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The practice of serial X-ray crystallography (SX) depends on efficient, continuous delivery of hydrated protein crystals while minimizing background scattering. Of the two major types of sample delivery devices, fixed-target devices offer several advantages over widely adopted jet injectors, including: lower sample consumption, clog-free delivery, and the ability to control on-chip crystal density to improve hit rates. Here we present our development of versatile, inexpensive, and robust polymer microfluidic chips for routine and reliable room temperature serial measurements at both synchrotrons and X-ray free electron lasers (XFELs). Our design includes highly X-ray-transparent enclosing thin film layers tuned to minimize scatter background, adaptable sample flow layers tuned to match crystal size, and a large sample area compatible with both raster scanning and rotation based serial data collection. The optically transparent chips can be used both for in situ protein crystallization (to eliminate crystal handling) or crystal slurry loading, with prepared samples stable for weeks in a humidified environment and for several hours in ambient conditions. Serial oscillation crystallography, using a multi-crystal rotational data collection approach, at a microfocus synchrotron beamline (SSRL, beamline 12-1) was used to benchmark the performance of the chips. High-resolution structures (1.3-2.7 A) were collected from five different proteins - hen egg white lysozyme, thaumatin, bovine liver catalase, concanavalin-A (type VI), and SARS-CoV-2 nonstructural protein NSP5. Overall, our modular fabrication approach enables precise control over the cross-section of materials in the X-ray beam path and facilitates chip adaption to different sample and beamline requirements for user-friendly, straightforward diffraction measurements at room temperature.

International audience; Controlled dehydration of macromolecular crystals can lead to significant improvements in crystalline order, which often manifests itself in higher diffraction quality. Devices that can accurately control the humidity surrounding crystals on a beamline have led to this technique being increasingly adopted as experiments become easier and more reproducible. However, these experiments are often carried out by trial and error, and in order to facilitate and streamline them four European synchrotrons have established a collaboration around the HC1b dehydration device. The MAX IV Laboratory, Diamond Light Source, BESSY II, and the EMBL Grenoble Outstation/ESRF have pooled information gathered from user experiments, and on the use of the device, to propose a set of guidelines for these experiments. Here, we present the status and automation of the installations, advice on how best to perform experiments using the device, and an analysis of successful experiments that begins to show some trends in the type of protocols required by some systems. The dehydration methods shown are applicable to any device that allows control of the relative humidity of the air surrounding a macromolecular crystal

The title compound, C13H20O3, crystallizes as a racemic mixture in which the two enantiomeric forms of the mol­ecule are related by an inversion center. The crystal structure confirms the one proposed on the basis of spectroscopic data and provides the information required to assign the relative stereochemistry of the chiral centers of the mol­ecule. The crystal packing is directed by intermolecular hydrogen bonds and short intramolecular C—H⋯O contacts.

The crystal structure of the adduct, C21H21NO2, of tetra­methyl­purpurogallin with nitro­so­benzene is reported. The compound exhibits a [3.2.2] bicyclic system corresponding to two seven-membered rings and one six-membered ring in distorted chair, boat and twist–boat conformations, respectively. One intramolecular and two intermolecular hydrogen bonds direct the packing and stabilize the mol­ecule.

Protein crystallography data collection at synchrotrons today is routinely carried out at cryogenic temperatures to mitigate radiation damage to the crystal. Although damage still takes place, at 100 K and below, the immobilization of free radicals increases the lifetime of the crystals by orders of magnitude. Increasingly, experiments are carried out at room temperature. The lack of adequate cryo-protectants, the induced lattice changes or internal disorders during the cooling process, and the convenience of collecting data directly from the crystallization plates, are some of the reasons. Moreover, recent studies have shown that flash-freezing affects the conformational ensemble of crystal structures [1], and can hide important functional mechanisms from observation [2]. While there has been a considerable amount of effort in studying radiation damage at cryo-temperatures, its effects at room temperature are still not well understood. We investigated the effects of data collection temperature on secondary local damage to the side chain and main chain from different proteins. Data were collected from crystals of thaumatin and lysozyme at 100 K and room temperature. To carefully control the total absorbed dose, full data sets at room temperature were assembled from a few diffraction images per crystal. Several data sets were collected at increasing levels of absorbed dose. Our analysis shows that while at cryogenic temperatures, radiation damage increases the conformational variability, _x0004_at room temperature it has the opposite effect_x0005_. We also observed that disulfide bonds appear to break up at a different relative rate at room temperature, perhaps because of a more active repair mechanism. Our analysis suggests that elevated conformational heterogeneity in crystal structures at room temperature is observed despite radiation damage, and not as a result thereof.