TY - JOUR A1 - Hennig, Andreas A1 - Hatami, Soheil A1 - Spieles, Monika A1 - Resch-Genger, Ute T1 - Excitation energy migration and trapping on the surface of fluorescent poly(acrylic acid)-grafted polymer particles N2 - The surface of poly(methyl methacrylate) particles with different amounts of a grafted layer of poly(acrylic acid) was labeled with varying degrees of an amino derivative of fluorescein isothiocyanate. The resulting fluorescent polymer particles were analyzed by absorption spectroscopy and by steady-state and time-resolved fluorescence spectroscopy including measurements of the fluorescence anisotropy. The combined results indicate that the overall decrease in fluorescence intensity with increasing surface concentrations of the fluorophore can be traced back to the formation of non-fluorescent aggregates. A mechanism is proposed, in which the excitation energy migrates between identical fluorophores until it is transferred to non-fluorescent aggregates acting as an energy trap. Increases in the surface fluorophore concentration increase both the probability for energy transfer between identical fluorophores and the probability for energy transfer to non-fluorescent aggregates. Furthermore, we suggest that this mechanism also applies to fluorescent protein conjugates and rationalizes the nonlinear dependence of the fluorescence emission on the labeling density. PY - 2013 U6 - https://doi.org/10.1039/c2pp25364j SN - 1474-905X SN - 1474-9092 VL - 12 IS - 5 SP - 729 EP - 737 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-28522 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sloniec, Jagoda A1 - Schnurr, M. A1 - Witte, C. A1 - Resch-Genger, Ute A1 - Schröder, L. A1 - Hennig, Andreas T1 - Biomembrane interactions of functionalized cryptophane-A: combined fluorescence and 129Xe NMR studies of a bimodal contrast agent N2 - 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. KW - Biosensors KW - Fluorescence KW - FRET KW - Hyperpolarization KW - Lipids KW - Xenon PY - 2013 U6 - https://doi.org/10.1002/chem.201203773 SN - 0947-6539 SN - 1521-3765 VL - 19 IS - 9 SP - 3110 EP - 3118 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-28980 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sloniec, Jagoda A1 - Resch-Genger, Ute A1 - Hennig, Andreas T1 - Photophysics and release kinetics of enzyme-activatable optical probes based on H-dimerized fluorophores on self-immolative linkers N2 - A series of activatable optical probes for the model enzyme penicillin G amidase based on intramolecular formation of non-fluorescent H-dimer between two identical dyes were synthesized. The probes are based on a self-immolative linker, which allows positioning both dyes in close spatial proximity to ensure efficient quenching of probes with absorption and fluorescence emission in the near-infrared (NIR) range. A detailed photophysical investigation of the novel optical probes led to a revision of a previously anticipated quenching mechanism and revealed their potential for optimizing the performance of activatable probes based on H-dimer formation. A kinetic analysis indicated that the fluorescence progress curves can be used to qualitatively extract enzyme kinetic parameters. PY - 2013 U6 - https://doi.org/10.1021/jp409388b SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 117 IS - 46 SP - 14336 EP - 14344 PB - Soc. CY - Washington, DC AN - OPUS4-30053 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -