The in crystallo optical spectroscopy laboratory icOS
Contact: Antoine Royant
The icOS Lab (formerly known as the Cryobench) is a facility dedicated to performing various complementary optical spectroscopic analyses on protein crystals under conditions (mini-diffractometer with an on-axis camera, sample changer, 100 K or room temperature) similar to those used during diffraction data collection on the Structural Biology Group beamlines of the ESRF. Available spectroscopic setups include UV-visible absorption, emission fluorescence and Raman. Lasers can also be used as actinic light sources to induce photochemical changes within samples. Samples are usually crystals, but nanolitre volumes of solution can be used. The icOS Lab is often used as an ‘offline’ facility (i.e. experiments are not performed at the same time as the corresponding X-ray diffraction experiments). However, an ‘online’ mode of operation allows the interleaved measurement of diffraction and spectroscopic data using either a UV/visible microspectrophotometer (‘online microspec’) or a Raman setup (‘online Raman’). As such, the icOS Lab provides complementary information that can be crucial to the correct interpretation of crystal structures. Applications include identifying the physiological state of the protein (e.g. the oxidation state of metal centres), monitoring the extent of radiation damage, and characterizing reaction intermediates in kinetic crystallography experiments.
1. Online Raman spectroscopy for structural biology on beamline ID29 of the ESRF. von Stetten D, Giraud, T, Bui S, Steiner RA, Fihman F, de Sanctis D, Royant A. (2017) J. Struct. Biol. 200, 124-127
2. In crystallo optical spectroscopy (icOS) as a complementary tool on the macromolecular crystallography beamlines of the ESRF. von Stetten D, Giraud T, Carpentier P, Sever F, Terrien M, Dobias F, Juers D H, Flot D, Mueller-Dieckmann C, Leonard G A, de Sanctis D, Royant A (2015) Acta Crystallogr. D71, 15-26