Special Issue "Protein Crystallization under the Presence of an Electric Field"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Biomolecular Crystals".

Deadline for manuscript submissions: closed (18 December 2017).

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Special Issue Editor

Prof. Dr. Abel Moreno
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Guest Editor
Instituto de Química, Universidad Nacional Autónoma de México. Av. Universidad 3000, Cd.Mx. 04510, Mexico
Interests: protein crystals; biocrystals; crystal growth; protein crystallography; crystal chemistry; biomineralization; biomimetics; biological macromolecules
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Special Issue Information

Dear Colleagues,

Nowadays, the use of electrically-assisted protein crystallization methods by using direct current (DC) or alternating current (AC), has revealed that, on average, crystals grow better in crystal quality and oriented to the cathode (when the protein molecule was positively charged), compared to the crystals grown on the anode (which is a negatively charged protein molecule). These electro-assisted crystallization techniques also enable the growth of protein crystals, as a function of temperature, under the influence of DC or AC electric fields. It has also permitted the isolation of protein polymorphs, as published elsewhere. According to recent publications, AC current could affect not only the number of crystals, but also their size, depending on its frequency. Up to now, the trend in crystal growth for protein models studied is as follows: The higher the AC the higher the number of crystals; in the near future this can be applicable to the free electron lasers (XFEL) experiments for solving complicated protein structures using the fourth generation of synchrotrons all over the world. There have been a significant number of publications focused on this topic recently, which is why the thematic issue in “Protein Crystallization under the Presence of an Electric Field” for the Crystals journal (ISSN 2073-4352, https://0-www-mdpi-com.brum.beds.ac.uk/journal/crystals) will be published soon. We encourage all specialists and experts on this topic to submit original contributions to this journal, and to the thematic issue for consideration and publication.

Prof. Dr. Abel Moreno
Guest Editor

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Keywords

  • Electric Fields

  • Protein Electrocrystallization

  • Electrochemically-assisted Protein Crystallization

  • Crystal Growth under the Presence of Electric Currents (DC/AC)

Published Papers (10 papers)

