. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. PHOSPHORUS IN THE FROG GASTRULA 319 After alkali digestion of the defatted material, the supernatant was poured off, DNA was precipitated by the addition of an HC1-TCA mixture and DNA phos- phorus determined according to the procedure outlined by Sze ( 1953). The residue remaining in the alkali digest was analyzed as "residue ; After precipitation of DNA, the remaining supernatant was precipitated with magnesia mixture overnight to obtain the inorganic phosphorus liberated from phosphoprotein. The result
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. PHOSPHORUS IN THE FROG GASTRULA 319 After alkali digestion of the defatted material, the supernatant was poured off, DNA was precipitated by the addition of an HC1-TCA mixture and DNA phos- phorus determined according to the procedure outlined by Sze ( 1953). The residue remaining in the alkali digest was analyzed as "residue ; After precipitation of DNA, the remaining supernatant was precipitated with magnesia mixture overnight to obtain the inorganic phosphorus liberated from phosphoprotein. The resulting filtrate was hydrolyzed in 60^ perchloric acid and analyzed as "ribonucleic acid ; All fractions isolated were hydrolyzed in 60c/( perchloric acid in a sand bath until clear, and inorganic phosphorus was precipitated as the magnesium am- monium complex with magnesia mixture. The precipitates were collected on filter paper and mounted on brass discs for counting, which was done with a Geiger- Muller end window tube ( ) using a Nucleonic RC 2 sealer. All samples were corrected for decay and the instrument was checked daily against a standard beta V i 0 FIGURE 1. Dissection of gastrula. V = ventral half; D = dorsal half. The precipitates were eluted in 1 N sulphuric acid and the phosphorus determined by the method of Berenblum and Chain (1938) using the vessel described by Wiame (1947). Six separate experiments were completed, each run in duplicate, with ap- propriate reagent blanks. The fractions isolated represent heterogeneous groups of phosphate compounds with a wTide range of different origins (Grant, 1953). Furthermore, there is considerable doubt as to the extent of purity of these isolated fractions, particularly those fractions that may be contaminated with inorganic phosphorus (Davidson et al., 1951). Because of the relative nature of the data, however, it was assumed that any significant differences between dorsal and ventral
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