Search results

1

Complex of rat transthyretin with tetraiodothyroacetic acid refined at 2.1 and 1.8 Å resolution.

100%

Muzioł T., Cody V., Luft J. R., Pangborn W., Wojtczak A.

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2001

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vol. 48

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issue 4

877-884

EN

The crystal structure of rat transthyretin (rTTR) complex with 3,5,3' ,5' -tetraiodothyroacetic acid (T4Ac) was determined at 1.8 Å resolution with low temperature synchrotron data collected at CHESS. The structure was refined to R = 0.207 and Rfree= 0.24 with the use of 8-1.8 Å data. The additional 8000 reflections from the incomplete 2.1-1.8 data shell, included in the refinement, reduced the Rfree index by 1.3%. Structure comparison with the model refined against the complete 8-2.1 Å data revealed no differences in the ligand orientation and the conformation of the polypeptide chain in the core regions. However, the high-resolution data included in the refinement improved the model in the flexible regions poorly defined with the lower resolution data. Also additional sixteen water molecules were found in the difference map calculated with the extended data. The structure revealed both forward and reverse binding of tetraiodothyroacetic acid in one binding site and two modes of forward ligand binding in the second site, with the phenolic iodine atoms occupying different sets of the halogen binding pockets.

2

Comparison of binding interactions of dibromoflavonoids with transthyretin.

100%

Muzioł T., Cody V., Wojtczak A.

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2001

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vol. 48

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issue 4

885-892

EN

The crystal structure of rat transthyretin (rTTR) complex with the dibromoflavone EMD21388 was determined to 2.3 Å resolution and refined to R = 0.203 and Rfree = 0.288. Two different orientations of EMD21388, which differ in the channel penetration by 1.6 Å, were found in the A/C binding site of rTTR. The single ligand position observed in the B/D site is intermediate between the two positions found in the A/C site. The position of the dibromoflavone in the B/D site is similar to that reported for dibromoaurone in human TTR. The bromine atoms of EMD21388 form strong interactions in the P3 and P3' pockets of rTTR. Due to the different molecular architectures of both ligands, dibromoflavone forms only one interaction with Lys-15 near the channel entrance, while direct interactions with the pair of Lys-15 were reported for dibromoaurone. The C3* methyl group of EMD21388 mediates the bridging interactions between two TTR subunits in the P2 pockets. The interactions of the O2* hydroxyl group of dibromoaurone with the Thr-119 side chain in the P3 pockets are not matched by similar interactions in EMD21388. Both these alternative interactions can explain the competitive binding of 3',5'-dibromoflavonoids to transthyretin.

3

Structure and functions of 5S rRNA.

100%

Barciszewska M. Z., Szymański M., Erdmann V. A., Barciszewski J.

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2001

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vol. 48

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issue 1

191-198

EN

The ribosome is a macromolecular assembly that is responsible for protein biosynthesis in all organisms. It is composed of two-subunit, ribonucleoprotein particles that translate the genetic material into an encoded polypeptides. The small subunit is the site of codon-anticodon interaction between the messenger RNA (mRNA) and transfer RNA (tRNA) substrates, and the large subunit catalyses peptide bond formation. The peptidyltransferase activity is fulfilled by 23S rRNA, which means that ribosome is a ribozyme. 5S rRNA is a conserved component of the large ribosomal subunit that is thought to enhance protein synthesis by stabilizing ribosome structure. This paper shortly summarises new results obtained on the structure and function of 5S rRNA.

4

Crystal structures and conformers of CyMe4-BTBP

100%

Lyczko K., Ostrowski S.

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issue 4

853-857

EN

The crystal structure of new conformation of the CyMe4-BTBP ligand (ttc) has been presented. The ttt conformer of this compound in a form of THF solvate has been also crystallized. The geometries of six possible conformations (ttt, ttc, tct, tcc, ctc and ccc) of the CyMe4-BTBP ligand have been modeled in the gas phase and in solutions (MeOH and H2O) by DFT calculations using B3LYP/6-31G(d,p) method. According to the calculations, in the three different media the conformers with trans orientation of the N atoms in the bipyridyl moiety are the most stable.

5

Position of Fe ions in MgO crystalline structure

100%

Szczerba J., Prorok R., Stoch P., Śnieżek E., Jastrzębska I.

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issue 1

143-145

EN

Magnesium oxide (MgO) is one of the most important raw materials in many branches of industry. Magnesium oxide is a popular refractory raw material because of its high refractoriness and high resistance to basic slags and environment. In many cases, use of MgO is limited by its properties, especially the presence of secondary phases like iron oxides. The amount and distribution of iron oxides can strongly influence the technological properties of MgO and depend on the manufacturing method, particularly the heat-treatment process. The aim of the study was to evaluate the influence of the heat-treatment process on amount and distribution of iron ions in a magnesium oxide lattice. The 57Fe Mössbauer effect measurements of fused and sintered magnesium oxide samples doped by the iron oxide were conducted. Investigation reveals in both cases the presence of Fe2+ as well as Fe3+ ions. Fe2+ ions occupy Mg2+ octahedral sites in the MgO lattice, whereas the Fe3+ ions are located in highly distorted octahedral coordination. The amount of Fe2+ varies from around 66% for fused samples to 30% for sintered samples.

