The genes for AChE and BChE encode the proteins responsible for enzyme activity. Additional gene products, PRiMA and PRaD, anchor AChE and BChE proteins into membranes. Soluble AChE and BChE tetramers are composed of 4 identical subunits plus one polyproline-rich peptide. Dilution does not release the polyproline-rich peptide from tetramers. However, protein denaturation, for example heating in a boiling water bath, dissociates the polyproline-rich peptide. Using mass spectrometry to sequence peptides released from soluble AChE and BChE tetramers, we find sequences that correspond to proline-rich regions from a variety of proteins. A typical peptide sequence contains 20 consecutive prolines in a 23-residue peptide LPPPPPPPPPPPPPPPPPPPPLP. There is no single, common consensus sequence i.e., no specific gene appears to be responsible for the polyproline-rich peptides found in soluble AChE and BChE tetramers. We propose that during metabolic turnover, protein fragments containing polyproline-rich sequences are scavenged by AChE and BChE dimers, to make stable AChE and BChE tetramers. The 40-residue, alpha-helical C-terminus of AChE or BChE is the tetramerization domain that binds the polyproline-rich peptide. Four parallel alpha helices wrap around a single antiparallel polyproline peptide to lock the tetramer in place. This organization was established by classical X-ray crystallography for isolated C-termini in complex with a proline-rich peptide. The organization was confirmed for intact, tetrameric BChE using cryoelectron microscopy. When 40 amino acids are deleted from the carboxy terminus, monomeric enzymes are created that retain full enzymatic activity.

In this work, we are the first to identify and report pharmaceutically effective cocrystals of poorly soluble drug Modafinil (MOD) using crystal engineering approach. A multi-component system of MOD with nicotinic acid (NIC) as coformer at 1:1 molar ratio was prepared to simultaneously improve solubility, dissolution and bioavailability by applying liquid assistant grinding technique. Nicotinic acid as a potential coformer for cocrystal preparation was predicted using a novel approach of Hansen Solubility Parameter (HSP) group contribution method. Various evaluation parameters pertaining to confirm cocrystal formation like Fourier Transformer Infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Powder X-Ray Diffraction (PXRD), and Field Emission Scanning Electron Microscopy (FESEM) were carried out. Further effect of precipitation inhibitors (HPMC) on in-vivo bioavailability enhancement was also studied. MOD-NIC cocrystals formation was confirmed by integrating results of instrumental techniques. Aqueous solubility and in-vivo pharmacokinetic study proved 5.96 and 1.88 times higher bioavailability respectively in case of prepared cocrystals compared to MOD alone whereas bioavailability further increased by 2.72 times when these cocrystals were administered in presence of precipitation inhibitor. Hence, solid state manipulation was successful for preparing modafinil cocrystals as a potential method for illustrating several properties. The concept of cocrystals coupled with precipitation inhibitors significantly enhanced the bioavailability of modafinil.

Study of physical properties associated with some binary mixtures of chiral ferroelectric liquid crystalline compounds

Barnali Barman^*, Malay Kumar Das

Department of Physics, University of North Bengal, 734 013, Siliguri, West Bengal, India

*E-mail ID: barnalibarman1991@gmail.com

Abstract

Among the various advanced technological materials in the modern era; Liquid Crystals (LCs) has become one of the most important self-organizing molecular materials with their growing applications in the various field of science. The research associated with the Ferroelectric Liquid Crystals (FLCs) has become a subject of most intense area during the past few decades owing to their valuable intrinsic fundamental properties.At present their successful utilization in flat television screens, fast electro-optical switching devices etc. makes them extremely demandable in the commercial field. The fulfilment of this promise depends greatly on an improved understanding on the physical properties of the FLC materials. However no single materials can exhibit all the desired properties for different applications. In order to fulfil all the requirements of the device manufacturer; preparation of suitable binary mixtures is one of the most simple and elegant way in the field of LC Research. Keeping this in mind some mixtures have prepared by using pure chiral FLC compounds [1,2,3] and investigated in the light of the static dielectric permittivity (ε), dielectric anisotropy (∆ε), spontaneous polarization (P_s), response time (τ), torsional bulk viscosity (h) and dielectric spectroscopy. The temperature variation of P_s of the studied mixtures provides a preliminary idea about the order of the associated phase transitions namely SmA*-SmC* and N*-SmC*. The activation energy of all the mixtures have been determined from the best fitted Arrhenius plot. This assignment mainly contributes to the preparation and investigation of some smart multifunctional FLC mixtures aimed for optoelectronic and photonic applications.

