A quality comparison of protein crystals grown under containerless conditions generated by diamagnetic levitation, silicone oil and agarose gel

Abstract

High-quality crystals are key to obtaining accurate three-dimensional structures of proteins using X-ray diffraction techniques. However, obtaining such protein crystals is often a challenge. Several containerless crystallization techniques have been reported to have the ability to improve crystal quality, but it is unknown which is the most favourable way to grow high-quality protein crystals. In this paper, a quality comparison of protein crystals which were grown under three containerless conditions provided by diamagnetic levitation, silicone oil and agarose gel was conducted. A control experiment on a vessel wall was also simultaneously carried out. Seven different proteins were crystallized under the four conditions, and the crystal quality was assessed in terms of the resolution limit, the mosaicity and the Rmerge. It was found that the crystals grown under the three containerless conditions demonstrated better morphology than those of the control. X-ray diffraction data indicated that the quality of the crystals grown under the three containerless conditions was better than that of the control. Of the three containerless crystallization techniques, the diamagnetic levitation technique exhibited the best performance in enhancing crystal quality. This paper is to our knowledge the first report of improvement of crystal quality using a diamagnetic levitation technique. Crystals obtained from agarose gel demonstrated the second best improvement in crystal quality. The study indicated that the diamagnetic levitation technique is indeed a favourable method for growing high-quality protein crystals, and its utilization is thus potentially useful in practical efforts to obtain well diffracting protein crystals.

Applications of gradient magnetic fields in studies of biological macromolecules

“…悬浮条件下的结晶 [54,58,63,69] , 不仅有利于实现磁场下 的晶体自由定向, 而且可以消除固态界面对晶体质 量的不良影响. 此外, 采用空气-液面界面的方式 [63] , 可以避免晶体的沉降, 也有助于改善晶体质量.…”

An Overview of Hardware for Protein Crystallization in a Magnetic Field

“…In 2013, Numoto et al [37] reported the orientation of membrane protein (light-harvesting complex 2) crystals under high magnetic force fields for the first time; the R value and mosaicity of the crystals grown with this magnet were significantly improved compared with controls. In 2013, Cao and her co-workers [36] compared the quality of protein crystals grown in three container-less environments (agarose gel, silicone oil and diamagnetic levitation) and concluded that the diamagnetic levitation technique had the greatest benefits for obtaining high-quality protein crystals.…”

An Analysis on Commercial Screening Kits and Chemical Components in Biomacromolecular Crystallization Screening

“…There are 135 258 structures determined by XRD, which account for 89.4% of the total number (151 364) of the Protein Data Bank (PDB, http://www.pdb.org, data on April 26, 2019). However, obtaining biomacromolecular diffraction‐quality crystals is still a bottleneck . In practice, the bottleneck mainly comprises two aspects: difficulties in screening and optimization.…”