title: Improvements in serial femtosecond crystallography of photosystem II by optimizing crystal uniformity using microseeding procedures.
abstract: In photosynthesis, photosystem II (PSII) is the multi-subunit membrane protein complex that catalyzes photo-oxidation of water into dioxygen through the oxygen evolving complex (OEC). To understand the water oxidation reaction, it is important to get structural information about the transient and intermediate states of the OEC in the dimeric PSII core complex (dPSIIcc). In recent times, femtosecond X-ray pulses from the free electron laser (XFEL) are being used to obtain X-ray diffraction (XRD) data of dPSIIcc microcrystals at room temperature that are free of radiation damage. In our experiments at the XFEL, we used an electrospun liquid microjet setup that requires microcrystals less than 40μm in size. In this study, we explored various microseeding techniques to get a high yield of monodisperse uniform-sized microcrystals. Monodisperse microcrystals of dPSIIcc of uniform size were a key to improve the stability of the jet and the quality of XRD data obtained at the XFEL. This was evident by an improvement of the quality of the datasets obtained, from 6.5Å, using crystals grown without the micro seeding approach, to 4.5Å using crystals generated with the new method.
authors.affiliation: Institut für Biologie, Humboldt-Universität zu Berlin, D-10099 Berlin, Germany ; Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universitüt, D-10623 Berlin, Germany.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Ibrahim
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Ruchira
authors.initials: R
authors.lastname: Chatterjee
authors.affiliation: Institut für Biologie, Humboldt-Universität zu Berlin, D-10099 Berlin, Germany ; Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universitüt, D-10623 Berlin, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Hellmich
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Rosalie
authors.initials: R
authors.lastname: Tran
authors.affiliation: Institut für Biologie, Humboldt-Universität zu Berlin, D-10099 Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bommer
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Vittal K
authors.initials: VK
authors.lastname: Yachandra
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Junko
authors.initials: J
authors.lastname: Yano
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA ; LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: Jan
authors.initials: J
authors.lastname: Kern
authors.affiliation: Institut für Biologie, Humboldt-Universität zu Berlin, D-10099 Berlin, Germany ; Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universitüt, D-10623 Berlin, Germany.
authors.forename: Athina
authors.initials: A
authors.lastname: Zouni