Isomorphous Crystals Research Articles

Isomorphism of Sr[Li3AlO4] and Sr[Li3GaO4] - Syntheses, Crystal Structure, and Europium(II) Luminescence.

While highly efficient red-emitting inorganic phosphors have been discovered in the substance class of alkaline earth oxo(nitrido)lithoaluminates, new narrow-band green- and yellow-emitting components are being sought to improve the performance of phosphor-converted light-emitting diodes (pc-LEDs). Various solid-state reactions were carried out under protective gas atmosphere in nickel crucibles and sealed tantalum ampules to synthesize Sr[Li3AlO4], Sr[Li3GaO4], and five substitutional derivates of Sr[Li3(Al1-x Ga x )O4] at moderate temperatures. The observation of a linear increase in the unit cell parameters as a function of the increasing gallium mole fraction x in Sr[Li3(Al1-x Ga x )O4] revealed Vegard behavior in the solid-solution series, which was derived from powder X-ray diffraction data. The isomorphic crystallization of the new oxolithogallate Sr[Li3GaO4] and the known oxolithoaluminate Sr[Li3AlO4] in an ordered variant of the U[Cr4C4] aristotype was verified on the basis of powder and single-crystal X-ray diffraction data. Photoluminescence spectroscopy was used to investigate the narrow-band emissions in the substitution series of Eu2+-activated Sr[Li3(Al1-x Ga x )O4] under blue-light excitation. The emission maximum was shifted to higher energies as the gallium mole fraction increased. Peak wavelengths were observed at λem = 572 nm (fwhm equals 47 nm, 1446 cm-1, 0.18 eV) for yellow-emitting Sr[Li3AlO4]:Eu2+ and at λem = 554 nm (fwhm equals 49 nm, 1589 cm-1, 0.20 eV) for green-emitting Sr[Li3GaO4]:Eu2+. Sr[Li3AlO4]:Eu2+ has excellent thermal quenching resistance with a photoluminescence emission intensity of >93% at T = 423 K relative to the room temperature value, making this inorganic phosphor a potential candidate for solid-state lighting applications.

MatchMaps: non-isomorphous difference maps for X-ray crystallography.

Conformational change mediates the biological functions of macromolecules. Crystallographic measurements can map these changes with extraordinary sensitivity as a function of mutations, ligands and time. A popular method for detecting structural differences between crystallographic data sets is the isomorphous difference map. These maps combine the phases of a chosen reference state with the observed changes in structure factor amplitudes to yield a map of changes in electron density. Such maps are much more sensitive to conformational change than structure refinement is, and are unbiased in the sense that observed differences do not depend on refinement of the perturbed state. However, even modest changes in unit-cell properties can render isomorphous difference maps useless. This is unnecessary. Described here is a generalized procedure for calculating observed difference maps that retains the high sensitivity to conformational change and avoids structure refinement of the perturbed state. This procedure is implemented in an open-source Python package, MatchMaps, that can be run in any software environment supporting PHENIX [Liebschner et al. (2019). Acta Cryst. D75, 861-877] and CCP4 [Agirre et al. (2023). Acta Cryst. D79, 449-461]. Worked examples show that MatchMaps 'rescues' observed difference electron-density maps for poorly isomorphous crystals, corrects artifacts in nominally isomorphous difference maps, and extends to detecting differences across copies within the asymmetric unit or across altogether different crystal forms.

Reaction amplification with a gain: Triplet exciton–mediated quantum chain using mixed crystals with a tailor-made triplet sensitizer

