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1
G, Nithya, Sudha R e Charles C. Kanakam. "Polymorphic behavior of an organic compound". Asian Journal of Pharmaceutical and Clinical Research 10, n. 4 (1 aprile 2017): 259. http://dx.doi.org/10.22159/ajpcr.2017.v10i4.16702.
Testo completoAbstract (sommario):
Objective: Polymorphic crystals were exhibited in many organic compounds. The frequency changes, relative intensities, band contours, and numberof bands were observed in the spectra of different polymorphism which may be due to molecule-molecule interactions in the crystal unit cells. Theshape of a molecule at its site in the unit cell is distorted by molecular interactions.Methods: The identification of a pure crystal form and to quantify a mixture of two forms infrared and Raman spectra of different crystalline formsof the same organic compound can be used. 2’-chloro-4-methoxy-3-nitro benzil (1) was synthesized and its two polymorphic forms were obtainedby recrystallization from the solvents acetone/chloroform and ethanol. The polymorphism present in the compound was confirmed by single crystalX-ray crystallography and differential scanning calorimetry.Results: The polymorph 1.1 crystallizes as triclinic P-1 space group in the solvent acetone – chloroform and the polymorph 1.2 crystallizes asmonoclinic P21/c space group in the solvent ethanol.Discussion: The intermolecular lattice energy and the interplay of molecular conformation in the crystallization and stability of polymorphs areidentified by X-ray crystal structures of conformational polymorphs.Keywords: Conformational polymorphism, Organic compounds, Single crystal growth, X-ray diffraction.
2
Ângelo, Marilene, Jennifer Jacon, Olimpia Maria Santos, Edith Cristina Cazedey, Rudy Bonfilio, Antônio Carlos Doriguetto e Magali Benjamim de Araújo. "Occurrence of polymorphism in famotidine raw materials". Acta Crystallographica Section A Foundations and Advances 70, a1 (5 agosto 2014): C1563. http://dx.doi.org/10.1107/s2053273314084368.
Testo completoAbstract (sommario):
Polymorphs are compounds with the same chemical composition, however the molecules are arranged in at least two different ways in the solid state. Famotidine is a histamine H2-receptor antagonist inhibitor of gastric secretion and widely used in gastric and duodenal ulcer disease. Two polymorphs are described for famotidine, A and B. The polymorph A is the most thermodynamically stable form and polymorph B is the kinetically favored form being marketed because it presents greater pharmacological activity. The aim of this study was to evaluate the occurrence of famotidine polymorphs in five raw materials acquired from different suppliers. The reference standard (USP) was also analyzed. All samples were characterized by powder X-ray diffraction (PXRD), infrared spectrophotometry (IR-ATR) and differential scanning calorimetry (DSC). PXRD analysis enables us to identify form B in five raw material samples and in the reference standard (USP). However, one of the raw materials additionally shows the presence of polymorphic form A. The DSC and IR-ATR techniques were essential to identify the polymorphic forms of famotidine confirming the results obtained by PXRD. Since the presence of polymorphs can compromise the effectiveness and safety of medicines and there is no official methodology of analysis and control of polymorphism in famotidine raw materials, the polymorphic contamination found in this study are being further analyzed and their physicochemical properties are being evaluated.
3
So, Hee-Soo, e Shinya Matsumoto. "Three differently coloured polymorphs of 3,6-bis(4-chlorophenyl)-2,5-dipropyl-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione". Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 75, n. 3 (23 maggio 2019): 414–22. http://dx.doi.org/10.1107/s2052520619004773.
Testo completoAbstract (sommario):
In this paper, the conformational polymorphism of a chlorinated diketopyrrolopyrrole (DPP) dye having flexible substituents in a non-hydrogen-bonding system is reported. The propyl-substituted DPP derivative (PR3C) has three polymorphic forms, each showing a different colour (red, orange and yellow). All polymorphs could be obtained concomitantly under various crystallization conditions. The results of the crystal structure analysis indicate that PR3C adopts different conformations in each polymorph. The packing effect caused by the difference in the arrangement of neighbouring molecules was found to play an important role in the occurrence of the observed polymorphism. The thermodynamic stability relationship between the three polymorphs was identified by thermal analysis and indicates that the yellow polymorph is the thermally stable form. The results indicate that the yellow form and orange form are enantiotropically related, and the other polymorph is monotropically related to the others.
4
Akune, Yoko, Risa Hirosawa, Atsushi Koseki e Shinya Matsumoto. "Role of halogen substituents in a series of polymorphic 2,5-diamino-3,6-dicyanopyrazine derivatives with highly flexible groups". Zeitschrift für Kristallographie - Crystalline Materials 232, n. 5 (1 maggio 2017): 395–405. http://dx.doi.org/10.1515/zkri-2016-2007.
Testo completoAbstract (sommario):
AbstractThe crystal structures of the ortho-X-benzyl derivatives, where X=F, Cl, Br, I, and Me, of 2,5-bis(N,N-dibenzylamino)-3,6-dicyanopyrazine dyes (C34H24N6X4) were analysed to evaluate the effect of a systematic series of structures on the occurrence of polymorphism. Detailed crystal structure analysis indicated that the thermally stable forms of the polymorphic derivatives (Cl and Br derivatives) were close-packed, whereas those of the non-polymorphic derivatives (F and I derivatives) were stabilised by an intermolecular interaction involving the ortho-substituents. In the thermally metastable forms of the polymorphic derivative, halogen-halogen and halogen-nitrogen interactions contributed to the stabilisation of these crystals in the same way as the thermally stable form of the non-polymorphic derivatives. This indicated that the ease of polymorph occurrence would require an appropriate balance between the crystal energy of the close-packed structure and that of the crystal structure generated mainly by the electrostatic interactions involving the halogens in these halogenated pyrazine derivatives. In addition, the similar tendency of the occurrence of polymorphs in these halogenated pyrazine derivatives was found in 19 sets of halogenated compounds having known crystal structures of F, Cl, Br and I derivatives including at least one polymorphic derivative in the crystal structure database.
5
Wantha, Lek. "Kinetics of the Solution-Mediated Polymorphic Transformation of Organic Compounds". Current Pharmaceutical Design 24, n. 21 (15 ottobre 2018): 2383–93. http://dx.doi.org/10.2174/1381612824666180601093228.
Testo completoAbstract (sommario):
Polymorphism is a behavior of a substance to crystallize into more than one district crystal structures. Preferential formation of a polymorph depends strongly on the kinetics of the relevant mechanisms. Solutionmediated polymorphic transformation is an important mechanism in crystallization of organic compounds from solution. Knowing its kinetics allows us to understand the process and control the polymorphic formation. In this review, concepts, kinetics, and process modeling of crystallization and solution-mediated polymorphic transformation are examined and summarized.
6
Hsu, Cheng-Hung, Wen-Ting Ke e Shan-Yang Lin. "Progressive Steps of Polymorphic Transformation of Gabapentin Polymorphs Studied by Hot-stage FTIR Microspectroscopy". Journal of Pharmacy & Pharmaceutical Sciences 13, n. 1 (8 aprile 2010): 67. http://dx.doi.org/10.18433/j3fs32.
Testo completoAbstract (sommario):
Purpose. The aim of this study was to determine the progressive processes of polymorphic transformation of different gabapentin (GBP) polymorphs by using hot-stage Fourier transform infrared (FTIR) microspectroscopy. Methods. Four polymorphs of GBP were previously prepared and then identified by differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, FTIR microspectroscopy and X-ray powder diffractometry. A novel hot-stage FTIR microspectroscopic technique was used to investigate the progressive steps of polymorphic transformation of each GBP polymorph sealed within two pieces of KBr plates. Results. Four polymorphs (Forms I, II, III and IV) of GBP were well characterized. The GBP form I was proven to be a monohydrate, but other GBP forms II-IV were anhydrous. Different thermal-induced progressive processes and steps of polymorphic interconversion of GBP polymorphs were clearly found from the changes in the three-dimensional IR spectral contour and peak intensity by using hot-stage FTIR microspectroscopy. The results also indicate that GBP form I was dehydrated and transformed to form III, and then converted to form IV; whereas GBP forms II and III directly transformed to form IV during heating. The GBP form IV was the last polymorph before the intramolecular lactamization of GBP. Conclusion. A one-step novel hot-stage FTIR microspectroscopy was successfully applied to simultaneously and continuously investigate the progressive processes and steps of thermal-induced polymorphic interconversion of GBP polymorph in the solid state.
7
Goossens, D. J., e E. J. Chan. "Synchrotron X-ray diffuse scattering from a stable polymorphic material: terephthalic acid, C8H6O4". Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 73, n. 1 (31 gennaio 2017): 112–21. http://dx.doi.org/10.1107/s2052520616018801.
