Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Polyribonucleotides”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMed1982

[Effect of amphotericin B on the interferonogenic activity of poly(G) . poly(C) and poly(G,I) . poly(C) in mice and their resistance to infection by the tick-borne encephalitis virus].

It was shown that amphotericin B, a polyenic macrolide markedly potentiated in mice the interferonogenic activity of the two-strand synthetic polyribonucleotide complexes, Poly (G) . Poly (C) and Poly (G, I) . Poly (C). At the same time amphotericin B used in high or low doses lowered or somewhat increased respectively the protective effect of Poly (G) . Poly (C) and Poly (G, I) . Poly (C) which was not adequate to the antibiotic effect on their interferonogenic activity. It was found that amphotericin B stimulated in the mice the infection caused by the forest spring encephalitis virus, accelerated the period of its manifestation and increased the death rate. This effect correlated with the concentration of amphotericin B and the dose of the virus. The relationship between the differential effect of amphotericin B on the interferonogenic and antiviral activity of polyribonucleotide interferonogenes and the stimulation of the viral infection by them is discussed.

Amphotericin B↗
PubMed1993

Polynucleotide binding to macrophage scavenger receptors depends on the formation of base-quartet-stabilized four-stranded helices.

Macrophage scavenger receptors exhibit unusually broad, but circumscribed, polyanionic ligand-binding specificity. For example, the polyribonucleotides poly(I) and poly(G) are ligands but poly(A) and poly(C) are not. To further investigate the molecular basis of this polynucleotide-binding specificity, we tested the capacity of various oligodeoxyribonucleic acids to inhibit the scavenger receptor-mediated degradation of 125I-labeled acetylated low density lipoprotein by Chinese hamster ovary cells expressing the type I bovine scavenger receptor. A series of short oligodeoxyriboguanines (dGn, where 5 < or = n < or = 37) were effective inhibitors. The dG6, dG12, and dA5G37 members of this series were shown by circular dichroism and UV spectroscopy to be assembled into four-stranded helices stabilized by G-quartets. [32P]dA5G37 bound directly to scavenger receptors. Partial or complete denaturation of the quadruplex structures of these oligonucleotides by boiling destroyed their inhibitory activity. Receptor activity was also inhibited by d(T4G4)4, a telomere-like oligonucleotide which forms an intramolecular quadruplex. In addition, conversion of the four-stranded potassium salt of poly(I) to the single-stranded lithium salt dramatically reduced its inhibitory activity. Addition of KCl to the Li+ salt resulted in the reformation of poly(I)'s quadruplex structure and restoration of its inhibitory activity. A variety of single-stranded and double-stranded oligo- and polydeoxyribonucleotides (e.g. dA37, HaeIII restriction fragments of phi X174) exhibited very little or no inhibitory activity. Thus, a base-quartet-stabilized four-stranded helix appears to be a necessary structural determinant for polynucleotide binding to and inhibition of scavenger receptors. This conformational requirement accounts for the previously unexplained polyribonucleotide-binding specificity of scavenger receptors. The spatial distribution of the negatively charged phosphates in polynucleotide quadruplexes may form a charged surface which is complementary to the positively charged surface of the collagenous ligand-binding domain of the scavenger receptor.

Animals↗
PubMed1979

Induction of interferon and radioprotective activity of polyriboguanylic-polyribocytidylic acid complex in mice.

The effect of polyriboguanylic-polyribocytidylic acid complex was investigated against acute X- and prolonged 60Co-gamma irradiation. Prophylactic administration of the polyribonucleotide complex increased endogenous spleen colony formation and the percentage of survival of irradiated BALB/c mice. The most pronounced effect was observed when the animals had been irradiated at the time of maximum interferon accumulation in blood, i.e. 24 hr after interferon induction by the polyribonucleotide complex.

Animals↗
PubMed1987

Studies of adenosine incorporation in Langendorff rat heart and rat heart mitochondria.

