In this work the X-Ray diffraction study of fluorine-functionalized thiosemicarbazone ligands and their corresponding cyclometallated compounds is discussed. The results are in agreement with previous characterization by IR spectroscopy, ¹H and ¹⁹F NMR spectroscopies.

Suitable crystals were obtained for a thiosemicarbazone ligand and a cyclometallated compound. The crystal structure analyses are in accordance with the proposed structures: a thiosemicarbazone ligand fluorine-functionalized and a cyclometallated compound in which the thiosemicarbazone is a tridentate [C, N, S] donor ligand. A comparative study of bond distances and angles is shown, providing information about the coordination of the ligand to the metal center.

Methanocaldococcus jannaschii, a hyperthermophilic and barophilic methanarchaeon, contains a single gene (MJ0285) encoding a 16.5-kDa polypeptide chain of a small heat-shock protein (sHSP). This sHSP—now called MjsHSP16.5—is upregulated in response to high growth temperature or pressure (1, 2) and functions as a broad substrate ATP-independent holding chaperone that transiently binds and prevents the misfolded proteins from aggregation (3-7). Despite being extensively studied for decades, the molecular mechanism of MjsHSP16.5 is still remained to be elucidated, which primarily required a higher resolution of MjsHSP16.5 structure. In this study, using the single-particle cryo-electron microscopy (cryo-EM) technique which has the capacity in achieving near-atomic resolution of macromolecular structures and preserving the macromolecular shapes in solution, we reconstructed the MjsHSP16.5 24-subunit oligomer to a 2.5-Å resolution. Despite a similar hollow spherical homo-oligomer, the MjsHSP16.5 cryo-EM structure is slightly bigger than its crystal structure and reveals a loosen subunit-subunit interactions. Furthermore, cryo-EM image reconstruction shows additional N-terminal residues which are absent in most of MjsHSP16.5 crystal structures. These residues likely involve the holding chaperone activity and the oligomer stabilization. Using dynamic light scattering (DLS) and negative-staining transmission electron microscopy (TEM), we observed that MjsHSP16.5 oligomer was shrunk upon heating, suggesting a large conformational change in MjsHSP16.5 at elevated temperature. To our knowledge, MjsHSP16.5 is the first sHSP to have the cryo-EM structure archiving a resolution at 2.5 Å.

1) BB Boonyaratanakornkit et al. Environmental Microbiology. 2005. 7(6), 789-797
2) BB Boonyaratanakornkit et al. Extremophiles. 2007. 11, 495–503
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4) R Kim et al. PNAS. 2003. 100(14), 8151-8155
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Perovskite solar cells are expected to be the next generation solar cells due to their low cost and easy fabrication process. The purpose of this study is to investigate the effects of co-addition of copper, sodium and ethylammonium (EA) to the CH₃NH₃PbI₃ perovskite compound. The conversion efficiencies were enhanced by the addition of copper and sodium to CH₃NH₃PbI₃. From the first-principles calculations of the band structures, the formation of a shallow band of copper d-orbitals, which functions as an acceptor level, would promote the carrier generation. The additional excitation process from copper d-orbitals to sodium s-orbitals would suppress the carrier recombination, thus improving the conversion efficiency. Furthermore, the stability of the crystals increased by the EA substitution at the CH₃NH₃ site from the results of the total energy calculations, which would lead to suppression of formation of lattice defects. The further addition of EA also improved the conversion efficiencies, which indicates the EA substitution would stabilize the crystal structure even in the presence of copper and sodium.

Crystalline form of proteins has great advantages for different industries such as pharmaceuticals, which also has a high demand of specific crystals size with narrow distribution. This is challenging due to the inherent difficulty of having reproducible, controllable, and profitable processes. The easiest way to control crystalline polydispersity is by directing the crystallization process. Nucleation, as the first stage of the process, predetermines the final number of crystals and control their size but difficult to control due to its stochastic nature. Therefore, overcoming the nucleation step seems the simple way to tune the final product. Seeding in a metastable solution seems the simple way to do it.

Hydrogels have demonstrated their ability to produce higher quality crystals, influencing nucleation and growth, while providing a non-convection medium. Thus, using the gelled batch method as a means of crystallization seems as a good option due to its simplicity and its ability to be scalable.

