A CCD system for UV imaging of biomolecules

An imaging system based on a cooled scientific grade charge coupled device (CCD) is under development for the imaging of biomolecules such as amino acids and proteins. The CCD has been incorporated, along with a deuterium lamp, into a vertical electrophoresis unit to allow UV imaging of separated biomolecules. The UV absorption of the various electrophoretic materials has been measured over a range of wavelengths, indicating that the optimum imaging wavelength lies between 260 and 280 nm. At these wavelengths, the CCD displays a quantum efficiency (QE) of around 12%. Measurements of system noise indicate that this QE figure is sufficiently high to allow signal changes of a few hundred photons to be measured, allowing very small amounts of the biomolecular material to be identified. The spatial resolution of the system, at around 30 μm, is an order of magnitude higher than the current imaging systems. We show how this will dramatically reduce the time required for accurate analysis of biomolecular fragments.