The acid-insoluble product isolated from well-oxygenated Langendorff rat heart after perfusion with [14C]adenosine was purified by phenol extraction and subjected to specific phosphorolysis by pure polynucleotide phosphorylase. TLC analysis of the reaction mixture showed that ADP was the only radioactive product, proving that the original substance was a polyribonucleotide. Studies of the time course of labelling and of the distribution of the acid-insoluble product between the mitochondrial and nuclear fractions showed that both are labelled even after 1 min at 25 degrees C, but at short times and low temperature more radioactivity is found in the mitochondria. The kinetics of adenosine incorporation resemble those expected for the labelling of hnRNA and mRNA. Isolated, respiring mitochondria incorporate adenosine and adenine nucleotides into acid insoluble form by a process dependent on oxidative phosphorylation and the adenine nucleotide translocase that is specific for adenine derivatives. The results are discussed in terms of the hypothesis that the polyribonucleotide might be a storage form of adenine nucleotides: it is concluded that the bulk of the labelled product is unlikely to play a major role in energy metabolism.

Adenine Nucleotides↗
PubMed1975

A tw0-component ribonucleotidyl transferase from E. coli.

Some properties of an enzyme designated as a two component ribonucleotidyl transferase from E. coli are presented. The enzyme in the presence of magnesium ions catalyzes the synthesis of polyribonucleotide chains using all four nucleoside triphosphates as substrates. The enzyme consists of two components; component A in the presence of Mg2+ catalyzes the synthesis of homo- and heteropolymers using ATP, CTP and UTP but not GTP as substrates. Component B itself does not catalyze any synthesis at all, but its addition to component A affects this component in two ways: quantitatively- the activity of component A considerably increases, and qualitatively- both components together are capable of catalyzing the synthesis of polyribonucleotides consisting of all four ribonucleotides.

Escherichia coli↗
PubMed1985

Inhibition of RNA-directed DNA polymerase from avian myeloblastosis virus by a 5-benzyl-6-aminouracil.

5-(p-Chlorobenzyl)-6-aminouracil (5-ClAU) inhibited RNA-dependent DNA polymerase (reverse transcriptase) from avian myeloblastosis virus. Inhibition was expressed only in the presence of a polyribonucleotide template such as mRNA or poly(rA), and kinetic analysis suggested that the action of 5-ClAU is competitive with template:primer. 5-ClAU did not inhibit HeLa DNA polymerase gamma, an enzyme that efficiently copies polyribonucleotide templates. A mechanism is proposed in which a 5-ClAU:template complex interferes with enzyme function, based partly on NMR studies indicating that 5-ClAU can form a hydrogen-bonded complex with deoxyadenosine in solution.

Animals↗
PubMed1988

Properties of the liquid crystals of some biopolymers.

Nematic liquid-crystalline solutions of polypeptides such as PBLG and PELG orient in the direction of a very low static electric field as if the polypeptide molecules were a collection of rod-like molecular clusters having a huge, permanent electric dipole moment. This dipole moment originates from fluctuation of the distribution of polymer helices in both directions of the rod-like molecular cluster with roughly equal likelihood. The molecular cluster of PBLG is estimated to be composed of some 5 x 10(5) molecules and has dimensions of a few to several micrometers x 0.1 microns phi in methylene bromide when the degree of polymerization (mean) is 650. The nematic solutions also orient in the direction of a static magnetic field. The peptide groups of the polypeptide form planes which are parallel to the polymer helix and the magnetic-field orientation is due to the demagnetizing field produced in the peptide groups perpendicular to their planes by the ring current of the pi electrons. The formation of rod-like molecular clusters is absolutely necessary to invite the magnetic-field orientation as in the electric-field orientation. The anisotropy of the magnetic susceptibility has been estimated to be on the order of 10(-8) emu/g, and the twist elastic constant of the cholesteric structure on the order of 10(-7) dyn/cm. Derivatives of PBLG with long alkyl chains as pendant groups assume thermotropic liquid crystals, in which melted alkyl chains behave as a solvent in a similar manner as in lyotropic liquid crystals of the parent PBLG. An analogy of thermotropic liquid crystals of the modified polypeptides with those of discotic liquid crystals in the columnar phase has been suggested. Concentrated solutions of a double-stranded helix of poly(A).poly(U) and a triple-stranded helix of poly(A).2poly(U) form liquid crystals both of the nematic and the cholesteric types. The nematic solutions of these polyribonucleotide complexes orient perpendicular to the direction of a static magnetic field owing to the diamagnetic dipole moments induced in the purine or pyrimidine bases of the polyribonucleotides perpendicular to their planes, which are roughly perpendicular to the polymer helices. Any rod-like polymer has a good chance to form liquid crystals in which the occurrence of forces acting among the molecules is not necessary. The PLGA-Na in a neutral aqueous solution undergoes a "coil-to-alpha helix transition" when the polymer concentration is increased.(ABSTRACT TRUNCATED AT 400 WORDS)

Biopolymers↗
PubMedDate not supplied

Varying role of alpha/beta interferon in the antiviral efficacy of synthetic immunomodulators against Semliki Forest virus infection.

