Optical Sciences

Biomolecules and nanostructures

The Optical Sciences group studies the interaction of light and matter. Our current focus is on detection and sensing/imaging with an emphasis on the development of integrated photonics. We are part of Twente University's Department of Science and Technology and member of the MESA+ institute.


Analysis of individual (macro)molecules and proteins using near-field optics

(full pdf)

van Hulst NF, Veerman JA, Garcia-Parajo MF, Kuipers L
vol 112 issue 18: p7799-p7810 MAY 8 2000

Recent achievements in single molecule detection using near- field optical excitation are presented. By proper control of technology, distinct advantages of near-field optics are exploited: (i) the nanometric excitation/emission volume (10(4)-10(5) nm(3)), which provides high spatial resolution, localization of a single molecule within a few nm, and reduced background; (ii) the sensitivity for single molecule orientation in all three dimensions; (iii) the high local brightness, allowing real-time single molecule detection down to mu s resolution; (iv) the simultaneous colocalization with nanometric surface topography. Real-time quantum jumps between singlet and triplet state of an individual molecule are observed. Distributions for triplet state lifetime and crossing yield are determined. Both triplet state lifetime and crossing yield of a single molecule appear to vary in time, due to the local heterogeneity. Individual dendritic molecules containing a single fluorescent core are investigated. The dendritic assemblies are discriminated from free fluorescent cores o­n the basis of accurate simultaneous localization of both the fluorescent core and the topography of the surrounding dendritic shell. Intramolecular rotational motion of the fluorescent core is observed. Individual green fluorescent proteins are visualized, both in fluorescence and topography. Photoinduced conformational changes to a nonemissive form of the protein are observed, leading to long dark intervals of several seconds. (C) 2000 American Institute of Physics. [S0021-9606(00)70216-9].
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