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E Taillandier

Publications and source records attributed to E Taillandier.

At least 55 records · Page 3Linked to original sources
PubMed1994

Thermal behavior and elastic properties of dimyristoyl phosphatidylcholine bilayers under the effect of pentoxifylline.

We have investigated the effect on dimyristoyl phosphatidylcholine bilayers of pentoxifylline, a derivative of xanthine by using two optical techniques, quasi-elastic light scattering (QLS) and Fourier transform infrared spectroscopy (FT-IR). The results show that in the presence of pentoxifylline, the bilayer phase transition point is lowered and that the elastic modulus is decreased. The FT-IR results indicate strong interactions in the aqueous interface regions of the bilayers. We discussed these results comparatively with those obtained from flavonoid derivatives whose effect was analogous and previously studied.

Dimyristoylphosphatidylcholine↗
PubMed1993

Structure and drug interactions of parallel-stranded DNA studied by infrared spectroscopy and fluorescence.

The infrared spectra of three different 25-mer parallel-stranded DNAs (ps-DNA) have been studied. We have used ps-DNAs containing either exclusively dA x dT base pairs or substitution with four dG x dC base pairs and have them compared with their antiparallel-stranded (aps) reference duplexes in a conventional B-DNA conformation. Significant differences have been found in the region of the thymine C = O stretching vibrations. The parallel-stranded duplexes showed characteristic marker bands for the C2 = O2 and C4 = O4 carbonyl stretching vibrations of thymine at 1685 cm-1 and 1668 cm-1, respectively, as compared to values of 1696 cm-1 and 1663 cm-1 for the antiparallel-stranded reference duplexes. The results confirm previous studies indicating that the secondary structure in parallel-stranded DNA is established by reversed Watson--Crick base pairing of dA x dT with hydrogen bonds between N6H...O2 and N1...HN3. The duplex structure of the ps-DNA is much more sensitive to dehydration than that of the aps-DNA. Interaction with three drugs known to bind in the minor groove of aps-DNA--netropsin, distamycin A and Hoechst 33258--induces shifts of the C = O stretching vibrations of ps-DNA even at low ratio of drug per DNA base pair. These results suggest a conformational change of the ps-DNA to optimize the DNA-drug interaction. As demonstrated by excimer fluorescence of strands labeled with pyrene at the 5'-end, the drugs induce dissociation of the ps-DNA duplex with subsequent formation of imperfectly matched aps-DNA to allow the more favorable drug binding to aps-DNA. Similarly, attempts to form a triple helix of the type d(T)n.d(A)n.d(T)n with ps-DNA failed and resulted in the dissociation of the ps-DNA duplex and reformation of a triple helix based upon an aps-DNA duplex core d(T)10.d(A)10.

Base Composition↗
PubMed1993

Triple helix formation by alpha-oligodeoxynucleotides: a vibrational spectroscopy and molecular modeling study.

The structures of triple helices alpha dT6.beta dAn.beta dTn, alpha dT12.beta dAn.beta dTn, alpha dC12+.beta dGn.beta dCn, and alpha dC12+.beta rGn.beta rCn have been studied by Fourier transform infrared spectroscopy, Raman spectroscopy, and molecular mechanics calculations. The sugar conformations in these triplexes have been determined by vibrational spectroscopy. Our results show the existence of only S-type sugars in the alpha dT12.beta dAn.beta dTn triple helix. Both S- and N-type sugar infrared and Raman markers have been detected in the spectra of alpha dC12+.beta dGn.beta dCn. Molecular mechanics refinements taking into account vibrational spectroscopy data constraints allow us to propose third strand hydrogen-bonding schemes and third strand polarities in triple helix models. For alpha dT12.beta dA12.beta dT12 the third strand forms reverse Hoogsteen hydrogen bonds with the beta dA12 strand and therefore is parallel to the purine strand. In contrast, for alpha dC12+.beta dG12.beta dC12 calculations show that only a model in which the third strand is Hoogsteen base paired and antiparallel to the purine strand of the Watson-Crick duplex is compatible with spectroscopic data.

Hydrogen Bonding↗
PubMed1993

A possible family of B-like triple helix structures: comparison with the Arnott A-like triple helix.

Recent experimental studies of the structure of triple helices show that their conformation in solution differs from the A-like structure derived from diffraction data on triple helix fibers by Arnott and co-workers. Here we show by means of molecular modeling that a family of triple helix structures may exist with similar conformational energies, but with a variety of sugar puckers. The characteristics of these putative triple helices are analyzed for three different base sequences: (T.AxT)n, (C.GxC+)n, and alternating (C.GxC+/T.AxT)n. In the case of (C.GxC+)n triple helix, infrared and Raman spectra have been obtained and clearly reveal the existence of both N- and S-type sugars in solution. The molecular mechanics calculations allow us to propose a stereochemically reasonable model for this triple helix, in good agreement with the vibrational spectroscopy results.

