Re: Functional proteins from a random library

From: Preston Garrison (
Date: Fri Apr 06 2001 - 21:04:35 EDT

  • Next message: "Re: ID.Weinberg 2"

    Paul Nelson wrote:

      Bill Dembski deals with experiments like this (as I
    >recall, he looks at ribozyme engineering) in his
    >forthcoming book, _No Free Lunch: Why Specified
    >Complexity Cannot Be Purchased without Intelligence_. Pools of ~10^13 mRNAs could not exist on the early
    >Earth, or anywhere, really, without the help either
    >of organisms or clever biochemists.

    Neither I nor the authors claimed that this work had anything to do
    with the origin of life.

    Indeed it is
    >possible to "back out" of experiments like these
    >one step at a time, removing the intelligently-
    >synthesized reagents (e.g., buffers) and artificial
    >conditions. [In some ribozyme engineering experiments, for instance, the RNAs are tethered to keep them from precipitating.] As intelligent control or intervention is removed, the results cease to be biologically relevant.

    We use synthesized reagants and artificial conditions to do all of
    biochemistry and genetics. Does that mean that biochemistry and genetics are biologically irrelevant? If intelligent control invalidates an experiment in this area, then _all_ experiments are invalidated.

    >A whole lot of specified information, provided by Szostak and his co-workers,
    >is needed even to reach the point where one can go fishing for functions in
    >large pools of mRNAs (and their products).

    This is utterly irrelevant to the question of where the sequence information came from. This is again an argument, in effect, that all experiments are invalid. No sequence information went into the library (or very little - there is probably some weak bias from aspects of the library construction). Sequences came out that bind ATP. The sequence information (the only kind of information that is relevant to interpreting the experiment) was not put in by the investigators.

    The experiments are designed to begin answering the specific question, "How rare are foldable/functional protein sequences in sequence space?" This is an interesting question from the standpoint of protein biophysics alone, but it is obviously relevant to the question of whether and how completely new proteins can arise in non-functional or frame shifted sequences of existing organisms.

    The only reason I alluded to Bill Dembski in particular in my message is that I gather that, in contrast to Behe, he believes that even individual proteins cannot arise by chance. The number I remember is 10^60 for the odds that he gives, which is too rare to find by chance. The results of these experiments begin to suggest that he is wrong about that one point, but obviously much remains to be done to see how rare different kinds of functions are.

    As it happens, I am sympathetic to the ID position, especially at the point of the origin of life, since I don't see any way that that nut can be cracked. It may be that, to Howard's and George's theological chagrin, the Lord did miracles along the way to get life going, and perhaps at points after that. But no one in science is going to listen to any argument from a messenger who comes also making the remarkably bad argument that an experiment proves nothing simply because it was designed (i.e., that it WAS an experiment.)

    Preston G.

    Preston Garrison, Ph.D.
    UTHSCSA-Biochem. Dept. Insert the usual disclaimers here.
    MSC 7760
    7703 Floyd Curl Dr.
    San Antonio, TX 78229-3900

    This archive was generated by hypermail 2b29 : Fri Apr 06 2001 - 21:02:32 EDT