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19 June 2003 Development of a molecular photonic wire by means of multiparameter single-molecule spectroscopy
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We report a new approach to an unidirectional photonic wire based on fluorescent dyes as chromophores and DNA as a rigid scaffold. The physical functioning of the wire is realized by dipole-dipole intreraction, i.e. resonant energy transfer, between chromophores. The use of four dyes (Alexa 430, TAMRA, Cy3.5, and Cy5) with different excited state energies creates an energy cascade constituting the driving force of the energy current and providing the unidirectionality of the device. The unique molecular properties of DNA, its scaffold-like structure, combined with straightforward synthesis methods allowed the engineering of a 30 base pair double-stranded DNA with inter-dye distances of 10 base pairs (3.4 nm), respectively, a range where electronic interactions between the chromophores can be neglected but dipole-dipole induced fluorescence resonance energy transfer (FRET) is expected to be still highly efficient. Steady-state and time-resolved ensemble spectroscopic measurements show an overall energy transfer efficiency of approximately 0.60. That is, the unidirectional transport of photonic energy over a distance of approximately 10 nm and a spectral separation of approximately 250 nm. Furthermore, pulsed diode laser excitation at 440 nm in combination with spectrally resolved fluorescence lifetime imaging microscopy (SFLIM) was applied to characterize the effectiveness of individual photonic wires dispersed on glass coverslips.
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Mike Heilemann, Volker Buschmann, Oliver Piestert, Philip Tinnefeld, Kenneth D. Weston, and Markus Sauer "Development of a molecular photonic wire by means of multiparameter single-molecule spectroscopy", Proc. SPIE 4962, Manipulation and Analysis of Biomolecules, Cells, and Tissues, (19 June 2003);

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