Synthèse d’aminoacides modifiés exotiques
Synthetic building-blocks to develop post translationally modified peptides
One of the most studied post-translational modification (aberrant or native) by the PeptLab unit is glycosylation. In fact, glycosylation is the most important co- or posttranslational modification (PTM) of secreted proteins and plays a crucial role in several immune functions. Two main forms of protein glycosylation are generally found: O- and N-protein glycosylation.
The synthesis of glycopeptides requires a combination of synthetic methods from both carbohydrate and peptide chemistry. To determine their activity relationships not only sugars but also control of their configuration and of the linkage with amino acids are needed.
Solid-Phase GlycoPeptide Synthesis (SPGPS) based on the building block approach is the most efficient method to obtain glycosylated peptides bearing different sugar moieties on the side chains of different amino acids. SPGPS requires an excess of building block units to achieve high yields, so it is necessary to prepare them in high quantity. For this reason it is fundamental to develop convenient synthetic pathways to glycosylated building blocks and efficient glycopeptide solid-phase synthetic pathways. In PeptLab several glycosylated building blocks orthogonally protected for SPGPS have been developed in large scale both by conventional approach and microwave assisted strategies.
In this context we developed the first synthesis of new Asparagine derivatives bearing alpha or beta- -ribose as pure anomers, linked by an N-glycosidic bond, on the side chain of the Asn residue orthogonally protected for Fmoc/tBu SPPS.
Moreover as glycation of proteins through non-enzymatic reactions between glucose or other reducing sugars and reactive amino groups represents one of the more abundant processes involved in post-translational modification of proteins, we focused our interest in developing Amadori-modified peptides. To this aim, in collaboration with Pr M. Chorev of the Harvard Medical School in Boston (USA), the synthesis of Nα-protected-Nε-glycated-Lys building blocks has been set up. Our strategy offers a controlled side-specific introduction of Nε-Amadori-modified Lys residue into synthetic peptides during a stepwise assembly either in solution or in solid phase methodologies.
Synthesis of new ribosylated Asn building blocks as useful tools for glycopeptide and glycoprotein synthesis. Bonache, M. A.; Nuti, F.; Le Chevalier Isaad, A.; Real-Fernández, F.; Chelli, M.; Rovero, P.; Papini, A. M. Tetrahedron Lett. 2009, 50, 4151–4153.
Building blocks for the synthesis of post-translationally modified glycated peptides and proteins. Carganico, S.; Rovero, P.; Halperin, J. A.; Papini, A. M.; Chorev, M. J. Peptide Sci. 2009, 15, 67–71.
Optimized strategies for the synthesis of bio molecules by the microwave approach
Peptides involved in disease activity are valuable synthetic tools for immunochemistry assays. Speediness represents a critical factor for the growing demand of such probes affecting the process of discovery of diagnostic/prognostic immunoassays. Conventional Solid-Phase Synthesis remains the principal strategy for production of immunochemical probes. Recently, the use of microwave energy was proposed to fulfill the requirement to couple a high-speed technology with an efficient solid-phase synthetic approach. Therefore, the PeptLab team’s research demonstrated that microwave energy can be particularly valuable to obtain N-glycosylated amino acids and complex peptide sequences, i.e. glycopeptides and multiple antigenic peptides, highly amphipathic peptides, as synthetic probes for specific and high affinity diagnostic immunoassays to follow up disease activity.
A peptide backbone (a) before and (b) during microwave irradiation. Reproduced by permission of The Royal Society of Chemistry and © 2006, CEM Corporation.
Conventional and microwave-assisted SPPS approach: a comparative synthesis of PTHrP(1-34)NH(2). Rizzolo, F.; Testa, C.; Lambardi, D.; Chorev, M.; Chelli, M.; Rovero, P.; Papini, A. M. J. Peptide Sci. 2011, 17, 708–714.
Microwave-assisted reaction of glycosylamine with aspartic acid. Real-Fernández, F.; Nuti, F.; Bonache, M. A.; Boccalini, M.; Chimichi, S.; Chelli, M.; Papini, A. M. Amino Acids 2010, 39, 599–604.
Advances in automatic, manual and microwave-assisted solid-phase peptide synthesis. Sabatino, G.; Papini, A. M. Curr. Opinion Drug Disc. Devel. 2008, 11, 762–770.
Optimized strategies for the synthesis of biomolecules by the microwave approach. Paolini, I., Rizzolo, F.; Papini, A. M. Chim. Oggi 2008, 26(Suppl), 16-18.