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Research

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Article
Enhancing Protein Crystallization under a Magnetic Field
Crystals 2020, 10(9), 821; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10090821 - 16 Sep 2020
Cited by 1 | Viewed by 933
Abstract
High-quality crystals are essential to ensure high-resolution structural information. Protein crystals are controlled by many factors, such as pH, temperature, and the ion concentration of crystalline solutions. We previously reported the development of a device dedicated to protein crystallization. In the current study, [...] Read more.
High-quality crystals are essential to ensure high-resolution structural information. Protein crystals are controlled by many factors, such as pH, temperature, and the ion concentration of crystalline solutions. We previously reported the development of a device dedicated to protein crystallization. In the current study, we have further modified and improved our device. Exposure to external magnetic field leads to alignment of the crystal toward a preferred direction depending on the magnetization energy. Each material has different magnetic susceptibilities depending on the individual direction of their unit crystal cells. One of the strategies to acquire a large crystal entails controlling the nucleation rate. Furthermore, exposure of a crystal to a magnetic field may lead to new morphologies by affecting the crystal volume, shape, and quality. Full article
(This article belongs to the Special Issue Protein Crystallization under the Presence of an Electric Field)
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Article
Tools to Ease the Choice and Design of Protein Crystallisation Experiments
Crystals 2020, 10(2), 95; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10020095 - 07 Feb 2020
Cited by 4 | Viewed by 1700
Abstract
The process of macromolecular crystallisation almost always begins by setting up crystallisation trials using commercial or other premade screens, followed by cycles of optimisation where the crystallisation cocktails are focused towards a particular small region of chemical space. The screening process is relatively [...] Read more.
The process of macromolecular crystallisation almost always begins by setting up crystallisation trials using commercial or other premade screens, followed by cycles of optimisation where the crystallisation cocktails are focused towards a particular small region of chemical space. The screening process is relatively straightforward, but still requires an understanding of the plethora of commercially available screens. Optimisation is complicated by requiring both the design and preparation of the appropriate secondary screens. Software has been developed in the C3 lab to aid the process of choosing initial screens, to analyse the results of the initial trials, and to design and describe how to prepare optimisation screens. Full article
(This article belongs to the Special Issue Protein Crystallization under the Presence of an Electric Field)
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Article
Monitoring the Production of High Diffraction-Quality Crystals of Two Enzymes in Real Time Using In Situ Dynamic Light Scattering
Crystals 2020, 10(2), 65; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10020065 - 23 Jan 2020
Cited by 2 | Viewed by 1938
Abstract
The reproducible preparation of well-diffracting crystals is a prerequisite for every structural study based on crystallography. An instrument called XtalController has recently been designed that allows the monitoring of crystallization assays using dynamic light scattering and microscopy, and integrates piezo pumps to alter [...] Read more.
The reproducible preparation of well-diffracting crystals is a prerequisite for every structural study based on crystallography. An instrument called XtalController has recently been designed that allows the monitoring of crystallization assays using dynamic light scattering and microscopy, and integrates piezo pumps to alter the composition of the mother liquor during the experiment. We have applied this technology to study the crystallization of two enzymes, the CCA-adding enzyme of the psychrophilic bacterium Planococcus halocryophilus, and the lysozyme from hen egg white in the presence of a synthetic chemical nucleant. We were able to (i) detect early nucleation events and (ii) drive the crystallization system (through cycles of dissolution/crystallization) toward growth conditions yielding crystals with excellent diffraction properties. This technology opens a way to the rational production of samples for crystallography, ranging from nanocrystals for electron diffraction, microcrystals for serial or conventional X-ray diffraction, to larger crystals for neutron diffraction. Full article
(This article belongs to the Special Issue Protein Crystallization under the Presence of an Electric Field)
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Article
Analysis of Glulisine Crystallisation Utilising Phase Diagrams and Nucleants
Crystals 2019, 9(9), 462; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9090462 - 03 Sep 2019
Cited by 2 | Viewed by 1515
Abstract
Glulisine is a US Food and Drug Administration (FDA) approved insulin analogue, used for controlling hyperglycaemia in patients with diabetes mellitus (DM). It is fast acting which better approximates physiological insulin secretion, improving patient outcome. Crystallisation of Glulisine was analysed by its crystallisation [...] Read more.