6

Crystal structure, infrared and raman spectra of tripotassium trisaccha-rinate dihydrate, K3(C7H4NO3S)3·2H2O

100%

Jovanovski G., Kaitner B., Grupce O., Naumov P.

Open Chemistry

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2004

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vol. 2

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issue 1

254-275

EN

The crystal structure of tripotassium trisaccharinate dihydrate, K3(C7H4NO3S)3·2H2O, is triclic, space group $$P \bar 1, Z = 2$$ . It consists of three crystallographically independent potassium and saccharinato ions as well as two structurally different water molecules. Potassium coordination polyhedra are irregular, with K1 and K3 six-coordinated and the third one K2 seven-coordinated. The K−O distances range from 2.652(9) to 3.100(2) Å(mean: 2.790 Å) whereas the K−N distance is 3.025(3) Å. The water molecules W2 is disordered over three positions with occupancies of approximately 0.6, 0.2 and 0.2. The hydrogen atom (H1W1) of the ordered water molecule (O1W) is hydrogen bonded to the sulfonyl oxygen atom (O11) (R(O...O)=2.976(3) Å), whereas the other hydrogen atom (H2W1) is bifurcated to the carbonyl oxygen atom (O13) (R(O...O)=2.851(3) Å) and the disordered water molecules (O23W) (R(O...O)=3.067(12) Å). The carbonyl oxygens (O13, O23 and O33) and one of the disordered water molecules (O22W) are involved in C−H...O hydrogen bonds (R(C−H...O)=3.027(4)–3.304(9) Å). Structural characteristics of the studied compound are compared with the analogous trisodium trisaccharinate dihydrate and dipotassium sodium trisaccharinate monohydrate. Infrared and Raman spectra of the title compound have been analyzed in relation to the structure, and compared with the spectra of trisodium trisaccharinate dihydrate.

7

New thallium(III) chloride complexes with pyridine carboxylic acids: from molecular compounds to supramolecular associations

100%

Toma M., Sánchez A., Casas J., Sordo J., García-Tasende M., Castellano E., Ellena J., Berdan I.

Open Chemistry

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2003

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vol. 1

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issue 4

441-464

EN

Reactions of TlCl3 with picolinic acid (Hpic), nicotinic acid (Hnic), isonicotinic acid (Hinic) and 3-hydroxy-picolinic acid (H3hpic) afford the isolation of new chlorothallium(III) complexes. The compounds are characterized by IR, Raman and multinuclear NMR (1H,13C,205Tl). The molecular structures of [TlCl2(pic)(Hpic)]·0.5H2O (1), [TlCl2(nic)(Hnic)] (2), [TlCl(inic)2]·0.6C2H5OH (3) and [TlCl(3hpic)2(h3hpic)] (4) are determined by single-crystal X-ray diffraction. A distorted octahedral TlCl2N2O2 core containing the O,N-chelating ligands is achieved in the monomeric complex 1. The coordination polyhedron in compounds 2–4 is pentagonal bipyramidal, i.e. TlCl2NO4 in 2, and TlClN2O4 in 3 and 4, respectively. O,O′,N-Bridging ligands result in a polymer chain for 2 and a three-dimensional polymeric association in 3, while compound 4 is monomeric (O, N-and O,O-chelating ligands).

8

X-ray powder diffraction study of chromium-vanadium oxide compounds prepared by “soft chemistry” methods

100%

Pozdnyakova O., Megyeri J., Kuzmann E., Szirtes L.

Open Chemistry

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2006

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vol. 4

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issue 4

760-772

EN

A novel aqueous method was used to synthesise mixed chromium-vanadium oxide hydrates with various chromium content, via the reaction of peroxo-polyacids of chromium and vanadium. The resulting materials are gelatinous. The dehydration of the gels result in a brown coloured amorphous powder. Depending on the chromium content, the compounds have a different characteristic crystallisation temperature upon the further heating. The crystalline compounds, except for the low chromium ones, go on a phase transition and decompose with increasing temperature. By refining the XRPD measurement data of the compounds, the type and parameters of the unit cells were determined. The experimental data were in concordance with the calculated values, using the PWC code. The lattice parameters and the crystalline structure were changed with the variation of chromium content.

9

X-Ray Diffraction Study of Bismuth Layer-Structured Multiferroic Ceramics

100%

Lisińska-Czekaj A., Czekaj D., Garbarz-Glos B., Bąk W., Kuźniarska-Biernacka I., Lisińska-Czekaj A., Czekaj D., Garbarz-Glos B., Bąk W., Kuźniarska-Biernacka I.

