Aβ(1-42) Tetramer and Octamer Structures Reveal Edge Conductivity Pores as a Mechanism for Membrane Damage

Authors

Sonia Ciudad^1,9, Eduard Puig¹, Thomas Botzanowski², Moeen Meigooni³, Andres S. Arango³, Jimmy Do³, Maxim Mayzel⁴, Mariam Bayoumi⁵, Stéphane Chaignepain¹, Giovanni Maglia⁶, Sarah Cianferani², Vladislav Orekhov^4,7, Emad Tajkhorshid³, Benjamin Bardiaux⁸, Natàlia Carulla¹

Organizations

1. University of Bordeaux, CBMN (UMR 5248)—CNRS—IPB, Institut Européen de Chimie et Biologie, 2 rue Escarpit, 33600, Pessac, France
2. Laboratoire de Spectrométrie de Masse BioOrganique, Université de Strasbourg, CNRS UMR7178, IPHC, Strasbourg, France
3. NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Center for Biophysics and Quantitative Biology and Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
4. Swedish NMR Centre, University of Gothenburg, Box 465, 405 30, Gothenburg, Sweden
5. Biochemistry, Molecular and Structural Biology Section, University of Leuven, Celestijnenlaan 200G, 3001, Leuven, Belgium
6. Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
7. Department of Chemistry and Molecular Biology, University of Gothenburg, Box 465, 405 30, Gothenburg, Sweden
8. Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, C3BI, Institut Pasteur; CNRS UMR3528; CNRS USR3756, Paris, France
9. Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Baldiri Reixac 10, 08028, Barcelona, Spain

Abstract

Polyrotaxane (PR) is a necklace-like supramolecule composed of cyclic components, such as cyclodextrin (CD), and a threading polymer capped with bulky end groups. PR exhibits peculiar mechanical properties attributed to the intermolecular cross-links with CD. Various CD molecules threaded on a linear PEG chain are often modified with chemical groups to add specific physicochemical properties. In general, the stoichiometry between CD and the PEG chain is a significant parameter that defines the unique physical properties of CD-based polyrotaxane (CD-PR). To date, mass spectrometry (MS) has been applied to investigate the molecular distribution of CD-PR, modifications of CD, and the threaded ratio of CD. However, only molecular weights (MWs) up to several 10s of kDa can be subjected to such analysis, whereas the MW of CD-PR used as industrial materials is much greater. Herein, we applied two ionic liquid matrices composed of 3-aminoquinoline and a high mass detector to analyze PRs using MALDI-TOF-MS. High to very high MW PRs in the range of 90–700 kDa were successfully analyzed using this method. The threaded ratio of CD was estimated from a single MW of CD, PEG, and PR. The ratios obtained were consistent with that obtained using 1H NMR. Furthermore, a single-stranded form of PR in γ-cyclodextrin threaded PR (γCD-PR) was clearly distinguished from a double-stranded form, which is only possible in γCD -PR because of its large host cavity.

CovalX Technology Used (Click each option to learn more)

MALDI-ToF
HM4

Outcomes

High-mass MLADI-MS analysis of cross-linked oligomer samples was performed to determine the stoichiometry of the species present in the βPFOsAβ(1-42) sample. To prepare the mixture for MALDI-TOF MS analysis, cross-linked samples were diluted in H2O down to 37.5 μM Aβ(1-42), then mixed (1:1 v/v) with a matrix solution of sinapic acid (10 mg mL−1) containing (1:1 v/v) acetonitrile/deionized water with 0.1% trifluoroacetic acid (TFA). The dried-droplet method was used to deposite the mixture (2 µl thereof) on the MALDI target plate. A MALDI-TOF mass spectrometer equipped with a CovalX HM3 high-mass detector was used in linear mode for the (sub-µM) detection of macromolecules up to 1500 kDa with low saturation. It was found that both Aβ(1-42) tetramers and Aβ(1-42) octamers were present in the βPFOsAβ(1-42) sample.