Fast Detection Allows Analysis of the Electronic Structure of Metalloprotein by X-ray Emission Spectroscopy at Room Temperature

The paradigm of “detection-before-destruction” was tested for a metalloprotein complex exposed at room temperature to the high X-ray flux typical of third-generation synchrotron sources. Following the progression of the X-ray-induced damage by Mn Kβ X-ray emission spectroscopy, we demonstrated the feasibility of collecting room-temperature data on the electronic structure of native Photosystem II, a trans-membrane metalloprotein complex containing a Mn4Ca cluster. The determined nondamaging observation time frame (about 100 ms using a continuous monochromatic beam, with a deposited dose of 1 × 107 photons/μm2 or 1.3 × 104 Gy, and about 66 μs in pulsed mode using a pink beam, with a deposited dose of 4 × 107 photons/μm2 or 4.2 × 104 Gy) is sufficient for the analysis of this protein’s electron dynamics and catalytic mechanism at room-temperature. Reported time frames are expected to be representative for other metalloproteins. The described instrumentation, based on the short working distance dispersive sp...