Testo completoAbstract (sommario):
Terephthalic acid (TPA, C8H6O4) is an industrially important chemical, one that shows polymorphism and disorder. Three polymorphs are known, two triclinic [(I) and (II)] and one monoclinic (III). Of the two triclinic polymorphs, (II) has been shown to be more stable in ambient conditions. This paper presents models of the local order of polymorphs (I) and (II), and compares the single-crystal diffuse scattering (SCDS) computed from the models with that observed from real crystals. TPA shows relatively weak and less-structured diffuse scattering than some other polymorphic materials, but it does appear that the SCDS is less well modelled by a purely harmonic model in polymorph (I) than in polymorph (II), according to the idea that the diffuse scattering is sensitive to anharmonicity that presages a structural phase transition. The work here verifies that displacive correlations are strong along the molecular chains and weak laterally, and that it is not necessary to allow the —COOH groups to librate to successfully model the diffuse scattering – keeping in mind that the data are from X-ray diffraction and not directly sensitive to H atoms.
8
Kuzmin, V. S., V. V. Chernyshev e A. I. Luttseva. "X-RAY POWDER DIFFRACTION IN QUALITY CONTROL OF MEDICINES". Bulletin of the Scientific Centre for Expert Evaluation of Medicinal Products 8, n. 3 (26 settembre 2018): 158–61. http://dx.doi.org/10.30895/1991-2919-2018-8-3-158-161.
Testo completoAbstract (sommario):
X-ray powder diffraction is one of the methods used for detection and analysis of polymorphic forms of pharmaceutical substances. The article elucidates the concept of polymorphism, briefly explains physical characteristics of this phenomenon, conditions of polymorphic transformations and the prevalence of polymorphic forms among drug substances. It should be noted that polymorphism is observed in drug substances belonging to different pharmacologic classes. Polymorphic forms of the same drug substance have different solubility, melting point, resistance to oxidation and to other destructive processes, and, consequently, different surface properties which affect both the rate of absorption of the drug substances and their stability as components of dosage forms. This calls for the need to control the quality of drug substances for potential presence of polymorphic forms. The use of diffraction methods for examination of cryomodified forms of various biologically active compounds obtained by evaporation and subsequent precipitation at low temperatures resulted in obtaining polycrystalline substances with new properties. The article provides results of examination of crystalline modifications of phenazepam in the form of α- and β-polymorphs, tilorone, fabomotizole, zolendronic acid and dehydroepiandrosterone. It was demonstrated that the use of X-ray diffraction analysis for examination and quality control of polymorphic forms of drugs is a necessary component of identification testing.
9
Wójcik, Grażyna, e Izabela Mossakowska. "Polymorphs of p-nitrophenol as studied by variable-temperature X-ray diffraction and calorimetry: comparison with m-nitrophenol". Acta Crystallographica Section B Structural Science 62, n. 1 (17 gennaio 2006): 143–52. http://dx.doi.org/10.1107/s010876810503418x.
Testo completoAbstract (sommario):
Crystal structures of two polymorphic forms of p-nitrophenol have been determined at several temperatures between 120 and 375 K. The thermal expansion tensor has been determined for both polymorphs. The rigid-body mean-square amplitudes of molecular translations and librations and the amplitudes of the internal torsions of the nitro group have been calculated at different temperatures. Differential scanning calorimetry was used to find the temperature and enthalpy of the polymorphic transformation. The results were compared with those recently obtained for m-nitrophenol polymorphs. Some conclusions concerning the polymorphism of p- and m-nitrophenols are presented.
10
Wardhana, Yoga Windhu, Risanteni Riskasari e Fikri Alatas. "Phase Transitions Among of Valsartan Polymorphs due to Grinding and Humidity Variations". Indonesian Journal of Pharmaceutics 3, n. 2 (3 agosto 2021): 82. http://dx.doi.org/10.24198/idjp.v3i2.35312.
Testo completoAbstract (sommario):
Phase transition between drugs with polymorphisms needs attention due to unconscious changes in quality. Valsartan (VAL) is a drug model with polymorphic events to be studied here. Two polymorphic forms were obtained from recrystallization with various organic solvents such as acetonitrile and n-butyl acetate. With untreated materials (from the market) were used as a comparison in this study. The phase transition of each polymorph was studied through grinding and humidity variations (RH 75% and 98%) treatment. The polymorph characterization was observed by microscope light polarization (PLM), Fourier Transform Infrared (FTIR), and Powdered X-ray Diffractometer (PXRD). The transition among polymorphic VAL was monitored by PXRD. There were significant differences in morphology, IR spectra, and diffractograms pattern. Found that the untreated VAL was amorphous, whereas the others were in high crystallinity. The polymorph form from n-butyl acetate was a metastable one that transformed easier into stable crystalline (from acetonitrile) than another polymorph.Keywords : Valsartan, Phase transition, Polymorphism, Recrystallization
11
DELGADO, G., M. GUILLEN e A. J. MORA. "4-METHYL HYPPURIC ACID: A CASE OF POLYMORPHISM AND SOLVATOMORPHISM". Periódico Tchê Química 16, n. 32 (20 agosto 2019): 812–19. http://dx.doi.org/10.52571/ptq.v16.n32.2019.830_periodico32_pgs_812_819.pdf.
Testo completoAbstract (sommario):
Polymorphism is known as the ability of a solid material to exist in more than one form or crystal structure, with important applications in the preparation of active pharmaceutical ingredients. Characterization of different polymorphs of the specific metabolite of 4-xylene can contribute to the chemical and pharmaceutical industry. Polymorphism is of particular importance in industrial processes, where different physical properties of polymorphic forms can substantially alter the viability and quality of a manufactured product. This is particularly so for the design and production of drugs in the pharmaceutical industry, as varying physical properties between different polymorphs can affect shelf life and durability, solubility, as well as bioavailability and manufacturing of the drug. The crystallization, spectroscopic and X-ray diffraction characterization of two polymorph and one solvatomorph of 4-methylhippuric acid are presented. These compounds crystallizes in different crystalline systems. Polymorph I (4mH-I) crystalize in an orthorhombic cell with space group P212121. Polymorph II (4mHII) crystallizes in a monoclinic space group P21/c. Solvatomorph (4mH-S) crystallizes in a triclinic P-1 cell. All polymorphs crystallize in neutral form. The crystal packing of the three compounds are governed by hydrogen bonds intermolecular interactions of the type N--H···O and O--H···O forming tridimensional networks.
12
Khoj, Manal A., Colan E. Hughes, Kenneth D. M. Harris e Benson M. Kariuki. "Polymorphic phase transformations of 3-chloro-trans-cinnamic acid and its solid solution with 3-bromo-trans-cinnamic acid". Acta Crystallographica Section C Structural Chemistry 74, n. 8 (13 luglio 2018): 923–28. http://dx.doi.org/10.1107/s2053229618009269.
Testo completoAbstract (sommario):
We have investigated the polymorphic phase transformations above ambient temperature for 3-chloro-trans-cinnamic acid (3-ClCA, C9H7ClO2) and a solid solution of 3-ClCA and 3-bromo-trans-cinnamic acid (3-BrCA, C9H7BrO2). At 413 K, the γ polymorph of 3-ClCA transforms to the β polymorph. Interestingly, the structure of the β polymorph of 3-ClCA obtained in this transformation is different from the structure of the β polymorph of 3-BrCA obtained in the corresponding polymorphic transformation from the γ polymorph of 3-BrCA, even though the γ polymorphs of 3-ClCA and 3-BrCA are isostructural. We also report a high-temperature phase transformation from a γ-type structure to a β-type structure for a solid solution of 3-ClCA and 3-BrCA (with a molar ratio close to 1:1). The γ polymorph of the solid solution is isostructural with the γ polymorphs of pure 3-ClCA and pure 3-BrCA, while the β-type structure produced in the phase transformation is structurally similar to the β polymorph of pure 3-BrCA.
13
Pogoda, Dorota, Jan Janczak e Veneta Videnova-Adrabinska. "New polymorphs of an old drug: conformational and synthon polymorphism of 5-nitrofurazone". Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 72, n. 2 (1 aprile 2016): 263–73. http://dx.doi.org/10.1107/s2052520615024956.
Testo completoAbstract (sommario):
Two new polymorphic forms of 5-nitrofurazone (5-nitro-2-furaldehyde semicarbazone) have been synthesized and structurally characterized by single-crystal and powder X-ray diffraction methods, vibrational spectroscopy (FT–IR and temperature Raman), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Hirshfeld surface analysis. The compound crystallizes in three different polymorphic formsP21/a(polymorph α),P21(polymorph β) andP21/c(polymorph γ), the crystal structures of two of which (polymorphs β and γ) represent new structure determinations. The solid-state molecular organization in the three crystal forms is analyzed and discussed in terms of molecular conformation, crystal packing and hydrogen-bonded networks. All three crystals are formed fromtransgeometrical isomers, but the molecular conformation of the α-polymorph issyn–anti–anti–anti, while that of β- and γ-polymorphs issyn–anti–syn–syn. As a consequence of this the hydrogen-bond donor and acceptor sites of the molecules are oriented differently, which in turn results in different hydrogen-bond connectivity and packing patterns.
