Eric Diesis

Slow isomerization of some proline-containing peptides inducing peak splitting during reversed-phase high-performance liquid chromatography

Abstract A slow conformational equilibrium, commensurable with the retention times, was shown to induce peak broadening or peak splitting during reversed-phase high-performance liquid chromatography of several medium-sized peptides. Elution at 50°C resulted in sharp unique peaks, while at sub-ambient temperature well resolved peaks were observed. Linear peptides which show this phenomenon had a Pro-Pro bond, but the phenomenon was also observed in the case of a cyclic peptide containing two non-vicinal proline residues.

Effect of a lipopeptidic formulation on macrophage activation and peptide presentation to T cells

We studied a 45-69 lipopeptide obtained by N-terminal modification with a N epsilon-palmitoyl lysine residue of the 45-69 peptide derived from the nef protein of HIV. T cells from animals immunized intraperitoneally with 45-69 lipopeptide proliferated in vitro in the presence of 45-69 peptide while no response was obtained after intraperitoneal immunization with 45-69 peptide. The efficiency of the 45-69 lipopeptide is supported by the covalent association to the N epsilon-palmitoyl lysine moiety. The immunogenicity of the 45-69 lipopeptide or of the unmodified peptide is dependent on the route of immunization but is not related to a mitogenic effect on cells or to an increase of the peptide antigenicity. Moreover, only 45-69 lipopeptide induces the secretion of cytokines such as IL-1, IL-6 and TNF-alpha by peritoneal macrophages. Finally, the use of 45-69 lipopeptide permits the activation of highly purified T cells without the addition of antigen-presenting cells. These results have implications for the formulation of synthetic vaccines.

Conversion of N-terminal cysteine to thiazolidine carboxylic acid during hydrogen fluoride deparotection of peptides containing Nπ-bom protected histidine

Formaldehyde released during hydrogen fluoride deprotection of peptides containing a histidine residue protected by the Nπ-benzyloxymethyl (Bom) group induces cyclisation of N-terminal cysteine to thiazolidine carboxylic acid (Thz).

In situ chemical modification of peptide microarrays: application to the study of the antibody responses to methylated antigens.

Peptide microarrays are useful tools for characterizing the humoral response against methylated antigens. They are usually prepared by printing unmodified and methylated peptides on substrates such as functionalized microscope glass slides. The preferential capture of antibodies by methylated peptides suggests the specific recognition of methylated epitopes. However, unmodified peptide epitopes can be masked due to their interaction with the substrate. The accessibility of unmodified peptides and thus the specificity of the recognition of methylated peptide epitopes can be probed using the in situ methylation procedure described here. Alternately, the in situ methylation of peptide microarrays allows probing the presence of antibodies directed toward methylated epitopes starting from easy-to-make and cost-effective unmodified peptide libraries. In situ methylation was performed using formaldehyde in the presence of sodium cyanoborohydride and nickel chloride. This chemical procedure converts lysine residues into mono- or dimethyl lysines.

Improvement of the T-cell response to a non immunogenic peptide by its tandem association with a highly efficient T-helper peptide.

The 45-69 peptide, an helper T-cell epitope derived from the HIV nef protein is strongly immunogenic. A T-cell proliferative response was observed following immunization of Lou/M rats with 45-69 peptide administered in low dose and without any adjuvant. It is already known that the T-cell response to the 115-131 peptide of Sm28GST antigen, a protein of the parasite Schistosoma mansoni, requires the presence of a carrier of the use of peptidic constructs. We demonstrate here that a T-cell response against the 115-131 peptide can be obtained in the absence of adjuvant using peptidic constructs (115-45 and 45-115 peptides) resulting from tandem synthesis of 115-131 and 45-69 peptides. A covalent association of both peptides is necessary, since the coinjection of 45-69 and 115-131 peptides is not sufficient to induce a detectable anti-115-131 T-cell response. The mutual orientation between the respective tandem peptides (45-115 and 115-45) is critical for the T-cell response. These peptidic constructs possess distinct properties of antigenicity and immunogenicity but both allowed to reveal the existence of a specific T-cell response normally undetectable using 115-131 peptide alone. This immunopharmacological approach should be useful in the rational design and construction of vaccines.