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E Taillandier

Publications and source records attributed to E Taillandier.

At least 91 records · Page 5Linked to original sources
PubMed1986

Interpretation of DNA vibration modes: I--The guanosine and cytidine residues involved in poly(dG-dC).poly(dG-dC) and d(CG)3.d(CG)3.

A normal coordinate analysis has been carried out on guanosine and cytidine residues appearing in oligo and polynucleotides by using a simplified valence force field that allows the vibrational spectra of 5'-dGMP and 2'-deoxycytidine molecules to be reproduced. The role of both C2'-endo and C3'-endo conformations on sugar pucker, as well as that of glycosidic torsion angle (X), on several characteristic vibration modes of these residues have been studied. The present calculations based on a non-redundant set of internal coordinates preserving the harmonic approximation of the potential field, allows us to explain quite satisfactorily the modifications of the vibrational spectra in the 1550-1250 cm-1 and 785-500 cm-1 regions, when the right----left-handed conformational transition occurs.

Cytidine↗
PubMed1986

Infrared spectral studies of the non regularly alternating purine-pyrimidine hexamers d(m5CGGCM5CG), d(CBr8GGCCBr8G) and d(CGCGGC).

The oligonucleotides d(m5CGGCm5CG), d(CBr8GGCCBr8G) and d(CGCGGC) have been prepared and studied by infrared spectroscopy. The three sequences contain two GC pairs which are out of purine-pyrimidine alternation with the rest of the sequence. From the IR data of the d(m5CGGCm5CG) hexamer, it is shown that all of the dG residues adopt a syn conformation. The marker IR bands for the C3' endo syn conformation are at 1410, 1354, 1320 and 925 cm-1 whereas those for the C2' endo anti conformation at 1420, 1374 and 890 cm-1 are clearly absent. This result implies that the two adjacent guanines of the d(m5CGGCm5CG) sequence are in syn conformation. It is suggested that duplex formation occurs in d(CGCGGC) films and that all of the guanines are in syn conformation. In contrast, the central non-brominated guanine of the d(CBr8GGCCBr8G) hexamer is found in anti conformation, as expected in a Z type structure of the non-alternating region.

Base Sequence↗
PubMed1985

Right-handed and left-handed helices of poly(dA-dC) X (dG-dT).

The secondary structures of poly(dA-dC) X (dG-dT) were studied using CD and IR spectroscopies. We give spectroscopic evidence of secondary structure transitions of poly(dA-dC) X (dG-dT) from a B to a Z-like helix, induced by transition metal ions (Ni2+) in presence of high concentrations of Cs+ and Na+. In the presence of Na+, the B in equilibrium Z transition occurs at any temperature, whereas premelting conditions are required in presence of Cs+. For these two alkali ions the Z-like form is only induced by Ni2+ ions through their specific interactions at N7 of purines, under conditions of low water activity due to the high alkali salt concentration. We also show that the CD spectrum obtained in presence of Cs+ ions and characterized by a negative band at 275 nm, cannot be interpreted in terms of Z-like left-handed helix but reflects a modified B right-handed helix.

Circular Dichroism↗
PubMed1985

Normal coordinate analysis of 5'-dGMP and its deuterated derivatives. A calculated approach to designate the guanine-residue vibration modes in B and Z forms of DNA.

By calculations based on the Wilson GF-method and using a valence force field, the vibration modes of 5'-dGMP have been assigned. Good agreement was obtained between the calculated and experimental results corresponding to the Raman and infrared spectra of 5'-dGMP. The calculations can also predict the displacement of infrared bands observed upon selective deuteration on C8 and simultaneously on the C8, N1 and N2 atoms of the guanine ring. In order to preserve the harmonic approximation of the potential field, the redundancy between the internal coordinates is entirely removed using a B X B matrix-product diagonalization procedure. In this treatment the local symmetry of different constituents of the molecule is taken into consideration, thus avoiding extensive linear combinations of internal coordinates. The extension of these calculations to the guanosine-moiety involved in the double helix structures of DNAs allowed us to reproduce a certain number of the characteristic guanine vibration modes altered by the B----Z transitions of poly(dG-dC).poly(dG-dC) and d(CG)3.d(CG)3.

DNA↗
PubMed1985

Z helix-coil transition of d(C-Br8G-C-G-C-Br8G) studied by CD, 1H-NMR and IR spectroscopies.