14
Acebedo-Martínez, Francisco Javier, Carolina Alarcón-Payer, Antonio Frontera, Rafael Barbas, Rafel Prohens, Milena Di Crisci, Alicia Domínguez-Martín, Jaime Gómez-Morales e Duane Choquesillo-Lazarte. "Novel Polymorphic Cocrystals of the Non-Steroidal Anti-Inflammatory Drug Niflumic Acid: Expanding the Pharmaceutical Landscape". Pharmaceutics 13, n. 12 (13 dicembre 2021): 2140. http://dx.doi.org/10.3390/pharmaceutics13122140.
Testo completoAbstract (sommario):
Any time the pharmaceutical industry develops a new drug, potential polymorphic events must be thoroughly described, because in a crystalline pharmaceutical solid, different arrangements of the same active pharmaceutical ingredient can yield to very different physicochemical properties that might be crucial for its efficacy, such as dissolution, solubility, or stability. Polymorphism in cocrystal formulation cannot be neglected, either. In this work, two different cocrystal polymorphs of the non-steroidal anti-inflammatory drug niflumic acid and caffeine are reported. They have been synthesized by mechanochemical methods and thoroughly characterized in solid-state by powder and single crystal X-ray diffraction respectively, as well as other techniques such as thermal analyses, infrared spectroscopy and computational methods. Both theoretical and experimental results are in agreement, confirming a conformational polymorphism. The polymorph NIF–CAF Form I exhibits improved solubility and dissolution rate compared to NIF–CAF Form II, although Form II is significantly more stable than Form I. The conditions needed to obtain these polymorphs and their transition have been carefully characterized, revealing an intricate system.
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van den Ende, Joost, e Herma Cuppen. "Solid-to-solid polymorphic transitions in amino acid crystals". Acta Crystallographica Section A Foundations and Advances 70, a1 (5 agosto 2014): C1627. http://dx.doi.org/10.1107/s2053273314083727.
Testo completoAbstract (sommario):
The properties of crystals are related to their structure and therefore they can be different for different polymorphs. For example, the pharmaceutical characteristics bioavailability and shelf life can depend on the formed polymorph and its stability. We aim to understand transitions between polymorphs that occur in the solid phase, with the ultimate goal to induce or inhibit these transitions. We apply Molecular Dynamics (MD) simulations as a computational microscope to study these processes at the molecular level. Our used model systems for polymorphic behavior of molecular crystals in a pharmaceutical context are amino-acid crystals, in particular DL-norleucine. The polymorphs of DL-norleucine consist of tightly packed hydrogen-bonded bilayers with straight side chains that are weakly bound through Van-der-Waals interactions. When DL-norleucine undergoes a polymorphic transition, the bilayers shift with respect to each other. In the simulations of the enantiotropically-related beta and alpha polymorph, we observe that the transformed lattice parameters and molecular properties behave identically with temperature for both polymorphs. Consequently, the polymorphs only differ in the orientation of the molecular bilayers in the a'c' and the b'c'-plane, which explains the ease of transitions between them. Moreover, in simulations of the beta polymorph at 350 K we observe partial phase transitions which we could follow with the help of specifically designed order parameters. The transitions are exclusively occurring in the b'c'-plane. This indicates a possible transformation mechanism in which first shifts of bilayers occur in this plane, followed by shifts in the a'c'-plane. Interestingly, the region of highest flexibility of the molecule shifts from the middle to the end of the carbon chain at the highest studied temperature.
16
Du, Dan, Guo-Bin Ren, Ming-Hui Qi, Zhong Li e Xiao-Yong Xu. "Solvent-Mediated Polymorphic Transformation of Famoxadone from Form II to Form I in Several Mixed Solvent Systems". Crystals 9, n. 3 (20 marzo 2019): 161. http://dx.doi.org/10.3390/cryst9030161.
Testo completoAbstract (sommario):
This paper discloses six polymorphs of famoxadone obtained from polymorph screening, which were characterized by XRPD, DSC, and SEM. A study of solvent-mediated polymorphic transformation (SMPT) of famoxadone from the metastable Form II to the stable Form I in several mixed solvent systems at the temperature of 30 °C was also conducted. The transformation process was monitored by Process Analytical Technologies. It was confirmed that the Form II to Form I polymorphic transformation is controlled by the Form I growth process. The transformation rate constants depended linearly on the solubility difference value between Form I and Form II. Furthermore, the hydrogen-bond-donation/acceptance ability and dipolar polarizability also had an effect on the rate of solvent-mediated polymorphic transformation.
17
Aramini, Andrea, Gianluca Bianchini, Samuele Lillini, Simone Bordignon, Mara Tomassetti, Rubina Novelli, Simone Mattioli et al. "Unexpected Salt/Cocrystal Polymorphism of the Ketoprofen–Lysine System: Discovery of a New Ketoprofen–l-Lysine Salt Polymorph with Different Physicochemical and Pharmacokinetic Properties". Pharmaceuticals 14, n. 6 (10 giugno 2021): 555. http://dx.doi.org/10.3390/ph14060555.
Testo completoAbstract (sommario):
Ketoprofen–l-lysine salt (KLS) is a widely used nonsteroidal anti-inflammatory drug. Here, we studied deeply the solid-state characteristics of KLS to possibly identify new polymorphic drugs. Conducting a polymorph screening study and combining conventional techniques with solid-state nuclear magnetic resonance, we identified, for the first time, a salt/cocrystal polymorphism of the ketoprofen (KET)–lysine (LYS) system, with the cocrystal, KET–LYS polymorph 1 (P1), being representative of commercial KLS, and the salt, KET–LYS polymorph 2 (P2), being a new polymorphic form of KLS. Interestingly, in vivo pharmacokinetics showed that the salt polymorph has significantly higher absorption and, thus, different pharmacokinetics compared to commercial KLS (cocrystal), laying the basis for the development of faster-release/acting KLS formulations. Moreover, intrinsic dissolution rate (IDR) and electronic tongue analyses showed that the salt has a higher IDR, a more bitter taste, and a different sensorial kinetics compared to the cocrystal, suggesting that different coating/flavoring processes should be envisioned for the new compound. Thus, the new KLS polymorphic form with its different physicochemical and pharmacokinetic characteristics can open the way to the development of a new KET–LYS polymorph drug that can emphasize the properties of commercial KLS for the treatment of acute inflammatory and painful conditions.
18
Horvath, Ulrike E. I., e Helgard G. Raubenheimer. "A third polymorph of (2-thiazolidinethionato)(triphenylphosphine)gold(I)". Acta Crystallographica Section E Structure Reports Online 62, n. 7 (28 giugno 2006): m1644—m1645. http://dx.doi.org/10.1107/s1600536806023178.
Testo completoAbstract (sommario):
The title compound, [Au(C3H4NS2)(C18H15P)], is a third polymorphic form of a compound previously reported by Grant, Forward & Fackler Jr [Z. Kristallogr. (1996). 211, 483–484]. At 100 K, the present polymorph shows triclinic symmetry, as do the other two polymorphs.
19
Falk, Jacqueline, Detlef Hofmann e Klaus Merz. "Controlled usage of H/D exchange to circumvent concomitant polymorphs of ROY". IUCrJ 5, n. 5 (27 luglio 2018): 569–73. http://dx.doi.org/10.1107/s2052252518009995.
Testo completoAbstract (sommario):
The hypothesis that H/D exchange affects the structural formation of organic compounds in the solid state is supported by a deeper understanding of the altering polymorphism of ROY (a substance striking for its high number of polymorphic forms) through deuteration. Therefore, ROY was deuterated at its amine function, which leads to a seemingly small yet effective modification of the hydrogen-bond strength. In contrast to the crystallization of the non-deuterated ROY in methanol or ethanol, which leads to the simultaneous formation of two forms (OP and Y polymorphs), so-called concomitant polymorphs, the crystallization of d 1-ROY leads to the selective formation of the Y polymorph exclusively. The preferred aggregation behavior of the Y form of d 1-ROY is assigned to the weakening of an intramolecular hydrogen bond and a consequently strengthened intermolecular hydrogen bond after deuteration.
20
Rajendrakumar, Satyasree, Anuja Surampudi Venkata Sai Durga, Jagadeesh Babu Nanubolu e Sridhar Balasubramanian. "Two novel polymorphic forms of iron-chelating agent deferiprone". Acta Crystallographica Section C Structural Chemistry 76, n. 2 (31 gennaio 2020): 193–200. http://dx.doi.org/10.1107/s2053229620000959.
