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Biomedical subjects

E Chargaff

Publications and source records attributed to E Chargaff.

At least 55 records · Page 3Linked to original sources
PubMed1970

Transferase from Escherichia coli effecting low-energy phosphate transfer to nucleosides and nucleotides.

This communication describes the partial purification of an enzyme in Escherichia coli that is capable of a low-energy transfer of organically bound phosphate to nucleosides, nucleoside 5'-phosphates, and deoxyribonucleoside 5'-triphosphates. With the exception of adenosine, the nucleosides give rise almost exclusively to 2'- and 3'-nucleotides. Thymidine and its derivatives are the best acceptors of phosphate groups. Since 5'-nucleotides are converted in high yields to the nucleoside 3',5'- or 2',5'-diphosphates, the enzyme may be regarded as a nucleotide phosphotransferase. In the ribonucleotide series, the aglycone affects the relative amounts of 2' and 3' derivatives. The noteworthy formation of nucleoside tetraphosphates suggests several regulatory functions of this enzyme which are discussed briefly.

Chromatography, DEAE-Cellulose↗
PubMed1969

Role of base-pairing in the control of an enzyme reaction.

In an attempt to ascertain whether specific base-pairing could have a regulating function in an enzyme system in which nucleotides serve as the substrate, we studied the effects of the addition of the various homopolymers of the ribonucleotide series on the action of adenylate kinase on ADP or CDP, and found that the results support this possibility. Poly U strongly inhibits the enzyme action on ADP, and poly G that on CDP, both to the extent of about 70 per cent. Lesser effects are shown when poly G is used with ADP and poly U with CDP. The other homopolymers tested, poly A and poly C, are ineffective.

Adenine Nucleotides↗
PubMed1969

Separation of microbial deoxyribonucleic acids into complementary strands.

DNA preparations from seven bacterial species and from the E. coli phage T4 can, after denaturation with alkali, be separated chromatographically into two distinct components (L and H) through intermittent gradient elution from methylated albumin kieselguhr columns. The direct chemical analysis of the L and H fractions isolated from DNA specimens of the AT type shows them to exhibit a high degree of complementarity; but despite a bias in the distribution of purines and pyrimidines, either fraction contains equimolar quantities of 6-amino and of 6-keto nucleotides. In the L and H components derived from DNA of the equimolar and GC types, the distribution bias appears limited to guanine and cytosine. It is suggested that the L and H fractions represent the complementary DNA strands.

Bacillus↗
PubMed1969

L-uridine: synthesis and behavior as enzyme substrate.

L-Uridine, the enantiomer of the normal RNA constituent D-uridine, was synthesized from L-ribose through coupling with bis(trimethylsilyl)-uracil. The synthetic product had the expected chemical and physical characteristics. When used as the acceptor for phosphate transfer by the nucleoside phosphotransferase of carrot, L-uridine is converted to 5'-L-uridylic acid. The Michaelis constants K(m) are 28 x 10(-3)M for L-uridine, 5 x 10(-3)M for D-uridine. The nucleoside phosphotransferase of human prostate, which phosphorylates D-uridine in the 5', 3', or 2' positions, fails to transfer phosphate to the 2' position of L-uridine, but does produce 5'-and 3'-L-uridylic acids.

Nucleotidyltransferases↗
PubMed1969

Complementary fractions of denatured DNA of coliphage T3 as templates for transcription.

This paper discusses the evidence that two fractions obtained by the chromatography of denatured DNA of phage T3 on columns of methylated albumin-kieselguhr represent the complementary strands. This evidence derives from a variety of temperature-absorbance measurements and from the base composition of the RNA products synthesized by RNA polymerase under the direction of the two single-stranded DNA templates.

Centrifugation, Density Gradient↗