The conformation of d(C-Br8G-C-G-C-Br8G) in aqueous solution was studied by CD and 1H-NMR spectroscopy and in condensed phase by IR spectroscopy. Whether in 0.1 M or 3 M NaCl solution or in film the only double helical structure adopted by brominated d(C-G)3 oligomer is the Z form. The IR spectrum of the film presents all the characteristic absorptions of the Z conformation and in particular is indicative of a syn conformation for the central guanosine as well as for the brominated one. Imino proton resonances of d(C-Br8G-C-G-C-Br8G) demonstrating the duplex formation were observed up to 60 degrees C. It is interesting to note that the significant highfield shifts of the dC H5" exocyclic sugar protons characteristic of the non exchangeable proton spectra of d(C-G)3 containing 5-methyl dC residues in the Z form were also detected in the proton spectrum of brominated oligomer. Whereas formation of the Z helix of methylated d(C-G)3 oligomers dependent on the salt concentration was found to occur via the preliminary formation of a B helix even in 4 M NaCl solution, the Z helix of d(C-Br8G-C-G-C-Br8G) is obtained directly from the coil form. However, IR data suggest that in the Z form of d(C-Br8G-C-G-C-Br8G), the overlapping of the base planes should be slightly different in comparison with the stacking observed in d(C-G)3 crystals. The kinetic data (activation energy and lifetime) of the Z helix-coil transition of brominated d(C-G)3 are compared to those of the B helix-coil transition observed for methylated d(C-G)3 in 0.1 M NaCl solution while the thermodynamic data of these two reactions (enthalpy and midpoint temperature) are slightly different.

Base Sequence↗
PubMed1985

[Calcium oxalate monohydrate (whewellite) renal lithiasis].

Pure calcium oxalate monohydrate lithiasis is rare--about 5 to 10% of total renal lithiases. The proportion is the same in men and women. Pure calcium oxalate stones are a polished dark brown color, and are very hard. They are visualized radiologically as regular and homogeneous. From a biological standpoint, this type of stone is frequently associated with normal calciuria and oxaluria. Pure calcium oxalate monohydrate stones rarely evolve.

Adult↗
PubMed1984

Left-handed helical structure of poly[d(A-C)].poly[d(G-T)] studied by infrared spectroscopy.

Infrared spectroscopic studies demonstrate the ability of poly[d(A-C)].poly[d(G-T)] to adopt a Z-type conformation. The Z form of the unmodified polynucleotide is induced by Ni2+ counterions and not by Na+. The B----Z equilibrium is shifted at room temperature, in the presence of 1 Ni2+/nucleotide, by an increase in the concentration of poly[d(A-C)].poly[d(G-T)]. The importance of specific binding of Ni2+ ions on the N7 site of purines in the stabilization of the Z form is also discussed.

Cations↗
PubMed1984

The B----Z transition in two synthetic oligonucleotides: d(C-2-amino-ACGTG) and d(m5CGCAm5CGTGCG) studied by IR, NMR and CD spectroscopies.

The sequences CA'CGTG (where A' = 2-aminodeoxyadenosine) and m5CGCAm5CGTGCG are prepared and studied by IR, CD and 1H-NMR. Infrared spectra demonstrate the capacity of the modified hexamer and decamer to adopt a Z conformation. The influence of the NH2 substitution on the adenine or of the methylated terminal part of the decamer acting with the increase of the DNA concentration stabilizes the Z conformation at room temperature in low humidity films. Very weak proportion of Z conformation is detected in UV dilute solutions. In more concentrated NMR solutions, the Z proportion induced by high salt content is only 20-25%. The effects of the concentration and of the covalent modification of the bases are discussed.

5-Methylcytosine↗
PubMed1984

Role of the protein alpha helixes in histone-DNA interactions studied by vibrational spectroscopy.

The localization of structurally important histone-DNA interactions has been investigated by vibrational spectroscopy. Histones H2A, H2B, and H4 and their fragments (H2A, 1-56, 1-89, 73-129; H2B, 1-59, 1-83; H4, 1-53, 1-67, 1-84, 69-84, 85-102) have been prepared, characterized, and used to reconstitute protein-DNA complexes. Evidence is given for the existence of a direct relationship between the presence of ordered alpha-helical structures in the histones and a stabilization of the DNA in a B geometry. Infrared linear and ultraviolet dichroism measurements indicate that the N-terminal fragments, rich in basic residues and mostly in a random conformation, remain without any influence on the secondary structure of the nucleic acid, leaving it free in the complexes to undergo a total B----A conformational transition. On the contrary, histone fragments that involve some alpha-helical parts of the protein partially stabilize the DNA in a B geometry. Histone fragments that contain all of the alpha helixes of the protein block the DNA in the same way as the whole corresponding histone. A model for histone-DNA interactions in the core particle is discussed.

Amino Acids↗
PubMed1984

Interaction of Z form poly(dG-dC).poly(dG-dC) with divalent metal ions: localization of the binding sites by I.R. spectroscopy.

The secondary structures of poly(dG-dC).poly(dG-dC) in the presence of alcaline , alcaline earth and first row transition metal ions (Na+, Mg2+, Co2+, Ni2+) are investigated by infrared spectroscopy. The conformational transitions are studied as a function of the hydration of the polynucleotide and counter-ion nature and content. The use of selectively deuterated poly(dG-dC).poly(dG-dC) on the 8-carbon of guanines allows to show that a direct interaction occurs between the N7 site of guanines and the transition metal ions Co2+ and Ni2+. In the case of Mg2+, for high ion/nucleotide ratios, the interaction occurs essentially at the level of the phosphate groups. This interaction leads to a modification of the left-handed conformation. Based on the IR spectroscopy results, an explanation is proposed for the different efficiencies of these various ions to induce the B----Z transition.