Photochemical valence bond isomerization of a crystalline Dewar benzene (DB) diacid monoanion salt with an acetophenone-linked piperazinium cation that serves as an intramolecular triplet energy sensitizer (DB-AcPh-Pz) exhibits a quantum chain reaction with as many as 450 product molecules per photon absorbed (Φ ≈ 450). By contrast, isomorphous crystals of the DB diacid monosalt of an ethylbenzene-linked piperazinium (DB-EtPh-Pz) lacking a triplet sensitizer showed a less impressive quantum yield of ca. Φ ≈ 22. To establish the critical importance of a triplet excited state carrier in the adiabatic photochemical reaction we prepared mixed crystals with DB-AcPh-Pz as a dilute triplet sensitizer guest in crystals of DB-EtPh-Pz. As expected from their high structural similarities, solid solutions were easily formed with the triplet sensitizer salt in the range of 0.1 to 10%. Experiments carried out under conditions where light is absorbed by the triplet sensitizer-linked DB-AcPh-Pz can be used to initiate a triplet state adiabatic reaction from 3DB-AcPh-Pz to 3HB*-AcPh-Pz, which can serve as a chain carrier and transfer energy to an unreacted DB-EtPh-Pz where exciton delocalization in the crystalline solid solution can help carry out an efficient energy transfer and enable a quantum chain employing the photoproduct as a triplet chain carrier. Excitation of mixed crystals with as little as 0.1% triplet sensitizer resulted in an extraordinarily high quantum yield Φ ≈ 517.

Linearly-Changed Thermal Behavior and Depressed Brill Transition in Long-Chain Polyamides Substituted by Methyl Side Groups.

Side substitution is an effective way of functionalizing and modifying the properties of polyamides. Meanwhile, side substitution would significantly influence the crystallization kinetics and polymorphic phase transition of polyamides, which, however, has not been well elucidated. Herein, we synthesized the side-substituted long-chain polyamides with various content of methyl pendent groups and investigated their crystallization and phase transition behaviors. We find that the thermal parameters of side-substituted polyamides vary linearly with the side group content, analogous to the isomorphic crystallization of random copolymers. All the solution-crystallized polyamides experience the α-γ Brill transition during heating, with the Brill transition temperature linearly decreasing as the side group content increases. Intriguingly, the γ-α transition of polyamides during cooling is suppressed with the presence of side methyl groups due to the difficulty in H-bond reorganization and gauche-trans conformational changes. This work has demonstrated the critical role of side substitution in the polymorphic crystallization and phase transition of long-chain polyamides.

Poisson’s ratio of fluorapatite crystals

Introduction. It is known that in the pathogenesis of caries and non-carious lesions of teeth, an important role is played by enamel resistance, which is determined by numerous factors, among which the structure and physical and mechanical properties of tooth tissues are considered to be among the most important. This report summarizes the literature data on the Poisson’s ratio of fluorapatite (FAp), a biomaterial and one of the mineral components of dental hard tissues. The literature search was carried out in electronic databases Scopus, Web of Science, PubMed, Medline, Elibrary, MatWeb for the period from January 1970 to March 2023 inclusive. Some of the data are supplemented by our own calculations based on formulas for crystalline hexagonal systems (systems). As is known, Poisson’s ratio determines the volumetric response of materials and biological tissues to mechanical load, but its anisotropic properties have not been studied in detail. Material and methods. Calculations of the Poisson’s ratio of fluorapatite were carried out in the computer algebra system Mathcad 15.0, using the online analysis of elasticity tensors ELATE, and an integrated molecular modeling system was used - the graphic package VESTA (Visualization for Electronic and STructural Analisis). Results and discussion. The Poisson’s ratio values of fluorapatite crystals varied: minimum values 0.057–0.283, maximum values 0.302–0.494, average values obtained by integration in all directions 0.24–0.308. The coefficient of elastic anisotropy of the fluorapatite crystal lattice, calculated based on the values of Poisson’s ratio, is 1.21–5.29. The results obtained were compared with those of hydroxyapatite (HAp) crystals, dentin, enamel and filling materials. The highest values of the parameters μ and μmax are found in dentin (0.312 and 0.54), the lowest μmin are also found in dentin (0.13). Conclusions. Fluorapatite crystals are elastically anisotropic, and Poisson’s ratio μmax/μmin varies over a wide range. The Poisson’s ratio of fluorapatite showed similarity with the transverse strain coefficient of isomorphic hydroxyapatite crystals (0.207–0.374), dentin (0.13–0.54), enamel (0.16–0.47) and dental composite filling materials (0.24–0 ,35). The latter should help improve the quality of restorations using filling materials for replacing hard dental tissues. It has been established that the organic component of dentin increases its Poisson’s ratio as a biocomposite and the anisotropy of elastic properties.

