Ultrasensitive Spectroscopy

Starting more than ten years ago, we have developed and applied a sophisticated method to measure selectively fluorescence generated by molecules close to surfaces which is known as “Supercritical Angle Fluorescence”(SAF)-Spectroscopy. Using this method, it s possible to detect fluorescence from a surface, even if there are high concentrated solutions of fluorescent molecules present above this surface. We could further develop this technique in two directions in the past reporting period:

a)   We developed a simple, low-cost device for sensitive detection of molecules – in particular during an affinity binding reaction. This device integrates the parabolic element in a disposable, i.e. a simple injection molded device.

b)  We were able to expand the SAF system further to a two channel device. With this device we are able to detect fluorescence out of two different detection volumes simultaneously. Although the SAF detection volume is quite small, even down to the attoliter range, the second one (a confocal detection volume) with an average volume in the order of a few femtoliter. This allows imaging of structures with an optical resolution down to 1 nm.

Deep-UV-Fluorescence Detection

In 2004 we published a paper presenting for the first time single molecule detection in the deep uv region of the electromagnetic spectrum. Using this instrument we were able to demonstrate to detect proteins in different environments, e.g. electrophoresis gels, with high sensitivity but without any tags. Presently, we are developing this technique further, in particular to identify structural changes and binding events between proteins without labels by detecting the fluorescence decay time and FRET signals.