Still gelling a crystallizable protein metastable solution introduce a new set of variables to be adjusted in order to: properly compartment the space (gel homogeneity, etc.), control the influence of the gel of the crystallization and seed stability, etc. In this work we present the preliminary results of our strategy to control the homogeneity and final size of the lysozyme crystals by means of agarose batch seeding. Our preliminary results clearly show that there is a direct correlation between the initial size of the seeds and the final size of the crystals, maintaining a narrow size distribution.^1–4

References:

(1) Nanev, C. N. Crystal Size Distribution Resulting from the Time Dependence of Crystal Nucleation.Cryst.Res.Technol.2018,53(5),1700248. https://doi.org/10.1002/crat.201700248.

(2) Pu, S.; Hadinoto, K. Continuous Crystallization as a Downstream Processing Step of Pharmaceutical Proteins: A Review. Chem. Eng. Res. Des. 2020, 160, 89–104. https://doi.org/10.1016/j.cherd.2020.05.004.

(3) Gavira, J. A. Current Trends in Protein Crystallization. Arch. Biochem. Biophys. 2016, 602, 3–11. https://doi.org/10.1016/j.abb.2015.12.010.

(4) Contreras-Montoya, R.; Arredondo-Amador, M.; Escolano-Casado, G.; Mañas-Torres, M. C.; González, M.; Conejero-Muriel, M.; Bhatia, V.; Díaz-Mochón, J. J.; Martínez-Augustin, O.; Sánchez de Medina, F.; Lopez-Lopez, M. T.; Conejero-Lara, F.; Gavira, J. A.; Álvarez De Cienfuegos, L. PAGE PENDING_Insulin Crystals Grown in Short-Peptide Supramolecular Hydrogels Show Enhanced Thermal Stability and Slower Release Profile. ACS Appl. Mater. Interfaces 2021. https://doi.org/10.1021/acsami.1c00639.

Over the last decade, continuous manufacturing techniques have been widely used in pharmaceutical manufacturing industries. However, despite the outstanding performance associated with the steady-state operation, continuous processes face common and important challenges of low efficiency and material waste during the start-up and shutdown. Considering that most pharmaceutical manufacturing is accomplished in a short operation window, an ideal start-up and shut down strategy will have a significant impact on the economic and environmental performance of the continuous pharmaceutical process. In this study, a combined start-up, steady-state, and shutdown optimization of a three-stage mixed suspension mixed product removal (MSMPR) crystallizer was compared against optimized batch and fed-batch crystallizers. The crystallization of aspirin (acetylsalicylic acid, ASA) in ethanol (solvent) and water (antisolvent) was used as a case study. The optimization problems were solved using a hybrid method, which combines a genetic algorithm and a sequential quadratic programming (SQP) method. The multistage continuous crystallizer was designed and optimized to maximize on-spec production over a total operating window of 800 min. It was shown that a max on-spec production of 5858 g can be achieved with the continuous process. A batch and a fed-batch crystallizer were designed and optimized to achieve the same production rate and help establish a reliable basis for rigorous technoeconomic analysis and comparison.

Cyclometallated compounds, specifically cyclopalladates, have been synthesized for years. In this work, we describe a new family of compounds in which an iron core has been additionally introduced into a Pd complex. This novel feature provides interesting properties to these compounds, such as the possibility of undergoing reduction˗oxidation processes due to the versatility of the iron nucleus. XRD studies of the resulting crystalline structure enable the study of the compound behavior.

Recently, many efforts have been made to find high values of reversible electrocaloric effect (ECE) induced temperature change DT, which is the most important parameter for creation of ECE-based cooling systems. The application of larger electric fields has shown promise as a way of increasing DT. However, there are only a small number of publications where ECE is directly measured at electric fields in the range above 20-30 kV/cm. The present work provides a detailed overview of ECE in (1-x)(0.8Na_0.5Bi_0.5TiO₃-0.2BaTiO₃)-xCaTiO₃ (x=0.05-0.125) solid solutions. For these compositions, we have measured DT as a function of temperature and applied fields of up to 100 kV/cm using the direct measurement method. At lower concentrations of CaTiO₃, values of DT above the electric field-induced first order phase transition reach 1ºC with a large contribution from an entropy jump. At higher CaTiO₃ concentrations, the electric field-induced phase transition is suppressed. This causes an expressed reduction of DT, despite a moderate reduction of electric field-induced dielectric polarization. Furthermore, a comparison of the direct measurement method of ECE temperature change with the indirect one using Maxwell’s relations is presented. Here, an inconsistency between the results obtained by both methods is demonstrated and interpreted.

