Tuesday April 21st, 2020

Recruitment of a PhD student : Ultra-efficient separation of intact proteins by capillary electrophoresis, CE-MS and Taylor dispersion analysis

Title :

Ultra-efficient separation of intact proteins by capillary electrophoresis, CE-MS and Taylor dispersion analysis “

Host structure : The work will take place at Institut des Biomolécules Max Mousseron

Application deadline : May 29, 2020

Duration : 3 years

Scientific context

Capillary electrophoresis (CE) is becoming increasingly important for the analysis of (intact) proteins due to its selectivity and high efficiency. This is especially the case when coupled to mass spectrometry (MS) since more sensitive interfaces for the CE-MS coupling are becoming available. Nevertheless, the separation efficiency of CE in the case of proteins does not often reach at all the theoretical expected values due to unwanted protein – capillary interactions inducing residual adsorption.



The scientific objective of this PhD program is to significantly improve the protein separation by decreasing the residual adsorption. For that, innovative coatings based on polyelectrolyte multilayers including zwitterionic groups or grafted PEG chains will be tested and evaluated toward the reduction of protein adsorption; with the goal to reach more than one million theoretical plates for protein separations.


In a first part of the project, glassy and flat 5-bilayers polyelectrolyte coatings will be tested as initial barrier against protein adsorption in CE. The residual adsorption will be experimentally quantified by the determination of the retention factor. The impact of the last polycationic layer on the residual adsorption will be assessed by testing different polymers such as: graft-pegylated polycations with different PEG lengths and proportions; and sulfobetaine derivatized polycations. All the new developed coatings will be characterized using quartz crystal microbalance (QCM) and atomic force microscopy (AFM) to get a clear picture of their structure, roughness and antifouling capabilities. These new coatings will be also evaluated toward their CE performances for protein separations, including monoclonal antibody analysis in conditions compatible with MS coupling. Assessment of CE-MS coupling applications with optimized coatings will be performed in collaboration with a German group (Prof. Christian Neusuess, Aalen University, Germany).
In a second part of the project, the impact of residual adsorption onto the size characterization of proteins by Taylor dispersion analysis (TDA) will be evaluated by comparing the diffusion coefficients of proteins obtained by TDA (using coated capillaries) and by DOSY-NMR (in bulk). The possible relative error on the determination of the diffusion coefficient due to residual adsorption in TDA will be determined and compared with the theory. This study will also allow investigating how electric fields influence residual adsorption by comparing results obtained from CE and TDA methods. TDA is a recently developed and promising method allowing characterizing average protein size and distribution.

PhD supervision

Dr. Laurent Leclercq (50%) laurent.leclercq@umontpellier.fr ; co-direction : Pr. H. Cottet (50%) herve.cottet@umontpellier.fr

With an hand-on training on state-of-the art analytical and characterization methods including CE, CE-MS, AFM, QCM, NMR; (2) Varied duties in a large, exciting and international organization; (3) As an employee in France, you will have access to health insurance.; (4) training abroad (Aalen Univ., Germany and congresses).

Scientific Collaborations. Polyelectrolyte multilayers assembly: Dr. Gaulthier Rydzek, ICGM, UM, gaulthier.rydzek@umontpellier.fr; CE-MS coupling: Prof. Christian Neusüß, Aalen University, Germany, Christian.Neusuess@hs-aalen.de

How to apply

The candidate must be motivated by analytical chemistry with an interest in interdisciplinary work (physicochemical study, polymers, chemical modifications, pharmaceutical applications). She or he should be autonomous, curious and open-minded. She or he must possess a master degree (or engineer diploma) in analytical chemistry or physical-chemistry (or equivalent). Knowledge of French language is a plus but not mandatory. Advanced English level is required.
Please send your resume, a motivation letter, a single pdf file gathering your master and bachelor grades and rankings (when available), as well as two recommendation letters. You must first apply by email at laurent.leclercq@umontpellier.fr and herve.cottet@umontpellier.fr . Please indicate in the mail subject “Application- PhD offer”. Deadline to apply is May 29, 2020 on the doctoral school website: https://edscb.u


Bibliographic references
[1] Donnelly, D. P., Rawlins, C. M., DeHart, C. J., Fornelli, L., Schachner, L. F., Lin, Z. et al. (2019). Best practices and benchmarks for intact protein analysis for top-down mass spectrometry. Nature methods, 16 (7), 587–594.
[2] S. Bekri, L. Leclercq, H. Cottet, Polyelectrolyte multilayer coatings for the separation of proteins by capillary electrophoresis: Influence of polyelectrolyte nature and multilayer crosslinking, J. Chromatogr. A 1399 (2015) 80-87.
[3] H. Katayama, Y. Ishihama, N. Asakawa, Stable capillary coating with successive multiple ionic polymer layers, Anal. Chem. 70 (1998) 2254-2260.
[4] L. Leclercq, M. Morvan, J. Koch, C. Neusüß, H. Cottet, Modulation of the electroosmotic mobility using polyelectrolyte multilayer coatings for protein analysis by capillary electrophoresis, Anal. Chim. Acta 1057 (2019) 152-161.
[5] R. Nehmé, C. Perrin, H. Cottet, M.D. Blanchin, H. Fabre, Influence of polyelectrolyte capillary coating conditions on protein analysis in CE, Electrophoresis 30 (2009) 1888-1898.
[6] Monitoring biopolymer degradation by Taylor dispersion analysis. J. Chamieh, J.-P. Biron, L; Cipelletti, H. Cottet, Biomacromolecules, 2015, 16, 3945-3951.
[7] On the optimization of operating conditions for Taylor Dispersion Analysis of Mixtures. H. Cottet, J. P. Biron, M. Martin, Analyst, 2014, 139, 3552-3562.
[8] A. Taichrib, M. Pioch, C. Neusüß, Toward a screening method for the analysis of small intact proteins by CE-ESI-TOF MS. Electrophoresis, 2012, 33, 1356.

Location : Montpellier

Duration : 3 years

Salary : approx. 1700 € /month (~1400 € net).