scholarly journals The interaction of aflatoxin B1 with polynucleotides and its effect on ribonucleic acid polymerase

1969 ◽  
Vol 114 (4) ◽  
pp. 679-687 ◽  
Author(s):  
A. M. Q. King ◽  
B. H. Nicholson
Keyword(s):  
Ionic Strength ◽  
Aflatoxin B1 ◽  
Polycytidylic Acid ◽  
Spectral Shifts ◽  
Bivalent Cations ◽  
Polyinosinic Acid ◽  
Polyadenylic Acid ◽  
Polyuridylic Acid ◽  
Calf Thymus

1. The interaction of aflatoxin B1 with different polynucleotides was studied spectrophotometrically. Equations were derived that enable the degree of binding to be determined without first determining the extinction coefficient of the bound form. 2. The interaction with calf thymus DNA obeys first-order relationships with an association constant of 0·40mm−1, but there is some evidence for a secondary binding process from results obtained at 390nm. 3. The spectral shifts decreased in the order polyadenylic acid+polyuridylic acid>DNA>polyadenylic acid>polyadenylic acid+polyinosinic acid. Polycytidylic acid, polyuridylic acid, polyinosinic acid (both single- and triple-stranded), AMP, CMP, GMP and UMP did not interact with aflatoxin. It was concluded that there is a requirement for the amino group of adenine (or possibly guanine) for binding of aflatoxin to polynucleotides to occur. 4. Binding is reversed by increasing ionic strength, and by Mn2+ and Mg2+ in the concentration range studied (0–5mm). The effect of the Mn2+ or Mg2+ was far greater than would be expected on the basis of their ionic strength. With both the bivalent cations and sodium chloride the reversal is greatest with double-stranded polynucleotides. 5. Inhibition in vitro of the DNA-dependent RNA polymerase of Escherichia coli by aflatoxin B1 was detected only in the absence of Mg2+ and at concentrations of Mn2+ below the optimum for RNA synthesis in vitro. 6. The degree of inhibition (maximally 30%) was dependent on the concentration of Mn2+ and decreased during incubation.

Ultraviolet circular dichroism studies on synthetic polynucleotides

1969 ◽  
Vol 47 (6) ◽  
pp. 637-642 ◽  
Author(s):  
Fred H. Wolfe ◽  
Kimio Oikawa ◽  
Cyril M. Kay
Keyword(s):  
Circular Dichroism ◽  
Wavelength Region ◽  
Ph Values ◽  
Polycytidylic Acid ◽  
Naturally Occurring ◽  
Polyinosinic Acid ◽  
Polyadenylic Acid ◽  
Polyuridylic Acid ◽  
Extreme Sensitivity ◽  
Circular Dichroïsm

The ultraviolet circular dichroism spectra of polyadenylic acid, polyguanylic acid, polycytidylic acid, polyinosinic acid, and polyuridylic acid have been examined at neutral and acidic pH values, and at moderate and low ionic strengths, over the wavelength range 300–185 mμ. Increased resolution of spectra below 225 mμ has revealed heretofore unexamined ellipticity bands in the low wavelength region, which are sensitive to conformational alterations for those polynucleotides which exhibit both single and multistranded secondary structures. It is concluded that these ellipticity bands, in view of their extreme sensitivity to conformation, will be of significance in increasing the usefulness of the homopolynucleotides as model compounds in conformational studies of naturally occurring RNAs.

scholarly journals A ribonuclease from human skeletal muscle

1970 ◽  
Vol 118 (1) ◽  
pp. 9-13 ◽  
Author(s):  
D. F. Goldspink ◽  
R. J. Pennington
Keyword(s):  
Gel Filtration ◽  
Maximal Activity ◽  
Exchange Chromatography ◽  
Heat Stable ◽  
Polycytidylic Acid ◽  
Bivalent Cations ◽  
Polyadenylic Acid ◽  
Polyuridylic Acid ◽  
Ammonium Sulphate Fractionation ◽  
Cyclic Phosphates

1. A ribonuclease has been prepared from human muscle by ammonium sulphate fractionation, heat treatment and ion-exchange chromatography. 2. The enzyme degrades polycytidylic acid and polyuridylic acid to the nucleoside 3′-phosphates, with nucleoside 2′:3′-cyclic phosphates as intermediates. Polyadenylic acid and polyguanylic acid are not attacked. 3. The enzyme has maximal activity at pH8.5. The molecular weight (by gel filtration) is between 11000 and 12000. It is relatively heat-stable. It exhibits optimum activity in a medium of high ionic strength, and is inhibited by several bivalent cations, particularly Zn2+.

