Information Technology Reference
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RNA and chemicals in its environment, transforming the RNA into its logical
successor.
Conrad and Liberman [9] developed this idea further, describing parallels
between physical and computational processes (e.g., biochemical reactions be-
ing used to implement basic switching circuits). They introduced the concept of
molecular level “word-processing” by describing it in terms of transcription and
translation of DNA, RNA processing, and genetic regulation. However, their
article lacks a detailed description of the biological mechanisms highlighted and
their relationship with “traditional” computing. As the authors acknowledge,
“Our aspiration is not to provide definitive answers . . . but rather to show that
a number of seemingly disparate questions must be connected to each other in
a fundamental way” [9, p. 240].
Conrad [8] expanded on this work, showing how the information process-
ing capabilities of organic molecules may, in theory, be used in place of digital
switching components (Figure 1.1a). Enzymes may cleave specific substrates by
severing covalent bonds within the target molecule. For example, restriction en-
donucleases cleave strands of DNA at specific points known as
restriction sites
.
Enzyme
Substrate
Ligand
(a)
(b)
Figure 1.1
(a) Components of enzy-
matic switch. (b) Enzyme recognizes
substrate and cleaves it. (c) Ligand
binds to enzyme, changing its confor-
mation. Enzyme no longer recognizes
substrate.
(c)