An Uncommon Solvent‐Controlled Photochromic Tetraphenylethylene‐Based Co‐crystal

AbstractA co‐crystal FJU‐182 with a closed cage structure with photochromic phenomenon was formed using a tetraphenylene derivatives 4,4′,4′′,4′′′‐(anthracene‐9,10‐diylidenebis(methanediyl‐ylidene))tetrabenzoic acid self‐assembled with 1,3‐di(4‐pyridyl)propane in a solvent. It was also found that isomorphic crystals grown from different solvents exhibited different fluorescence. The electron paramagnetic resonance and X‐ray photoelectron spectroscopy data showed that the photochromic mechanism of crystal FJU‐182 was due to photoinduced electron transfer, while the different color change of crystals grown from different solvents was attributed to the size of solvent molecules. The I−V curves of the crystals FJU‐182 before and after illumination were also tested, and it was found that the conductivity of the crystals before the color change would be 3–8 times higher than the conductivity of the crystals after the color development. FJU‐182 provides a new case for electrochemical devices with photoelectric response.

Measurements of Energetic States Resulting from Ion Exchanges in the Isomorphic Crystals of Apatites and Bioapatites.

Developments in the field of nanostructures open new ways for designing and manufacturing innovative materials. Here, we focused on new original ways of calculating energy changes during the substitution of foreign ions into the structure of apatites and bioapatites. Using these tools, the energetic costs of ion exchanges were calculated for the exemplary cases known from the literature. It was established that the most costly were ion exchanges of some cations inside apatites and of anions, and the least costly exchanges in tetrad channel positions. Real energy expenses for bioapatites are much smaller in comparison to mineral apatites due to the limited involvement of magnesium and carbonates in the structure of hard tissues. They are of the order of several electron volts per ion. The rigorous dependences of the energy changes and crystallographic cell volumes on the ionic radii of introduced cations were proved. The differentiation of the positioning of foreign ions in locations of Ca(I) and Ca(II) could be calculated in the case of a Ca-Pb reaction in hydroxyapatite. The energetic effects of tooth aging were indicated. The ability of energy change calculation during the ion exchange for isomorphic substances widens the advantages resulting from X-ray diffraction measurements.

Design and Validation of Isomorphic Crystal Library for Nonlinear Optics and THz Wave Generation

AbstractDevelopment of new organic crystals possessing large second‐order optical nonlinearity is very challenging because of strong tendency of centrosymmetric dipole–dipole molecular assembly in crystals. This tendency makes it difficult to develop various analogous crystals that allow fine tuning of optical and physical properties to enhance the device performance. A design approach of an isomorphic crystal library consisting of 11 highly efficient nonlinear optical salt crystals is reported. Analyzing the so‐called isomorphic tolerance space in previously reported mother crystals (PMnXQ chromophores, where PM denotes piperidin‐4‐ylmethanol electron donor, n corresponds to the substituted position of halogen (X) group on the quinolinium (Q) electron acceptor), various substituents are introduced into the PMnXQ crystals at different positions, considering their space‐filling characteristics and interionic interaction ability. All 11 PMnXQ crystals exhibit an isomorphic (or pseudo‐isomorphic) crystal structure, in which the cationic chromophores form a perfectly parallel assembly for maximizing the second‐order nonlinear optical susceptibility. The optical, physical, and crystal characteristics of newly designed, synthesized, and grown isomorphic PMnXQ crystals show both similarities and differences. Excellent THz wave‐generation performance is demonstrated in both kHz‐ and MHz‐repetition optical pump systems with new PMnXQ crystals. Therefore, the design approach using isomorphic tolerance space is very attractive for developing diverse isomorphic analogous organic crystals.

C-H▪▪▪S Hydrogen Bonds in Ampicillin and Amoxicillin Crystals Investigated by Sulfur K-Edge X-Ray Absorption Near-Edge Structure Spectroscopy and Single-Crystal X-Ray Structure Analysis.

Sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy was evaluated for its ability to detect non-conventional C-H▪▪▪S hydrogen bonds in crystals of the sulfur-containing penam antibiotics ampicillin and amoxicillin. The XANES spectra of the nearly isomorphous crystals of ampicillin trihydrate and amoxicillin trihydrate were very similar, whereas that of ampicillin anhydrate displayed unique features. Single-crystal X-ray structure analyses revealed that the C-H▪▪▪S hydrogen bond geometries and the chemical types of the hydrogen donors differed between the isomorphous trihydrate crystals and ampicillin anhydrate crystal. These observations demonstrate that the shapes of the sulfur K-edge XANES spectra are dependent on the nature of the C-H▪▪▪S hydrogen bonds. Sulfur K-edge XANES spectroscopy shows promise for use in the detection and analysis of non-covalent interactions, including hydrogen bonds to sulfur atoms, within active pharmaceutical ingredients.

MO049: Correlation of Findings in Urinary Sediment Microscopy and Histological Lesions in Kidney Biopsy: Red Flags Not to be Missed

Abstract BACKGROUND AND AIMS Urinary sediment (U-Sed) is a noninvasive laboratory test that can be performed by an automated analyzer or manually by trained personnel. Manual U-Sed remains the diagnostic standard because it excels at distinguishing isomorphic from dysmorphic red blood cells, identifying renal tubular epithelial cells, lipids, crystals and the composition of casts. Findings in U-Sed reflect damage that is occurring within the kidney, which can be documented by kidney biopsy. This study aimed to investigate the prevalence of a complete profile of U-Sed particles and its associations with histological lesions on kidney biopsy, regardless of renal diagnosis. METHOD This retrospective study included 131 patients who had contemporary manual U-Sed evaluation and kidney biopsy at our institution, from 2018 to 2021. Renal transplant patients were excluded. A comprehensive set of urinary particles and histological lesions were quantified, and we analyzed their associations. Urinary particles evaluated included casts, erythrocytes, leukocytes, renal tubular epithelial cells, urothelial transitional cells (superficial and deep), lipids, crystals, squamous cells and bacteria. They were semi-quantified from 0 (absent) to 3 + . Renal biopsies samples were reviewed, and a systematic evaluation of 32 histological lesions was performed. When present, lesions were semi-quantified from 0 (absent) to 3 + . Appropriate tests were performed STATA v.16.1. RESULTS We found an elevated frequency of findings suggestive of proliferative renal disease, such as dysmorphic hematuria (n = 71, 54.2%), leukocyturia (n = 62, 47.3%), renal tubular epithelial cells (n = 53, 40.5%) and lipiduria (n = 45, 34.4%), and a low frequency of particles evoking urological damage, such as isomorphic hematuria (n = 29, 22.1%), crystals (n = 12, 9.2%) and urothelial transitional cells (n = 26, 9.9%). The association of histological lesions and urinary particles was explored with a multivariate model that identified U-Sed characteristics, which favored the presence of acute tubular necrosis, endocapillary hypercellularity, neutrophils and/or karyorrhexis, wire loops and/or hyaline deposits, fibrinoid necrosis and cellular/fibrocellular crescents (summarized in Table 1). CONCLUSION In a population of patients submitted to kidney biopsy, we found that the presence of some urinary particles (renal tubular epithelial cells, lipids and dysmorphic erythrocytes), which are seldom reported by automated analyzers, conferred an increased likelihood of active proliferative histological lesions. It is important not to misidentify them, as their presence are red flags for relevant proliferative histological lesions. Moreover, given the flare/remission characteristics of proliferative glomerular disease, U-Sed could play a major role in measuring the degree of activity without requiring repeat kidney biopsies.

Photochromic Polyoxometalate/Perylenediimide Donor-Acceptor Hybrid Crystals with Interesting Luminescent Properties.