References

[1]A.Bubnov,M.Kaspar,V.Novotna,V.Hamplova,M.Glogarova,N.Kapernaum,F.Giesselmann; Liq. Cryst.2008, 35, 1329-1337.doi.org/10.1080/02678290802585525.

[2]B.Barman, B.Das, M.K.Das, V. Hamplová, A.Bubnov, Journal of Molecular Liquids.2019, 283.472-781. doi.org/10.1016/j.molliq.2019.03.071.

[3]M.K.Das,B.Barman,B.Das,V.Hamplová,A.Bubnov,Crystals.2019,9,473;doi:10.3390/cryst9090473.

Among the drugs used worldwide, 50-60% are isolated or produced from plants; about half of these drugs are alkaloids or nitrogen-containing compounds. Within the alkaloids, quinazoline derivatives are of particular interest as they have a wide range of biological activity [1,2]. Their versatility stimulates the synthesis of new compounds containing the quinazoline fragment, with the aim of even increased biological activity. Continuing our research in this direction [3], the crystal structures of 3- (3,4-dimethoxyphenylethylamino)-methylidene-1,2,3,9-tetrahydropyrrolo [2,1-b] quinazolin-9-one (1) and 4-(3,4-dimethoxyphenylethylamino)-methylidene-2,3,4,10-tetrahydro-1H-pyrido [2,1-b] -quinazolin-10-one (2) were studied. The structures of compounds 1 and 2 were established by single crystal X-ray diffraction. Their molecular and crystal structures were described in the context of intra and inter-molecular interactions and of stereoisomerism.

For molecular crystals, Hirshfeld surface analyses may provide insight into intermolecular interactions, and energy framework analyses allow to quantify different contributions to the overall energy. These analyses were performed to pinpoint intermolecular interactions in 1 and 2. According to our results, the molecules are associated by intra- and intermolecular hydrogen bonds, C—H···π and C—O···π stacking interactions. The three-dimensional Hirshfeld surface analysis and two-dimensional fingerprint plots revealed that the structures are dominated by H···H, H···C/C···H and H···O/O···H contacts. The intermolecular energy analysis revealed a significant contribution of electrostatic and dispersion components for the stabilization of molecular packing.

Design and optimisation are two important steps for crystallisation process. In this paper, the combined cooling and anti-solvent crystallisation of acetylsalicylic acid (ASA) in ethanol(solvent) and water(anti-solvent) mixture is studied by means of population balance modelling. An average crystal size of 387 is obtained from an optimised temperature, anti-solvent flow rate and residence time profile of three stages crystallisation process based on the steady state optimisation. An attainable region of average crystal size of different residence time is also developed which can provide help for crystallisation process design. Aiming at improving the benefit of crystallisation process, dynamic optimisation of start-up and shut-down process are also developed. By manipulating the anti-solvent flow rate profile, the start-up time is shortened to 86.62% in Strat up optimisation. Besides, the effect of seed on start-up time is also researched in the start-up optimisation. And in shut down process, additional quantity of crystal which meets the standard quality (average crystal size within 95%) is recycled by optimising the anti-solvent flow rate profile. This study shows that the optimisation of temperature, anti-solvent flow rate and residence time will strongly affect the crystal quality. And optimisation of anti-solvent flow rate, seeds and will also provide additional benefits in start-up and shut down of crystallisation process.

