Friedrich Cramer

Untersuchungen über die bilding von N1-oxyden bei cytosin und cytosinderivaten

Abstract Cytosine and some of its derivatives are transformed to the N 1 -oxides by oxydation with perphthalic acid at pH 7.0. The N 1 -oxides are characterized by their ultraviolet-light spectra. Yields, R F values and ultraviolet-light characteristics of the N 1 -oxides are given. The rate of the oxidation of cytidine (pH7 and 2) and that of adenosine (pH7 for comparison) can be followed spectroscopically.

Die oxydation von adenosinderivaten zu N1-oxyden und der einbau von ADP-N1-oxyd in poly-a durch bakterien-rohextrakte

Abstract ADP- N 1 -oxide is prepared from ADP by oxidation with perphthalate at pH 7 in 49% yield. The N -oxide is incorporated into poly-A by extracts of Azotobacter vinelandii as shown from the isolated polynucleotide.

Polynucleotid-synthese mit bakterien-rohextrakten

Abstract Normally, non-purified polynucleotide phosphorylase does not show a net synthesis of polynucleotides from nucleoside diphosphates. This is due to the large amount of inorganic phosphate formed by various phosphatases from the nucleoside diphosphates. This inorganic phosphate shifts the equilibrium to the side of the monomer. Net synthesis of poly A by means of non-purified Azotobacter vinelandii extracts is achieved in the following ways: 1. 1. Dialysis of the extract removes phosphate and Mg 2+ . 2. 2. Addition of ATP blocks the myokinase activity completely. Since degradation of ADP goes via the equilibrium ADP⇌AMP+ATP, all ADP is used for poly A synthesis. Under these conditions, ATP is not the substrate of poly A synthesis. 3. 3. Addition of 0.4 M urea to the system increases the yield of poly A 2 times. Even after 50 h no degradation of the polymer (75% yield) is observed. This phenomenon might be due to either a competitive inhibition of the phosphorolysis of poly A or a change in the folding of the polymer.

Einfluss von harnstoff auf die enzymatische synthese und phosphorolyse von polynucleotiden

Abstract Polynucleotide phosphorylase (nucleosidediphosphate: polynucleotide nucleotidyl-transferase, EC 2.7.7.8) (crude extracts of Azotobacter vinelandii can be used for the synthesis of polynucleotides in improved yields when urea (0.8–2.0 M) is added. The following polynucleotides were synthesised: Poly-A (78%), Poly-C (84%), Poly-U (55%). The effect of urea is ascribed to an inhibition of the phosphorolysis, since phosphorolysis is not observed at urea concentrations, at which synthesis still proceeds. Thus the enzyme looses its reversibility in the presence of urea. Polyribonucleotides exhibit an increase of ultraviolet absorption (loss of hypochromicity) even at low urea concentrations, indicating a slight change of secondary structure under these conditions.