The self-assembly of electron-deficient protonated N, N'-dipyridyltetrachloroperylenediimide (4Cl-DPPDI) and electron-rich polyoxometalate acids HnXM12O40 (POMs; X = P or Si; M = W or Mo) resulted in four isomorphous donor-acceptor hybrid crystals 1-4 with segregated POM anions and one-dimensional racemic hydrogen-bonded 4Cl-DPPDI networks as electron-donor and -acceptor components, respectively. Because of the compact contacts between the POM anions and 4Cl-DPPDI tectons induced by anion-π interactions, besides enhanced photochromism, these four unique isostructural hybrids exhibited unusual room-temperature phosphorescence (RTP) emissions. More interestingly, owing to the facial compact contacts of two racemic 4Cl-DPPDI tectons induced by lone pair-π-assisted π-π interactions, they also showed unprecedented photon upconversion by triplet-triplet annihilation (TTA).

Unusual Surface Texture, Dimensions and Morphology Variations of Chiral and Single Crystals**

We demonstrate here a unique metallo-organic material where the appearance and the internal crystal structure are in contradiction. The egg-shaped (ovoid) crystals have a brain-like texture. Although these micro-sized crystals are monodispersed; like fingerprints their grainy surfaces are never exactly alike. Remarkably, our X-ray and electron diffraction studies unexpectedly revealed that these structures are single-crystals comprising a continuous coordination network of two differently shaped homochiral channels. By using the same building blocks under different reaction conditions, a rare series of crystals have been obtained that are uniquely rounded in their shape. In stark contrast to the brain-like crystals, these isostructural and monodispersed crystals have a comparatively smooth appearance. The sizes of these crystals vary by several orders of magnitude.

Карієсрезистентність – критерій стоматологічного статусу дітей та підлітків

Prevention of dental caries in children is one of the current problems of modern pediatric dentistry, which is due to the high prevalence and intensity of this disease. Analysis of the results of epidemiological studies conducted among children of different ages in the regions of Ukraine shows a significant increase in caries growth in recent years, both temporary and permanent teeth, which leads to in-depth study of the hardness of dental tissues to cariogenic factors in connection with the need in the constant improvement of methods of treatment and prevention of this pathology. The purpose of the study was to analyze the value of enamel caries resistance as a detector of resistance of dental hard tissues to carious process and its complications. The subject of the research is the work of domestic and foreign researchers on this topic. In the course of the research the bibliosemantic method and structural-logical analysis were used. Today, dental caries is the most common disease in different age groups, which is confirmed by the prevalence – 90-100% and a sharp trend of increasing its intensity. Given the high rates of this pathology, it should be remembered that its untimely treatment leads to the following complications: pulpitis, periodontitis, tooth extraction. An important concept that indicates the possibility of caries is caries resistance, which indicates the level of resistance of the enamel to caries and has an informative diagnostic value for the dentist. According to modern ideas, in the pathogenesis of dental caries the leading role is played by caries-resistant enamel. Its mineral base is formed by isomorphic crystals of apatite, which contain various chemical elements, and their amount in the body is closely related to the amount in the environment. It is established that more than 40 chemical elements take part in the process of tooth mineralization, the most important of which belongs to calcium, phosphorus, fluoride. Insufficient amount or excess of certain micronutrients in the environment, especially in soils and drinking water, can change their content in the body and, consequently, in the hard tissues of the teeth, affecting their resistance to caries. It is well known that the influence of a number of adverse environmental factors leads to a decrease in the resistance of the body as a whole and, as a consequence, to a decrease in the caries resistance of the enamel of the hard tissues of the teeth. Sensitivity to the effects of adverse factors increases significantly in the prepubertal period, a time not only of intensive growth of the child and the formation of his personality, but also a period of mineralization of more than half of permanent teeth. Therefore, exactly at this time dentists should pay special attention to the prevention of caries of permanent teeth in children by improving the conditions of secondary mineralization of tooth enamel, thereby increasing their level of caries resistance

Crystallization of Proteins on Chip by Microdialysis for In Situ X-ray Diffraction Studies.