The question of whether interferon alpha/beta is the common mechanism of antiviral action of synthetic immunomodulators was investigated in B6C3F1 mice infected with Semliki Forest virus. Mice were treated with various concentrations of normal sheep serum or potent anti-alpha/beta interferon antiserum, inoculated with the immunomodulators, and infected 24 hours later with virus. Three patterns emerged. The antiviral action of the pyrimidinone (ABMP) and the oral interferon inducer (CL246,738) appeared to be mediated primarily by interferon alpha/beta; their protective ability was almost completely abrogated by treatment with low levels of anti-alpha/beta interferon antiserum. The antiviral action of two other immunomodulators, a mismatched polyribonucleotide (Ampligen) and a polyanionic copolymer (MVE-2) at least partially involved interferon. Activity of these compounds was reduced, but not consistently eliminated by treatments with high doses of antiserum. The antiviral activity of another polyribonucleotide, polyriboinosinic-cytidylic acid complexed with lysine carboxymethylcellulose (poly ICLC), was not affected by treatment with even the highest amount of antiserum (two injections of 100,000 neutralizing units each). Almost complete protection by poly ICLC was observed despite the fact that this high concentration of antiserum, when given alone, caused a decrease in natural resistance to Semliki Forest virus infection. Taken together, these results indicate that induction of interferon alpha/beta does not appear to be the major common mechanism of antiviral activity among these diverse synthetic immunomodulators.

Acridines↗
PubMed1981

Formation of peptides from amino acids by single or multiple additions of ATP to suspensions of nucleoproteinoid microparticles.

When lysine-rich proteinoid, which catalyzes the formation of peptides from amino acids and ATP, is complexed with acidic proteinoid to form microspheres of mixed constitution, the normal synthesis by basic proteinoid alone is multiplied several-fold. The product consists not only of small peptides but also of a high-molecular-weight fraction of substituted proteinoid. Suspensions of particles of lysine-rich proteinoid complexed with polyadenylic acid catalyze the synthesis of peptides from each of the amino acids tested with ATP. When equimolar solutions of mixtures of glycine and phenylalanine with ATP are tested in suspensions of complexes of lysine-rich proteinoid and each of various polyribonucleotides, both homopeptides and heteropeptides are produced. Glycylphenylalanine or phenylalanylglycine is the principal product; the preference is related to which polyribonucleotide is in the complex. The rate of conversion of amino acid to peptide is a function of whether ATP is added in a single batch or in repeated amounts adding to the same amount as in the single batch. Related experiments indicate a relatively rapid initial rate of decay of ATP in the system. These results are discussed relative to the mechanisms for continuous generation in modern organisms, as are the results in peptide formation.

Adenosine Triphosphate↗
PubMed1968

Chain extension of ribonucleic acid by enzymes from rat liver cytoplasm.

1. The 105000g supernatant fraction of rat liver catalyses the incorporation of ribonucleotides from ribonucleoside triphosphates into polyribonucleotide material. The reaction requires Mg(2+) ions and is enhanced by the addition of an ATP-generating system and RNA, ATP, UTP and CTP but not GTP are utilized in this reaction. In the case of UTP, the product is predominantly a homopolymer containing 2-3 uridine residues, and there is evidence that these may be added to the 3'-hydroxyl ends of RNA or oligoribonucleotide primers. 2. The microsome fraction of rat liver incorporates ribonucleotides from ATP, GTP, CTP and UTP into polyribonucleotide material. This reaction requires Mg(2+) ions and is enhanced slightly by the addition of an ATP-generating system, and by RNA but not DNA. Supplementation of the reaction mixture with the three complementary ribonucleoside 5'-triphosphates greatly increases the utilization of a single labelled ribonucleoside 5'-triphosphate. The optimum pH is in the range 7.0-8.5, and the reaction is strongly inhibited by inorganic pyrophosphate and to a much smaller degree by inorganic orthophosphate. It is not inhibited by actinomycin D or by deoxyribonuclease. In experiments with [(32)P]UTP in the absence of ATP, GTP and CTP, 80-90% of (32)P was recovered in UMP-2' or -3' after alkaline hydrolysis of the reaction product. When the reaction mixture was supplemented with ATP, GTP and CTP, however, about 40% of the (32)P was recovered in nucleotides other than UMP-2' or -3'. Although the reactions seem to lead predominantly to the synthesis of homopolymers, the possibility of some formation of some heteropolymer is not completely excluded.

