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1.
Chembiochem ; 22(13): 2300-2305, 2021 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-33914399

RESUMO

Extracellular matrix glycoproteins play a major role in bone mineralization and modulation of osteogenesis. Among these, the intrinsically disordered protein osteopontin (OPN) is associated with the inhibition of formation, growth and proliferation of the bone mineral hydroxyapatite (HAP). Furthermore, post-translational modifications like phosphorylation can alter conformations and interaction properties of intrinsically disordered proteins (IDPs). Therefore, the actual interaction of OPN with a HAP surface on an atomic level and how this interaction is affected by phosphorylation is of great interest. Here, we study the interaction of full-length OPN on the surface of suspended HAP nanoparticles by solution NMR spectroscopy. We report the binding modes of this IDP and provide evidence for the influence of hyperphosphorylation on the binding character and an explanation for the differing roles in biomineralization. Our study moreover presents an easy and suitable option to measure interaction of nanoparticles in a stable suspension with full-length proteins.


Assuntos
Durapatita/química , Osteopontina/química , Sítios de Ligação , Espectroscopia de Ressonância Magnética , Soluções , Propriedades de Superfície
2.
J Phase Equilibria Diffus ; 39(1): 17-34, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-31997975

RESUMO

The binary bismuth-rhodium (Bi-Rh) phase diagram was reinvestigated from 23 to 60 at.% Rh with focus on the BiRh phase, applying powder-x-ray diffraction (XRD), high temperature powder-XRD, differential thermal analyses and scanning electron microscopy. The phase boundaries of the BiRh phase at 750 °C and the temperature of its peritectic decomposition were refined. In addition, the existence of the two phases Bi4Rh and Bi2Rh (in two modifications depending on temperature) could be confirmed. Most of the reaction temperatures reported in the literature could be verified within a range of about ± 10 °C. Nevertheless, a few temperatures had to be revised, such as those of the peritectic reactions L + Rh  ⇌  BiRh at 979 °C and L + BiRh  ⇌  ß-Bi2Rh at 785 °C. No evidence could be found for the presence of a stable Bi3Rh phase in well annealed samples; from the present results it must be concluded that Bi3Rh is actually metastable. On the other hand, a new orthorhombic phase BiRh0.81 was discovered which crystallizes in the MnP structure type (Pmna). It was found that the temperatures of the transition between the low-temperature modification α-Bi2Rh and its high-temperature form ß-Bi2Rh depend considerably on the presence or absence of metastable Bi3Rh and stable BiRh0.81, respectively.

3.
Inorg Chem ; 56(6): 3532-3549, 2017 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-28252952

RESUMO

As ribonucleotide reductase (RNR) plays a crucial role in nucleic acid metabolism, it is an important target for anticancer therapy. The thiosemicarbazone Triapine is an efficient R2 inhibitor, which has entered ∼20 clinical trials. Thiosemicarbazones are supposed to exert their biological effects through effectively binding transition-metal ions. In this study, six iminodiacetate-thiosemicarbazones able to form transition-metal complexes, as well as six dicopper(II) complexes, were synthesized and fully characterized by analytical, spectroscopic techniques (IR, UV-vis; 1H and 13C NMR), electrospray ionization mass spectrometry, and X-ray diffraction. The antiproliferative effects were examined in several human cancer and one noncancerous cell lines. Several of the compounds showed high cytotoxicity and marked selectivity for cancer cells. On the basis of this, and on molecular docking calculations one lead dicopper(II) complex and one thiosemicarbazone were chosen for in vitro analysis as potential R2 inhibitors. Their interaction with R2 and effect on the Fe(III)2-Y· cofactor were characterized by microscale thermophoresis, and two spectroscopic techniques, namely, electron paramagnetic resonance and UV-vis spectroscopy. Our findings suggest that several of the synthesized proligands and copper(II) complexes are effective antiproliferative agents in several cancer cell lines, targeting RNR, which deserve further investigation as potential anticancer drugs.


Assuntos
Antineoplásicos/farmacologia , Inibidores Enzimáticos/farmacologia , Compostos Organometálicos/farmacologia , Ribonucleotídeo Redutases/antagonistas & inibidores , Animais , Antineoplásicos/síntese química , Antineoplásicos/química , Apoptose/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Cobre/química , Cobre/farmacologia , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Humanos , Iminoácidos/química , Iminoácidos/farmacologia , Camundongos , Modelos Moleculares , Estrutura Molecular , Compostos Organometálicos/síntese química , Compostos Organometálicos/química , Ribonucleotídeo Redutases/isolamento & purificação , Ribonucleotídeo Redutases/metabolismo , Relação Estrutura-Atividade , Tiossemicarbazonas/química , Tiossemicarbazonas/farmacologia , Células Tumorais Cultivadas
4.
CALPHAD ; 49: 101-109, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26082567

RESUMO

Melting temperatures of Sn-Ag-Cu (SAC) alloys in the Sn-rich corner are of interest for lead-free soldering. At the same time, nanoparticle solders with depressed melting temperatures close to the Sn-Pb eutectic temperature have received increasing attention. Recently, the phase stability of nanoparticles has been the subject of plenty of theoretical and empirical investigations. In the present study, SAC nanoparticles of various sizes have been synthesized via chemical reduction and the size dependent melting point depression of these particles has been specified experimentally. The liquidus projection in the Sn-rich corner of the ternary SAC system has also been calculated as a function of particle size, based on the CALPHAD-approach. The calculated melting temperatures were compared with those obtained experimentally and with values reported in the literature, which revealed good agreement. The model also predicts that with decreasing particle size, the eutectic composition shifts towards the Sn-rich corner.

