A guide to sample delivery systems for serial crystallography.

Crystallography has made a notable contribution to our knowledge of structural biology. For traditional crystallography experiments, the growth of crystals with large size and high quality is crucial, and it remains one of the bottlenecks. In recent years, the successful application of serial femtosecond crystallography (SFX) provides a new choice when only numerous microcrystals can be obtained. The intense pulsed radiation of X-ray free-electron lasers (XFELs) enables the data collection of small-sized crystals, making the size of crystals no longer a limiting factor. The ultrafast pulses of XFELs can achieve 'diffraction before destruction', which effectively avoids radiation damage and realizes diffraction near physiological temperatures. More recently, the SFX has been expanded to serial crystallography (SX) that can additionally employ synchrotron radiation as the light source. In addition to the traditional ones, these techniques provide complementary opportunities for structural determination. The development of SX experiments strongly relies on the advancement of hardware including the sample delivery system, the X-ray source, and the X-ray detector. Here, in this review, we categorize the existing sample delivery systems, summarize their progress, and propose their future prospectives.

A periodic magnetic field as a special environment for scientific research created by rotating permanent magnet pairs.

A magnetic field is an often-encountered physical environment that can affect many processes, including chemical, physical, and biochemical processes. Utilization of magnetic fields is thus very helpful in a wide variety of applications, such as scientific research in various disciplines, materials processing (e.g., crystal growth and separation) in industry, and nuclear fusion. There are many different types of magnetic fields generated by different magnets, such as superconducting magnets, electromagnets, hybrid magnets, pulsed magnets, and permanent magnets. In this paper, we introduce a newly designed periodic magnetic field generated by rotating permanent magnet pairs. Preliminary tests showed that the periodic magnetic field is valuable in water evaporation, silver deposition, and protein crystallization. Apparently, in such a new environment that can generate a periodic magnetic field, a periodic force field will also be simultaneously generated on the sample. Further work shall be carried out to explore the potential applications of this magnetic field.

Myocyte enhancer factor 2C and its directly-interacting proteins: A review.

Myocyte enhancer factor 2C (MEF2C) is a transcription factor of MADS box family involved in the early development of several human cells including muscle (i.e., skeletal, cardiac, and smooth), neural, chondroid, immune, and endothelial cells. Dysfunction of MEF2C leads to embryo hypoplasia, disorganized myofibers and perinatal lethality. The main role of MEF2C is its regulation of muscle development. It has been reported that MEF2C-knockout mice die on embryonic day 9.5 from unnatural development of cardiovascular. The effects of MEF2C are mediated by its directly-interacting proteins; therefore, the investigation of these interactions is critical in order to clarify MEF2C's biological function. In this study, we review twenty-five proteins that directly interact with MEF2C, including nineteen proteins related to muscle development, four proteins related to neural cell development, one protein related to chondroid cell development, four proteins related to immune cell development, and two proteins related to endothelial cell development. Among these proteins, the interaction of MEF2C with MRFs is important for differentiation of developing muscle cells. MEF2C interacts with Sox18 for endothelial vessel morphogenesis. The interaction of MEF2C with Cabin1 is important for maintaining T-cell inactivation. Investigating the interactions of MEF2C and its directly-interacting proteins is not only helpful to understand of the physiological function of MEF2C, but also provides a target for future rational drug design.

An Overview of Hardware for Protein Crystallization in a Magnetic Field.

Protein crystallization under a magnetic field is an interesting research topic because a magnetic field may provide a special environment to acquire improved quality protein crystals. Because high-quality protein crystals are very useful in high-resolution structure determination using diffraction techniques (X-ray, neutron, and electron diffraction), research using magnetic fields in protein crystallization has attracted substantial interest; some studies have been performed in the past two decades. In this research field, the hardware is especially essential for successful studies because the environment is special and the design and utilization of the research apparatus in such an environment requires special considerations related to the magnetic field. This paper reviews the hardware for protein crystallization (including the magnet systems and the apparatus designed for use in a magnetic field) and progress in this area. Future prospects in this field will also be discussed.

Preparation of cross-linked hen-egg white lysozyme crystals free of cracks.

Cross-linked protein crystals (CLPCs) are very useful materials in applications such as biosensors, catalysis, and X-ray crystallography. Hence, preparation of CLPCs is an important research direction. During the preparation of CLPCs, an often encountered problem is that cracks may appear in the crystals, which may finally lead to shattering of the crystals into small pieces and cause problem in practical applications. To avoid cross-link induced cracking, it is necessary to study the cracking phenomenon in the preparation process. In this paper, we present an investigation on how to avoid cracking during preparation of CLPCs. An orthogonal experiment was designed to study the phenomenon of cross-link induced cracking of hen-egg white lysozyme (HEWL) crystals against five parameters (temperature, solution pH, crystal growth time, glutaraldehyde concentration, and cross-linking time). The experimental results showed that, the solution pH and crystal growth time can significantly affect cross-link induced cracking. The possible mechanism was studied, and optimized conditions for obtaining crack-free CLPCs were obtained and experimentally verified.