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Study of peptide-peptide interactions by Taylor dispersion analysis: application to the monitoring of beta-amyloid peptide aggregation

ABG-76704 Sujet de Thèse
18/05/2018 < 25 K€ brut annuel
Institut des biomolécules Max Mousseron
Montpellier - Occitanie - France
Study of peptide-peptide interactions by Taylor dispersion analysis: application to the monitoring of beta-amyloid peptide aggregation
  • Chimie
Chimie analytique, analytical chemistry, Weak interactions, aggregation, Taylor dispersion analysis, beta-amyloid peptide, Alzheimer, dynamic light scattering

Description

Context. Peptide-peptide interactions, and protein-protein interactions, PPI, are involved in many biological cellular mechanisms and in many diseases (such as neurodegenerative diseases) [P1-P2]. Amyloid β (Aβ) peptides of 39−43 amino acids are the major components of senile plaques in Alzheimer’s disease (AD). The Aβ aggregation is a complicated process owing to the vast heterogeneity of the aggregates, the number of peptides for each aggregate, and the sensitivity of the process to pH, agitation, temperature, concentration, ionic strength, surfactants, sample preparation, and the sequence (Aβ1−40 vs Aβ1−42) [P3]. Aβ monomers in solution are random coils. By formation of β-sheets, the aggregation of Aβ peptides tends to form fibrils under kinetic control rather than thermodynamic control, adding complexity to the determination of the factors governing the fibril formation. The neurotoxicity is most likely due to the soluble forms of Aβ oligomers rather than the fibrils, which are under solid forms. The role of metal ions (Cu2+, Zn2+, and Fe3+) and plasmatic proteins such as human serum albumin (HSA) in the aggregation process remains an important and challenging issue for which new analytical method should be proposed [P4].
Taylor dispersion analysis (TDA) has not been applied yet to the study of PPI [P5-P7], except in a very recent paper dealing with highly concentrated peptide formulations [P8]. This method allows one to determine the hydrodynamic radius (or diffusion coefficient) of a solute through the analysis of the dispersion of a solute plug injected into an open capillary tube, under laminar flow conditions. TDA holds great potentiality for PPI, in view of the advantages of this technique: TDA is an absolute method (no calibration is needed) that requires small sample quantities (a few nL), yielding an unbiased determination of the size of a peptide or protein, for sizes ranging from one angstrom to a few hundred nm. Moreover, we have recently demonstrated that it is possible to retrieve from TDA data the full size distribution (hydrodynamic radius or diffusion coefficient of the suspended solutes) [P8-10].

Objectives. The goal of this PhD proposal is to assess the contribution of TDA to the investigation of nano-object interactions, and notably for PPI. The aggregation of Aβ peptides will be studied for the evaluation of TDA on a biologically relevant application.

Methodologies. In a first project phase, a simple model system will be studied at physiological pH to investigate, in the diluted regime, the effect of the interactions between the polypeptides (repulsive, attractive, neutral) on the concentration dependence of the diffusion coefficient.
In the second project phase, DLS and TDA will be compared for the kinetic study of Aβ peptides aggregation in well-defined experimental conditions (ionic strength, peptide concentration range, pH, nature of the adding salt and buffering reagent). We expect the typical range of molar mass for monitoring Aβ aggregation to be between 4.5 kDa (Aβ monomer), 9 kDa for Aβ dimer, 16 kDa for preglobulomers (~4 Aβ chains), up to a few hundred of kDa for the largest oligomers. The ultimate goal is to get a better knowledge on the influence of key biological parameters, such as the presence of HSA, the presence of metals (Zn2+, Cu2+, Fe2+, Fe3+), and the sequence of the Aβ chains.
In a last part of the project, the influence of potential drugs and inhibitors (Carnosine, beta-sheet breakers, quinone or polyphenol inhibitors) of Aβ aggregation will be tested using the developed TDA method.