Algorithms↗
PubMed1993

A and Z canonical conformations in d(CnGCGn) crystals characterized by microFTIR and microRaman spectroscopies.

Two crystals d(C2GCG2) and d(C5GCG5) have been studied under microscope by Fourier transform ir spectroscopy and Raman spectroscopy. The x-ray diffraction study of the latter crystal had shown that the d(C5GCG5) sequence is the first DNA dodecamer known to adopt a canonical A conformation [N. Verdaguer, J. Aymami, D. Fernandez-Forner, I. Fita, M. Coll, T. Huynh-Dinh, J. Igolen, and J. A. Subirana (1991) Journal of Molecular Biology, Vol. 221, pp. 623-635]. Characteristic ir marker bands and Raman marker peaks of the A conformation have thus been obtained and are compared with previously proposed assignments correlated to fiber diffraction x-ray results obtained on polymers. The d(C2GCG2) sequence crystal had previously been studied in an intermediate form between B and Z [L. Urpi, J. P. Ridoux, J. Liquier, N. Verdagner, I. Fita, J. A. Subirana, F. Iglesias, T. Huynh-Dinh, J. Igolen, and E. Taillandier (1989) Nucleic Acids Research, Vol. 17, pp. 6669-6679]. In this paper we present results obtained from a crystal with this oligonucleotide in Z conformation. The effect of the crystallization conditions on the geometry of the obtained oligomer helix is discussed. The influence of the addition, to the central tetramer CGCG, of dCn stretches (at the 5' end) and dGn stretches (at the 3' end) of different lengths, on the conformational flexibility of the nucleic acid, is considered.

Base Sequence↗
PubMed1992

Thermal behavior and elastic properties of phospholipid bilayers under the effect of a synthetic flavonoid derivative, LEW-10.

We have investigated the effect on phospholipidic bilayers of LEW-10, a synthetic flavonoid, derivative of diosmin. Two optical techniques, Quasi-elastic Light Scattering (QLS) and Fourier Transform Infrared Spectroscopy (FT-IR) were used. The results show that in the presence of LEW-10, the phase transition of the bilayers is lowered and that the elastic modulus is decreased. The FT-IR results indicate interactions in the aqueous interface regions of the bilayers. We also discuss LEW-10 comparatively with another derivative, LEW-7/S1, whose effect has been previously studied.

Carbohydrate Sequence↗
PubMed1992

FTIR study of specific binding interactions between DNA minor groove binding ligands and polynucleotides.

The use of FTIR spectroscopy is made to study the interactions between polynucleotides and two series of minor groove binding compounds. The latter were developed and described previously as part of an ongoing program of rational design of modified ligands based on naturally occurring pyrrole amidine antibiotic netropsin, and varying the structure of bisbenzimidazole chromosomal stain Hoechst 33258. Characteristic IR absorptions due to the vibrations of thymidine and cytosine keto groups in polynucleotides containing AT and GC base pairs respectively are used to monitor their interaction with the added ligands. Although the two thiazole based lexitropsins based on netropsin structure differ in the relative orientation of nitrogen and sulfur atoms with respect to the concave edge of the molecules, they interact exclusively with the thymidine C2 = O carbonyl groups in the minor groove of the alternating AT polymer as evidenced by specific changes in the IR spectra. In the second series of compounds based on Hoechst 33258, the structure obtained by replacing the two benzimidazoles in the parent compound by a combination of pyridoimidazole and benzoxazole, exhibits changes in the carbonyl frequency region of poly dG.poly dC which is attributed to the ligand interaction at the minor groove of GC base pairs. In contrast, Hoechst 33258 itself interacts only with poly dA.poly dT. Weak or no interaction exists between the ligands and any of the polynucleotides at the levels of the phosphate groups or the deoxyribose units.

Bisbenzimidazole↗
PubMed1992

Triple helical polynucleotidic structures: an FTIR study of the C+ .G. Ctriplet.

