DISCO, a novel low-energy beamline covering the spectrum range from the VUV to the visible, has received its first photons at the French synchrotron SOLEIL. In this article the DISCO design and concept of three experimental stations serving research communities in biology and chemistry are described. Emphasis has been put on high flux generation and preservation of polarization at variable energy resolutions. The three experiments include a completely new approach for microscopy and atmospheric pressure experiments as well as a ;classical' synchrotron radiation circular dichroism station. Preliminary tests of the optical design and technical concept have been made. Theoretical predictions of the beam have been compared with the first images produced by the first photons originating from the large-aperture bending-magnet source. Results are also reported concerning the cold finger used to absorb hard X-ray radiation in the central part of the synchrotron beam and to avoid heavy thermal load on the following optics. Wavelength selection using monochromators with different gratings for each experimental set-up as well as beam propagation and conditioning throughout the optical system are detailed. First photons comply very well with the theoretical calculations.

Use of deep ultraviolet (DUV, below 350 nm) fluorescence opens up new possibilities in biology because it does not need external specific probes or labeling but instead allows use of the intrinsic fluorescence that exists for many biomolecules when excited in this wavelength range. Indeed, observation of label free biomolecules or active drugs ensures that the label will not modify the biolocalization or any of its properties. In the past, it has not been easy to accomplish DUV fluorescence imaging due to limited sources and to microscope optics. Two worlds were coexisting: the spectrofluorometric measurements with full spectrum information with DUV excitation, which lacked high-resolution localization, and the microscopic world with very good spatial resolution but poor spectral resolution for which the wavelength range was limited to 350 nm. To combine the advantages of both worlds, we have developed a DUV fluorescence microscope for cell biology coupled to a synchrotron beamline, providing fine tunable excitation from 180 to 600 nm and full spectrum acquired on each point of the image, to study DUV excited fluorescence emitted from nanovolumes directly inside live cells or tissue biopsies.