Testo completoAbstract (sommario):
Thalassemia is a genetic blood disorder requiring life-long blood transfusions. This process often results in iron overload and can be treated by an iron-chelating agent, like deferiprone (3-hydroxy-1,2-dimethylpyridin-4-one), C7H9NO2, in an oral formulation. The first crystal structure of deferiprone, (Ia), was reported in 1988 [Nelson et al. (1988). Can. J. Chem. 66, 123–131]. In the present study, two novel polymorphic forms, (Ib) and (Ic), of deferiprone were identified concomitantly with polymorph (Ia) during the crystallization experiments. Polymorph (Ia) was redetermined at low temperature for comparison of the structural features and lattice energy values with polymorphs (Ib) and (Ic). Polymorph (Ia) crystallized in the orthorhombic space group Pbca, whereas both polymorphs (Ib) and (Ic) crystallized in the monoclinic space group P21/c. The asymmetric units of (Ia) and (Ib) contain one deferiprone molecule, while polymorph (Ic) has three crystallographically independent molecules (A, B and C). All three polymorphs have similar hydrogen-bonding features, such as an R 2 2(10) dimer formed by O—H...O hydrogen bonds, an R 4 3(20) tetramer formed by C—H...O hydrogen bonds and π–π interactions, but the polymorphs differ in their molecular arrangements in the solid state and are classified as packing polymorphs. O—H...O and C—H...O hydrogen bonds lead to the formation of two-dimensional hydrogen-bonded parallel sheets which are interlinked by π–π stacking interactions. In the three-dimensional crystal packing, the deferiprone molecules were aggregated as corrugated sheets in polymorphs (Ia) and (Ic), whereas in polymorph (Ib), they were aggregated as a square-grid network. The characteristic crystalline peaks of polymorphs (Ia), (Ib) and (Ic) were established through powder X-ray diffraction analysis. The Rietveld analysis was also performed to estimate the contribution of the polymorphs to the bulk material.
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Yang, Yuxin, Jia Liu, Anna Hu, Ting Nie, Zeneng Cheng e Wenjie Liu. "A Critical Review on Engineering of d-Mannitol Crystals: Properties, Applications, and Polymorphic Control". Crystals 12, n. 8 (1 agosto 2022): 1080. http://dx.doi.org/10.3390/cryst12081080.
Testo completoAbstract (sommario):
d-mannitol is a common six-carbon sugar alcohol, which is widely used in food, chemical, pharmaceutical, and other industries. Polymorphism is defined as the ability of materials to crystallize into different crystal structures. It has been reported for a long time that d-mannitol has three polymorphs: β, δ, and α. These different polymorphs have unique physicochemical properties, thus affecting the industrial applications of d-mannitol. In this review, we firstly introduced the characteristics of different d-mannitol polymorphs, e.g., crystal structure, morphology, molecular conformational energy, stability, solubility and the analytical techniques of d-mannitol polymorphisms. Then, we described the different strategies for the preparation of d-mannitol crystals and focused on the polymorphic control of d-mannitol crystals in the products. Furthermore, the factors of the formation of different d-mannitol polymorphisms were summarized. Finally, the application of mannitol polymorphism was summarized. The purpose of this paper is to provide new ideas for a more personalized design of d-mannitol for various applications, especially as a pharmaceutical excipient. Meanwhile, the theoretical overview on polymorphic transformation of d-mannitol may shed some light on the crystal design study of other polycrystalline materials.
22
Takeguchi, Seiya, Arisa Sato, Hironori Hondoh, Mio Aoki, Hidetaka Uehara e Satoru Ueno. "Multiple β Forms of Saturated Monoacid Triacylglycerol Crystals". Molecules 25, n. 21 (2 novembre 2020): 5086. http://dx.doi.org/10.3390/molecules25215086.
Testo completoAbstract (sommario):
We have investigated the polymorphism of triacylglycerol (TAG) crystals as they affect the qualities such as shelf life, mouth feel, and texture of chocolate and other products. Saturated monoacid TAGs, like trilaurin, are considered as models for TAG crystallization; however, there is still debate about the number of their polymorphs that exist. In this study, we characterized a set of novel polymorphs, β forms of saturated monoacid TAGs, which were obtained via different pathways depending on the crystallization history, by polarized light microscopy, X-ray diffraction, and differential scanning calorimetry. Saturated monoacid TAGs were crystallized as the unstable polymorphs, the α or β’ forms first, and then they were transformed into β forms by solid–solid transformations. The β form that had transformed from β’ changed its morphology by a polymorphic transformation, while the β form made from the α form kept its spherulite morphology. The β forms obtained showed different melting points. Additional heat treatment promoted further polymorphic transformation. Four novel β forms were found for each of the saturated monoacid TAGs, trilaurin, trimyristin, tripalmitin, and tristearin. They showed similar polymorphism with the same subcell packing.
23
Paczkowska, Magdalena, Gabriela Wiergowska, Andrzej Miklaszewski, Anna Krause, Magdalena Mroczkowka, Przemysław Zalewski e Judyta Cielecka-Piontek. "The Analysis of the Physicochemical Properties of Benzocaine Polymorphs". Molecules 23, n. 7 (16 luglio 2018): 1737. http://dx.doi.org/10.3390/molecules23071737.
Testo completoAbstract (sommario):
The study was a pioneering attempt to assess the influence of the structural polymorphism (forms I, II, III) of benzocaine on its solubility, apparent solubility, and chemical stability, which are vital parameters for preformulation and formulation work. The impact of differences in the solubility of selected polymorphs of benzocaine on their permeability through artificial biological membranes (PAMPA system) was evaluated. The polymorphs of benzocaine were obtained by means of techniques commonly used for the preparation of various pharmaceutical dosage forms: ball milling, micro milling, and cryogenic grinding, which allowed for the appearance or preservation of form III, the initial conformation of benzocaine. Ball milling resulted in the conversion of form III to I, whereas micro milling yielded form II. As a result of cryogenic grinding, form III of benzocaine was preserved. The identification of all polymorphic forms of benzocaine was confirmed via X-ray powder diffraction (PXRD) supported by FT-IR spectroscopy coupled with density functional theory (DFT) calculations. The differences in solubility, dissolution, and permeability through artificial biological membranes resulting from the polymorphic forms of benzocaine were established by using chromatographic determinations. Accelerated stability tests indicated that all polymorphic forms were chemically stable at a required level.
24
Hean, Duane, Andreas Lemmerer e Joseph Michael. "Rampant Polymorphism in Pharmaceuticals: An Isoniazid Derivative". Acta Crystallographica Section A Foundations and Advances 70, a1 (5 agosto 2014): C653. http://dx.doi.org/10.1107/s2053273314093462.
Testo completoAbstract (sommario):
Investigations into the polymorphic forms of Active Pharmaceutical Ingredients (APIs) are of vital importance to drug formulations and are often kept a closely guarded secret by pharmaceutical companies. This secrecy is maintained as the nature of the polymorph could either make or break a drug formulation. Polymorphism is the ability of a solid crystalline form to exist in more than one structural arrangement. The variation in the crystalline forms often displays different mechanical, thermal, and chemical properties. These changes can remarkably influence the bioavailability, hygroscopicity, stability and other performance characteristics of the API [1]. Isoniazid, a well-known pharmaceutical, is used as a first-line treatment against Mycobacterium tuberculosis (TB) which is known to possess multiple polymorphs. Derivatives of isoniazid were developed in response to TB drug resistance. One such derivative, isonicotinic acid-(1-phenyl-ethylidenehydrazide) (IPH) [2] was found to exhibit an array of polymorphic behaviour as a result of its hydrogen bond acceptors, donors and conformational freedom along its backbone. To date only one crystal structure of IPH has been reported in the literature [3]. We have discovered and isolated an additional five novel polymorphs of IPH from various crystallization techniques, namely slow cooling, rapid evaporation, sublimation, as well as from hot-stage experiments. All of the polymorphs display hydrogen bonding through the carbonyl acceptor and hydrazide donor. However the torsion of these hydrogen bond acceptors and donors, relative to the molecular backbone, deviate due to the conformational flexibility of the molecule. Structural information of the polymorphs was obtained by SCXRD, PXRD, IR and Raman. The thermal phase relationships of these polymorphs were also investigated using DSC and HSM. Elucidating these novel polymorphs and establishing phase relationships are a key step in the design of isoniazid based pharmaceuticals.
25
Shiau, Lie-Ding. "Modelling of the Polymorph Nucleation based on Classical Nucleation Theory". Crystals 9, n. 2 (28 gennaio 2019): 69. http://dx.doi.org/10.3390/cryst9020069.
Testo completoAbstract (sommario):
To elucidate the relative nucleation rates of different polymorphs, a competitive kinetic model is developed based on classical nucleation theory to describe the time evolution of two different polymorphic cluster size distributions controlled by the association and dissociation of the solute molecules during polymorph nucleation. Although there is only one type of the solute molecules, the agglomerated solute clusters are divided into two types–A form and B form, which resemble the structures and morphologies of the different mature polymorphs and eventually lead to the formation of two polymorphic crystals. A dissociation kernel is incorporated into the proposed model to account for gradual dissolution of the solute clusters smaller than a critical nucleus size due to the thermodynamic instability. By fitting the experimental induction period data and the final measured weight fractions of eflucimibe polymorphs with the proposed model, the association and dissociation rate constants for two polymorphs are determined. The developed model is satisfactory to explain the competitive mechanism of polymorph nucleation for eflucimibe that B form dominates at higher supersaturation while A form dominates at lower supersaturation. The results also indicate that A form is more stable than B form with a transition energy of 3.1kJ/mole at 35°C.