Triple helixes containing one homopurine poly dG or poly rG strand and two homopyrimidine poly dC or poly rC strands have been prepared and studied by FTIR spectroscopy in H2O and D2O solutions. The spectra are discussed by comparison with those of the corresponding third strands (auto associated or not) and of double stranded poly dG.poly dC and poly rG.poly rC in the same concentration range and salt conditions. The triplex formation is characterized by the study of the base-base interactions reflected by changes in the spectral domain involving the in-plane double bond vibrations of the bases. Modifications of the initial duplex conformation (A family form for poly rG.poly rC, B family form for poly dG.poly dC) when the triplex is formed have been investigated. Two spectral domains (950-800 and 1450-1350 cm-1) containing absorption bands markers of the N and S type sugar geometries have been extensively studied. The spectra of the triplexes prepared starting with a double helix containing only riboses (poly rC+.poly rG.poly rC and poly dC+.poly rG.poly rC) as well as that of poly rC+.poly dG.poly dC present exclusively markers of the North type geometry of the sugars. On the contrary in the case of the poly dC+.poly dG.poly dC triplex both N and S type sugars are shown to coexist. The FTIR spectra allow us to propose that in this case the sugars of the purine (poly dG) strand adopt the S type geometry.

Fourier Analysis↗
PubMed1991

Triple helical polynucleotidic structures: sugar conformations determined by FTIR spectroscopy.

Fourier Transform Infrared Spectra of triple stranded polynucleotides containing homopurine dA or rA and homopyrimidine dT or rU strands have been obtained in H2O and D2O solutions as well as in hydrated films at various relative humidities. The spectra are interpreted by comparison with those of double stranded helixes with identical base and sugar composition. The study of the spectral domain corresponding to in-plane double bond stretching vibrations of the bases shows that whatever the initial duplex characterized by a different IR spectrum (A family form poly rA.poly rU, heternomous form poly rA.poly dT, B family form poly dA.poly dT), the triplexes present a similar IR spectrum reflecting similar base interactions. A particular attention is devoted to the 950-800 cm-1 region which contains marker bands of the sugar conformation in the nucleic acids. In solution the existence of only N (C3'endo-A family form) type of sugar pucker is detected in poly rU.poly rA.poly rU and poly dt.poly rA.poly rU. On the contrary absorption bands characteristic of both N (C3'endo-A family form) and S (C2'endo-B family form) type sugars are detected for poly rU.poly rA.poly dT, poly rU.poly dA.poly dT and poly dT.poly rA.poly dT. Finally mainly S (C2'endo-B family form) type sugars are observed in poly dT.poly dA.poly dT.

Carbohydrates↗
PubMed1991

Molecular modelling of 9-aminoellipticine interactions with abasic oligonucleotides.

We have used molecular mechanics to study the insertion of the DNA intercalating agent 9-aminoellipticine (9AE) into single and double stranded abasic oligonucleotides containing abasic sites in the aldose or furanose conformations. 9AE-abasic oligonucleotide complexes have been considered with 9AE bound at abasic sites as a covalent complex, a reversible complex or a Schiff base. Results are in good agreement with experimental data available on abasic oligonucleotides (melting temperature measurement, NMR results) and allow an analysis of different possible structures for 9AE-abasic oligonucleotide complexes. Hypotheses concerning the role of 9AE-abasic site complexes in enzymatic inhibition are formulated from these data.

Base Sequence↗
PubMed1990

Interpretation of DNA vibrational spectra by normal coordinate analysis.

1. In the following article we undertake a brief review of the most prominent DNA vibrational markers as observed experimentally by Raman and i.r. spectroscopies on polynucleotides and explain how a simplified valence force field can account for the evolution of the DNA vibrational spectra. 2. Our discussion made as a review of our previous investigations on the interpretation of DNA vibration modes, is based on some of the most characteristic and structure dependent DNA vibrational markers.

DNA↗
PubMed1990

The infrared and Raman spectra of the duplex of d(GGTATACC) in the crystal show bands due to both the A-form and the B-form of DNA.

The deoxyoligonucleotide, d(GGTATACC), forms a duplex structure that crystallizes in the DNA A form. This has been shown by both X-ray diffraction studies and Raman spectroscopy (1,2). The presence of the DNA B form has been reported using diffuse X-ray scattering from a crystal of the closely related sequence d(GGBrUABrUACC)(3). In this paper the infrared spectrum of the d(GGTATACC) crystal is presented and curve resolution of both the Raman and IR spectra have been carried out. The percentage of A and B forms have been estimated. The %B form in the crystal has been estimated from the IR spectra to be about 15% and from Raman to be about 20%. Moreover the IR spectrum of the A conformation in the crystal is slightly different from the IR spectrum of the A conformation in polynucleotide fibers in particular in the region of the phosphate stretching vibrations and of the in-plane double bond vibrations of the bases. We show that it is feasible to obtain IR as well as Raman spectra of small crystals of oligonucleotides and that this is a good method of identifying all of the different conformations that may be in the crystal.