Glulisine is a US Food and Drug Administration (FDA) approved insulin analogue, used for controlling hyperglycaemia in patients with diabetes mellitus (DM). It is fast acting which better approximates physiological insulin secretion, improving patient outcome. Crystallisation of Glulisine was analysed by its crystallisation phase diagram and nucleation-inducing materials. Both the hanging drop vapour diffusion and microbatch-under-oil methods were used and compared. We have shown that the same protein can have different solubility behaviours depending on the nature of the salt in the precipitating agent. In the case of Glulisine with magnesium formate, lowering the precipitant concentration drove the system further into supersaturation resulting in the formation of crystals and precipitation. This was the opposite effect to the usual scenario where raising the precipitant concentration leads to supersaturation. Glulisine with sodium potassium tartrate tetrahydrate (NaKT) followed the expected trend of forming crystals or precipitate at higher concentrations and clear drops at lower concentrations of the precipitant. The outcomes of crystallisation using the different crystallisation methods is also described. Glulisine was successfully crystallised and the crystals diffracted up to a resolution limit of 1.4 Å. Full article
(This article belongs to the Special Issue Protein Crystallization under the Presence of an Electric Field)
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Article
A Graphene-Based Microfluidic Platform for Electrocrystallization and In Situ X-ray Diffraction
Crystals 2018, 8(2), 76; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst8020076 - 01 Feb 2018
Cited by 8 | Viewed by 3350
Abstract
Here, we describe a novel microfluidic platform for use in electrocrystallization experiments. The device incorporates ultra-thin graphene-based films as electrodes and as X-ray transparent windows to enable in situ X-ray diffraction analysis. Furthermore, large-area graphene films serve as a gas barrier, creating a [...] Read more.
Here, we describe a novel microfluidic platform for use in electrocrystallization experiments. The device incorporates ultra-thin graphene-based films as electrodes and as X-ray transparent windows to enable in situ X-ray diffraction analysis. Furthermore, large-area graphene films serve as a gas barrier, creating a stable sample environment over time. We characterize different methods for fabricating graphene electrodes, and validate the electrical capabilities of our device through the use of methyl viologen, a redox-sensitive dye. Proof-of-concept electrocrystallization experiments using an internal electric field at constant potential were performed using hen egg-white lysozyme (HEWL) as a model system. We observed faster nucleation and crystal growth, as well as a higher signal-to-noise for diffraction data obtained from crystals prepared in the presence of an applied electric field. Although this work is focused on the electrocrystallization of proteins for structural biology, we anticipate that this technology should also find utility in a broad range of both X-ray technologies and other applications of microfluidic technology. Full article
(This article belongs to the Special Issue Protein Crystallization under the Presence of an Electric Field)
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Article
Crystallization under an External Electric Field: A Case Study of Glucose Isomerase
Crystals 2017, 7(7), 206; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst7070206 - 06 Jul 2017
Cited by 12 | Viewed by 2935
Abstract
Electric fields have been employed to promote macromolecular crystallization for several decades. Although crystals grown in electric fields seem to present higher diffraction quality, these methods are not widespread. For most configurations, electrodes are in direct contact with the protein solution. Here, we [...] Read more.
Electric fields have been employed to promote macromolecular crystallization for several decades. Although crystals grown in electric fields seem to present higher diffraction quality, these methods are not widespread. For most configurations, electrodes are in direct contact with the protein solution. Here, we propose a configuration that can be easily extended to standard crystallization methods for which the electrodes are not in direct contact with the protein solution. Furthermore, the proposed electrode configuration supplies an external DC electric field. Glucose Isomerase from Streptomyces rubiginosus crystals were grown at room temperature using the microbatch method in the presence of 1, 2, 4, and 6 kV. Several crystallization trials were carried out for reproducibility and statistical analysis purposes. The comparison with crystals grown in the absence of electric fields showed that crystallization in the presence of electric fields increases the size of crystals, while decreasing the number of nucleations. X-ray diffraction analysis of the crystals showed that those grown in the presence of electric fields are of higher crystal quality. Full article
(This article belongs to the Special Issue Protein Crystallization under the Presence of an Electric Field)
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Article
Electro-Infiltration of Cytochrome C into a Porous Silicon Network, and Its Effect on Nucleation and Protein Crystallization—Studies of the Electrical Properties of Porous Silicon Layer-Protein Systems for Applications in Electron-Transfer Biomolecular Devices
Crystals 2017, 7(7), 194; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst7070194 - 28 Jun 2017
Viewed by 2018
Abstract
In this work, we report the electrical properties of cytochrome C (Cyt C) inside porous silicon (PSi). We first used two techniques of protein infiltration: classic sitting drop and electrochemical migration methods. The electrochemically assisted cell, used for the infiltration by electro-migration, improved [...] Read more.