26
Schmidtmann, Marc, Derek S. Middlemiss e Chick C. Wilson. "Isotopomeric polymorphism in a “doubly-polymorphic” multi-component molecular crystal". CrystEngComm 17, n. 28 (2015): 5273–79. http://dx.doi.org/10.1039/c5ce00123d.
Testo completoAbstract (sommario):
Isotopomeric polymorphism is observed in complexes of isonicotinamide with oxalic acid, highly unusual here in that each isotopic complex is itself polymorphic, a situation of “double polymorphism”. The four polymorphic forms exhibit different degrees of hydron transfer.
27
Chistyakov, Dmitry, e Gleb Sergeev. "The Polymorphism of Drugs: New Approaches to the Synthesis of Nanostructured Polymorphs". Pharmaceutics 12, n. 1 (1 gennaio 2020): 34. http://dx.doi.org/10.3390/pharmaceutics12010034.
Testo completoAbstract (sommario):
Among the significant problems of modern pharmacology are the low solubility and bioavailability of drugs. One way to resolve this problem is to obtain new polymorphic forms of drugs with improved physicochemical properties. Various approaches have been developed with this aim, including the preparation of co-crystals, the use of nanoparticles, or the use of compounds in the form of a salt. A promising direction in pharmacology concerns the production of new stable polymorphic structures. In this mini-review, we consider certain aspects of drug polymorphism, methods for the synthesis of polymorphs, and the stability, size, and transformation of crystalline polymorphs. Moreover, we summarize our results from several studies demonstrating the problems associated with the synthesis of new polymorphous modifications based on inert gases and cryotemperatures. The results indicate that the problems specific to drug polymorphisms have only been partly resolved, are of current interest, and require further development.
28
Mnguni, Malitsatsi J., Joseph P. Michael e Andreas Lemmerer. "Binary polymorphic cocrystals: an update on the available literature in the Cambridge Structural Database, including a new polymorph of the pharmaceutical 1:1 cocrystal theophylline–3,4-dihydroxybenzoic acid". Acta Crystallographica Section C Structural Chemistry 74, n. 6 (23 maggio 2018): 715–20. http://dx.doi.org/10.1107/s2053229618006861.
Testo completoAbstract (sommario):
An analysis and classification of the 2925 neutral binary organic cocrystals in the Cambridge Structural Database is reported, focusing specifically on those both showing polymorphism and containing an active pharmaceutical ingredient (API). The search was confined to molecules having only C, H, N, O, S and halogens atoms. It was found that 400 out of 2925 cocrystals can be classified as pharmaceutical cocrystals, containing at least one API, and that of those, 56 can be classified as being polymorphic cocrystals. In general, the total number of polymorphic cocrystal systems of any type stands at 125. In addition, a new polymorph of the pharmaceutical cocrystal theophylline–3,4-dihydroxybenzoic acid (1/1), C7H8N4O2·C7H6O4, is reported.
29
Britton, Doyle, Victor G. Young, Wayland E. Noland, Matthew J. Pinnow e Christopher M. Clark. "Four polymorphs (polytypes) of 5,6-dimethylbenzofurazan 1-oxide". Acta Crystallographica Section B Structural Science 68, n. 5 (13 settembre 2012): 536–42. http://dx.doi.org/10.1107/s0108768112037457.
Testo completoAbstract (sommario):
5,6-Dimethylbenzofurazan 1-oxide (Me2BF), C8H8N2O2, occurs in four polymorphic forms that are polytypes of each other. Each polymorph of Me2BF contains molecules disordered about pseudo-twofold axes and arranged head-to-tail in ribbons, with the ribbons forming approximately planar layers held together by weak C—H...N and C—H...O interactions. Adjacent layers interact in different ways in the different polymorphs. In addition to twinning in the individual polymorphs, four examples of allotwining, that is, oriented overgrowths between different polymorphs, were found.
30
Modec, Barbara. "Polymorphism ofmer-μ-oxalato-bis[chloridotripyridinecobalt(II)] pyridine disolvate". Acta Crystallographica Section C Crystal Structure Communications 69, n. 4 (6 marzo 2013): 340–43. http://dx.doi.org/10.1107/s010827011300499x.
Testo completoAbstract (sommario):
Single crystals of a triclinic polymorphic form ofmer-μ-oxalato-bis[chloridotripyridinecobalt(II)] pyridine disolvate, [Co2(C2O4)Cl2(C5H5N)6]·2C5H5N, have been prepared by solvothermal methods. The structure and geometric parameters strongly resemble those of the previously reported monoclinic polymorph [Bolte (2006).Acta Cryst.E62, m597–m598]. In both polymorphic forms, the dinuclear complex molecules are located on a crystallographic centre of inversion, with the CoIIcations in a distorted octahedral environment consisting of a chloride ligand, three pyridine ligands and a chelating bis-bidentate oxalate ligand. This last serves as a bridging ligand between two CoIIcations. The polymorphs differ in the mutual orientation of their pyridine ligands in the dinuclear molecules and in their intermolecular connectivity. In the triclinic polymorph, C—H...O, C—H...Cl, C—H...π and π–π interactions link the dinuclear molecules into a three-dimensional structure. Pyridine solvent molecules are attached to this structureviaweak interactions.
31
Mareczek, Lena, Carolin Riehl, Meike Harms e Stephan Reichl. "Understanding the Multidimensional Effects of Polymorphism, Particle Size and Processing for D-Mannitol Powders". Pharmaceutics 14, n. 10 (7 ottobre 2022): 2128. http://dx.doi.org/10.3390/pharmaceutics14102128.
Testo completoAbstract (sommario):
The relevance of the polymorphic form, particle size, and processing of mannitol for the mechanical properties of solid oral dosage forms was examined. Thus, particle and powder properties of spray granulated β D-mannitol, β D-mannitol, and δ D-mannitol were assessed in this study with regards to their manufacturability. D-mannitol is a commonly used excipient in pharmaceutical formulations, especially in oral solid dosage forms, and can be crystallized as three polymorphic forms, of which β is the thermodynamically most stable form and δ is a kinetically stabilized polymorph. A systematic analysis of the powders as starting materials and their respective roller compacted granules is presented to elucidate the multidimensional effects of powder and granules characteristics such as polymorphic form, particle size, and preprocessing on the resulting tablets’ mechanical properties. In direct compression and after roller compaction, δ polymorph displayed superior tableting properties over β mannitol, but was outperformed by spray granulated β mannitol. This could be primarily correlated to the higher specific surface area, leading to higher bonding area and more interparticle bonds within the tablet. Hence, it was shown that surface characteristics and preprocessing can prevail over the impact of polymorphism on manufacturability for oral solid dosage forms.
32
Guzmán-Ornelas, Milton-Omar, Marcelo Heron Petri, Mónica Vázquez-Del Mercado, Efraín Chavarría-Ávila, Fernanda-Isadora Corona-Meraz, Sandra-Luz Ruíz-Quezada, Perla-Monserrat Madrigal-Ruíz, Jorge Castro-Albarrán, Flavio Sandoval-García e Rosa-Elena Navarro-Hernández. "CCL2 Serum Levels and Adiposity Are Associated with the Polymorphic Phenotypes -2518A on CCL2 and 64ILE on CCR2 in a Mexican Population with Insulin Resistance". Journal of Diabetes Research 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/5675739.
Testo completoAbstract (sommario):
Genetic susceptibility has been described in insulin resistance (IR). Chemokine (C-C motif) ligand-2 (CCL2) is overexpressed in white adipose tissue and is the ligand of C-C motif receptor-2 (CCR2). TheCCL2G-2518A polymorphism is known to regulate gene expression, whereas the physiological effects of theCCR2Val64Ile polymorphism are unknown. The aim of the study is to investigate the relationship between these polymorphisms with soluble CCL2 levels (sCCL2), metabolic markers, and adiposity. In a cross-sectional study we included 380 Mexican-Mestizo individuals, classified with IR according to Stern criteria. Polymorphism was identified using PCR-RFLP/sequence-specific primers. Anthropometrics and metabolic markers were measured by routine methods and adipokines and sCCL2 by ELISA. The CCL2 polymorphism was associated with IR (polymorphicA+phenotype frequencies were 70.9%, 82.6%, in individuals with and without IR, resp.). Phenotype carriers CCL2 (A+) displayed lower body mass and fat indexes, insulin and HOMA-IR, and higher adiponectin levels. Individuals with IR presented higher sCCL2 compared to individuals without IR and was associated with CCR2 (Ile+) phenotype. The double-polymorphic phenotype carriers (A+/Ile+) exhibited higher sCCL2 than double-wild-type phenotype carriers (A−/Ile−). The present findings suggest that sCCL2 production possibly will be associated with the adiposity and polymorphic phenotypes ofCCL2andCCR2, in Mexican-Mestizos with IR.