This protocol describes the manufacturing of reproducible and inexpensive microfluidic devices covering the whole pipeline for crystallizing proteins on-chip with the dialysis method and allowing in situ single-crystal or serial crystallography experiments at room temperature. The protocol details the fabrication process of the microchips, the manipulation of the on-chip crystallization experiments and the treatment of the in situ collected X-ray diffraction data for the structural elucidation of the protein sample. The main feature of this microfabrication procedure lies on the integration of a commercially available, semipermeable regenerated cellulose dialysis membrane in between two layers of the chip. The molecular weight cut-off of the embedded membrane varies depending on the molecular weight of the macromolecule and the precipitants. The device exploits the advantages of microfluidic technology, such as the use of minute volumes of samples (<1 µL) and fine tuning over transport phenomena. The chip coupled them with the dialysis method, providing precise and reversible control over the crystallization process and can be used for investigating phase diagrams of proteins at the microliter scale. The device is patterned using a photocurable thiolene-based resin with soft imprint lithography on an optically transparent polymeric substrate. Moreover, the background scattering of the materials composing the microchips and generating background noise was evaluated rendering the chip compatible for in situ X-ray diffraction experiments. Once protein crystals are grown on-chip up to an adequate size and population uniformity, the microchips can be directly mounted in front of the X-ray beam with the aid of a 3D printed holder. This approach addresses the challenges rising from the use of cryoprotectants and manual harvesting in conventional protein crystallography experiments through an easy and inexpensive manner. Complete X-ray diffraction data sets from multiple, isomorphous lysozyme crystals grown on-chip were collected at room temperature for structure determination.

Crystallization of Proteins on Chip by Microdialysis for &lt;i&gt;In Situ&lt;/i&gt; X-ray Diffraction Studies

This protocol describes the manufacturing of reproducible and inexpensive microfluidic devices covering the whole pipeline for crystallizing proteins on-chip with the dialysis method and allowing in situ single-crystal or serial crystallography experiments at room temperature. The protocol details the fabrication process of the microchips, the manipulation of the on-chip crystallization experiments and the treatment of the in situ collected X-ray diffraction data for the structural elucidation of the protein sample. The main feature of this microfabrication procedure lies on the integration of a commercially available, semipermeable regenerated cellulose dialysis membrane in between two layers of the chip. The molecular weight cut-off of the embedded membrane varies depending on the molecular weight of the macromolecule and the precipitants. The device exploits the advantages of microfluidic technology, such as the use of minute volumes of samples (<1 µL) and fine tuning over transport phenomena. The chip coupled them with the dialysis method, providing precise and reversible control over the crystallization process and can be used for investigating phase diagrams of proteins at the microliter scale. The device is patterned using a photocurable thiolene-based resin with soft imprint lithography on an optically transparent polymeric substrate. Moreover, the background scattering of the materials composing the microchips and generating background noise was evaluated rendering the chip compatible for in situ X-ray diffraction experiments. Once protein crystals are grown on-chip up to an adequate size and population uniformity, the microchips can be directly mounted in front of the X-ray beam with the aid of a 3D printed holder. This approach addresses the challenges rising from the use of cryoprotectants and manual harvesting in conventional protein crystallography experiments through an easy and inexpensive manner. Complete X-ray diffraction data sets from multiple, isomorphous lysozyme crystals grown on-chip were collected at room temperature for structure determination.

Polar and Helical Isomorphous Crystals of Proline Derivatives: Influence of a Fluorine Atom on the Electric Susceptibility

Two novel nonlinear optical isomorphous crystals of proline derivatives with alkyne functionality have been obtained (Boc-L-ProNH(CH2)2CCH and Boc-cis-4-fluoro-L-ProNH(CH2)2CCH). Both derivatives, which differ only by the substitution of a H atom to a F atom, adopt the same polar and columnar right-handed helix arrangement in the crystalline state. In addition, adjacent polar helical columns all point in the same direction, thus generating a macrodipole and a crystalline system conducive for second harmonic generation (SHG) properties. This isomorphous crystal system constitutes an interesting tool to study the effect of the fluorine atom on the dipole moment and on the first hyperpolarizability. Starting from the PBC optimized geometries of the crystals, the macroscopic second-order nonlinearity, χ(2), of the newly synthesized crystals has been estimated by quantum chemical calculations. These χ(2) responses are of the same order of magnitude as those of inorganic proline derivatives while smaller than those observed in crystals of push–pull π-conjugated molecules.Graphic

Structural analysis of rice Os4BGlu18 monolignol β-glucosidase.