Binding affinities of folic acid and related pterins with biological macromolecules under physiological conditions

Pteridines ◽  
2015 ◽  
Vol 26 (1) ◽  
pp. 23-29
Author(s):  
Michael Soniat ◽  
Christopher B. Martin
Keyword(s):  
Folic Acid ◽  
Neutral Lipids ◽  
Micrococcus Luteus ◽  
Biological Macromolecules ◽  
Binding Affinities ◽  
Physiological Conditions ◽  
Polycytidylic Acid ◽  
Polyadenylic Acid ◽  
Calf Thymus ◽  
Photochemical Damage

AbstractFolic acid and pterin derivatives are important heterocyclic compounds found in a variety of biological systems and have been shown to be photochemically active. Understanding the amount of binding that various pterins have with biological macromolecules under physiological conditions is important in predicting what specific biomolecules will bind with pterins and may, therefore, result in photochemical damage from charge-transfer reactions. The relative binding of folic acid, or pteroyl-L-glutamic acid (PteGlu), 6-methylpterin (Mep), 6-hydroxymethylpterin (Hmp), 6-formylpterin (Fop), and 6-carboxypterin (Cap) with bovine serum albumin (BSA), electrically neutral lipid (ENL), polyguanylic acid (Poly G), polycytidylic acid (Poly C), polyadenylic acid (Poly A), polythymidylic acid (Poly T), Micrococcus luteus DNA (72% GC), Escherichia coli DNA (50% GC), calf thymus DNA (42% GC), and Clostridium perfrigens DNA (27% GC) in neutral phosphate buffer were studied. Our results indicate that PteGlu demonstrated strong binding to neutral lipids, while the other pterins showed minimal binding, and BSA had a significant binding to PteGlu, Cap, and especially Fop. Our results also reveal a high affinity for DNA by PteGlu, which suggests that a relatively high percentage of folic acid is bound to DNA before photochemistry occurs.

Zum Wirkungsmechanismus von 1-Nitroso-3-nitro-1-methyl-guanidin bei der Mutationsauslösung

1967 ◽  
Vol 22 (5) ◽  
pp. 512-517 ◽  
Author(s):  
P. Chandra ◽  
A. Wacker ◽  
R. Süssmuth ◽  
F. Lingens
Keyword(s):  
Methyl Group ◽  
Polycytidylic Acid ◽  
Polyadenylic Acid ◽  
Polyuridylic Acid ◽  
Acceptor Activity ◽  
Maximum Inhibition

The effect of NNMG on the template activities of different polynucleotides (polyuridylic acid, polycytidylic acid, polyadenylic acid and copolymer of adenylic and guanylic acid 5,5:1) and t-RNS was studied. The maximum inhibition of the messenger activity was found for poly-C, followed by poly-Α and poly-U. The acceptor activity of t-RNA was found to be inhibited by NNMG: maximum for proline, followed by serine, leucine, phenylalanine and lysine. The mechanism of these inhibitions was studied using NNMG radioactively labelled on the methyl group. Different amounts of radioactivity were found in the various polynucleotides and t-RNS.

Triplex-forming oligonucleotides: principles and applications

2002 ◽  
Vol 35 (1) ◽  
pp. 89-107 ◽  
Author(s):  
Karen M. Vasquez ◽  
Peter M. Glazer
Keyword(s):  
Nucleic Acids ◽  
Dna Recombination ◽  
Stable Complex ◽  
X Ray ◽  
Triplex Formation ◽  
Polycytidylic Acid ◽  
Genome Modification ◽  
Fiber Diffraction ◽  
Polyadenylic Acid

