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Hilla P, Vaara J. NMR chemical shift of confined 129Xe: coordination number, paramagnetic channels and molecular dynamics in a cryptophane-A biosensor. Phys Chem Chem Phys 2023; 25:22719-22733. [PMID: 37606522 DOI: 10.1039/d3cp02695g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2023]
Abstract
Advances in hyperpolarisation and indirect detection have enabled the development of xenon nuclear magnetic resonance (NMR) biosensors (XBSs) for molecule-selective sensing in down to picomolar concentration. Cryptophanes (Crs) are popular cages for hosting the Xe "spy". Understanding the microscopic host-guest chemistry has remained a challenge in the XBS field. While early NMR computations of XBSs did not consider the important effects of host dynamics and explicit solvent, here we model the motionally averaged, relativistic NMR chemical shift (CS) of free Xe, Xe in a prototypic CrA cage and Xe in a water-soluble CrA derivative, each in an explicit H2O solvent, over system configurations generated at three different levels of molecular dynamics (MD) simulations. We confirm the "contact-type" character of the Xe CS, arising from the increased availability of paramagnetic channels, magnetic couplings between occupied and virtual orbitals through the short-ranged orbital hyperfine operator, when neighbouring atoms are in contact with Xe. Remarkably, the Xe CS in the present, highly dynamic and conformationally flexible situations is found to depend linearly on the coordination number of the Xe atom. We interpret the high- and low-CS situations in terms of the magnetic absorption spectrum and choose our preference among the used MD methods based on comparison with the experimental CS. We check the role of spin-orbit coupling by comparing with fully relativistic CS calculations. The study outlines the computational workflow required to realistically model the CS of Xe confined in dynamic cavity structures under experimental conditions, and contributes to microscopic understanding of XBSs.
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Affiliation(s)
- Perttu Hilla
- NMR Research Unit, P.O. Box 3000, FI-90014 University of Oulu, Finland.
| | - Juha Vaara
- NMR Research Unit, P.O. Box 3000, FI-90014 University of Oulu, Finland.
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Hilla P, Vaara J. Energetics and exchange of xenon and water in a prototypic cryptophane-A biosensor structure. Phys Chem Chem Phys 2022; 24:17946-17950. [PMID: 35748333 DOI: 10.1039/d2cp01889f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A microscopic description of the energetics and dynamics of xenon NMR biosensors can be experimentally difficult to achieve. We conduct molecular dynamics and metadynamics simulations of a prototypical Xe@cryptophane-A biosensor in an explicit water solvent. We compute the non-covalent Xe binding energy, identify the complexation mechanism of Xe, and calculate the exchange dynamics of water molecules between the solution and the host. Three distinct, hitherto unreported Xe exchange processes are identified, and water molecules initialize each one. The obtained binding energies support the existing literature. The residence times and energetics of water guests are reported. An empty host does not remain empty, but is occupied by water. The results contribute to the understanding and development of Xe biosensors based on cryptophane derivatives and alternative host structures.
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Affiliation(s)
- Perttu Hilla
- NMR Research Unit, P.O. Box 3000, FI-90014 University of Oulu, Finland.
| | - Juha Vaara
- NMR Research Unit, P.O. Box 3000, FI-90014 University of Oulu, Finland.
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Jayapaul J, Schröder L. Molecular Sensing with Host Systems for Hyperpolarized 129Xe. Molecules 2020; 25:E4627. [PMID: 33050669 PMCID: PMC7587211 DOI: 10.3390/molecules25204627] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 09/27/2020] [Accepted: 09/30/2020] [Indexed: 12/12/2022] Open
Abstract
Hyperpolarized noble gases have been used early on in applications for sensitivity enhanced NMR. 129Xe has been explored for various applications because it can be used beyond the gas-driven examination of void spaces. Its solubility in aqueous solutions and its affinity for hydrophobic binding pockets allows "functionalization" through combination with host structures that bind one or multiple gas atoms. Moreover, the transient nature of gas binding in such hosts allows the combination with another signal enhancement technique, namely chemical exchange saturation transfer (CEST). Different systems have been investigated for implementing various types of so-called Xe biosensors where the gas binds to a targeted host to address molecular markers or to sense biophysical parameters. This review summarizes developments in biosensor design and synthesis for achieving molecular sensing with NMR at unprecedented sensitivity. Aspects regarding Xe exchange kinetics and chemical engineering of various classes of hosts for an efficient build-up of the CEST effect will also be discussed as well as the cavity design of host molecules to identify a pool of bound Xe. The concept is presented in the broader context of reporter design with insights from other modalities that are helpful for advancing the field of Xe biosensors.
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Affiliation(s)
| | - Leif Schröder
- Molecular Imaging, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany;
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Schnurr M, Volk I, Nikolenko H, Winkler L, Dathe M, Schröder L. Functionalized Lipopeptide Micelles as Highly Efficient NMR Depolarization Seed Points for Targeted Cell Labelling in Xenon MRI. ACTA ACUST UNITED AC 2020; 4:e1900251. [PMID: 32293139 DOI: 10.1002/adbi.201900251] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 11/28/2019] [Indexed: 01/07/2023]
Abstract
Improving diagnostic imaging and therapy by targeted compound delivery to pathological areas and across biological barriers is of urgent need. A lipopeptide, P-CrA-A2, composed of a highly cationic peptide sequence (A2), an N-terminally attached palmitoyl chain (P) and cryptophane molecule (CrA) for preferred uptake into blood-brain barrier (BBB) capillary endothelial cells, was generated. CrA allows reversible binding of Xe for NMR detection with hyperpolarized nuclei. The lipopeptide forms size-optimized micelles with a diameter of about 11 nm at low micromolar concentration. Their high local CrA payload has a strong and switchable impact on the bulk magnetization through Hyper-CEST detection. Covalent fixation of CrA does not impede micelle formation and does not hamper its host functionality but simplifies Xe access to hosts for inducing saturation transfer. Xe Hyper-CEST magnetic resonance imaging (MRI) allows for distinguishing BBB endothelial cells from control aortic endothelial cells, and the small micelle volume with a sevenfold improved CrA-loading density compared to liposomal carriers allows preferred cell labelling with a minimally invasive volume (≈16 000-fold more efficient than 19 F cell labelling). Thus, these nanoscopic particles combine selectivity for human brain capillary endothelial cells with great sensitivity of Xe Hyper-CEST MRI and might be a potential MRI tool in brain diagnostics.
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Affiliation(s)
- Matthias Schnurr
- Molecular Imaging, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125, Berlin, Germany
| | - Ines Volk
- Peptide-Lipid Interaction / Peptide Transport, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125, Berlin, Germany
| | - Heike Nikolenko
- Peptide-Lipid Interaction / Peptide Transport, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125, Berlin, Germany
| | - Lars Winkler
- Molecular Imaging, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125, Berlin, Germany
| | - Margitta Dathe
- Peptide-Lipid Interaction / Peptide Transport, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125, Berlin, Germany
| | - Leif Schröder
- Molecular Imaging, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125, Berlin, Germany
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Jayapaul J, Schröder L. Nanoparticle-Based Contrast Agents for 129Xe HyperCEST NMR and MRI Applications. CONTRAST MEDIA & MOLECULAR IMAGING 2019; 2019:9498173. [PMID: 31819739 PMCID: PMC6893250 DOI: 10.1155/2019/9498173] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 10/15/2019] [Indexed: 02/06/2023]
Abstract
Spin hyperpolarization techniques have enabled important advancements in preclinical and clinical MRI applications to overcome the intrinsic low sensitivity of nuclear magnetic resonance. Functionalized xenon biosensors represent one of these approaches. They combine two amplification strategies, namely, spin exchange optical pumping (SEOP) and chemical exchange saturation transfer (CEST). The latter one requires host structures that reversibly bind the hyperpolarized noble gas. Different nanoparticle approaches have been implemented and have enabled molecular MRI with 129Xe at unprecedented sensitivity. This review gives an overview of the Xe biosensor concept, particularly how different nanoparticles address various critical aspects of gas binding and exchange, spectral dispersion for multiplexing, and targeted reporter delivery. As this concept is emerging into preclinical applications, comprehensive sensor design will be indispensable in translating the outstanding sensitivity potential into biomedical molecular imaging applications.
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Affiliation(s)
- Jabadurai Jayapaul
- Molecular Imaging, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
| | - Leif Schröder
- Molecular Imaging, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
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Jayapaul J, Schröder L. Complete Generation of a 129Xe Biosensor on the Solid Support by Systematic Backbone Assembly. Bioconjug Chem 2018; 29:4004-4011. [PMID: 30428668 DOI: 10.1021/acs.bioconjchem.8b00814] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Xenon biosensors are an emerging tool for different molecular imaging approaches. For many applications, their development requires peptide synthesis steps, followed by the selective installation of a xenon host onto the peptide backbone in solution. In this study, three different strategies were attempted for generating entire Xe biosensors on the solid support. Notably, one strategy involving CryA-da was beneficial by directly integrating this host into the growing construct on a low loaded resin via modification of the administered subcomponent equivalents and by prolonging the coupling procedure. Subsequently, installation of additional amino acids or of additional labels onto the growing construct was achieved by a procedure in which an excess amine was administered to the activated CryA-da (acid) anchored onto the resin. Further, the as-generated Xe biosensor was tested for its NMR and MRI capabilities in H2O and compared to the performance of CryA-ma. Xe NMR of the biosensor indicated a clear CEST response and the Xe MR images revealed similar contrast compared to the reference host. These observations suggest that functionalizing CryA-da on both sides with multiple labels did not alter significantly its NMR capabilities. Hereby, we could show the successful and complete synthesis of a CryA-da-based xenon biosensor on the solid support without any notable side reactions and without the necessity of multiple purification steps.
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Affiliation(s)
- Jabadurai Jayapaul
- Molecular Imaging, Department of Structural Biology , Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) , Robert-Rössle-Strasse 10 , 13125 Berlin , Germany
| | - Leif Schröder
- Molecular Imaging, Department of Structural Biology , Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) , Robert-Rössle-Strasse 10 , 13125 Berlin , Germany
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Brotin T, Jeanneau E, Berthault P, Léonce E, Pitrat D, Mulatier JC. Synthesis of Cryptophane-B: Crystal Structure and Study of Its Complex with Xenon. J Org Chem 2018; 83:14465-14471. [DOI: 10.1021/acs.joc.8b02246] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Thierry Brotin
- Laboratoire de Chimie, Univ Lyon, Ecole Normale Supérieure de Lyon, CNRS UMR 5182, Université Lyon 1, 46 allée d’Italie, Lyon F69364, France
| | - Erwann Jeanneau
- Centre de Diffractométrie Henri Longchambon, Université Lyon 1, 5 rue de la Doua, Villeurbanne 69100, France
| | - Patrick Berthault
- NIMBE, CEA, CNRS, Université de Paris Saclay, CEA Saclay, Gif-sur-Yvette 91191, France
| | - Estelle Léonce
- NIMBE, CEA, CNRS, Université de Paris Saclay, CEA Saclay, Gif-sur-Yvette 91191, France
| | - Delphine Pitrat
- Laboratoire de Chimie, Univ Lyon, Ecole Normale Supérieure de Lyon, CNRS UMR 5182, Université Lyon 1, 46 allée d’Italie, Lyon F69364, France
| | - Jean-Christophe Mulatier
- Laboratoire de Chimie, Univ Lyon, Ecole Normale Supérieure de Lyon, CNRS UMR 5182, Université Lyon 1, 46 allée d’Italie, Lyon F69364, France
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