Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Poly G”

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 145 records · Page 8Linked to original sources
PubMed1990

[Effect of non-steroidal anti-inflammatory agents on interferon induction].

Nonsteroid antiinflammatory agents (NAIA) such as antipyrine, butadion, acetylsalicylic acid, sodium salicylate, stampyrine and 4-iodantipyrine are not interferonogenic. Still, they stimulated interferonogenic action of poly(G).poly(C) in studies on animals. Relation between the interferon-stimulating action of the NAIA and their effect on activity of prostaglandin and the influence on the immune system was suggested.

Animals↗
PubMed1985

[Interferon-inducing and antiviral effects of inosiplex in combination with high-molecular interferon inducers].

It has been shown that the immunostimulant inosiplex (IP) is capable of inducing interferon production in mice and of stimulating interferon induction by high-molecular inducers. The combined use of IP and poly (G)-poly (C) or dsRNA (RFf2) leads to a longer interferon circulation in the blood. All the combination schemes ensuring the effect of interferon production prolongation were tested for anti-viral activity. The prophylactic administration of the drugs permitted the attainment in mice of the increased resistance to experimental influenza.

Animals↗
PubMedDate not supplied

[The search for preparations suppressing the reproduction of the AIDS virus].

Trials of clinically advantageous national inducers, thymus hormones, as well as human recombinant alpha 2-interferon were carried out in cultures of continuous lymphoblastoid cells H9/IIIB infected with HIV virus. The virus-inhibiting effect for HIV was observed with interferon in doses of 10-100 IU/ml. At a concentration of interferon of 1000 IU/ml, virus replication was inhibited completely, the interferon doses used exerting no marked toxic or antiproliferative effect on the cells. Human interferon inducers, poly(G).poly(C), PXL-6, dsRNA in concentrations of 50-100 micrograms/ml inhibited virus reproduction significantly. The highest antiviral effect was achieved with yeast dsRNA. The preparations of immunomodulators, thymarin, the 5th and 7th fractions of thymosin, noticeably stimulated proliferation of infected T-lymphocytes, reducing the relative number of cells carrying the virus-specific antigen. Combined use of preparations with different mechanisms of the antiviral effect may be advantageous in prevention and treatment of AIDS.

Antiviral Agents↗
PubMed1992

[Resistance of natural and synthetic polyribonucleotide inducers of interferon to human blood ribonucleases].

The resistance of polyribonucleotide inductors of interferon to blood ribonucleases was studied. Blood resistance of larifan and ridostin in the free and shielded state as well as that of the complexes of poly(I)-poly(C) and poly(G)-poly(C) were also investigated. A protective action of polylysine against the inductors was detected which, in case it had no effect on the biological activity of the drugs, could provide its recommendation as a compound for shielding the inductors.

Carboxymethylcellulose Sodium↗
PubMedDate not supplied

[Interferon induction via peroral administration of high-molecular polynucleotides].

High molecular polynucleotides, poly(I).poly(C) and poly(G).poly(C), incorporated into liposomes may be used for serum interferon induction when administered orally. Titres of interferon induced by this method are sufficiently high (320-640 units/ml) and close to those induced by the same preparations administered parenterally (640-1280 units/ml). The use of liposomal polynucleotides results in prolonged (up to 24 hours) circulation of interferon in the blood of mice at a sufficiently high level. Liposomal polynucleotides are low-toxic upon oral intake. The liposome-polynucleotide complex is sufficiently stable on storage, and retains the interferon-inducing activity, if given orally, after 6 months of storage at 4 degrees C in the liquid form.

Administration, Oral↗
PubMed1998

Insight into externally bound 5,10,15,20-tetrakis(2-N-methylpyridyl) porphyrinatopalladium(II), PdP(2), with B-form DNA duplexes poly(G-c)2, poly(A-t)2, and CT DNA by using combined MCD, CD, and optical data.