Monolignol glucosides are storage forms of monolignols, which are polymerized to lignin to strengthen plant cell walls. The conversion of monolignol glucosides to monolignols is catalyzed by monolignol β-glucosidases. Rice Os4BGlu18 β-glucosidase catalyzes hydrolysis of the monolignol glucosides, coniferin, syringin, and p-coumaryl alcohol glucoside more efficiently than other natural substrates. To understand more clearly the basis for substrate specificity of a monolignol β-glucosidase, the structure of Os4BGlu18 was determined by X-ray crystallography. Crystals of Os4BGlu18 and its complex with δ-gluconolactone diffracted to 1.7 and 2.1 Å resolution, respectively. Two protein molecules were found in the asymmetric unit of the P212121 space group of their isomorphous crystals. The Os4BGlu18 structure exhibited the typical (β/α)8 TIM barrel of glycoside hydrolase family 1 (GH1), but the four variable loops and two disulfide bonds appeared significantly different from other known structures of GH1 β-glucosidases. Molecular docking studies of the Os4BGlu18 structure with monolignol substrate ligands placed the glycone in a similar position to the δ-gluconolactone in the complex structure and revealed the interactions between protein and ligands. Molecular docking, multiple sequence alignment, and homology modeling identified amino acid residues at the aglycone-binding site involved in substrate specificity for monolignol β-glucosides. Thus, the structural basis of substrate recognition and hydrolysis by monolignol β-glucosidases was elucidated.

Synthesis, crystal structure and theoretical calculations of two rare-earth borates with DUV cut-off edges

Two isomorphic rare-earth borate crystals, YZnB5O10and GdZnB5O10, show three-dimensional structures constructed from two-dimensional {[B5O10]5−}nlayers with the Y or Gd, and zinc ions filled in the interlayers, and exhibit DUV cut-off edges (&lt;190 nm).

The flexibility of long chain substituents influences spin-crossover in isomorphous lipid bilayer crystals.

[Fe(bpp)2][BF4]2 (bpp = 2,6-di{pyrazol-1-yl}pyridine) derivatives with a bent geometry of hexadec-1-ynyl or hexadecyl pyrazole substituents are isomorphous, and high-spin at room temperature. However, only the latter compound undergoes an abrupt, stepwise spin-transition on cooling. This may reflect the different conformational flexibilities of their long chain substituents.

New Salt and Cocrystal of Mequitazine: Impact of Coformer Flexibility and Hydrogen Bond Donors on Polymorphism

New multicomponent crystals of mequitazine (MQZ) with succinic acid (SUC), fumaric acid (FUM), glycolic acid (GLC), and glycolamide (GLA) were obtained after liquid-assisted grinding. The hydrate/anhydrate availability in the crystals differed owing to slight differences in the coformer structure. Therefore, the causes of these differences in the crystal structure were investigated. The structures of crystals, for which single crystals were difficult to obtain, were obtained using powder diffraction crystal structure analyses. The crystal structures, including the disordered structure and the structure in which the H atom position could not be identified, were validated via dispersion-corrected density functional theory calculations using the Quantum ESPRESSO code. MQZ-SUC and MQZ-FUM formed isostructural anhydrates, but only MQZ-SUC formed a hydrate by twisting the alkyl straight chain; hence, the difference between the dihedral angles that the coformer can form led to a small change in polymorphism. MQZ-GLC hydrate and MQZ-GLA anhydrate had no isomorphic crystals, MQZ-GLC formed a hydrate, and MQZ-GLA formed an anhydrate. Differences in the number of hydrogen bond donors in the coformer led to major changes in polymorphism. The results of this study might be useful for coformer selection and controlling multicomponent crystal polymorphism.