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.


Genetic applications of single molecular detection

  • María García-Parajó - Former member

  • Combined near-field fluorescence and shear force microscopy is applied to image and study genetic material with single molecular cytochemical sensitivity. The combination brings together several advantages: (I) resolution beyond the diffraction limit, while retaining the advantages of multi-colour detection and single molecule sensitivity; (II) complemented with molecular resolution topographical imaging, using shear force feedback, for unambiguous localisation of fluorophores. Thus mapping and co-localisation studies of genetic material are performed at an individual molecular level. The location of maximum fluorescence of the molecule is determined with an accuracy of ~ 1 nm. The in-plane orientation of the molecular dipole is readily determined for all molecules in a single image using polarisation excitation/detection. With the same probe shear force phase feedback is used for topographic imaging of DNA complexes, with 0.2 nm vertical sensitivity. Dynamic environmental effects on nucleotide photophysics will be investigated on single molecular basis.

    Shear force image (left) and near-field optical image (right) of 1000bpairs (340 nm length) DNA fragments labelled with Rhodamine 6G (R-6G). The scan size is 1.5 x 1.5 µm2. The sample consists of only one fluorophore per strand. The shear force image shows well resolved DNA strands with a resolution comparable to standard atomic force microscopy. Vertical sensitivity is 0.2nm. The near-field image shows the intensity of individual R-6G fluorophores. The FWHM of the individual spots is 70nm.


    The following articles have been published regarding this project:

    Near-field optical microscopy for DNA studies at the single molecular level

    (abstract) (full pdf)
    Garcia-Parajo MF, Veerman JA, van Noort SJT, de Grooth BG, Greve J, van Hulst NF
    vol 6 issue 1: p43-p53 MAR 1998

    Near-field optical and shear-force microscopy of single fluorophores and DNA molecules

    (abstract) (full pdf)
    Garcia-Parajo MF, Veerman JA, Ruiter AGT, van Hulst NF
    vol 71 issue 1-4: p311-p319 MAR 1998

    Near-field fluorescence imaging of genetic material: Toward the molecular limit

    vanHulst NF, GarciaParajo MF, Moers MHP, Veerman JA, Ruiter AGT
    vol 119 issue 2: p222-p231 1997
    Printable version