The Soret (B0) region of free and externally DNA-bound 5,10,15,20-tetrakis(2-N-methylpyridyl) porphyrinatopalladium(II), PdP(2), was investigated by electronic magnetic circular dichroism (MCD), natural circular dichroism (CD), and optical (UV-visible) absorption spectroscopies. We conclude that four-coordinate, "thick" PdP(2) binds to the exterior of each of poly(A-T)2 and calf thymus DNA (CT DNA) by two distinctly different AT-specific minor and major groove modes, with site 5'TA3' being favored for both modes. The minor groove mode involves an edge-on orientation of PdP(2), for which porphyrin electric dipole transition moments (edtms) mu x (most perturbed direction of the bound porphyrin) and mu y (least perturbed direction) have approximate orientation angles of alpha/beta/beta' = approximately 90 degrees/0 degree/0 degree and approximately 45 degrees/0 degree/90 degrees, respectively. Major groove binding is by a face-on mode, which results in the porphyrin plane being approximately parallel to the helix axis, such that mu x (most perturbed direction) and mu y (least perturbed direction) have approximate orientation angles of alpha/beta/beta' = approximately 45 degrees/180 degrees/90 degrees and approximately 45 degrees/180 degrees/270 degrees, respectively. The Soret MCD and optical band alterations upon binding (i.e., sign retention of the tetragonal, genuine MCD (+) A-term on becoming the (+) pseudo-A-term of similar amplitude and small DNA-induced optical red (delta lambda) and hypochromic (H) shifts) are all consistent with exterior binding perturbations of the porphyrin's p pi MOs (1a1u 3a2u 4eg) by the A and T bases of each polymer being weaker than caused by intercalation. Furthermore, that the (+) A-term of PdP(2) retains the (+) sign upon binding informs that the 4eg splitting, or delta LUMO, is less than the energy separation magnitude of 1a1u-3a2u, or delta HOMO. For the third system, PdP(2)/poly (G-C)2, the B0 CD spectrum has two extremely weak (+) and (-) CD bands at higher and lower energy, respectively, indicating that weak outside binding (wob) interactions are taking place between the cationic porphyrin and the electron-rich phosphate backbone of this rigid polymer. The composite of our CD, MCD, and optical data are suggestive of a face-on mode at the GC major groove. Band parameter extraction is performed on the Soret CD and MCD bands of each of the three bound systems, and it is determined that (1) very little spatial rotation of molecular charge is induced during CD excitation and (2) the excited state angular momentum, 'Lj', changes very little upon binding of PdP(2) to each duplex. These findings are also consistent with each PdP(2)/B-DNA interaction not being very strong.

Base Pairing↗
PubMed1978

Protonated polynucleotides structures - 22.CD study of the acid-base titration of poly(dG).poly(dC).

The acid-base titration (pH 8 --> pH 2.5 --> pH 8) of eleven mixing curve samples of the poly(dG) plus poly(dC) system has been performed in 0.15 M NaCl. Upon protonation, poly(dG).poly(dC) gives rise to an acid complex, in various amounts according to the origin of the sample. We have established that the hysteresis of the acid-base titration is due to the non-reversible formation of an acid complex, and the liberation of the homopolymers at the end of the acid titration and during the base titration: the homopolymer mixtures remain stable up to pH 7. A 1G:1C stoichiometry appears to be the most probable for the acid complex, a 1G:2C stoichiometry, as found in poly(C(+)).poly(I).poly(C) or poly(C(+)).poly(G).poly(C), cannot be rejected. In the course of this study, evidence has been found that the structural consequences of protonation could be similar for both double stranded poly(dG).poly(dC) and G-C rich DNA's: 1) protonation starts near pH 6, dissociation of the acid complex of poly(dG).poly(dC) and of protonated DNA take place at pH 3; 2) the CD spectrum computed for the acid polymer complex displays a positive peak at 255 nm as found in the acid spectra of DNA's; 3) double stranded poly(dG).poly(dC) embedded in triple-stranded poly(dG).poly(dG).poly(dC) should be in the A-form and appears to be prevented from the proton induced conformational change. The neutral triple stranded poly(dG).poly(dG).poly(dC) appears therefore responsible, although indirectly, for the complexity and variability of the acid titration of poly(dG).poly(dC) samples.

Circular Dichroism↗
PubMedDate not supplied

[A novel method of analysis of ligand-polynucleotide adsorption isotherms].

The adsorption of ethidium bromide on the synthetic double-stranded polyribonucleotide poly(G)poly(C) was investigated by adsorption spectroscopy. The adsorption isotherms were analyzed in the framework of the Crothers-Gursky model. It was shown that adsorption parameters (e.g., binding constant) may also be determined from the analysis of dispersion of some bound molecules. In some cases this method may be more convenient.

Adsorption↗
PubMed1992

Base release from DNA and polynucleotides upon 193 nm laser excitation.

Release of bases form calf thymus DNA and three polynucleotides, induced by 20 ns excitation at 193 nm in aqueous solution at pH 7, was detected by HPLC. The quantum yields of formation of free bases (phi B) from double-stranded DNA (0.4 mM) are independent of intensity, indicating a one-quantum mechanism of N-glycosidic bond cleavage. The phi B values increase in the order guanine, thymine, adenine, cytosine, the latter being phi C approximately 7 x 10(-4) for double-stranded DNA under Ar and O2. The larger phi B values in N2O-saturated solution, e.g., phi C = 1.2 x 10(-3), are ascribed to additional base release via OH-adduct radicals. The phi B values of homopolynucleotides increase in the order poly(G), poly(A) and poly(C), e.g. phi C = 7 x 10(-3) under Ar, as do the efficiencies for base release per radical cation (eta B). A comparison of the eta B values with the efficiencies of single-strand breakage for poly(C), poly(A) and DNA shows a similar trend; both are markedly larger for pyrimidines than for purines. Pathways to undamaged bases, initiated from base radical cations, are proposed.

