Biology - Molecular Theory of the Living Cell - page 88

10. Amino acid residues of protein domains carry information (Lockless
and Ranganathan 1999; S

€

uel et al. 2003; Socolich et al. 2005; Poole and

Ranganathan 2006).

4.4 The Chemistry and Thermodynamics of Information

The concept of information in computer science is heavily influenced by the
Shannon information theory (Shannon and Weaver 1949) and by symbol strings
such as Expression 4.7 . Biological information , however, may be too rich and deep
to be adequately captured by the quantitative theories of information developed
so far, including that of Shannon. The statement made by Prigogine (1991) two
decades ago still holds:
Traditional information theory was too vague, ... , because it is not deeply enough rooted

in physics and chemistry ... (4.9)

The connection among (1) irreversible thermodynamics, (2) chemistry, and (3)
information production was illustrated by Prigogine (1991) using a simple example.
He considered a chemical system containing two monomers X and Y which can
polymerize whenever the concentration of one of them exceeds some critical level.
If the system is at equilibrium, the concentrations of these monomers would
fluctuate randomly, obeying the Poisson law, leading to the production of a random
or disordered polymer as shown in Reaction 4.10 . However, when the system is
under nonequilibrium conditions and exhibits irreversible dynamics with some
regularity, the resulting polymer can encapsulate these regularities into nonrandom
monomer sequences. One such sequence is shown in Reaction 4.11 , which exhibits
a long-range correlation among the trimeric units XYX whose correlation distance
increases with time.

Reversible Processes ! XXYXYYYXYXYYXXXYXX (4.10)

Irreversible Processes ! XYX YXYXYY XYX YYY XYX (4.11)

Process 4.11 illustrate what Prigogine means when he states that:
... chemistry plays a very specific role ... it may “encapsulate” irreversible time into
matter ... In this way, irreversible processes may be made more permanent and transmitted
over longer periods of time. This is of special importance for us, as we should be able to
describe in these terms a world where the very existence of biological systems implies some
recording of irreversible processes in matter ... . ... chemical molecules produced under
non-equilibrium conditions keep some memory of the deviations from equilibrium which
exists at the moment of their production. (4.12)

Process 4.11 together with Statement 4.12 may be viewed as defining a novel
principle in nature which may be referred to as the Principle of Encoding Time into
Matter or alternatively the Principle of Encoding Dissipatons into Equilibrons