Adenosine Triphosphate↗
PubMed1973

Poly(inosinic acid)-poly(cytidylic acid) inhibition of DNA synthesis in synchronized HeLa cells.

Inhibition by double-stranded polyribonucleotides of DNA synthesis in synchronized HeLa cultures is dose- and time-dependent. Inhibition by poly(I.C) primarily affected late G(1) and early S phases of the cell cycle. Single-stranded polynucleotides, native calf-thymus DNA, and yeast RNA had no effect. Radioautography showed that after 2-hr exposure the synthetic polyribonucleotides were predominantly inside the nucleus. The results extend the spectrum of action of double-stranded RNA.

Autoradiography↗
PubMed2002

Application of the Poisson Boltzmann polyelectrolyte model for analysis of equilibria between single-, double-, and triple-stranded polynucleotides in the presence of K(+), Na(+), and Mg(2+) ions.

The Poisson Boltzmann (PB) cell model of polyelectrolyte solution has been used for numerical calculations of the change in electrostatic free energy, DeltaG(el), for transformations between different structural forms (tri-, double-, and single-stranded) of the polyribonucleotides poly(rA).poly(rU)2, poly(rA).poly(rU), poly(rA), and poly(rU). In particular, the dependence on monovalent salt concentration, MCl (M = Na or K) in the absence and in the presence of MgCl(2) has been calculated. The results were obtained for conditions relevant to available experimental values of structural transition ("melting") temperatures (T(m)) and other thermodynamic quantities. Using the experimental T(m) values and theoretical electrostatic DeltaG(el), DeltaH(el), and DeltaS(el) functions, non-electrostatic contributions to the corresponding thermodynamic parameters of the poly(rA)/poly(rU) melting transitions were determined in MCl solutions in the absence of Mg(2+). Qualitative and to a large extent quantitative reproduction of the experimental calorimetry enthalpy, entropy and heat capacity values was found from the results of the PB theory. Furthermore, dependencies of T(m) on MCl concentration in the presence of MgCl(2) for the poly(rA)/poly(rU) transitions were also calculated. Compared to a model considering Mg(2+) as a fully-hydrated ion, much better agreement between experimental and PB theory was achieved by assuming the ion size of Mg(2+) to be given by that of a bare non-hydrated ion smaller than that of hydrated Na(+) or K(+). In agreement with data of experimental studies reported in literature, this result indicates that magnesium(II) can bind to RNA as a bare ion in a way that is different from that of DNA. Generally, we can conclude that the PB polyelectrolyte theory can provide an adequate description of thermally induced structural transitions in polydeoxy- and polyribonucleotides in different salt solutions in spite of the rather simplified model treating the solvent as dielectric continuum, the polyion as a uniformly charged cylinder, and the mobile ions as hard spheres in the absence of excluded volume effects.

DNA↗
PubMed1974

Sequence analysis of nonradioactive RNA fragments by periodate-phosphatase digestion and chemical tritium labeling: characterization of large oligonucleotides and oligonucleotides containing modified nucleosides.

A tritium derivative method for sequence analysis of polyribonucleotides is detailed, which is based on borotritide reduction of oligonucleotide dialdehydes generated by treatment of polyribonucleotides with alkaline phosphatase and excess periodate at pH 8 (borate buffer; no primary amine present in the reaction mixture). While neither phosphatase nor periodate possess any intrinsic exonuclease activity their combination mimics an RNA-specific exonuclease ("pseudo-exonuclease"). Procedures are described for separation and characterization of tritiumlabeled oligonucleotide derivatives. The sequence is deduced by identification of labeled 3'-termini following separation of the reduced nucleotide intermediates according to chain length. The sensitivity of the method is indicated by the fact that as little as 0.01 O.D.260 unit of a nonradioactive decanucleotide is sufficient for sequence determination.

