@misc{BeckHildebrandtLoehmannsroeben2006,
  author    = {Beck, Michael and Hildebrandt, Niko and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {Quantum dots as acceptors in FRET-assays containing serum},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-9504},
  year      = {2006},
  abstract  = {Quantum dots (QDs) are common as luminescing markers for imaging in biological applications because their optical properties seem to be inert against their surrounding solvent. This, together with broad and strong absorption bands and intense, sharp tuneable luminescence bands, makes them interesting candidates for methods utilizing F{\"o}rster Resonance Energy Transfer (FRET), e. g. for sensitive homogeneous fluoroimmunoassays (FIA). In this work we demonstrate energy transfer from Eu<SUP>3+</SUP>-trisbipyridin (Eu-TBP) donors to CdSe-ZnS-QD acceptors in solutions with and without serum. The QDs are commercially available CdSe-ZnS core-shell particles emitting at 655 nm (QD655). The FRET system was achieved by the binding of the streptavidin conjugated donors with the biotin conjugated acceptors. After excitation of Eu-TBP and as result of the energy transfer, the luminescence of the QD655 acceptors also showed lengthened decay times like the donors. The energy transfer efficiency, as calculated from the decay times of the bound and the unbound components, amounted to 37\%. The F{\"o}rster-radius, estimated from the absorption and emission bands, was ca. 77 {\AA}. The effective binding ratio, which not only depends on the ratio of binding pairs but also on unspecific binding, was obtained from the donor emission dependent on the concentration. As serum promotes unspecific binding, the overall FRET efficiency of the assay was reduced. We conclude that QDs are good substitutes for acceptors in FRET if combined with slow decay donors like Europium. The investigation of the influence of the serum provides guidance towards improving binding properties of QD assays.},
  subject      = {Quantenpunkt},
  language  = {en}
}
@article{BeckStielLeupoldetal.2001,
  author    = {Beck, Michael and Stiel, H. and Leupold, Dieter and Winter, Bernd and Pop, D. and Vogt, U. and Spitz, Christian},
  title     = {Evaluation of the energetic position of the lowest excited singlet state of ß-carotene by NEXAFS and photoemission spectroscopy},
  year      = {2001},
  language  = {en}
}
@article{GruszeckiStielNiedzwiedzkietal.2005,
  author    = {Gruszecki, Wieslaw I. and Stiel, H. and Niedzwiedzki, Dariusz and Beck, Michael and Milanowska, J. and Lokstein, Heiko and Leupold, Dieter},
  title     = {Towards elucidating the energy of the first excited singlet state of xanthophyll cycle pigments investigated by x-ray absorption spectroscopy},
  year      = {2005},
  language  = {en}
}
@article{HildebrandtCharbonniereBecketal.2005,
  author    = {Hildebrandt, Niko and Charbonniere, Lo{\"i}c J. and Beck, Michael and Ziessel, Raymond F. and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {Quantum dots as efficient energy acceptors in a time-resolved fluoroimmunoassay},
  issn      = {1433-7851},
  year      = {2005},
  language  = {en}
}
@article{LegallStielBecketal.2007,
  author    = {Legall, Herbert and Stiel, Holger and Beck, Michael and Leupold, Dieter and Gruszecki, Wieslaw I. and Lokstein, Heiko},
  title     = {Near edge X-ray absorption fine structure spectroscopy (NEXAFS) of pigment-protein complexes : peridinin- chlorophyll a-protein (PCP) of Amphidinium carterae},
  issn      = {0165-022X},
  doi       = {10.1016/j.jbbm.2006.08.005},
  year      = {2007},
  abstract  = {Peridinin-chlorophyll a protein (PCP) is a unique water soluble antenna complex that employs the carotenoid peridinin as the main light-harvesting pigment. In the present study the near edge X-ray absorption fine structure (NEXAFS) spectrum of PCP was recorded at the carbon Kedge. Additionally, the NEXAFS spectra of the constituent pigments, chlorophyll a and peridinin, were measured. The energies of the lowest unoccupied molecular levels of these pigments appearing in the carbon NEXAFS spectrum were resolved. Individual contributions of the pigments and the protein to the measured NEXAFS spectrum of PCP were determined using a "building block" approach combining NEXAFS spectra of the pigments and the amino acids constituting the PCP apoprotein. The results suggest that absorption changes of the pigments in the carbon near K-edge region can be resolved following excitation using a suitable visible pump laser pulse. Consequently, it may be possible to study excitation energy transfer processes involving "optically dark" states of carotenoids in pigment-protein complexes by soft X-ray probe optical pump double resonance spectroscopy (XODR).},
