Tuesday 25 April 2017

PROTEINS X EARTH

The number of different existing proteins can be estimated to be of the order of thousands
of billions – say, 1014 (100,000 billion) to be generous. These proteins are the product of
billions of years of evolution, but we all accept the view that present-day proteins have the
imprints and basically similar structures and functions as those of early life on Earth. The
number of 1014 different proteins is certainly impressive, and yet it is ridiculously small
compared to the theoretical number of possible proteins. If in each position of the chain we
can have any one of the 20 amino acids (also referred to as “residues”), then, for a chain
length of 100 residues, the number of mathematically possible different chains is 20100
(which is approximately equal to 10^130).

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