Alkaline Phosphatase↗
PubMed1989

Exoribonuclease activity of purified reverse transcriptase preparations from retroviruses.

Highly purified and commercially available preparations of reverse transcriptases from retroviruses contain a 3' to 5' exoribonuclease activity capable of hydrolyzing synthetic homopolyribonucleotides having a 3'-OH end. The exoribonuclease activity of reverse transcriptase preparations from Rous associated virus-2 was further characterized. This exoribonuclease activity cleaves poly(C) and poly(U) exonucleolytically from the 3'-OH end to produce nucleoside 5'-phosphates. Poly(A), poly(G), circular polyribonucleotide, and double-stranded polyribonucleotide were not hydrolyzed by the activity. This is a novel type of exoribonuclease activity.

Buffers↗
PubMed1976

Template activity of synthetic deoxyribonucleotide polymers in the eukaryotic DNA-dependent RNA polymerase reaction.

Template specificities of the eukaryotic DNA-dependent RNA polymerases A and B from rat liver, pea, and cauliflower have been investigated using synthetic polydeoxyribonucleotides. Polymerases A and B from the three species exhibit different specificities for single-stranded homopolymers: polymerase A preferentially reads poly(dT) and poly (dC). and polymerase B poly (dC). This preferential reading appears to be a property of eukaryotic DNA-dependent RNA polymerases. Polymerases A and B transcribe synthetic polyribonucleotides also, but at a reduced rate. The polyribonucleotides which can be read by DNA-dependent RNA polymerases have a base sequence similar to that of the polydeoxyribonucleotides, which are effeciently transcribed, suggesting that the base sequence of the template rather than its conformation is crucial in the template specificity for synthetic polymers. Competition experiments with polydeoxyribonucleotides indicate that the enzymes have different binding specificities, which are not the same as their template specificities.

Animals↗
PubMed1979

Primary structure of the nucleic acid from the 1,4-alpha-glucan branching enzyme.

The primary structure of the nucleic acid from the branching enzyme 1,4-alpha-D-glucan: 1,4-alpha-D-glucan 6-alpha-(1,4-alpha-glucano)-transferase (2.5-S RNA) isolated from rabbit muscles has been elucidated. The polyribonucleotide consists of 31 nucleotides; the unique features of the polyribonucleotide are the unusually high content of modified nucleotides (32%) and guanine residues (40%). Apparently 2.5-S RNA belongs to a class of nucleic acids unknown up to now. It is the first time that the structure of a nucleic acid component from a ribonucleoenzyme has been defined. This work is a preprequisite for gaining insight into the intimate activating effect of the poly-ribonucleotide on the enzyme action.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1964

SPECIFICITY OF POTASSIUM-ACTIVATED PHOSPHODIESTERASE OF ESCHERICHIA COLI.

A potassium-activated phosphodiesterase that hydrolyzes polyribonucleotides to 5'-mononucleotides has been purified approximately 600-fold from extracts of Escherichia coli B. The purified enzyme appears to be specific for single-stranded polyribonucleotides: helical forms are not hydrolyzed, nor do they inhibit the hydrolysis of single-stranded chains.

Adenine Nucleotides↗
PubMed1994

Identification of Whole Fixed Bacterial Cells with Nonradioactive 23S rRNA-Targeted Polynucleotide Probes.

Polyribonucleotide probes (ca. 200 to 300 nucleotides in length) carrying multiple reporter molecules were produced by in vitro transcription with labeled UTP derivatives (fluorescein-12-UTP, 7-amino-4-methyl-coumarin-3-acetyl-6-UTP, tetramethylrhodamine-6-UTP, or digoxigenin-11-UTP). Despite their length, these molecules penetrated into whole fixed gram-negative cells and hybridized specifically to their target sites on the 23S rRNA. Fluorescence intensities were quantified for target and nontarget cells by the combination of a charge-coupled device videocamera and an image-processing system. Polyribonucleotide probes confer up to 26 times more fluorescence to target cells than oligonucleotide probes do. Probe sensitivity and specificity were strongly influenced by the stringency of hybridization. The use of differently labeled probes allowed the simultaneous detection of three populations. Identification of introduced test organisms in activated-sludge samples proved the applicability of this method for the in situ identification of microorganisms in complex microbial communities.

Journal Article↗