Partenaires

CNRS


Rechercher


Accueil > Publications > Recherche par années > Années 1990 > 1997

1997

Page(s) : < | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |

(+)-episesaminone, a Sesamum indicum furofuran lignan. Isolation and hemisynthesis

Several lignans from Sesamum sp. contain an unusual oxygen insertion between their furano and aromatic rings. As part of our ongoing studies to clarify the biosynthetic pathway to the sesame lignans, the furanoketone, (+)-episesaminone, was isolated and fully characterized in part via hemisynthesis from (+)-sesamolin.

Lire la suite

A multigram, stereoselective synthesis of D-[C-13(5)]ribose from D-[C-13(6)]glucose and its conversion into [C-13(5)]nucleosides

The preparation of C-13-labeled ribonucleosides starting from D-[C-13(6)]glucose in 45% overall yield is described. The key of this short synthetic way is the dehomologation of di-O-isopropylidene hexofuranose 2 with periodic acid and NaBH4 that afforded stereoselectively the labeled ribofuranose derivative 3 in high yield. (C) 1997 Elsevier Science Ltd.

Lire la suite

A mutation in the XPB/ERCC3 DNA repair transcription gene, associated with trichothiodystrophy

Trichothiodystrophy (TTD) is a rare, autosomal recessive disorder characterized by sulfur-deficient brittle hair and nails, mental retardation, impaired sexual development, and ichthyosis. Photosensitivity has been reported in approximately 50% of the cases, but no skin cancer is associated with TTD. Virtually all photosensitive TTD patients have a deficiency in the nucleotide excision repair (NER) of UV-induced DNA damage that is indistinguishable from that of xeroderma pigmentosum (XP) complementation group D (XP-D) patients. DNA repair defects in XP-D are associated with two additional, quite different diseases ; XP, a sun-sensitive and cancer-prone repair disorder, and Cockayne syndrome (CS), a photosensitive condition characterized by physical and mental retardation and wizened facial appearance. One photosensitive TTD case constitutes a new repair-deficient complementation group, TTD-A. Remarkably, both TTD-A and XP-D defects are associated with subunits of TFIIH, a basal transcription factor with a second function in DNA repair. Thus, mutations in TFIIH components may, on top of a repair defect, also cause transcriptional insufficiency, which may explain part of the non-XP clinical features of TTD. Besides XPD and TTDA, the XPB gene product is also part of TFIIH. To date, three patients with the remarkable conjunction of XP and CS but not TTD have been assigned to XP complementation group B (XP-B). Here we present the characterization of the NER defect in two mild TTD patients (TTD6VI and TTD4VI) and confirm the assignment to X-PB. The causative mutation was found to be a single base substitution resulting in a missense mutation (T119P) in a region of the XPB protein completely conserved in yeast, Drosophila, mouse, and man. These findings define a third TTD complementation group, extend the clinical heterogeneity associated with XP-B, stress the exclusive relationship between TTD and mutations in subunits of repair/transcription factor TFIIH, and strongly support the concept of "transcription syndromes."

Lire la suite

A potential function for computer simulation studies of proton transfer in acetylacetone

A potential energy model is developed to study the intramolecular proton transfer in the enol form of acetylacetone. It makes use of the empirical valence bond approach developed by Warshel to combine standard molecular mechanics potentials for the reactant and product states to reproduce the interconversion between these two states. Most parameters have been fitted to reproduce the key features of an ab initio potential surface obtained from 4-31G* Hartree-Fock calculations. The partial charges have been fitted to reproduce the electrostatic potential surface of 6-31G* Hartree-Fock wave functions, subject to total charge and symmetry constraints, using a fitting procedure based on generalized inverses. The resulting potential energy function reproduces the features most important for proton transfer simulations, while being several orders of magnitude faster in evaluation time than ab initio energy calculations. (C) 1997 by John Wiley & Sons, Inc.

Lire la suite

Accurate numerical approximation to the Gauss-Lorentz lineshape

The Gauss-Lorentz lineshape often observed in EPR or NMR is shown to be simply related to the complex error function. Using numerical algorithms developed for the evaluation of this function, experimental lineshapes can be accurately and rapidly simulated. Formulas are presented for the derivatives of the line profile with respect to the parameters and for the approximate computation of the overall linewidth. It is observed that accurate integrals require use of a wide integration interval. (C) 1997 Academic Press.

Lire la suite

Amphiphilic peptides as models for protein-membrane interactions : interfacial behaviour of sequential Lys- and Leu-based peptides and their penetration into lipid monolayers

Synthetic peptides constructed with doublets of hydrophobic residues tandemly repeated with doublets of positively charged residues, (Leu-Lys-Lys-Leu)(n), were used as models for the study of protein-membrane interactions. Their behaviour has been compared with that of their strictly alternating iso peptides, (Leu-Lys)(n). Both peptides present a random coil structure in pure water. In saline solutions, (Leu-Lys-Lys-Leu)(n) peptides adopt an a-helical structure whereas (Leu-Lys)(n) transit into a ß-sheet structure.

Lire la suite

An interleaved heteronuclear NMRI-NMRS approach to non-invasive investigation of exercising human skeletal muscle

Novel tools are presented that aim at more comprehensive NMR investigations of human skeletal muscle metabolism, in particular during exercise protocols. They integrate imaging (NMRI) and spectroscopy (NMRS) experiments in a single dynamic examination. The first. sequence that we propose combines NMR-plethysmography, H-1-NMRS of deoxymyoglobin and P-31-NMRS.

Lire la suite

Antisense properties of end-modified oligonucleotides targeted to Ha-ras oncogene

Phosphodiester oligodeoxyribonucleotides linked to an intercalating agent or a dodecanol tail or both complementary to the 12th codon region of Ha-ras mRNA were compared with the unmodified oligonucleotides of the same size and sequence with respect to their ability to induce RNaseH cleavage and antisense activity in cell culture. The hydrophobic tail not only protected the oligonucleotide from nucleases but also enhanced RNase H cleavage of the target. Oligonucleotides carrying both an acridine and a dodecanol substituent inhibited the proliferation of HBL100ras1 cells (human mammary cells stably transformed with the T24 Ha-ras gene carrying a G—>T point mutation in codon 12) at a 20-fold to 30-fold lower concentration than unmodified ones. Therefore, these modified oligonucleotides may prove useful for antisense applications.

Lire la suite

Appearance of lipidic signals in ’’stressed’’ cells : Study of myogenic cultured cells by two-dimensional nuclear magnetic resonance

The proton NMR spectra of regenerating muscle show high resolution fatty acid signals as the spectra of other stressed cells such as ischemic cardiac cells, stimulated immune cells or malignant cells. We report here the in vitro study, by 2D H-1 NMR, of the fusion of myogenic cells. High resolution fatty acid signals are only detected during cell fusion, demonstrating a higher mobility of the acyl chains.

Lire la suite

Page(s) : < | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |