Biomembrane Interactions of Functionalized Cryptophane-A: Combined Fluorescence and 129Xe NMR Studies of a Bimodal Contrast Agent

Authors

  • Jagoda Sloniec,

    1. Division 1.10 Biophotonics, BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Strasse 11, 12489 Berlin (Germany), Fax: (+49) 30-8192-5005
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    • These authors contributed equally to this work.

  • Matthias Schnurr,

    1. ERC Project BiosensorImaging, Leibniz-Institut für Molekulare, Pharmakologie (FMP), Campus Berlin-Buch, Robert-Rössle-Strasse 10, 13125 Berlin (Germany)
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    • These authors contributed equally to this work.

  • Dr. Christopher Witte,

    1. ERC Project BiosensorImaging, Leibniz-Institut für Molekulare, Pharmakologie (FMP), Campus Berlin-Buch, Robert-Rössle-Strasse 10, 13125 Berlin (Germany)
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  • Dr. Ute Resch-Genger,

    1. Division 1.10 Biophotonics, BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Strasse 11, 12489 Berlin (Germany), Fax: (+49) 30-8192-5005
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  • Dr. Leif Schröder,

    Corresponding author
    1. ERC Project BiosensorImaging, Leibniz-Institut für Molekulare, Pharmakologie (FMP), Campus Berlin-Buch, Robert-Rössle-Strasse 10, 13125 Berlin (Germany)
    • ERC Project BiosensorImaging, Leibniz-Institut für Molekulare, Pharmakologie (FMP), Campus Berlin-Buch, Robert-Rössle-Strasse 10, 13125 Berlin (Germany)
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  • Dr. Andreas Hennig

    Corresponding author
    1. Division 1.10 Biophotonics, BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Strasse 11, 12489 Berlin (Germany), Fax: (+49) 30-8192-5005
    • Division 1.10 Biophotonics, BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Strasse 11, 12489 Berlin (Germany), Fax: (+49) 30-8192-5005
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Abstract

Fluorescent derivatives of the 129Xe NMR contrast agent cryptophane-A were obtained by functionalization with near infrared fluorescent dyes DY680 and DY682. The resulting conjugates were spectrally characterized, and their interaction with giant and large unilamellar vesicles of varying phospholipid composition was analyzed by fluorescence and NMR spectroscopy. In the latter, a chemical exchange saturation transfer with hyperpolarized 129Xe (Hyper-CEST) was used to obtain sufficient sensitivity. To determine the partitioning coefficients, we developed a method based on fluorescence resonance energy transfer from Nile Red to the membrane-bound conjugates. This indicated that not only the hydrophobicity of the conjugates, but also the phospholipid composition, largely determines the membrane incorporation. Thereby, partitioning into the liquid-crystalline phase of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine was most efficient. Fluorescence depth quenching and flip-flop assays suggest a perpendicular orientation of the conjugates to the membrane surface with negligible transversal diffusion, and that the fluorescent dyes reside in the interfacial area. The results serve as a basis to differentiate biomembranes by analyzing the Hyper-CEST signatures that are related to membrane fluidity, and pave the way for dissecting different contributions to the Hyper-CEST signal.

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