title: Biomembrane interactions of functionalized cryptophane-A: combined fluorescence and 129Xe NMR studies of a bimodal contrast agent.
abstract: Fluorescent derivatives of the (129)Xe 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 (129)Xe (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.
authors: Division 1.10 Biophotonics, BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Strasse 11, 12489 Berlin, Germany.
authors: Jagoda
authors: J
authors: Sloniec
authors: Matthias
authors: M
authors: Schnurr
authors: Christopher
authors: C
authors: Witte
authors: Ute
authors: U
authors: Resch-Genger
authors: Leif
authors: L
authors: Schröder
authors: Andreas
authors: A
authors: Hennig
mesh_terms: D003287:Contrast Media / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008560:Membrane Fluidity; D008856:Microscopy, Fluorescence; D015394:Molecular Structure; D010743:Phospholipids / Q000737:chemistry*; D011083:Polycyclic Compounds / Q000737:chemistry*; D055672:Static Electricity; D014979:Xenon Isotopes / Q000737:chemistry*
chemical_list: D003287:Contrast Media; D005456:Fluorescent Dyes; D010743:Phospholipids; D011083:Polycyclic Compounds; D014979:Xenon Isotopes; C545484:cryptophane A