Adenine↗
PubMed1993

Energetics of Z-DNA formation in poly d(A-T), poly d(G-C), and poly d(A-C) poly d(G-T).

The conformational change for the alternating purine-pyrimidine polydeoxyribonucleotides i.e. poly d(A-T), poly d(G-C), and poly d(A-C) poly d(G-T) from a right-handed conformation at room temperature to the left-handed Z-DNA like double helix at elevated temperatures has been studied by UV spectroscopy, Raman spectroscopy, and by adiabatic differential scanning microcalorimetry (DSC) in the presence of Na+ and Mg2+ or Ni2+ respectively as counterions. The differential UV spectra reveal through a hyperchromic shift at around 280nm and a hypochromic shift at 260nm that a conformational change to the left-handed conformation occurs. The Raman spectra clearly show characteristic changes, a drastic decrease of the band at 680cm-1 and the appearance of a new band at 628cm-1, due to the change of the purine bases to the syn conformation upon inversion of the helix-handedness. The course of the transition as function of temperature can be followed quantitatively by plotting the change in the excess heat capacity vs. temperature. The transition enthalpy delta H for the B- to Z-DNA transition per mole base pairs (mbp) amounts to 2.0 +/- 0.2kcal for poly d(G-C), to 4.0 +/- 0.4kcal for poly d(A-T), and to 3.1 +/- 0.3kcal for poly d(A-C) poly d(G-T). The enthalpy change due to the Z-DNA to coil transitions (per mole base pairs) amounts to 11kcal for poly d(G-C), 10.5kcal for poly d(A-T) and 11.3kcal for poly d(A-C) poly d(G-T).

Calorimetry, Differential Scanning↗
PubMed1992

Domains required for nucleic acid binding activities in chloroplast ribonucleoproteins.

Five ribonucleoproteins (or RNA-binding proteins) from tobacco chloroplasts have been identified to date; each of these contains an acidic N-terminal domain (24-64 amino acids) and two conserved RNA-binding domains (82-83 amino acids). All five ribonucleoproteins can bind to ssDNA and dsDNA but show high specificity for poly(G) and poly(U). Here we present the nucleic acid binding activity of each domain using a series of deletion mutant proteins made in vitro from the chloroplast 29 kDa ribonucleoproteins. The acidic domain does not have a positive effect on binding activities and proteins lacking this domain show higher affinities for nucleic acids than the wild-type proteins. Mutant proteins containing single RNA-binding domains can bind to poly(G) and poly(U), though with lower affinities than proteins containing two RNA-binding domains. The spacer region (11-37 amino acids) between the two RNA-binding domains does not interact with poly(G) or poly(U) by itself, but is required for the additive activity of the two RNA-binding domains. Proteins consisting of two RNA-binding domains but lacking the spacer have the same activity as those containing only one RNA-binding domain. Possible roles for each domain in chloroplast ribonucleoproteins are discussed.

Amino Acid Sequence↗
PubMed1983

Binding of eucaryotic elongation factor Tu to nucleic acids.

The binding of eucaryotic elongation factor Tu (eEF-Tu) to nucleic acids was investigated. eEF-Tu binds to a variety of different nucleic acids with high affinity, showing a strong preference for 18 S and 28 S rRNA over transfer RNA and for ribose-containing polymers over polydeoxyribonucleotides. The factor binds at multiple sites on 28 S rRNA without strong cooperativity. eEF-Tu binds strongly to poly(G) and poly(U) but weakly, if at all, to poly(A) and poly(C). Experiments employing an airfuge demonstrate that eEF-Tu can form a quaternary complex containing the factor, 28 S rRNA, aminoacyl-tRNA, and GTP. The existence of two distinct RNA binding sites on eEF-Tu suggests that rRNA may play a role in the recognition of eEF-Tu.aminoacyl-tRNA.GTP complexes by polysomes. Support for this suggestion comes from experiments which show that poly(G) inhibits the factor-dependent binding of aminoacyl-tRNA to mRNA-programmed 80 S ribosomes. In addition, it is shown that eEF-Tu possesses an intrinsic GTPase activity which is stimulated significantly by 28 S rRNA, poly(G), and poly(U). The binding of eEF-Tu to poly(G) lowers the activation energy for eEF-Tu GTPase from 74.3 to 65.9 kJ . mol-1 and approximately doubles the Vmax of the enzymatic reaction. The results are discussed in relation to the binding of eEF-Tu to ribosomes during protein synthesis.