In this work, we report the electrical properties of cytochrome C (Cyt C) inside porous silicon (PSi). We first used two techniques of protein infiltration: classic sitting drop and electrochemical migration methods. The electrochemically assisted cell, used for the infiltration by electro-migration, improved the Cyt C nucleation and the crystallization behavior due to the PSi. We were able to carry out the crystallization thanks to the previous infiltration of proteins inside the Si pores network. We then continued the protein crystal growth through a vapor diffusion set-up. Secondly, we applied both forward and reverse bias currents only to the infiltrated Cyt C. Finally, the electrical characteristics were compared to the control (the protein molecules of which were not infiltrated) and to the samples without protein infiltration. The linker used in the sitting drop method influenced the electrical properties, which showed a modification in the current density. The simple drop method showed a current density of ~42 A/cm2; when employing the electrochemical cell technique, the current density was ~318 A/cm2; for the crystallized structures, it was ~0.908 A/cm2. Full article
(This article belongs to the Special Issue Protein Crystallization under the Presence of an Electric Field)
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Article
Crystal Growth of High-Quality Protein Crystals under the Presence of an Alternant Electric Field in Pulse-Wave Mode, and a Strong Magnetic Field with Radio Frequency Pulses Characterized by X-ray Diffraction
Crystals 2017, 7(6), 179; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst7060179 - 19 Jun 2017
Cited by 9 | Viewed by 2847
Abstract
The first part of this research was devoted to investigating the effect of alternate current (AC) using four different types of wave modes (pulse-wave) at 2 Hz on the crystal growth of lysozyme in solution. The best results, in terms of size and [...] Read more.
The first part of this research was devoted to investigating the effect of alternate current (AC) using four different types of wave modes (pulse-wave) at 2 Hz on the crystal growth of lysozyme in solution. The best results, in terms of size and crystal quality, were obtained when protein crystals were grown under the influence of electric fields in a very specific wave mode (“breathing” wave), giving the highest resolution up to 1.34 Å in X-ray diffraction analysis compared with controls and with those crystals grown in gel. In the second part, we evaluated the effect of a strong magnetic field of 16.5 Tesla combined with radiofrequency pulses of 0.43 μs on the crystal growth in gels of tetragonal hen egg white (HEW) lysozyme. The lysozyme crystals grown, both in solution applying breathing-wave and in gel under the influence of this strong magnetic field with pulses of radio frequencies, produced the larger-in-size crystals and the highest resolution structures. Data processing and refinement statistics are very good in terms of the resolution, mosaicity and Wilson B factor obtained for each crystal. Besides, electron density maps show well-defined and distinctly separated atoms at several selected tryptophan residues for the crystal grown using the “breathing wave pulses”. Full article
(This article belongs to the Special Issue Protein Crystallization under the Presence of an Electric Field)
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Article
Effect of an External Electric Field on the Kinetics of Dislocation-Free Growth of Tetragonal Hen Egg White Lysozyme Crystals
Crystals 2017, 7(6), 170; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst7060170 - 10 Jun 2017
Cited by 8 | Viewed by 1937
Abstract
Dislocation-free tetragonal hen egg white (HEW) lysozyme crystals were grown from a seed crystal in a cell. The rates of tetragonal HEW lysozyme crystal growth normal to the (110) and (101) faces with and without a 1-MHz external electric field were measured. A [...] Read more.
Dislocation-free tetragonal hen egg white (HEW) lysozyme crystals were grown from a seed crystal in a cell. The rates of tetragonal HEW lysozyme crystal growth normal to the (110) and (101) faces with and without a 1-MHz external electric field were measured. A decrease in the typical growth rates of the crystal measured under an applied field at 1 MHz was observed, although the overall driving force increased. Assuming that the birth and spread mechanism of two-dimensional nucleation occurs, an increase in the effective surface energy of the step ends was realized in the presence of the electric field, which led to an improvement in the crystal quality of the tetragonal HEW lysozyme crystals. This article also discusses the increase in the effective surface energy of the step ends with respect to the change in the entropy of the solid. Full article
(This article belongs to the Special Issue Protein Crystallization under the Presence of an Electric Field)
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Review

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Review
Recent Insights into the Crystallization Process; Protein Crystal Nucleation and Growth Peculiarities; Processes in the Presence of Electric Fields
Crystals 2017, 7(10), 310; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst7100310 - 15 Oct 2017
Cited by 11 | Viewed by 3019
Abstract
Three-dimensional protein molecule structures are essential for acquiring a deeper insight of the human genome, and for developing novel protein-based pharmaceuticals. X-ray diffraction studies of such structures require well-diffracting protein crystals. A set of external physical factors may promote and direct protein crystallization [...] Read more.
Three-dimensional protein molecule structures are essential for acquiring a deeper insight of the human genome, and for developing novel protein-based pharmaceuticals. X-ray diffraction studies of such structures require well-diffracting protein crystals. A set of external physical factors may promote and direct protein crystallization so that crystals obtained are useful for X-ray studies. Application of electric fields aids control over protein crystal size and diffraction quality. Protein crystal nucleation and growth in the presence of electric fields are reviewed. A notion of mesoscopic level of impact on the protein crystallization exercised by an electric field is also considered. Full article
(This article belongs to the Special Issue Protein Crystallization under the Presence of an Electric Field)
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