This work has been funded by the Latvia Science Council grant LZP-2020/2-0080.

Rapidly expanding and new applications of liquid crystal materials cover a wide range of technology products. A very incomplete list includes conventional and miniature high-resolution displays, AR/VR glasses, smart windows, dynamic lenses, tunable filters and retarders, electrically controlled sensors, reconfigurable antennas for wireless and space communications, and many other commercially available devices. The aforementioned devices are enabled by the collective reorientation of thermotropic molecular liquid crystals under the action of applied electric fields. The reorientation effects in liquid crystals can be altered by ionic contaminants typically present in mesogenic materials in small quantities. Therefore, information about ions in liquid crystals is very important because it allows for a proper selection of liquid crystal materials and uncompromised performance of liquid crystal devices. This information can be obtained by performing electrical measurements of liquid crystal materials. Measurements of basic electrical parameters (DC conductivity, charge mobility and ion density) are carried out using sandwich-like liquid crystal cells of finite thickness. Once a cell is filled with liquid crystal materials, interactions between ions and the cell substrates will result in the time dependence of the ion density and DC electrical conductivity until a steady state is reached. In this paper, we show how complementary information about ionic processes in liquid crystal cells can be obtained by analyzing their transient and steady state electrical properties.

Abstract: High resolution birefringence measurements and Modulated Differential Scanning Calorimetry have been carried out in order to investigate the critical behaviour near the Isotropic to Smectic-A, Smectic-A to Smectic-C_a* phase transitions associated with two well known antiferroelectric liquid crystalline materials R- and S-enantiomers of MHPOBC [4-(1-methylheptyloxycarbonyl) phenyl 4¢-octyloxybiphenyl-4-carboxylate] and their racemic mixture. The heat capacity anomaly and the birefringence data serve as order parameter and the critical exponents extracted from these order parameters corresponding to the various transitions associated with the investigated materials indicates the nature of the transition whether it is first order or second order. The data have been analyzed in detail with the renormalization-group expression with correction-to-scaling terms. A comparison of specific heat-capacity critical exponent found from the mean-square fluctuations of the tilt angle <δq²(T)> and the critical exponent (α′) explored from the birefringence differential quotient Q (T) for the SmA-SmC_a* phase transition has also been done for pure R-MHPOBC and S-MHPOBC. The nature of phase transition associated with the racemic mixture of MHPOBC has also been discussed in the light of precise birefringence and specific heat capacity measurements.

In this work, we report the investigation of various experimental conditions and their influence on polymorphism of 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophen carbonitrile, commonly known as ROY. These conditions include an in-house developed microfluidic chip with controlled mixing of parallel flows. ROY is known for its ability to form a large variety of polymorphs, including at least ten forming under standard conditions. Nucleation is triggered by adding water as antisolvent to ROY dissolved in acetone. We observe that different ROY concentrations and different solvent to antisolvent ratios naturally favor different polymorphs. Nonetheless, identical samples prepared with different mixing methods, such as shaking and magnetic stirring, consistently lead to the formation of different polymorphs. In addition, different mixing rates that can be linked to shear stress, strongly influence the crystallization. A fourth parameter, namely confinement of the sample is also found to be critical. Untangling all those parameters and their influences on polymorphism call for an experimental setup allowing all four to be controlled accurately. To that end, we developed a novel customized microfluidic setup allowing reproducible and controlled mixing conditions. Two parallel flows of antisolvent and ROY dissolved in solvent are injected into a transparent microchannel. Next, slow and progressive mixing can be obtained by molecular diffusion. Additionally, the microfluidic chip is equipped with a piezoceramic element, allowing the implementation of various mixing rates by acoustic mixing. With this device, we demonstrate the importance of parameters other than concentration involved in polymorphism of ROY.