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主题:【原创】量子生物学 I 摘要和前言 -- witten1

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家园 Delbruck's model

I have to read it further to get it..

but you may understand it much faster,

"Delbruck concluded that mutations are quantum transitions resulting from either random thermal fluctuations or the absorption of radiant energy, spontaneous mutations arising predominantly from thermal fluctuations rather than from natural radiation. Schrdinger, although relying heavily on Delbruck's work, failed to mention the discoveries of H. J. Muller on radiation-induced mutagenesis or the important role of complementariness in the specific attraction between molecules and their enzymatic synthesis, which was already suggested by Haldane (1937) and Pauling and Delbruck (1940). "

http://www.genetics.org/content/153/3/1071.full

Delbruck's model: Much of Schrdinger's discussion in What Is Life? was based on an article by Timofeef-Ressovsky et al. (1935) on the mutation rate induced by X rays in Drosophila melanogaster. A third section of that article was by Delbruck (a model of genetic mutation based on atomic physics). Perutz (1987) summarized Delbruck's results.

After briefly reviewing the gene concept, Delbruck dealt with the nature of mutations and the stability of the gene. Since no direct methods for studying the chemical nature of the gene were then available, the problem was attacked indirectly by studying the nature and limits of gene stability and by asking whether the known facts about genes are consistent with the known facts of the atomic theory, especially with reference to the behavior of well-defined assemblies of atoms. Delbruck considered both vibrational and electronic transitions. He derived the relationship between the rate of such transition (W) and its activation energy (U). Delbruck stated that chemical bond energies are of the order of several electron volts, but argued that the activation energies of molecules cover an even wider range than his estimates indicate, so that reaction rates of any magnitude can result from a given set of circumstances. He concluded that evolution had stabilized the molecular structure of genes to the extent that their natural frequency of rearrangement is smaller by several orders of magnitude than the frequency of their reproduction. A single ionization, because of its much greater energy, should be sufficient to produce any given mutation, regardless of its natural frequency. On the basis of Delbruck's speculations with respect to the atomic structure of a gene, Schrdinger pointed out that “there is a fair chance of producing a mutation when an ionization occurs not more than about 10 atoms away from a particular spot on the chromosome.” However, Perutz (1987) summarized evidence indicating that Schrdinger's estimate was incorrect. An article published while Schrdinger's book was in press showed that the biological effects of ionizing radiation are due primarily to the generation of hydroxyl radicals and hydrogen atoms in the surrounding water (Weiss 1944). Other evidence since then has shown that the hydroxyl radicals and hydrated electrons can diffuse to their targets even if they are generated more than a thousand atomic diameters away (see Perutz 1987).

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