  language  = {en}
}
@misc{LoehmannsroebenBeckHildebrandtetal.2006,
  author    = {L{\"o}hmannsr{\"o}ben, Hans-Gerd and Beck, Michael and Hildebrandt, Niko and Schm{\"a}lzlin, Elmar and van Dongen, Joost T.},
  title     = {New challenges in biophotonics : laser-based fluoroimmuno analysis and in-vivo optical oxygen monitoring},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10120},
  year      = {2006},
  abstract  = {Two examples of our biophotonic research utilizing nanoparticles are presented, namely laser-based fluoroimmuno analysis and in-vivo optical oxygen monitoring. Results of the work include significantly enhanced sensitivity of a homogeneous fluorescence immunoassay and markedly improved spatial resolution of oxygen gradients in root nodules of a legume species.},
  subject      = {Sauerstoff},
  language  = {en}
}
@misc{NiederkruegerSalbBecketal.2006,
  author    = {Niederkr{\"u}ger, Matthias and Salb, Christian and Beck, Michael and Hildebrandt, Niko and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Marowsky, Gerd},
  title     = {Improvement of a fluorescence immunoassay with a compact diode-pumped solid state laser at 315 nm},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10150},
  year      = {2006},
  abstract  = {We demonstrate the improvement of fluorescence immunoassay (FIA) diagnostics in deploying a newly developed compact diode-pumped solid state (DPSS) laser with emission at 315 nm. The laser is based on the quasi-three-level transition in Nd:YAG at 946 nm. The pulsed operation is either realized by an active Q-switch using an electro-optical device or by introduction of a Cr<SUP>4+</SUP>:YAG saturable absorber as passive Q-switch element. By extra-cavity second harmonic generation in different nonlinear crystal media we obtained blue light at 473 nm. Subsequent mixing of the fundamental and the second harmonic in a β-barium-borate crystal provided pulsed emission at 315 nm with up to 20 μJ maximum pulse energy and 17 ns pulse duration. Substitution of a nitrogen laser in a FIA diagnostics system by the DPSS laser succeeded in considerable improvement of the detection limit. Despite significantly lower pulse energies (7 μJ DPSS laser versus 150 μJ nitrogen laser), in preliminary investigations the limit of detection was reduced by a factor of three for a typical FIA.},
  subject      = {Immunoassay},
  language  = {en}
}
@article{SellrieBeckHildebrandtetal.2010,
  author    = {Sellrie, Frank and Beck, Michael and Hildebrandt, Niko and Micheel, Burkhard},
  title     = {A homogeneous time-resolved fluoroimmunoassay (TR-FIA) using antibody mediated luminescence quenching},
  issn      = {1759-9660},
  doi       = {10.1039/C0ay00306a},
  year      = {2010},
  abstract  = {The determination of low-molecular weight substances (haptens) is demonstrated with a homogeneous time-resolved immunoassay using antibody-induced luminescence quenching. Our novel assay technology uses the newly developed monoclonal antibody (G24-BA9) to quench the luminescence of europium trisbipyridine (EuTBP). We performed a competitive biotin immunoassay including an EuTBP-biotin conjugate, the anti-EuTBP antibody G24-BA9 and streptavidin as assay components. Steric hindrance allows only the binding of either G24-BA9 (to the EuTBP moiety) or streptavidin (to the biotin moiety) to the EuTBP-biotin conjugate. Addition of the analyte biotin resulted in the binding of streptavidin to biotin and a concomitant preferred binding of G24-BA9 to EuTBP-biotin. Since G24-BA9 quenches the luminescence of EuTBP within the conjugate, the luminescence signal could be used to indicate and quantify the presence of free biotin in the system. All experiments were carried out in solution in the presence of 5\% serum demonstrating the possibility of using our novel assay for a very fast determination of low molecular weight substances in biological fluids.},
  language  = {en}
}