Protein molecular deformation and protein crystal damage induced by shock waves traveling in liquid microjets

Femtosecond crystallography studies done at X-ray laser facilities are an emerging method that provides new insights into the biological function of complex proteins. Second-generation X-ray lasers enable acquisition rates exceeding a million diffraction images per second, and to supply fresh protein crystals at these rates, they must be carried by high-velocity liquid microjets. These microjets also guide the shock waves generated by previous X-ray pulses. The effect of shocks generated by previous X-ray pulses on lysozyme and carboxyhemoglobin crystals was investigated experimentally. The molecular structure of the lysozyme did not change after shocks with amplitudes up to 140 MPa, but the quality of diffraction data decreased for shocks above 30−45 MPa, indicating crystal damage. In contrast, the molecular structure of carboxyhemoglobin changed after shocks ranging from 35 to 70 MPa. These results suggest the shocks induced brittle failure in lysozyme but plastic deformation in carboxyhemoglobin, and were used to estimate under what conditions X-ray laser crystallography data is likely to be affected by such shocks.