33
An, Ji-Hun, Wonno Youn, Alice Kiyonga, Changjin Lim, Minho Park, Young-Ger Suh, Hyung Ryu, Jae Kim, Chun-Woong Park e Kiwon Jung. "Kinetics of the Solution-Mediated Polymorphic Transformation of the Novel l-Carnitine Orotate Polymorph, Form-II". Pharmaceutics 10, n. 4 (1 ottobre 2018): 171. http://dx.doi.org/10.3390/pharmaceutics10040171.
Testo completoAbstract (sommario):
Research studies related to the polymorphs of l-Carnitine orotate (CO), a medication used for the treatment and prevention of liver diseases, are insignificant or almost nonexistent. Accordingly, in the present study, l-Carnitine orotate (CO) was prepared for investigating CO polymorphs. Here, a reactive crystallization was induced by reacting 1g of l-Carn (1 equivalent) and 0.97 g of OA (1 equivalent) in methanol (MeOH); as a result, CO form-I and CO form-II polymorphs were obtained after 1 h and 16 h of stirring, respectively. The characterization of CO polymorphs was carried out utilizing Powder X-ray diffraction (PXRD), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and solid-state Nuclear Magnetic Resonance Spectroscopy (solid-state CP/MAS 13C-NMR). The solution-mediated polymorphic transformation (SMPT) of CO polymorphs was investigated in MeOH at controlled temperature and fixed rotational speed. The results revealed that CO form-I is a metastable polymorph while CO form-II is a stable polymorph. From the same results, it was confirmed that CO form-I was converted to CO form-II during the polymorphic phase transformation process. Moreover, it was assessed that the increase in temperature and supersaturation level significantly promotes the rate of nucleation, as well as the rate of mass transfer of CO form-II. In addition, nucleation and mass transfer equations were employed for the quantitative determination of SMPT experimental results. Lastly, it was suggested that CO form-II was more thermodynamically stable than CO form-I and that both polymorphs belong to the monotropic system.
34
Jurek, Paul, Garry E. Kiefer e Frank R. Fronczek. "Crystal structures of two polymorphic forms of DOTAM-mono-acid dihydrate". Acta Crystallographica Section C Structural Chemistry 74, n. 5 (6 aprile 2018): 542–47. http://dx.doi.org/10.1107/s2053229618004631.
Testo completoAbstract (sommario):
The structural chemistry of 2-[4,7,10-tris(carbamoylmethyl)-1,4,7,10-tetraazacyclododecan-1-yl]acetic acid dihydrate, C16H31N7O5·2H2O, is described. The macrocyclic compound, also known by the abbreviation DOTAM-mono-acid, crystallized at room temperature and was isolated concomitantly as two polymorphic forms. The structures of both polymorphs were determined at 90 K. The first polymorph crystallized as a zwitterionic dihydrate [systematic name: 4,7,10-tris(carbamoylmethyl)-1-(carboxylatomethyl)-1,4,7,10-tetraazacyclododecan-1-ium dihydrate] in the space group P21/n, with Z′ = 1. The second polymorph crystallized as a zwitterionic dihydrate in the space group P21 at 90 K, with Z′ = 2. The two independent molecules are related by a local center. In each polymorph, the zwitterion is formed between the negatively-charged carboxylate group and the ring N atom that bears the acetate pendant arm. Extensive inter- and intramolecular hydrogen bonding exists in both polymorphic structures. In polymorph 1, an intermolecular hydrogen-bonding network propagating parallel to the a direction creates an infinite chain. A second hydrogen-bonding network is observed through a water molecule of hydration in the b direction. Polymorph 2 also has two intermolecular hydrogen-bonding networks. One propagates parallel to the a direction, while the other propagates in the [\overline{1}10] direction. Increasing the temperature of polymorph 2 yields the same structure at T = 180 K, but the pseudocenter becomes exact at 299 K. The higher-temperature structure has Z′ = 1 in the space group P21/c.
35
Mapp, Lucy, Mateusz Pitak, Simon Coles e Srinivasulu Aitipamula. "Charge density studies on 1:1 co-crystals of ethenzamide and saccharin". Acta Crystallographica Section A Foundations and Advances 70, a1 (5 agosto 2014): C964. http://dx.doi.org/10.1107/s2053273314090354.
Testo completoAbstract (sommario):
The study of multi-component crystals, as well as the phenomenon of polymorphism, both have relevance to crystal engineering. Obtaining a specific polymorph is crucial as different polymorphs usually exhibit different physical and chemical properties and often the origin of this behaviour is unknown. This is especially important in the pharmaceutical industry. Herein, we present results of comparative studies of an analgesic drug, ethenzamide and its co-crystals with saccharin. The co-crystalisation of ethenzamide (2-ethoxybenzamide, EA) with saccharin (1,1-dioxo-,1,2-benzothiazol-3-one, SAC) with a 1:1 stoichiometric ratio resulted in two polymorphic forms of the co-crystal. Form I crystallises in the triclinic P-1 space group, whereas form II crystallises in monoclinic space group P21/n. Previous crystal structure analyses on forms I and II revealed that in both polymorphs the primary carboxy-amide-imide heterosynthon is the same, however the secondary level of interactions which extends the hydrogen bond network is different. Form I consists of extended linear tapes via N-H···O hydrogen bonds, whereas form II is composed of stacks of tetrameric motifs including N-H···O hydrogen bonds and C-H···O interactions. These two forms of EA-SAC can be classified as synthon polymorphs at a secondary level of hydrogen bonding [1]. In our approach an accurate, high resolution charge density distribution analysis has been carried out to obtain greater insight into the electronic structures of both types of the EA-SAC co-crystals and relate differences in electronic distribution with their polymorphic behaviour. To describe the nature and role of inter and intra-molecular interactions in a quantitative manner, the Hansen-Coppens formalism [2] and Bader's AIM theory [3] approach have been applied.
36
Guzzi, A. F., F. S. L. Oliveira, M. M. S. Amaro, P. F. Tavares-Filho e J. E. Gabriel. "In silico prediction of the functional and structural consequences of the non-synonymous single nucleotide polymorphism A122V in bovine CXC chemokine receptor type 1". Brazilian Journal of Biology 80, n. 1 (febbraio 2020): 39–46. http://dx.doi.org/10.1590/1519-6984.188655.
Testo completoAbstract (sommario):
Abstract The current study aimed to assess whether the A122V causal polymorphism promotes alterations in the functional and structural proprieties of the CXC chemokine receptor type 1 protein (CXCR1) of cattle Bos taurus by in silico analyses. Two amino acid sequences of bovine CXCR1 was selected from database UniProtKB/Swiss-Prot: a) non-polymorphic sequence (A7KWG0) with alanine (A) at position 122, and b) polymorphic sequence harboring the A122V polymorphism, substituting alanine by valine (V) at same position. CXCR1 sequences were submitted as input to different Bioinformatics’ tools to examine the effects of this polymorphism on functional and structural stabilities, to predict eventual alterations in the 3-D structural modeling, and to estimate the quality and accuracy of the predictive models. The A122V polymorphism exerted tolerable and non-deleterious effects on the polymorphic CXCR1, and the predictive structural model for polymorphic CXCR1 revealed an alpha helix spatial structure typical of a receptor transmembrane polypeptide. Although higher variations in the distances between pairs of amino acid residues at target-positions are detected in the polymorphic CXCR1 protein, more than 97% of the amino acid residues in both models were located in favored and allowed conformational regions in Ramachandran plots. Evidences has supported that the A122V polymorphism in the CXCR1 protein is associated with increased clinical mastitis incidence in dairy cows. Thus, the findings described herein prove that the replacement of the alanine by valine amino acids provokes local conformational changes in the A122V-harboring CXCR1 protein, which could directly affect its post-translational folding mechanisms and biological functionality.
37
CRARY, KARL, STEPHANIE WEIRICH e GREG MORRISETT. "Intensional polymorphism in type-erasure semantics". Journal of Functional Programming 12, n. 6 (novembre 2002): 567–600. http://dx.doi.org/10.1017/s0956796801004282.
Testo completoAbstract (sommario):
Intensional polymorphism, the ability to dispatch to different routines based on types at run time, enables a variety of advanced implementation techniques for polymorphic languages, including tag-free garbage collection, unboxed function arguments, polymorphic marshalling and attened data structures. To date, languages that support intensional polymorphism have required a type-passing (as opposed to type-erasure) interpretation where types are constructed and passed to polymorphic functions at run time. Unfortunately, type-passing suffers from a number of drawbacks: it requires duplication of run-time constructs at the term and type levels, it prevents abstraction, and it severely complicates polymorphic closure conversion. We present a type-theoretic framework that supports intensional polymorphism, but avoids many of the disadvantages of type passing. In our approach, run-time type information is represented by ordinary terms. This avoids the duplication problem, allows us to recover abstraction, and avoids complications with closure conversion. In addition, our type system provides another improvement in expressiveness; it allows unknown types to be refined in place, thereby avoiding certain beta-expansions required by other frameworks.