1. Triple-helical nucleic acids 891.1 History 891.2 Use of oligomers in triplex formation 902. Modes of triplex formation 902.1 Intermolecular triplexes 902.2 Intramolecular triplexes (H-DNA) 922.3 R-DNA (recombination DNA) 922.4 PNA (peptide nucleic acids) 933. Triplex structural models 933.1 YR-Y triplexes 943.2 GT-A base triplets 943.3 TC-G base triplets 943.4 TA-T and C+G-C base triplets 943.5 RR-Y triplexes 944. Modifications of TFOs 954.1 Backbone modification of oligonucleotides 954.2 Modification of the ribose in oligonucleotides 964.3 Base modification of oligonucleotides 975. Gene targeting and modification via triplex technology 985.1 Transcription and replication inhibition 995.2 TFO-directed mutagenesis 995.3 TFO-induced recombination 1005.4 Future challenges in triplex-directed genome modification 1006. References 101The first description of triple-helical nucleic acids was by Felsenfeld and Rich in 1957 (Felsenfeld et al. 1957). While studying the binding characteristics of polyribonucleotides by fiber diffraction studies, they determined that polyuridylic acid [poly(U)] and polyadenylic acid [poly(A)] strands were capable of forming a stable complex of poly(U) and poly(A) in a 2:1 ratio. It was therefore concluded that the nucleic acids must be capable of forming a helical three-stranded structure. The formation of the three-stranded complex was preferred over duplex formation in the presence of divalent cations (e.g. 10 mm MgCl2). The reaction was quite specific, since the (U-A) molecule did not react with polycytidylic acid [(poly(C)], polyadenylic acid or polyinosinic acid [(poly(I)] (Felsenfeld et al. 1957). It was later found that poly(dT-dC) and poly(dG-dA) also have the capacity to form triple-stranded structures (Howard & Miles, 1964; Michelson & Monny, 1967). Other triple helical combinations of polynucleotide strands were identified from X-ray fiber-diffraction studies including, (A)n.2(I)n and (A)n.2(T)n (Arnott & Selsing, 1974). X-ray diffraction patterns of triple-stranded fibers of poly(A).2poly(U) and poly(dA).2poly(dT) showed an A-form conformation of the Watson–Crick strands. The third strand was bound in a parallel orientation to the purine strand by Hoogsteen hydrogen bonds (Hoogsteen, 1959; Arnott & Selsing, 1974). In 1968, the first potential biological role of these structures was identified by Morgan & Wells (1968). Using an in vitro assay, they found that transcription by E. coli RNA polymerase was inhibited by an RNA third strand. Thus, the recent developments identifying the potential of triplex formation for gene regulation and genome modification came more than 20 years after this first study of transcription inhibition by triplex formation.

Nucleosomes are assembled into discrete size structures by histone H1 in vitro

1986 ◽  
Vol 64 (5) ◽  
pp. 463-473 ◽  
Author(s):  
Teni Boulikas
Keyword(s):  
Ionic Strength ◽  
Histone H1 ◽  
Higher Order ◽  
Third Order ◽  
Calf Thymus ◽  
Exogenous Histone ◽  
Structural Subunit ◽  
Chromatin Structural ◽  
Low Ionic Strength

The involvement of histone H1 in the formation and maintenance of higher order chromatin structures in vitro was investigated biochemically. Addition of exogenous histone H1 to isolated calf thymus mononucleosomes in low ionic strength buffer resulted in the formation of electrophoretically distinct mononucleosome assemblies (supernucleosomes). The smaller super-nucleosomes were composed of about 12, 18, 24, or 30 nucleosomes and one to two molecules of histone H1 per nucleosome. It was difficult to determine accurately the size of the larger supernucleosomes, but their bands from native gels contained probably between 60 and 300 nucleosomes or more. Similar supemucleosome size classes were also obtained when oligonucleosomes instead of mononucleosomes were employed. When the assembly of mono- and oligo-nucleosomes with histone H1 took place in 0.15 M NaCl, discrete supernucleosomes containing only mono- or di-nucleosomes, but not a mixture of both, were formed. It is proposed that the small supernucleosomes containing oligomers of 6 nucleosomes may represent integral multiples of the second-order chromatin structural subunit, whereas the larger supernucleosomes containing about 60 to 300 or more nucleosomes may correspond to chromatin domains or third-order chromatin structures observed by other techniques.

scholarly journals The histochemical demonstration of hydrolase activities with films of homopolyribonucleotides.

1975 ◽  
Vol 23 (1) ◽  
pp. 51-58 ◽  
Author(s):  
R Daoust
Keyword(s):  
Ribonucleic Acid ◽  
Histochemical Demonstration ◽  
Tissue Sections ◽  
Polycytidylic Acid ◽  
Polyadenylic Acid ◽  
Polyuridylic Acid

Films of polycytidylic acid, polyuridylic acid and polyguanylic acid were exposed to tissue sections and the results were compared with those obtained in previous studies on polyadenylic acid and ribonucleic acid. Important variations were observed in the distribution of the hydrolases acting on the different polyribonucleotides, suggesting that a variety of nucleases with marked proclivity for particular nucleotide residues can be demonstrated by the use of films of homopolymers.

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