Einzelmolekül-Spektroskopie zur Krebsdiagnostik: Kurze, farbstoffmarkierte Peptid-Epitope sind durch einen effizienten Elektronentransfer zwischen Tryptophan und Fluorophor (1, siehe Bild) stark in ihrer Fluoreszenz gelöscht. Die spezifische Erkennung der Peptid-Epitope durch den Antikörper induziert eine Konformationsänderung, die die Fluoreszenzlöschung aufhebt. Der fluoreszierende Antikörper-Peptid-Komplex kann durch konfokale Fluoreszenzmikroskopie auf Einzelmolekülniveau in verdünnten Blutserumproben detektiert werden.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text A. Schulz, V. Buschmann, T. Hübner, H. Neuweiler, M. Sauer, and J. Wolfrum, "Detection of target molecules on the single molecule level using confocal fluorescence microscopy in combination with microelectrophoresis," in Laser Applications to Chemical and Environmental Analysis, T. Li, ed., Vol. 36 of OSA Trends in Optics and Photonics Series (Optica Publishing Group, 2000), paper FB3. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Intermolecular static and dynamic fluorescence quenching constants of eight coumarin derivatives by nucleobase derivatives have been determined in aqueous media. One common sequence of the quenching efficiency has been found for the nucleobases. The feasibility of a photoinduced electron transfer reaction for the nucleobase-specific quenching of fluorescent dyes is investigated by the calculation of the standard free energy changes with the Rehm-Weller equation. A complete set of one-electron redox potential data for the nucleobases are determined electrochemically in aprotic solvents for the first time, which are compared with values obtained by various other methods. Depending on the redox properties of the fluorescent dyes, the sequences of the quenching efficiencies can be rationalized by the orders of electrochemical oxidation potentials (vs NHE) of nucleosides (dG (+1.47 V) < dA ( dC approximate to dT < U (greater than or equal to +2.39 V)) and reduction potentials (de (( -2.76 V) < dA < dC approximate to dT < U (-2.07 V)). The correlation between the intermolecular dynamic quenching constants and the standard free energy of photoinduced electron transfer according to the classical Marcus equation indicates that photoinduced electron transfer is the rate-limiting step. However, an additional, water-specific gain of free energy between -0.5 and -0.9 eV shows that additional effects, like a coupled proton transfer and a hydrophobic effect, have to be considered, too. Furthermore, the capability of the nucleobases to form ground state complexes with fluorescent dyes is influenced by their redox potentials. The relevance of these observations to current efforts for DNA sequencing with a detection by laser-induced fluorescence and their application to other dyes are discussed.