38
Subramanian, V., S. Gurtu, R. C. Nageswara Rao e S. N. Nigam. "Identification of DNA polymorphism in cultivated groundnut using random amplified polymorphic DNA (RAPD) assay". Genome 43, n. 4 (1 agosto 2000): 656–60. http://dx.doi.org/10.1139/g00-034.
Testo completoAbstract (sommario):
Construction of a genetic linkage map is necessary to apply marker-assisted selection tools in a crop improvement program. Except for the recent studies from two laboratories, most of the previous studies have shown little or no DNA polymorphism in cultivated groundnut (Arachis hypogaea L.). In the present study, 70 selected genotypes, representing variability for several morphological, physiological, and other characters, were studied for polymorphism employing random amplified polymorphic DNA (RAPD) assay with 48 oligonucleotide primers. Of the 48 oligonucleotide primers only 7 (14.6%) yielded polymorphic amplification products. The total number of bands from the 7 primers was 408, of which 27 were polymorphic. Detection of polymorphism in cultivated groundnut opens up the possibility of development of its molecular map by judicious selection of genotypes that show DNA polymorphism. This approach will be useful for developing marker-assisted selection tools for genetic enhancement of groundnut for desirable traits.Key words: Arachis hypogaea L., RAPD, DNA polymorphism, oligonucleotide, random primers.
39
Shishkina, Svitlana V., Anna M. Shaposhnyk, Vyacheslav N. Baumer, Natali I. Voloshchuk, Pavlo S. Bondarenko e Igor V. Ukrainets. "1-Allyl-4-hydroxy-2,2-dioxo-N-(4-methoxyphenyl)-1H-2λ6,1-benzothiazine-3-carboxamide: polymorphic transition due to grinding with the loss of the biological activity". Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 78, n. 1 (25 gennaio 2022): 70–79. http://dx.doi.org/10.1107/s2052520621013093.
Testo completoAbstract (sommario):
A study of two polymorphic forms of 1-allyl-4-hydroxy-2,2-dioxo-N-(4-methoxyphenyl)-1-2λ6,1-benzothiazine-3-carboxamide (a structural analogue of piroxicam) has revealed some regularities in the crystal structure formation due to different evaporation rates from the tested solvents. The monoclinic polymorph crystallized from ethyl acetate is formed due to a large number of very weak C—H...O and C—H...π interactions as well as one strong stacking interaction. The triclinic polymorph crystallized from N,N-dimethylformamide is formed due to a small number of weak specific interactions and a maximal number of strong stacking interactions. The stacked dimer is a complex building unit in both polymorphic structures. Further analysis showed that the monoclinic structure is layered while the triclinic one is columnar. The two polymorphic structures also differ in their biological activity (antidiuretic and analgesic). The monoclinic polymorph possesses very high biological activity while the triclinic polymorph is almost inactive. The polymorphic transition of the biologically active metastable monoclinic structure into the inactive stable triclinic one within four weeks of grinding is caused by orientational factors rather than conformational ones and is accompanied by a change in the redistribution of interaction energies in the crystal from anisotropic to more isotropic. Thus, a slow polymorphic transition after grinding results in a loss of the biological activity.
40
Sun, Mengying, Xiurong Hu, Xinbo Zhou e Jianming Gu. "Determination of minor quantities of linezolid polymorphs in a drug substance and tablet formulation by powder X-ray diffraction technique". Powder Diffraction 32, n. 2 (2 marzo 2017): 78–85. http://dx.doi.org/10.1017/s0885715617000069.
Testo completoAbstract (sommario):
Linezolid (LZD) is one of the first commercially available synthetic oxazolidinone antibiotics and is widely used for the treatment of multidrug-resistant Gram-positive bacterial infection. LZD was found to have five polymorphic forms. The most stable and commercialized polymorphs are known as forms II and IV. Trace content of form II in LZD form IV will cause to transition LZD form IV to II rapidly. Powder X-ray diffraction (PXRD) methods were evaluated for the determination of the polymorphic content of the drug substance and drug product. The estimated limit of detection values of the single peak method for LZD polymorph form II in drug substance and tablet formulation were 0.4 and 0.6%, respectively, while the limit of detection value of Rietveld Refinement (full-profile fitting) evaluated LZD polymorph form II in drug substance was 0.2%. The results clearly show that levels <1 wt.% (in active pharmaceutical ingredients) and 2 wt.% (in tablets) LZD form II in form IV can be detected and quantified by PXRD. Validation of the analytical method proved that the method is repeatable, sensitive, and accurate.
41
Kinelovskii S.A. "Similarity between shock-induced polymorphic transitions in the silica system". Technical Physics 92, n. 6 (2022): 695. http://dx.doi.org/10.21883/tp.2022.06.54415.320-21.
Testo completoAbstract (sommario):
A set of experimental data on the thermodynamic parameters of polymorphic transitions in the silica system is considered. Analysis of these parameters in dimensionless form is performed. A fundamental result of the analysis is that the thermodynamic parameters of all silica polymorphs after transitions are described by a single universal Hugoniot of polymorphic transition. It is shown that the two-shock model of polymorphic transformations proposed earlier by the author describes all the results obtained in the analysis. A joint consideration of the experimental data and model calculations leads to the conclusion that during a polymorphic transformation, the density of the new phase is determined from the condition that the elastic pressure components after the first shock and after the polymorphic transition are equal. Keywords: silica, quartz, coesite, stishovite, fused quartz, quartz ceramic, polymorphic transformation, similarity, Hugoniot.
42
Кинеловский, С. А. "Подобие ударно-волновых полиморфных переходов в системе кремнезема". Журнал технической физики 92, n. 6 (2022): 822. http://dx.doi.org/10.21883/jtf.2022.06.52511.320-21.
Testo completoAbstract (sommario):
A set of experimental data on the thermodynamic parameters of polymorphic transitions in the silica system is considered. Analysis of these parameters in dimensionless form is performed. A fundamental result of the analysis is that the thermodynamic parameters of all silica polymorphs after transitions are described by a single universal Hugoniot of polymorphic transition. It is shown that the two-shock model of polymorphic transformations proposed earlier by the author describes all the results obtained in the analysis. A joint consideration of the experimental data and model calculations leads to the conclusion that during a polymorphic transformation, the density of the new phase is determined from the condition that the elastic pressure components after the first shock and after the polymorphic transition are equal.
43
Tian, Ruizheng, Cunhuan Zhang, Yixiao Huang, Xin Guo e Maohua Chen. "A Novel Software and Method for the Efficient Development of Polymorphic SSR Loci Based on Transcriptome Data". Genes 10, n. 11 (11 novembre 2019): 917. http://dx.doi.org/10.3390/genes10110917.
Testo completoAbstract (sommario):
Traditional methods for developing polymorphic microsatellite loci without reference sequences are time-consuming and labor-intensive, and the polymorphisms of simple sequence repeat (SSR) loci developed from expressed sequence tag (EST) databases are generally poor. To address this issue, in this study, we developed a new software (PSSRdt) and established an effective method for directly obtaining polymorphism details of SSR loci by analyzing diverse transcriptome data. The new method includes three steps, raw data processing, PSSRdt application, and loci extraction and verification. To test the practicality of the method, we successfully obtained 1940 potential polymorphic SSRs from the transcript dataset combined with 44 pea aphid transcriptomes. Fifty-two SSR loci obtained by the new method were selected for validating the polymorphic characteristics by genotyping in pea aphid individuals. The results showed that over 92% of SSR loci were polymorphic and 73.1% of loci were highly polymorphic. Our new software and method provide an innovative approach to microsatellite development based on RNA-seq data, and open a new path for the rapid mining of numerous loci with polymorphism to add to the body of research on microsatellites.
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Venter, Gertruida J. S., Andreas Roodt e Reinout Meijboom. "Polymorphism in iodotris(tri-p-tolylphosphine)silver(I)". Acta Crystallographica Section B Structural Science 65, n. 2 (20 febbraio 2009): 182–88. http://dx.doi.org/10.1107/s0108768109001372.
Testo completoAbstract (sommario):
The reaction of silver(I) iodide with tri(p-tolyl)phosphine in MeCN solution in 1:3 molar ratio yields a polymorph of the complex of the formula [AgI{P(4-MeC6H4)3}3], with the Ag atom in a distorted tetrahedral environment. A polymorphic structure of this complex (a) is compared with previously published crystal structures (b), determined at different temperatures. The two polymorphs are compared using r.m.s. overlay calculations as well as half-normal probability plots.
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Hughes, John, e John Launchbury. "Projections for polymorphic first-order strictness analysis". Mathematical Structures in Computer Science 2, n. 3 (settembre 1992): 301–26. http://dx.doi.org/10.1017/s0960129500001493.
