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Woodstock , Lowell W., and Folke Skooc . (U. Wisconsin, Madison.) Relationships between growth rates and nucleic acid contents in the roots of inbred lines of corn. Amer. Jour. Bot. 47(9) : 713–716. Illus. 1960.—A study has been made of the rates of elongation and nucleic acid contents of the roots of inbred lines of Zea mays, var. W-158, A-374B, W-58, W-28, 8A, and W-148. A direct proportionality was found between the ribosenucleic acid contents (μg./root) of the apical 3 or 6 mm. of the roots (roughly equivalent to their growing tips) and their rates of elongation. This strict, quantitative relationship to growth rate appears to be specific for RNA; it was not found for DNA, and it was independent of the size of the root. A detailed study of one line (W-58) has shown, furthermore, that the ribosenucleic acid content in the root tip decreases with time in proportion to the decrease in the growth rate of the root. 相似文献
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Question of the ribosyl moiety in the promotion of callus growth by exogenously added cytokinins 总被引:1,自引:0,他引:1
S M Hecht R M Bock R Y Schmitz F Skoog N J Leonard J L Occolowitz 《Biochemistry》1971,10(23):4224-4228
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Relative values of Vmax/Km for hydrolysis of 40 peptide p-nitroanilides catalyzed by human Cl-s and human acrosin are reported. For Cl-s, Ac-Lys(gamma Cbz)-Gly-Arg is the optimum sequence, but 25% of the substrates have (Vmax/Km)rel greater than 0.25 compared to this sequence. The best acrosin substrate tested has the sequence Tos-Gly-Pro-Arg, although (Vmax/Km)rel greater than 0.15 for more than half of the substrates. Proline at P2 is preferred by acrosin. Both enzymes prefer arginine at P1 greater than or equal to 3-fold over lysine and will not accept citrulline. In addition, occupancy of site S3 may yield an increase in Vmax/Km of greater than or equal to 10-fold with either enzyme, but many residues are accepted at S2, S3 and S4. Thus, an acrosin assay using Tos-Gly-Pro-Arg p-nitroanilide as a substrate is more than 20-times as sensitive as existing assays with blocked arginine derivatives. 相似文献
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