Greetings and Salutations,
Some of you may recall an argument Glenn Morton and I had a while back over
the work of John J. Toole in synthesizing ribozymes (catalytic strands of
RNA) to bind human thrombin using a process of natural selection. I was
reading that article again the other day and I seem to have made an error.
In the post I sent on this subject, I tried to point out that binding of gamma
thrombin had not been obtained in the experiment despite the large numbers of
molecules that were tested. From this, I concluded that Toole's work was
evidence that barriers to the "evolution" of certain functions are too great
to be overcome even when using large numbers of different molecules.
I still believe this to be true, unfortunately I can no longer claim empirical
confirmation on the basis of the work by Toole. The reason for this is that
I was mistaken about the composition of the human thrombin used in the
experiments and in the number of successful variants that were sequenced in
the subsequent studies by Bock et al. and Paborsky et al. I thought the
human thrombin used in the experiments contained both alpha and gamma thrombin
and that a representative sample of the successful variants had been sequenced
(as had been done in the work of Gerald Joyce). On reading those papers over
again, I find I was mistaken. The articles do not state that human thrombin
comes in both alpha and gamma varieties and only one successful thrombin
aptamer was sequenced. (32 were sequenced by Toole but only one by Paborsky
et al.)
This does not change my analysis of the work of Joyce or my opinions on the
difficulties of molecular evolution, but I felt you should be aware of the
error. (No matter how painful it is to admit that I was wrong to Glenn)
In Christ,
rob
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