Testo completoAbstract (sommario):
We apply the categorical properties of polymorphic functions to compile-time analysis, specifically projection-based strictness analysis. First we interpret parameterised types as functors in a suitable category, and show that they preserve monics and epics. Then we define “strong” and “weak” polymorphism, the latter admitting certain projections that are not polymorphic in the usual sense. We prove that, under the right conditions, a weakly polymorphic function is characterised by a single instance. It follows that the strictness analysis of one simple instance of a polymorphic function yields results that apply to all. We show how this theory may be applied. In comparison with earlier polymorphic strictness analysis methods, ours can apply polymorphic information to a particular instance very simply. The categorical approach simplifies our proofs, enabling them to be carried out at a higher level, and making them independent of the precise form of the programming language to be analysed. The major limitation of our results is that they apply only to first-order functions.
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Xu, Zhenkang, Laura Gutierrez, Matthew Hitchens, Steve Scherer, Amy K. Sater e Dan E. Wells. "Distribution of Polymorphic and Non-Polymorphic Microsatellite Repeats in Xenopus tropicalis". Bioinformatics and Biology Insights 2 (gennaio 2008): BBI.S561. http://dx.doi.org/10.4137/bbi.s561.
Testo completoAbstract (sommario):
The results of our bioinformatics analysis have found over 91,000 di-, tri-, and tetranucleotide microsatellites in our survey of 25% of the X. tropicalis genome, suggesting there may be over 360,000 within the entire genome. Within the X. tropicalis genome, dinucleotide (78.7%) microsatellites vastly out numbered tri- and tetranucleotide microsatellites. Similarly, AT-rich repeats are overwhelmingly dominant. The four AT-only motifs (AT, AAT, AAAT, and AATT) account for 51,858 out of 91,304 microsatellites found. Individually, AT microsatellites were the most common repeat found, representing over half of all di-, tri-, and tetranucleotide microsatellites. This contrasts with data from other studies, which show that AC is the most frequent microsatellite in vertebrate genomes (Toth et al. 2000). In addition, we have determined the rate of polymorphism for 5,128 non-redundant microsatellites, embedded in unique sequences. Interestingly, this subgroup of microsatellites was determined to have significantly longer repeats than genomic microsatellites as a whole. In addition, microsatellite loci with tandem repeat lengths more than 30 bp exhibited a significantly higher degree of polymorphism than other loci. Pairwise comparisons show that tetranucleotide microsatellites have the highest polymorphic rates. In addition, AAT and ATC showed significant higher polymorphism than other trinucleotide microsatellites, while AGAT and AAAG were significantly more polymorphic than other tetranucleotide microsatellites.
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Trontelj, Zvonko, Janez Pirnat, Vojko Jazbinšek, Janko Lužnik, Stane Srčič, Zoran Lavrič, Samo Beguš, Tomaž Apih, Veselko Žagar e Janez Seliger. "Nuclear Quadrupole Resonance (NQR)—A Useful Spectroscopic Tool in Pharmacy for the Study of Polymorphism". Crystals 10, n. 6 (31 maggio 2020): 450. http://dx.doi.org/10.3390/cryst10060450.
Testo completoAbstract (sommario):
Nuclear Quadrupole Resonance (NQR) spectroscopy has been known for 70 years. It is suitable for the study of measured (poly)crystalline chemical compounds containing quadrupole nuclei (nuclei with spin I ≥ 1) where the characteristic NQR frequencies represent the fingerprints of these compounds. In several cases, 14N NQR can distinguish between the polymorphic crystalline phases of active pharmaceutical ingredients (APIs). In order to further stimulate 14N NQR studies, we review here several results of API polymorphism studies obtained in Ljubljana laboratories: (a) In sulfanilamide, a clear distinction between three known polymorphs (α, β, γ) was demonstrated. (b) In famotidine, the full spectra of all seven different nitrogen positions were measured; two polymorphs were distinguished. (c) In piroxicam, the 14N NQR data helped in confirming the new polymorphic form V. (d) The compaction pressure in the tablet production of paracetamol, which is connected with linewidth change, can be used to distinguish between producers of paracetamol. We established that paracetamol in the tablets of six different manufacturers can be identified by 14N NQR linewidth. (e) Finally, in order to get an extremely sensitive 14N NQR spectrometer, the optical detection of the 14N NQR signal is mentioned.
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Al-Hmoud, Linda, Deeb Abu Fara, Iyad Rashid, Babur Z. Chowdhry e Adnan A. Badwan. "Influence of Chitin Source and Polymorphism on Powder Compression and Compaction: Application in Drug Delivery". Molecules 25, n. 22 (12 novembre 2020): 5269. http://dx.doi.org/10.3390/molecules25225269.
Testo completoAbstract (sommario):
The objective of the research reported herein is to compare the compaction properties of three different chitin extracts from the organisms most used in the seafood industry; namely crabs, shrimps and squids. The foregoing is examined in relation to their polymorphic forms as well as compression and compaction behavior. Chitin extracted from crabs and shrimps exhibits the α-polymorphic form whilst chitin extracted from squid pins displays a β-polymorphic form. These polymorphs were characterized using FTIR, X-ray powder diffraction and scanning electron microscopy. Pore diameter and volume differ between the two polymorphic powder forms. The β form is smaller in pore diameter and volume. Scanning electron microscopy of the two polymorphic forms shows clear variation in the arrangement of chitin layers such that the α form appears more condensed due to the anti-parallel arrangement of the polymer chains. True, bulk and tapped densities of these polymorphs and their mixtures indicated poor flowability. Nevertheless, compression and compaction properties obtained by applying Heckle and Kawakita analyses indicated that both polymorphs are able to be compacted with differences in the extent of compaction. Chitin compacts, regardless of their origin, showed a very high crushing strength with very fast dissolution which makes them suitable for use as fast mouth dissolving tablets. Moreover, when different chitin powders are granulated with two model drugs, i.e., metronidazole and spiramycin they yielded high crushing strength and their dissolution profiles were in accordance with compendial requirements. It is concluded that the source of chitin extraction is as important as the polymorphic form when compression and compaction of chitin powders is carried out.
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Rico, Arantza, M. Elena Führer, Amaya Ortiz-Barredo e Jesús Murillo. "Polymerase Chain Reaction Fingerprinting of Erwinia amylovora has a Limited Phylogenetic Value but Allows the Design of Highly Specific Molecular Markers". Phytopathology® 98, n. 3 (marzo 2008): 260–69. http://dx.doi.org/10.1094/phyto-98-3-0260.
Testo completoAbstract (sommario):
Erwinia amylovora, the causal agent of fire blight, is genetically very homogeneous, and current methodologies provide insufficient or contradictory information about the probable dispersal routes of the pathogen. With the final aim to obtain specific and reliable molecular markers for different lineages of the pathogen, we studied the molecular basis of rep-polymerase chain reaction (PCR) polymorphism using seven different arbitrary primers to fingerprint 93 E. amylovora strains from different countries, including Spain. Polymorphism was very low, and was displayed by only 11 E. amylovora strains, which produced 22 polymorphic bands. Five of 11 polymorphic bands cloned contained DNA that was present in more than 85% of the strains, whereas six bands were due to DNA present exclusively in the strains producing the rep-PCR polymorphism. Also, five of the polymorphic bands were due to the possession of either the ubiquitous plasmid pEA29, of plasmid pEU30, which was exclusively found in strains from North America, or of a 35-kb cryptic plasmid, present only in 28 strains from Northern Spain. We designed primer pairs from several cloned polymorphic bands that allowed the specific identification of the strains producing the polymorphism. Our results indicate that rep-PCR is not adequate for constructing genealogies of E. amylovora, although the strategy illustrated here, as well as the designed primers, can be used effectively in epidemiological studies with this pathogen.
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Czernek, Jiří, e Jiří Brus. "Polymorphic Forms of Valinomycin Investigated by NMR Crystallography". International Journal of Molecular Sciences 21, n. 14 (11 luglio 2020): 4907. http://dx.doi.org/10.3390/ijms21144907.
Testo completoAbstract (sommario):
A dodecadepsipeptide valinomycin (VLM) has been most recently reported to be a potential anti-coronavirus drug that could be efficiently produced on a large scale. It is thus of importance to study solid-phase forms of VLM in order to be able to ensure its polymorphic purity in drug formulations. The previously available solid-state NMR (SSNMR) data are combined with the plane-wave DFT computations in the NMR crystallography framework. Structural/spectroscopical predictions (the PBE functional/GIPAW method) are obtained to characterize four polymorphs of VLM. Interactions which confer a conformational stability to VLM molecules in these crystalline forms are described in detail. The way how various structural factors affect the values of SSNMR parameters is thoroughly analyzed, and several SSNMR markers of the respective VLM polymorphs are identified. The markers are connected to hydrogen bonding effects upon the corresponding (13C/15N/1H) isotropic chemical shifts of (CO, Namid, Hamid, Hα) VLM backbone nuclei. These results are expected to be crucial for polymorph control of VLM and in probing its interactions in dosage forms.