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Protein crystallization is a delicate process that is always sensitive to environmental factors. When the environmental factors are not well controlled or not controlled at all, identical crystallization droplets from the same mother liquid may yield different crystallization results. One environmental factor, the weather conditions during crystallization solution preparation, is not usually considered as a parameter for protein crystallization. In this paper, it is shown that the weather parameters during preparation of the crystallization experiment, including the ambient temperature, humidity, pressure and particulate matter in the air, can all affect the reproducibility of lysozyme crystallization. An identical lysozyme crystallization experiment was repeated for an entire year, and the weather conditions when each crystallization experiment was set up were recorded along with the crystallization results. Among the parameters recorded, the humidity during the experiment setup showed the strongest effect on lysozyme crystallization. On the basis of these results, it is suggested that the weather conditions during crystallization solution preparation should be considered as a potential factor that can influence protein crystallization. [ABSTRACT FROM AUTHOR]

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 R merge. 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. [ABSTRACT FROM AUTHOR]

The pH of a solution is an important parameter in crystallization that needs to be controlled in order to ensure success. The actual pH of the crystallization droplet is determined by the combined contribution of the buffers in the screening and protein solutions, although the contribution of the latter to the pH is often ignored. In this study, the effects of the buffer and protein solution pH values on the results of screening are systematically investigated. It was found that these parameters significantly affected the results and thus the following strategy for the selection of appropriate pH values is proposed: (i) when screening with only one protein solution, the pH should be as low, as high or as divergent from the pI as possible for a basic, acidic or neutral protein, respectively, within its stable pH range; (ii) when screening with two protein solutions, the pH values should be well separated from one another; and (iii) when multiple pH values are utilized, an even distribution of pH values is the best approach to increase the success rate of crystallization. [ABSTRACT FROM AUTHOR]

In vapor diffusion protein crystallization screening, it has been reported that replacing the reservoir solution with desiccant can increase the crystallization success rate. Therefore, the desiccation method is a potentially powerful method in practical protein crystallization screening. However, this method is difficult to apply broadly because the optimal amount of desiccant for a specific screening task is unknown. Utilizing an unsuitable amount of desiccant can result in even worse screening results than would be obtained from the traditional vapor diffusion method. Here, it is shown that by employing a modified strategy, named the gradual desiccation method, the problem can be solved without knowing the optimal amount of desiccant, and the crystallization success rate can be further increased compared with the one-time desiccation method. [ABSTRACT FROM AUTHOR]

It is well known that the crystallization of proteins is strongly dependent on the crystallization conditions, which are sometimes very sensitive to environmental disturbances. Parameters such as the concentration of precipitants or protein, pH, temperature and many others are known to affect the probability of crystallization, and the task of crystallizing a new protein often involves a trial-and-error test using numerous combinations of crystallization conditions. These crystallization parameters, such as the concentration of either the protein or the precipitant, are important because they directly affect the driving force of crystallization: the supersaturation of the solution. Although it is common sense that the concentration can affect the crystallization process, the sensitivity of the crystallization process to variations in the concentration has seldom been addressed. Owing to the difficulty of directly preparing solutions with very small concentration variations, it is hard to carry out an investigation of their effect on the crystallization process. In this paper, a simple but novel method for studying the effect of minute concentration variations on the success rate of protein crystallization is presented. By evaporating the crystallization droplet, a fine concentration gradient could be created. With this fine-tuned concentration gradient, it was possible to observe the effects of minute variations in the concentration or supersaturation on the crystallization. A very minor change in concentration (as low as 0.13% of the initial concentration, i.e. 0.026 mg ml−1 for lysozyme and 0.052 mg ml−1 for NaCl in the current study) or a very minor change in supersaturation (as small as 0.018) could cause a clear difference in the crystallization success rate, indicating that the crystallization of proteins is very sensitive to the concentration level. Such sensitive behaviour may be one reason for the poor reproducibility of protein crystallization. [ABSTRACT FROM AUTHOR]

• DESs can act as effective additives to improve the quality of protein crystals. • The presence of DESs does not change the structure of proteins. • DESs primarily affected crystallization via hydrogen bonding and hydrophobic interactions with proteins. Protein crystallization is an essentially important process for its valuable applications in molecular structure determination of proteins, the study of biomolecular interaction mechanism, research and development of special functional crystal materials, theoretical study of crystallization mechanism, industrial production of proteins, and so on. Improving the quality of protein crystals is desirable research because it can provide high-quality samples or products for these studies and applications. Here we report that the utilization of DESs as additives in protein crystallization can significantly affect the crystallization process and effectively improve the crystal quality. We synthesized 9 types of DESs, studied their physicochemical properties, and selected 3 DESs suitable as additives for protein crystallization. Using three model proteins (lysozyme, thaumatin, and proteinase K), we confirmed that DESs can significantly affect the protein crystallization process. Crystals obtained at appropriate concentrations of DESs have higher quality, higher diffraction resolution, and better diffraction data collection. A comparison of the 3D structure of protein molecules showed that the addition of DESs did not affect the molecular structure of the proteins. These results proved that the presence of DESs during protein crystallization can help to improve crystal quality without affecting the structure of proteins, showing that DESs can be employed as a novel class of additives for protein crystallization. [ABSTRACT FROM AUTHOR]

Protein crystallization is sensitive to the environment, while audible sound, as a physical and environmental factor during the entire process, is always ignored. We have previously reported that protein crystallization can be affected by a computer-generated monotonous sound with fixed frequency and amplitude. However, real-world sounds are not so simple but are complicated by parameters (frequency, amplitude, timbre, etc.) that vary over time. In this work, from three sound categories (music, speech, and environmental sound), we selected 26 different sounds and evaluated their effects on protein crystallization. The correlation between the sound parameters and the crystallization success rate was studied mathematically. The results showed that the real-world sounds, similar to the artificial monotonous sounds, could not only affect protein crystallization, but also improve crystal quality. Crystallization was dependent not only on the frequency, amplitude, volume, irradiation time, and overall energy of the sounds but also on their spectral characteristics. Based on these results, we suggest that intentionally applying environmental sound may be a simple and useful tool to promote protein crystallization. [ABSTRACT FROM AUTHOR]

We have proposed a rational strategy for selecting a suitable pH of protein solution based on protein biochemical properties. However, it is difficult to use this strategy for biochemical properties unknown proteins. In this paper, a simpler and faster pH buffer strategy was proposed. An additional pH-controlling buffer was added to crystallization droplet mixed with protein solution and commercial crystallization reagents to adjust its pH. The results revealed that protein crystallization success rates were enhanced by this strategy due to expansion of the pH screening space, which was closely related with protein solubility. Thus, the possibility of reaching supersaturation was increased by using this strategy. [ABSTRACT FROM AUTHOR]