Cations, Divalent↗
PubMed1984

[Polymorphism of the left-handed helix (Z form) of poly(dG-dC).poly(dG-dC) induced by MgCl2, studied by infrared spectroscopy].

The existence of a left-handed double-helical DNA, called Z-DNA was proved by X-ray crystallographic analysis of the hexanucleotide d(CpGpCpGpCpG). The possible biological relevance of the Z conformation is enhanced by recent studies using immunostaining. Antibodies against Z-DNA have been raised and used to detect the Z conformation in polytene and mammal chromosomes. In this work we have studied the conditions necessary to generate the transition from the right-handed to the left-handed conformation of poly d(G-C).poly d(G-C) exposed to various concentrations of MgCl2 and various relative humidities. The infrared (IR) spectra were used to characterize the different conformations. Only below 0.5 Mg2+ ion per nucleotide we have observed the right-handed helix. Above 1 Mg2+ ion per nucleotide, the left-handed helix is always present under low and high relative humidity conditions. Furthermore, under low relative humidity and high salt content conditions we found a new IR spectrum which can be correlated with a polymorphic Z form, called here Z degree form.

DNA↗
PubMed1984

[Monohydrate and dihydrate oxalic lithiasis. Calculi, their macroscopic structure (radiographic and therapeutic impact). Calciuria and oxaluria].

Calculi of pure calcium oxalate monohydroxide are hard, polish, dark brown stones, of a very tenuous crystalline structure. On the contrary, calculi of pure bihydroxide oxalate are clear irregular stones with a spiky surface. They are more friable and less hard than monohydroxide oxalate stones. Monohydroxide oxalate stones radiologically are regular and homogeneous, whereas bihydroxide oxalate stones have an irregular aspect. Monohydroxide oxalic lithiasis is less frequent than bihydroxide oxalic lithiasis. The proportion of monohydroxide lithiasis is the same in men and women whereas bihydroxide lithiasis is more frequent in men. Of a biologic point of view, in monohydroxide lithiasis, calciuria and oxaluria are often normal while proportion of hypercalciuria and hyperoxaluria is more important in bihydroxide lithiasis. Evolutivity is clearly inferior in monohydroxide lithiasis than in bihydroxide lithiasis.

Adult↗
PubMed1984

Z-form induction in DNA by carcinogenic nickel compounds: an optical spectroscopy study.

The B----Z conformational transition of double-stranded poly(dG-dC) induced by various nickel salts (chloride, sulfate, subsulfide, carbonate) has been studied by ultraviolet absorption and circular dichroism. The spectra of the nickel compounds, both free and complexed with DNA, have been obtained in the visible and near infrared regions. In all cases the nickel adopts the hexacoordinated ionic form [Ni(H2O6]2+ and induces the B----Z transition of the nucleic acid at submillimolar concentrations (typically 0.4 mM). The addition to the poly(dG-dC)-poly(dG-dC) of an antitumoral drug, pentaziridinocyclodiphosphathiazene (SOAz), inhibits the B----Z transition even at a ten-fold higher nickel concentration (4 mM). Possible implications for carcinogenesis are discussed.

Antineoplastic Agents↗
PubMed1983

Z-DNA immunoreactivity in fixed metaphase chromosomes of primates.

Antibodies against Z-DNA bind to fixed metaphase chromosomes of man and Cebus albifrons (Platyrrhini, Primate). By indirect immunofluorescence and indirect immunoperoxidase techniques, a heavy staining is detected in some segments of chromosomes of C. albifrons. These segments correspond to R-band-positive heterochromatin, which has a high G + C-base content. Euchromatin of human and Cebus chromosomes show a weak and heterogeneous staining that consistently reproduces an R- and T-banding pattern in both species. Because chromosome homologies previously were demonstrated between these distantly related species by chromosome banding, our results suggest that Z-DNA has been conserved during the course of primate evolution.

Animals↗
PubMed1982

In vitro recognition of DNA base pairs by histones in histone-DNA complexes and reconstituted core particles: an ultraviolet resonance Raman study.

Resonance Raman spectra of complexes between DNA and the four core histones, alone or associated, have been investigated in vitro using excitations at 300 and 257 nm, which give complementary informations about the DNA bases. H2A and H2B fractions recognize the G-C base pairs, while H3 and H4 (arginine rich fractions) recognize the A-T base pairs. The associated fractions form complexes with DNA which yield about the same DNA spectral modifications as the DNA-H4 complexes. This reveals the important role of the arginine rich fractions in the core particle formation and confirms the preferential in vitro assembly of nucleosome cores on A-T rich regions of DNA (25).

Animals↗