Biomedical subjects

R Bennes

Publications and source records attributed to R Bennes.

11 recordsLinked to original sources

PubMed1998

Aggregates of an amphiphilic synthetic peptide bind and deliver all-trans retinol and all-trans retinoic acid into fibroblast cells.

The structure and conformational behaviour of a vector peptide, designed by association of a fusion peptide and a nuclear localization sequence, are described. A beta-sheet domain is observed in which fluorescence measurements show that ten peptide molecules bind one all-trans retinol or all-trans retinoic acid molecule with a strong affinity (K'd = 40 nM). Stoichiometry and affinity of the binding can be compared with those of cellular retinoid binding proteins, the structure of which is an anti-parallel beta barrel. Analogy between the system under study and cellular retinoid-binding proteins is discussed. Peptide-helped internalization and subsequent perinuclear localization of retinol in human fibroblast cells confirm this analogy. Also, this last result shows that the peptide is an efficient carrier for insoluble substances like retinoids.

Amino Acid Sequence↗

PubMed1998

[Synthetic peptide as retinoid vector and antiproliferative agent].

First part: Structure, conformational behaviour and vectorization properties of a peptide (PFNLS) designed by association of a fusion peptide and a nuclear localization sequence is described. Tryptophan fluorescence quenching measurements show that ten peptide molecules bind one all trans retinol or all trans retinoic acid molecule with a strong affinity (Kd' = 40 nM). And is able to help the internalization of all-trans retinol in human fibroblasts. Stoichiometry, structure and affinity of the binding can be compared with those of cellular retinoid binding proteins (CRBP), the structure of which is an antiparallel beta barrel. Second part: Cytotoxic properties of the amphiphilic synthetic peptide are presented. Comparative analysis of proliferating, differentiated and confluent H9C2 adherent cells shows a correlation between toxicity and cell cycle stage (proliferating cells). Electrophysiological measurements on Xenopus laevi oocytes bathed in the peptide also demonstrate the induction of cationic currents, which are voltage dependent. These results allow us to hypothesize that the observed toxicity is related to membrane hyperpolarization of proliferating cells at the G1/S cell cycle phase transition. An important point is that in the case of the "peptide-retinoid" complex, no cytotoxicity is observed.

Amino Acid Sequence↗

PubMed1997

Cell cycle dependent toxicity of an amphiphilic synthetic peptide.

The cytotoxic properties of an amphiphilic synthetic peptide are presented. Comparative analysis of proliferating, differentiated and confluent H9C2 adherent cells and L1210 cells in suspension shows a correlation between toxicity and cell stage (proliferating cells). Electrophysiological measurements on Xenopus laevis oocytes bathed in the peptide also demonstrated the induction of cationic currents, which is voltage and phosphate dependent. These results allow us to hypothesize that the observed toxicity is related to membrane hyperpolarization of proliferating cells at the G1/S cell cycle phase transition.

Amino Acid Sequence↗

PubMed1995

Sequences of actin implicated in the polymerization process: a simplified mathematical approach to probe the role of these segments.

Regulation of actin polymerization and depolymerization is essential for the functions of actin in non-muscle cells and is mediated by a large number of heterologous actin-binding proteins which questions their true impact on the polymerization process. As a model, we report here the modulating effect of monospecific antibody fragments (Fab) as in vitro effectors on actin polymerization kinetics. Polymerization curves were obtained through fluorescence measurements. They were fitted using analytical equations derived from classical models describing the actin polymerization process with the aim of identifying kinetic steps potentially altered by the effectors. The study was limited to three short segments bore by the 300-328 sequence which is located in actin subdomain 3 and implicated in one of the monomer-monomer interfaces. We observed that antibodies which inhibited actin polymerization reacted with both G- and F-actins, modulated both nucleation and elongation steps, enhanced actin monomer dissociation from the filament and apparently did not act as capping or sequestering proteins. Among the antibody populations specific for a restricted and selected sequence in subdomain 3 of actin (sequence 300-326), only those directed to epitopes located near Met 305 and 325 were effective. In contrast, antibodies directed towards the alpha-helix located between the two preceding epitopes had no effect. All the results analyzed here emphasize the important role of some discrete regions and their conformational state in regulation of the interconversion between monomeric and polymeric actins which could be controlled in different ways by the various actin-binding proteins.