References

P1. Protein-Protein Interactions: Methods for Detection and Analysis, E. M. Phizicky, S. Fields, Microbiological Reviews, 1995, 59, 94–123.
P2. A Human Protein-Protein Interaction Network: A Resource for Annotating the Proteome. Ulrich Stelzl et al. Cell, 2005, 122, 957-968.
P3. Polymorph-specific kinetics and thermodynamics of β-amyloid fibril growth, W. Qiang, K. Kelley, R. Tycko, J. Am. Chem. Soc., 2013, 135, 6860−6871.
P4. Amyloid  Protein and Alzheimer’s disease: when computer simulations complement experimental studies. J. Nasica-Labouze et al. Chemical Reviews, 2015, 115, 3518-3563.
P5. Assessment of net charge and protein-protein interactions of different monoclonal antibodies. C. Lehermayr, H. C. Mahler, K. Mäder, S. Fischer, J. Pharm. Sci. 2011, 100, 2551-2562.
P6. Measuring arbitrary diffusion coefficient distributions of nano-objects by Taylor dispersion analysis. L. Cipelletti, J.-P. Biron, M. Martin, H. Cottet, Anal. Chem., 2015, 87, 8489–8496.
P7. Polydispersity analysis of Taylor dispersion data: the cumulant method. L. Cipelletti, J.-P. Biron, M. Martin, H. Cottet, Anal. Chem. 2014, 86, 6471–6478.
P8. Taylor Dispersion Analysis as a promising tool for assessment of peptide-peptide interactions. U. B. Hogstedt, G. Schwach, M. van de Weert, J. Ostergaard, Eur. J. Pharm. Sci., 2016, 93, 21-28.
P9. On the optimization of operating conditions for Taylor Dispersion Analysis of Mixtures. H. Cottet, J. P. Biron, M. Martin, Analyst, 2014, 139, 3552-3562.
P10. Monitoring biopolymer degradation by Taylor dispersion analysis. J. Chamieh, J.-P. Biron, L; Cipelletti, H. Cottet, Biomacromolecules, 2015, 16, 3945-3951.

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Présentation établissement et labo d'accueil

Institut des biomolécules Max Mousseron

The « Institute des Biomolécules Max Mousseron » (IBMM or UMR5247 CNRS-University of Montpellier 1-University of Montpellier 2), whose director is professor Pascal Dumy, is a research institute of international renown and one of the four Founder Institutes of the Balard Chemistry Pole of Montpellier.
The research activities concentrate on essential biomolecules such as lipids, nucleosides, nucleotides and nucleic acids, peptides and proteins, glycosides, biopolymers, prebiotic molecules and fluorinated molecules.
The research programmes conducted on biomolecules concern their design, their synthesis and their pharmacology. These biomolecules and their families of compounds are used as basic molecules in pharmacology for studying their related physiological and pathological mechanisms, they are also the essential precursor molecules for future medications. The research activities of the IBMM are situated at the junction of chemistry and biology, they aim to study and understand the action mechanisms of biomolecules and the treatment of human and animal pathologies (infectious, cardiovascular, degenerative pathologies, cancer…) with applications in tomorrow’s molecular medicine. Simultaneously, the applications of biomolecules cover vast fields such as cosmetology, agrofood industry, veterinary industry and environment-friendly agrochemistry and within a sustainable development framework (green chemistry).
The assets of the IBMM lie in the diversity of the skills and in the complementarity of the different teams of the Institute, in the international recognition of the teams, in the numerous academic and industrial collaborations developed and in its technology valorisation, innovation and transfer actions. The IBMM is also an attractive centre for future junior researchers thanks to the diverse tuitions and training periods opportunities it offers on the basis of its expertise capacities and of its know-how in terms of design, analysis and discovery of the future medications which characterise the Montpellier site in the field of biomolecules.

Profil du candidat

The candidate must be motivated by this topic at the interface between chemistry, physical-chemistry and biology and must be able to become autonomous. She or he must possess a master’s degree in analytical chemistry or physical-chemistry (or equivalent).
Knowledge of French language is a plus but not mandatory.
Advanced English level is required.

Date limite de candidature

27/05/2018
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