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A new physical scheme is presented for the detection of copper, based on the use of a fluorescently labeled dendrimer anchored on a gold nanowire. Upon light illumination surface plasmon resonance was generated from the gold nanowire, which promoted quenching of the dendrimer fluorescence as a result of the energy transfer between the dendrimer and the copper ions. The monotonic dependence of the fluorescence quenching on copper concentration was exploited to reach a copper detection sensitivity of 2 nM. In addition, the fluorescence of the labeled dendrimers was quenched specifically by copper in a matrix of common metal ions. Using simulations we calculated the enhanced optical near field for a dendrimer-coated gold nanowire illuminated by a TM-polarized plane wave, which provided a physical basis for the sensitive copper detection using the current experimental scheme. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes (SWNTs) and lysophospholipids readily assemble into supramolecular complexes in aqueous solutions. Upon light excitation the fluorescence of rhodamine-labeled lysophospholipids was redshifted and quenched due to the optical absorption of the SWNTs. Utilizing fluorescence energy transfer, the authors detected the translocation and disassembly of SWNT complexes in MCF breast cancer cells. These lipid-coated SWNT complexes enable drugs to be delivered at an effective dose and their subsequent release to be monitored in real time. [ABSTRACT FROM AUTHOR]

The conformational changes of a 22 base-pair double-stranded DNA, anchored via one end to a quartz substrate, have been characterized using a single-pair fluorescence resonance energy transfer technique. Base-pair mismatch, a major form of DNA damage, has been found to decrease the energy transfer between a fluorescence donor and an acceptor attached to the two ends of DNA molecules with 3 and 7 mismatches, by 4.4% and 10.4%, respectively, as compared to that for perfectly matched DNA. This result suggests that the disruption of the hydrogen bonds in damaged DNA leads to increased contour length and improved flexibility. [ABSTRACT FROM AUTHOR]

While present studies on the integration of single-walled carbon nanotubes (SWNTs) with biomolecules have centered primarily on deoxyribonucleic acid and proteins, this report is focused on the binding of SWNTs with ribonucleic acid polymer poly(rU). We present fluorescence and spectroscopic evidences for the binding of poly(rU) molecules along the contour of isolated SWNTs which suggests that the π-stacking may dominate the hydrophobic interaction between the poly(rU) bases and the π-electrons of the SWNTs. [ABSTRACT FROM AUTHOR]

Reports that the degree of polarization of the scattered evanescent wave is measured with a laser-trapped particle for different incident angles. Improvement in the contrast of the evanescent wave interference pattern imaged in a particle-trapped near-field scanning optical microscope.