6. aff(Ai) > aff (Cinit) > aff (Cf ), 1 ≤ i ≤ 2.
The simple idea used in the implementation of the AND gate follows from
the fact that the output 0 occurs even if only one of the inputs is 0. The algorithm
for the AND gate is the same as for the OR gate. The working of the AND
gate should be easy to understand as it is very similar to the working of the OR
gate.
NOT Gate
Since the NOT gate requires only one input, we take the peptide sequence as
P = xx2z
and take only the antibodies A1 and B1. The model is as follows:
1. The antibody Cinit denotes the bit 0.
2. The antibody Cf (labeled antibody) denotes the bit 1.
3. epitope(B2) = {z},
4. epitope(A2) = {x2z},
5. epitope(Cinit) = {xx2}, epitope(Cf) = {x}.
6. aff(Ai) > aff (Cinit) > aff (Cf ), 1 ≤ i ≤ 2.
The algorithm for NOT gateisasfollows:
1. Take the peptide sequence P in an aqueous solution.
2. Add the antibody Cinit.
3. Add antibody corresponding to the input bit.
4. Add antibody Cf .
It can be noted that the initial bit denoting 0 is toggled only if the input bit
is 0.
4 Extension to XOR, NOR,andNAND Gates
The same idea used in the implementation of the OR and AND gates is extended
to XOR, NOR and NAND. First we take the XOR gate; the other two gates
follow from OR and AND gates very easily.