The complex and intricate microstructure of B19’ martensite in shape memory nickel titanium alloys is generally explained with the Phenomenological Theory of Martensitic Crystallography (PTMC). For the last decade, we have developed an alternative approach that supposes the existence of a “natural” parent-daughter orientation relationship (OR). As the previous TEM studies could not capture the global crystallographic characteristics of the B2-B19’ transformation required to discriminate the models, we used Electron BackScatter Diffraction (EBSD) and Transmission Kikuchi Diffraction (TKD) to investigate a polycrystalline NiTi alloy constituted of B19’ martensite. The EBSD maps show the large martensite plates and reveal a coexistence of different ORs. The TKD maps permit to image the “twins” and confirm a continuum of orientations. The results are interpreted without PTMC, with anew hypotheses. The predominant OR in EBSD is the “natural” OR for which the dense directions and dense planes of B2 and B19’ phases are parallel, i.e. (010)_B19’ // (110)_B2 & [101]_B19’ // [ -111]_B2 . The natural OR was used to automatically reconstruct the prior parent B2 grains in the EBSD and TKD maps. From the distortion matrix associated to this OR, we calculated that the habit plane could be (1-12)_B2 // (10-1 )_B19’. The traces of these planes are in good agreement with the EBSD maps. We interpret the other ORs as “closing-gap” ORs derived from the natural OR to allow the compatibility between the distortion variants. Each of them restores a parent symmetry element between the variants that was lost by distortion but preserved by correspondence. The oral presentation is divided in three parts: 0-26 min : Introduction, some words about the limits of the PTMC, 26-50 min : Experimental EBSD and TKD Results, 50-80 min : Interpretations and conclusions. All the details can be found in https://doi.org/10.3390/cryst10070562.

Eu-doped (mol 3%) and undoped polycrystalline Ca₁₀(PO₄)OH₂ hydroxyapatite (HAp) [1-2] were synthesized by using the chemical-precipitation technique [3]. Some precautions were observed: the temperature was kept low at 25° C so that to inhibit the increasing of the average size of the particles; pH was kept constantly high (10 ± 0.05) in order to minimize the formation of secondary phases and to prevent the aggregation of the particles during their formation. The multi-methodological characterization achieved through powder X-Ray diffraction (PXRD) and photoluminescence (PL) techniques, showed that the Eu entered in Ca1 site in the dried (120 °C) doped samples and in those calcinated (450 °C) at low temperature: these samples show low crystallinity (3% and 7%, respectively), good luminescence and very low crystallite size (around 25 nm). On the contrary, Eu-doped sample calcinated at 900°C showed very high crystallinity (87%), with a crystallite size of 148 nm, while PL spectroscopy suggested that this sample presents the highest and narrowest emission bands. Specifically, the PL emissions peak at 573 nm, corresponding to the ⁵D₀–⁷F₀ of the Eu³⁺ transition in Ca2 site [4], was more than 10 times more intense than the emission peak at 592 of Eu³⁺ in Ca1 site, indicating the complete migration of Eu³⁺ ions in the Ca2 sites of HAp framework for the high temperature sample [3]. FTIR and Raman spectra showed slight band shifts with increasing annealing temperature of the samples [3]. Results show that low crystalline HAp obtained at 120° and 450°, could be employed as luminescent drug carriers, while high crystalline HAp, annealed at 900°, could be suitable materials for biological optical imaging.

[1] Dorozhkin, S.V. Calcium Orthophosphates: Occurrence, Properties and Major Applications. Bioceram Dev Appl 2014, 4.

[2] Hughes, J.M.; Rakovan, J. The Crystal Structure of Apatite, Ca₅(PO₄)₃(F,OH,Cl). Reviews in Mineralogy and Geochemistry 2002, 48, 1–12.

[3] Baldassarre, F.; Altomare, A.; Corriero, N.; Mesto, E.; Lacalamita, M.; Bruno, G.; Sacchetti, A.; Dida, B.; Karaj, D.; Ventura, G.D.; Capitelli, F.; Siliqi, D. Crystal Chemistry and Luminescence Properties of Eu-Doped Polycrystalline Hydroxyapatite Synthesized by Chemical Precipitation at Room Temperature. Crystals 2020, 10, 250.