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10

Crystal structure and spectral characterization of dimethylthallium (III) complexes with 2-mercaptonicotinic acid and esters

88%

Toma M., Sánchez A., García-Tasende M., Casas J., Sordo J., Castellano E., Ellena J.

Open Chemistry

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2004

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vol. 2

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issue 3

534-552

EN

Synthesis, spectral properties and crystal structure of dimethylthallium(III) complexes with 2-mercaptonicotinic acid (2mna), 2-mercapto-methyl-nicotinate (2mmn), 2-mercapto-ethyl-nicotinate (2men) and 2-mercapto-isopropyl-nicotinate (2min) are reported. The compounds were characterized using IR, multinuclear NMR (1H,13C,205Tl) and mass spectrometry (electrospray, ES-API). The molecular structures of [TlMe2(2mna)]·H2O, (1), [TlMe2(2mmn)], (2), [TlMe2(2men)], (3) and [TlMe2(2min)], (4) were determined by the single-crystal X-ray diffraction. In 1, the monodeprotonate O,S-bidentate ligand chelates one dimethylthallium (III) unit and simultaneously bridges (O and S) between two of these organometallic units. The Tl-O1′ and Tl-S″ interactions are leading to polymeric chain linked in a three-dimensional network by the hydrogen bonds formed between the water molecule and the oxygen O (2) atom of the acid. The thallium atom is in a distorted octahedral environment with a [TlC2O2S2] kernel. Compounds 2, 3 and 4 are similar, in all the cases already mentioned the ligand is NH deprotonated and is strongly coordinated to two dimethylthallium (III) units through the N and S atoms. Two additional weak interactions with the O and S atoms lead to a [TlC2NOS2] kernel for the metal atom, in which the coordination polyhedron is a very distorted octahedron with the methyl groups occupying the apical positions.

11

A Novel Theoretical Study of Elastic and Electronic Properties of M₂CdC (M = Zr, Hf, and Ta) MAX Phases

75%

Mebrek M., Mokaddem A., Doumi B., Yakoubi A., Mir A.

Acta Physica Polonica A

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2018

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vol. 133

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issue 1

76-81

EN

In this study, we have investigated the structural, electronic, and elastic properties of the M₂CdC (M = Ta, Zr, and Hf) MAX phases, using the first-principle methods based on the density functional theory. The calculated formation energies revealed that these compounds are thermodynamically stable in the hexagonal MAX phase. The stability is confirmed by the elastic constants and the conditions of mechanical stability criterion. Also, we have determined the bulk and shear modules of the Young modulus and the Poisson coefficient. The band structures indicate that the three materials are electrically conductive. The chemical bond in M₂CdC is covalent-ionic in nature with the presence of metallic character. For the density of states the hybridization peak between M d and C p occurs in the lower energy range. We have found that there is no gap for these materials due to the existence of a maximum peak of DOS around Fermi level.

12

Crystal structure and spectroscopic properties of 4-acetaminopyridine and its protonated form

63%

Koleva B., Nikolova R., Tchapkanov A., Kolev T., Mayer-Figge H., Spiteller M., Sheldrick W.

Polish Journal of Chemical Technology

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2009

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vol. 11

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issue 3

35-40

EN

4-Acetaminopyridine dihydrate and its protonated form, stabilized as the hydrochloride salt have been synthesized and spectroscopic elucidated in solution and in the solid-state by means of the inear-polarized solid state IR-spectroscopy (IR-LD), UV-spectroscopy, TGA, DSC, and the positive and negative ESI MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and the electronic spectra. The spectroscopic and theoretical data are compared with the structure of the first compound obtained by single crystal X-ray diffraction. The effect of Npy protonation on the optical and magnetic properties of a 4-acetaminopyridine is discussed.

Refine search results

Complex of rat transthyretin with tetraiodothyroacetic acid refined at 2.1 and 1.8 Å resolution.

Comparison of binding interactions of dibromoflavonoids with transthyretin.

Structure and functions of 5S rRNA.

Crystal structures and conformers of CyMe4-BTBP

Position of Fe ions in MgO crystalline structure

Crystal structure, infrared and raman spectra of tripotassium trisaccha-rinate dihydrate, K3(C7H4NO3S)3·2H2O

New thallium(III) chloride complexes with pyridine carboxylic acids: from molecular compounds to supramolecular associations

X-ray powder diffraction study of chromium-vanadium oxide compounds prepared by “soft chemistry” methods

X-Ray Diffraction Study of Bismuth Layer-Structured Multiferroic Ceramics

Crystal structure and spectral characterization of dimethylthallium (III) complexes with 2-mercaptonicotinic acid and esters

A Novel Theoretical Study of Elastic and Electronic Properties of M₂CdC (M = Zr, Hf, and Ta) MAX Phases

Crystal structure and spectroscopic properties of 4-acetaminopyridine and its protonated form