Biomedical subjects
Publications and source records attributed to B Calas.
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.
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.
(D-Trp)6-LHRH:pGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-GlyNH2 was prepared by solid-phase peptide synthesis using the nitro group to protect the guanidine side chain of the arginyl residue. Removal of the side-chain protecting groups was carried out by catalytic transfer hydrogenation (CTH) using palladium acetate/ammonium formate or palladium on charcoal/formic acid. We show in this paper that this deprotection method induces i) reduction of the tryptophan residue and ii) epimerization at the histidine level (with palladium acetate/ammonium formate). Despite the formation of significant amounts of reduced peptide, CTH enabled us to obtain (D-Trp)6-LHRH in relatively good yield.
We have determined the specificity of sera elicited by glutaraldehyde-stabilized bovine aortic actin. This modification induces a high titre of antibodies directed against the N-terminal (residues 1-39) and the C-terminal region of smooth-muscle actins. The crude antisera were purified on peptide (corresponding to the 1-9 or 1-8 N-terminal sequences of smooth-muscle isoactins)-polyacrylic-resin columns. By fractionating the antisera we obtained oligoclonal antibody populations specific for each isoactin.
DiMe-C7 (pGlu-Gln-Phe-MePhe-MeGly-Leu-MetNH2), a metabolically stable analogue of Substance P, was prepared by solid-phase peptide synthesis using a polyacrylamide resin and a labile anchorage derived from glycolic acid. Myotropic activities in guinea pig ileum (ED50 = 4.0 +/- 1.5 10(-8) M) and guinea pig trachea (ED50 = 8.6 +/- 3.5 10(-8) M) are discussed in comparison with the corresponding activities of Substance P.
The authors describe 315 cases of total maxillo-facial fracture and the conclusions to be drawn from them: --Endobuccal and orthopaedic surgical treatment under general anaesthetic, the osteosynthetic material being perfectly well tolerated: less than 3% having to be removed. --Treatment requiring a careful pre-operative radio-clinical assessment which can never be adequately carried out in an emergency, therefore treatment is delayed (5th and 8th days) except in cases of special emergency (wounds). --Delayed sequelae, bearing in mind the often spectacular lesions, are relatively rare.
The process by which analogs in peptide chemistry are currently designed does not include any quantitative basis for amino acid substitutions from pharmacological leads. Here, we show that substitution matrices such as PAM 250 can provide quantitative constraints compatible with biological activity. This article describes its use in a strategy of rational amino acid substitution in peptides and proteins: we have computed a chemically derived matrix equivalent to the well-known PAM 250 matrix, reflecting the natural mutability rates of amino acids in protein evolutions but that can be extended to all the noncoded amino acids. Some of these noncoded amino acids are widely used to mimic secondary structure, to constrain backbone conformation, or to evade protease degradation. An automated sequence mutation (ASM) strategy has been defined to generate mutations within constraints. Application of such a substitution matrix to quantitative structure-function relationship studies will be of use in the design of proteins and peptides destined to become pharmaceutical drugs. In particular, issues such as which functionally conserved substitutions are able to satisfy conformational restrictions, oral bioavailability, or formulation demands can be quantitatively addressed.
We describe the use of 6 M HCl to remove the Boc group in solid-phase peptide synthesis. Three peptides, 4-10 amino acid residues in length, have been successfully synthesized using 6 M HCl and were found to be comparable in purity to the same peptides prepared using the standard 50% trifluoroacetic acid in dichloromethane method of N-alpha-Boc removal.
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.
The aim of this study was to obtain gonadoptropin-releasing hormone (GnRH) receptor antibodies of high affinity for receptor immunoanalysis. According to the complementary peptide theory, complementary nucleic acid segments encode for the hormone ligand and the receptor binding site, respectively. On this premise, we used as immunogen, GnRH complementary peptide [N-terminal]Ser-Arg-Ala-Gln-Ser-Ile-Gly-Pro-Val-Leu conjugated with a carrier protein. High antibody titers were obtained in rabbits, rats and mice. Our antisera recognized the hydrophobic middle part of the GnRH complementary peptide. A band of protein with a molecular weight similar to that of the GnRH receptor (60 kDa) was specifically detected by immunoblot of solubilized rat pituitary membranes with the highest titering rabbit antiserum. In bioassays on sheep pituitary cells in vitro, some antisera inhibit basal or GnRH-induced LH secretion. In order to elicit antibodies of high affinity, we used a selective receptor assay on rat brain and pituitary sections where the ligand was the labeled agonist Des-Gly10-D-Ala6 GnRH. None of the highest titering antisera prevented the binding of such a high affinity ligand. The complementary peptide approach thus appears not to be optimal for obtaining high affinity antibodies against the GnRH receptor binding site.
A peptide corresponding to the amino acid sequence of human gamma-interferon, residues 7-20, was synthesized by a solid phase procedure using polyacrylic resin and methionine as anchor. Fluorenemethoxycarbonyl and t-butyloxycarbonyl strategies were compared. After completion of the synthesis, side chain deprotections were performed on the peptide still attached to the resin. The purity of the peptide linked to the matrix was determined by amino acid analysis and solid phase sequencing. The presence of methionine allowed the peptide to be detached from the support by CNBr cleavage. The immune responses of the free peptide, the peptide linked to bovine serum albumin and the peptide resin adduct were compared. Peptide bound to polyacrylamide gave similar results to those obtained using classical immunization procedures.
Polyacrylamide-based solid-phase supports were used in the production of a synthetic peptide analogous to amino acid sequence 1-9 from bovine aortic actin. Different peptidyl-resins were prepared and directly used to induce an antibody response in rabbits. Antisera that recognized the resin-bound peptide were compared. Some of them reacted with native aortic actin; this response was highly specific for the smooth muscle alpha actin isotype. We also immunized rabbits with the 1-9 peptide linked to bovine serum albumin. In this case, antisera were less reactive with native aortic actin, and cross-reacted with the two closely related smooth muscle alpha and macrophage actin isotypes. This method provides a rapid and simple procedure for generating peptide immunogens and antibodies to them, by the combination of peptidyl-resin immunizations and resin-bound peptide immunoassays.