Base Sequence↗
PubMed1989

Conformations in crystals and solutions of d(CACGTG), d(CCGCGG) and d(GGCGCC) studied by vibrational spectroscopy.

Crystals of self complementary DNA hexamers d(CACGTG), d(CCGCGG) and d(GGCGCC) were grown by vapour diffusion technique and studied by microRaman and microIR spectroscopies. The oligonucleotides were studied in parallel in solution by vibrational spectroscopy. A B- greater than Z transition was detected by Raman spectroscopy during the crystallization process for d(CACGTG). Vibrational spectroscopy shows that the d(GGCGCC) crystals adopt a B geometry. On the contrary the d(CCGCGG) sequence which is shown to be able to undergo in solution or in films quite easily the B- greater than Z transition, remains trapped in crystals in a geometry which may correspond to an intermediate conformation often proposed in models of the B- greater than Z transition. The crystals used in this study were characterized by X-ray diffraction. The unit cell and space group have been determined.

Base Sequence↗
PubMed1989

The effect of loperamide on the thermal behavior of dimyristoylphosphatidylcholine large unilamellar vesicles.

The effect of loperamide, a drug belonging to the opiate family, on dimyristoyl phosphatidylcholine large unilamellar vesicles (DMPC LUV) was investigated by quasielastic light scattering (QLS) and Fourier transform infrared spectroscopy (FT-IR). Both techniques show that, in the presence of loperamide, DMPC LUV undergoes a two step transition in cooling: one step around the transition point of pure lipid vesicles, the other at a lower temperature. The temperature of the latter step transition is different for the head and tail regions of the drug-containing vesicles: FT-IR spectra demonstrate that the hydrophobic acyl chains transition starts at a temperature well above that of the interfacial region whereas the transition of the entire vesicle, explored by QLS, is broad and covers both temperature ranges. These transitions are thermally reversible in the FT-IR which measures local order but aggregation effects prevent the thermal reversibility of the QLS results. The nature of the drug-lipid interaction is also discussed.

Dimyristoylphosphatidylcholine↗
PubMed1989

Interpretation of DNA vibration modes: III--The behaviour of the sugar pucker vibration modes as a function of its pseudorotation parameters.

A systematic study of the sugar pucker characteristic vibration modes as a function of its geometrical conformations, has been performed. The present investigation is based on the Wilson GF method and a non-redundant valence force field. The calculated results allow to assign the modes arising mainly from the sugar motions and present in quasi whole vibrational spectra related to the right or left-handed double-helices (i.e., 1050 cm-1, 960 cm-1 and 890 cm-1). Moreover, the conformation dependent modes as those at 860 cm-1 and around 810 cm-1 (A form) as well as the one located around 830 cm-1 (B form) are interpreted by the present investigation. The possibility of the interaction of the latter modes with the phosphate group motions along the DNA double-helical chains are also discussed.

DNA↗
PubMed1989

Interpretation of DNA vibration modes: IV--A single-helical approach to assign the phosphate-backbone contribution to the vibrational spectra in A and B conformations.

A calculated approach based on the Higgs method for assigning the vibration modes of an infinite helicoidal polymeric chain has been performed on the basis of a reliable valence force field. The calculated results allowed the phosphate-backbone marker modes of the A and B forms, to be interpreted. In the dynamic models used, the bases have been omitted and no interchain interaction was considered. The calculation can also interprete quite satisfactorily the characteristic Raman peaks and infrared bands in the 1250-700 cm-1 spectral region arising from the sugar or sugar-phosphate association and reproduce their evolution upon the B----A DNA conformational transition. They clearly show that the phosphate-backbone modes in the above mentioned spectral region constitute the optical branches of the phonon dispersion curves with no detectable variation in the first Brillouin-zone.

Animals↗
PubMed1989

FTIR study of netropsin binding to poly d(A-T) and poly dA.poly dT.

Complexes between netropsin and two polynucleotides containing only AT base pairs (poly d(A-T) and poly dA.poly dT) have been prepared at various drug/base pair ratios and studied in solution by Fourier Transform Infrared Spectroscopy. The drug is shown to interact in the narrow groove of poly d(A-T) with the C2O2 carbonyl of thymines and the N3 groups of adenines. Moreover the spectral modifications allow us to propose the existence of interactions at the level of the deoxyribose. No effect is detected on the phosphate groups when netropsin is progressively added. In the case of poly dA.poly dT the interaction seems much weaker as if the high propeller twist of the homopolymer would make the accessibility of the drug to the minor groove more difficult.

Base Composition↗