[4] Nikolaev, A.; Kolesnikov, I.; Frank-Kamenetskaya, O.; Kuz’mina, M. Europium concentration effect on characteristics and luminescent properties of hydroxyapatite nanocrystalline powders. Journal of Molecular Structure 2017, 1149, 323–331.

Accompanying with the fast development of modern technologies, computers and cellphones are applied in people’s work and life, which brings more convenience and fun. However, due to the wide viewing angle (WVA) characteristic of these electronic products, people can be peered by others when they glaze over the materials, which leads to the leakage of personal privacy and commercial secrets. Consequently, liquid crystal displays (LCDs) simultaneously with narrow viewing angle (NVA) characteristic are needed to avoid the risk of secret leakage, thus electrically switchable viewing angle devices are attracting considerable attention because of the information protection. Herein, we have developed an electrically switchable viewing angle device that fabricated by dichroic dyes doped polymer stabilized cholesteric liquid crystals (DD-PSCLCs). By fixing the pitch of CLCs at the infrafed light region, when CLCs are at the planar state, the device is transparent at zero field. When applying the electric field, CLCs are switched to the focal conic texture, thus the device is scattered. Therefore, the fabricated device can make the viewing angle of LCDs electrically switchable between WVA mode and NVA mode by small voltage, which makes contribution to privacy protection.

The treatment of experimental X-ray diffraction data (XRD) normally involves several steps of processing and analysis. A visual inspection of the data during the treatment is often important to follow and validate the final result. This is especially important for non-routine experiments or also when decisions on the experimental conditions should be taken on the fly e.g. in case of synchrotron beamtime limitations. In such circumstances, the availability of specific tools providing good plotting capabilities and processing options in a user-friendly environment is really helpful. The d1Dplot and d2Dplot software (for 1D and 2D-XRD, respectively) have been developed prioritizing these aspects.

D1Dplot focuses on the visualization and processing of powder diffraction data and includes the ability to generate comprehensive 2D plots of multiple patterns to easily follow e.g. solid-state chemical reactions. It also includes general tools for data processing and gives the user the possibility of creating a compound database for phase identification.

D2Dplot is a full package for 2D-XRD data [1]. It allows inspecting and interacting directly with the images. Besides general processing tools (point selection, excluded zones, background extraction, powder pattern generation, azimuthal plots) it includes specific data analysis features such as a database for the fast identification of compounds and a routine for through-the-substrate methodology [2]. The software has proved useful in the analysis of minerals [3], cultural heritage samples [4], kidney stones or crocodile teeth [5].

Both programs can be downloaded from the ALBA Synchrotron Light Source website (https://www.cells.es/en/beamlines/bl04-mspd/preparing-your-experiment) and can be used free of charge for non-commercial and academic purposes.

Many of the liquid crystal devices are driven by electric fields. Ions, typically present in molecular liquid crystal materials in minute quantities, can compromise the performance of mesogenic materials (in the simplest case, through a well-known screening effect). Even highly purified liquid crystals can be contaminated with ions during their production and handling. Therefore, measurements of the concentration of ions became an important part of the material characterization of liquid crystals. Interestingly, even a brief analysis of existing publications can reveal a quite broad variability of the values of the concentration of ions measured by different research groups for the same liquid crystals. It reflects the complexity of ion generation mechanisms in liquid crystal materials and their dependence on numerous factors. In this paper, an overview of ion generation mechanisms in liquid crystals and modern ion measurement techniques is followed by the discussion of frequently overlooked factors affecting the measured values of the ion concentration. Ion-generating and ion-capturing properties of the alignment layers (or substrates) of liquid crystal cells are considered and used to evaluate a true concentration of ions in liquid crystals. In addition, practical recommendations aimed at improving the measurements of the ion density in liquid crystals are also discussed.