Actins↗

PubMed1994

The human testis determining factor SRY: a new member of the HMG box protein family.

The product of the sex-determining gene SRY is a member of the HMG box containing protein superfamily. The HMG box is a DNA-binding domain of about 80 amino acids shared by many proteins with diverse functions. It seems that the functions of the full length protein are restricted to the HMG box but their molecular basis remains to be determined. We have summarized here the properties of this binding domain described so far in the literature and, using a synthetic peptide mimicking the DNA binding domain (SRY80), we have confirmed the existence of DNA minor groove contacts with this domain. Using intrinsic fluorescence of the tryptophane, the interaction between SRY80 and the putative target sequence AACAAAT was also quantified. In conclusion, we also consider the possible putative action of SRY to fulfill its role in sex determination.

Amino Acid Sequence↗

PubMed1993

Influence of the nature of the aromatic side-chain on the conductance of the channel of linear gramicidin: study of a series of 9,11,13,15-Tyr(O-protected) derivatives.

This paper describes the single channel properties of a series of synthetic analogues of gramicidin A, where all four tryptophans are replaced either by tyrosine or by several O-protected (benzyl, methyl, ethyl or t-butyl) derivatives. It is shown that, although all analogues bear similar dipole moment on their side-chains, the conductance depends on the hydrophobicity of these protecting groups. An analysis of the conductance data suggests that the conductance is governed by the binding process and a possible explanation, based on conformational considerations, is proposed.

Amino Acid Sequence↗

PubMed1991

Micelle formation of endothelin-1.

Circular dichroism of endothelin-1 synthesized through a continuous flow process reveals, when dissolved in water, a strong concentration dependence of the spectrum. Furthermore, the general feature of the spectrum rules out the possibility of the existence of any alpha and beta structures. In addition, surface tension and conductivity measurements suggest that the peptide aggregates through formation of micelles.

Circular Dichroism↗

PubMed1990

Evidence for aggregation of endothelin 1 in water.

In this report it is shown by CD spectroscopy that endothelin 1, when dissolved in water, is able to present intermolecular interactions leading to formation of aggregates. Surface tension and conductivity measurements suggest that the aggregation occurs through formation of micelles with a CMC of about 2.2 x 10(-5) M.

Chromatography, High Pressure Liquid↗

PubMed1989

Single channels and surface potential of linear gramicidins.

The single channel data for 4 different linear gramicidins containing either 4 Trp, 4 Phe, 4 Tyr or TyrBzl have been analyzed on the basis of 3 barriers-2 sites model. They form 2 families which differ by their single channel behavior and thus different energy profiles of the channel. A relationship between the surface potential and the entry barrier is proposed.

Conductometry↗

PubMedDate not supplied

Solid-phase synthesis and cellular localization of a C- and/or N-terminal labelled peptide.

We report the solid-phase synthesis by the Fmoc strategy of a peptide containing a cysteamide group at its C-terminus. This peptide was subjected to further modifications including the linkage of fluorophores, namely lucifer yellow and coumarin respectively, at the C- and/or N-terminals. After incubation with living cultured cells these two probes were localized and it is concluded that the post-synthesis modifications can strongly modify the localization of the peptide.

Amino Acid Sequence↗

PubMedDate not supplied

Endothelin 1: conformation and aggregation.

The features of the far UV CD spectrum of endothelin 1 (ET 1) in water-containing solutions rules out the presence of any alpha-helical contribution, thus questioning the conclusions made by several authors on the basis of NMR investigations. We propose here a structural model, based on a succession of beta turns, which is consistent with both the NMR and the CD data. Using electron microscopy, we show that ET 1 can form "micelles," and the micelles self-associate into percolation clusters which have a fractal dimension of 1.23 in a 2D space. These data, too, are in agreement with our proposed structural model.

Amino Acid Sequence↗