Escherichia coli↗
PubMed1999

[Antiviral activity of poly(A)-poly(U) duplexes modified with cis-diammine-dichloroplatinum (II)].

Polyribonucleotide duplex poly(A).poly(U) was modified with cis-diammine dichloroplatinum (II) (cis-DDP). It was shown that the antiinfluenza protective activity of the modified duplex in mice increased with the degree of modification (rb) rising up to 0.2. The effect was different from that for poly(I).poly(C) and poly(G).poly(C). The interferon titers in the murine brain increased in parallel with increasing of the antiviral activity. It was assumed that the structural specificity of the poly(A).poly(U) duplex was responsible for the phenomenon and that cis-DDP interaction with N(7) atoms of the adenine heterocycles blocked the "abnormal" Hoogsteen pairing of adenines with uracils. As a result the antiviral activity increased because of lowering the quantity of the intramolecular defects and increasing the length of the regular double-stranded regions.

Animals↗
PubMed2001

Hydrogen peroxide triggers the formation of a disulfide dimer of muscle acylphosphatase and modifies some functional properties of the enzyme.

Acylphosphatase is expressed in vertebrates as two molecular forms, the organ common and the muscle types. The former does not contain cysteine residues, whereas the latter contains a single conserved cysteine (Cys-21). We demonstrated that H(2)O(2) at micromolar levels induces, in vitro, the formation of a disulfide dimer of muscle acylphosphatase, which displays properties differing from those of the reduced enzyme. In particular, we observed changes in the kinetic behavior of its intrinsic ATPase activity, whereas the kinetic behavior of its benzoyl phosphatase activity does not change. Moreover, the disulfide dimer is capable of interacting with some polynucleotides such as poly(G), poly(C), and poly(T) but not with poly(A), whereas the reduced enzyme does not bind polynucleotides. Experiments performed with H(2)O(2) in the presence of increasing SDS concentrations demonstrated that disulfide dimer formation is prevented by SDS concentrations higher than 300 microm, suggesting that a non-covalently-linked dimer is present in non-denaturing solvents. Light-induced cross-linking experiments performed on the Cys-21 --> Ser mutant in the pH range 3.8-9.0 have demonstrated that a non-covalently-linked dimer is in fact present in non-denaturing solutions and that an enzyme group with a pK(a) of 6.4 influences the monomer-dimer equilibrium.

Acid Anhydride Hydrolases↗
PubMed1976

Temperature dependence of the 31P chemical shifts of nucleic acids. A prode of phosphate ester torsional conformations.

The temperature dependence of the 31P chemical shifts of the ribodinucleoside monophosphates, ApA, GpC, CpC, UpU, and ApU, of the deoxyribonucleic acids, d-ApT, TpT, d-ApA, and d-pApT, and of the homopolyribonucleic acids poly(G), poly(U), poly(A) is shown to provide information on the helix-coli transition in nucleic acids. The base stacked, helical structure with a gauche,gauche phosphate ester torsional conformation is 0.2-0.6 ppm upfield from the random coil conformation. In contrast, the 31P chemical shifts of dimethyl and diethyl phosphate do not change significantly with temperature. These results support our earlier hypothesis that 31P shifts are sensitive probes of torsional conformations with phosphate esters in gauche,gauche conformations having 31P shifts upfield from nongauche conformations.

Deoxyribonucleotides↗
PubMed1986

Thymine and guanine base specificity of human myeloma proteins with anti-DNA activity.

To further our understanding of the molecular basis of DNA-autoantibody interactions, we have characterized the specificities of three IgG human myeloma proteins that bind DNA. We measured their binding to synthetic single- and double-stranded homopolynucleotides, random and alternating copolymers, oligonucleotides, and nucleotides or nucleosides conjugated to non-nucleic acid carriers. All three antibodies bound single-stranded nucleic acids, including both polyribonucleotides and polydeoxyribonucleotides. They varied in relative affinities for polynucleotides of varying base composition. Polymers containing the purines guanine or hypoxanthine and/or the pyrimidine thymine were most reactive with all three proteins. A myeloma protein that reacted with poly(G), poly(I), or poly(dT) also bound to the corresponding nucleosides or nucleotides conjugated to bovine serum albumin. None of the antibodies reacted with base-paired double-helical polynucleotides (double-stranded RNA, RNA-DNA hybrid or double-stranded DNA). The results indicate that base specificity is prominent in their reactions and that the accessible epitopes in single-stranded polynucleotides become masked upon base pairing in double-stranded helices. These findings suggest a model in which positions N1 and O6 of guanine and hypoxanthine and N3 and O4 of thymine interact with amino acids of the antibody-combining site.

Autoantibodies↗