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.
Nanoscale Organization of the Pathogen Receptor DC-SIGN Mapped by Single-Molecule High-Resolution Fluorescence Microscopy(full pdf)
Bärbel I. de Bakker, Frank de Lange, Alessandra Cambi, Jeroen P. Korterik, Erik M. H. P. van Dijk, Niek F. van Hulst, Carl G. Figdor, and Maria F. Garcia-Parajo
vol 8 issue 10 p1473-1480 July 16, 2007
DC-SIGN, a C-type lectin exclusively expressed on dendritic cells (DCs), plays an important role in pathogen recognition by binding with high affinity to a large variety of microorganisms. Recent experimental evidence points to a direct relation between the function of DC-SIGN as a viral receptor and its spatial arrangement on the plasma membrane. We have investigated the nanoscale organization off luorescently labeled DC-SIGN on intact isolated DCs by means of near-field scanning optical microscopy (NSOM) combined with single-molecule detection. Fluorescence spots of different intensity and size have been directly visualized by optical means with a spatial resolution ofless than 100 nm. Intensity- and size-distribution histograms ofthe DCSIGN fluorescent spots confirm that approximately 80% of the receptors are organized in nanosized domains randomly distributed on the cell membrane. Intensity-size correlation analysis revealed remarkable heterogeneity in the molecular packing density ofthe domains. Furthermore, we have mapped the intermolecular organization within a dense cluster by means of sequential NSOM imaging combined with discrete single-molecule photobleaching. In this way we have determined the spatial coordinates of 13 different individual dyes, with a localization accuracy of 6 nm. Our experimental observations are all consistent with an arrangement of DC-SIGN designed to maximize its chances ofbinding to a wide range of microorganisms. Our data also illustrate the potential of NSOM as an ultrasensitive, high-resolution technique to probe nanometer-scale organization of molecules on the cell membrane.