Nucleinsäuren in Chloroplasten I. Charakterisierung der DNS und RNS von Antirrhinum majus
2014
Ruppel, Hans Georg
The occurrence of nucleic acids in chloroplast preparations and leaves of Antirrhinum majus has been investigated.Chloroplast preparations isolated from freeze-dried leaves in a non-aqueous medium were found to contain DNA. Characterization of the DNA was based on chemical analyses and density gradient centrifugation. The chloroplast DNA has a density of 1.698 g/cm³ corresponding to a guaninecytosine content of 37 — 38%. The hyperchromic effect of the DNA has shown its double-stranded structure. Leaf DNA has also been characterized by density gradient centrifugation and shown to contain as major component the nuclear DNA with a density of 1.689 g/cm³ which corresponds to a guanine-cytosine content of about 31% and a minor component identified as chloroplast DNA.Extraction of the total nucleic acids of chloroplast preparations and their chromatographic separation on methylated serum albumin column yielded 5 fractions as follows: Soluble RNA (fraction I) with s=3.8—4.0, DNA (fraction II) containing small but detectable amounts of an unknown RNA component, two RNA fractions presumable of ribosomal origin with s = 17 (fraction III) and s = 26 (fraction IV), and a RNA fraction heterogeneous in molecular size (fraction V) with s=23 — 50. The soluble RNA has a high GC-content whereas fraction V shows a relative high adenine content. Compared with the nucleic acids from leaves the chloroplast preparations contain the same fractions, differing only in the higher content of fraction III related to the amount of fraction IV. Beside the DNA fraction of leaf extract with the sedimentation coefficient of s = 12 — 13 a further UV-absorbing component with s=5.0—5.5 has been found. Its character is unknown.
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