5.
CALPHAD ; 47: 56-62, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25540475

RESUMO

In the present study standard enthalpies of formation were measured by reaction and solution calorimetry at stoichiometric compositions of Cd2Pr, Cd3Pr, Cd58Pr13 and Cd6Pr. The corresponding values were determined to be -46.0, -38.8, -35.2 and -24.7 kJ/mol(at), respectively. These data together with thermodynamic data and phase diagram information from literature served as input data for a CALPHAD-type optimization of the Cd-Pr phase diagram. The complete composition range could be described precisely with the present models, both with respect to phase equilibria as well as to thermodynamic input data. The thermodynamic parameters of all intermetallic compounds were modelled following Neumann-Kopp rule. Temperature dependent contributions to the individual Gibbs energies were used for all compounds. Extended solid solubilities are well described for the low- and high-temperature modifications of Pr and also for the intermetallic compound CdPr. A quite good agreement with all viable data available from literature was found and is presented.

6.
Intermetallics (Barking) ; 32(5-6): 200-208, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27087754

RESUMO

The Ni-rich part of the ternary system Al-Ge-Ni (xNi > 50 at.%) was investigated by means of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM). The two isothermal sections at 550 °C and 700 °C were determined. Within these two sections a new ternary phase, designated as τ4, AlyGe9-yNi13±x (hP66, Ga3Ge6Ni13-type) was detected and investigated by single crystal X-ray diffraction. Another ternary low temperature phase, τ5, was found only in the isothermal section at 550 °C around the composition AlGeNi4. This compound was found to crystallise in the Co2Si type structure (oP12, Pnma). The structure was identified by Rietveld refinement of powder data. The NiAs type (B8) phase based on binary Ge3Ni5 revealed an extended solid solubility of Al and the two isotypic compounds AlNi3 and GeNi3 form a complete solid solution. Based on DTA results, six vertical sections at 55, 60, 70, 75 and 80 at.% Ni and at a constant Al:Ni ratio of 1:3 were constructed. Furthermore, the liquidus surface projection and the reaction scheme (Scheil diagram) were completed by combining our results with previous results from the Ni-poor part of the phase diagram. Six invariant ternary reactions were identified in the Ni-rich part of the system.

7.
Intermetallics (Barking) ; 39: 38-49, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27087757

RESUMO

The quaternary system Al-Fe-Si-Ti was studied in the iron-rich corner for sections at 50, 60 and 70 at.% Fe at 900 °C. Isothermal phase equilibria were investigated by a combination of optical microscopy, X-ray powder diffraction (XRD) followed by Rietveld refinement and Electron Probe Microanalysis (EPMA). Phase boundaries of the phases, in particular of the Laves phase (Fe2Ti) and of the extended phase field of A2/B2/D03, were investigated. Selected samples containing the Laves phase and the B2 phase were characterized by microhardness measurements at different compositions throughout the quaternary homogeneity range of the phases.

8.
Intermetallics (Barking) ; 28(15): 84-91, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27087753

RESUMO

The ternary phase diagram Al-Ge-Ni was investigated between 0 and 50 at.% Ni by a combination of differential thermal analysis (DTA), powder- and single-crystal X-ray diffraction (XRD), metallography and electron probe microanalysis (EPMA). Ternary phase equilibria and accurate phase compositions of the equilibrium phases were determined within two partial isothermal sections at 400 and 700 °C, respectively. The two binary intermediate phases AlNi and Al3Ni2 were found to form extended solid solutions with Ge in the ternary. Three new ternary phases were found to exist in the Ni-poor part of the phase diagram which were designated as τ1 (oC24, CoGe2-type), τ2 (at approximately Al67.5Ge18.0Ni14.5) and τ3 (cF12, CaF2-type). The ternary phases show only small homogeneity ranges. While τ1 was investigated by single crystal X-ray diffraction, τ2 and τ3 were identified from their powder diffraction pattern. Ternary phase reactions and melting behaviour were studied by means of DTA. A total number of eleven invariant reactions could be derived from these data, which are one ternary eutectic reaction, six transition reactions, three ternary peritectic reactions and one maximum. Based on the measured DTA values three vertical sections at 10, 20 and 35 at.% Ni were constructed. Additionally, all experimental results were combined to a ternary reaction scheme (Scheil diagram) and a liquidus surface projection.

9.
J Alloys Compd ; 512(1-2): 252-263, 2012 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-22287828

RESUMO

The phase equilibria and invariant reactions in the system Al-Cu-Si were investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe micro analysis (EPMA). Isothermal phase equilibria were investigated within two isothermal sections. The isothermal section at 500 °C covers the whole ternary composition range and largely confirms the findings of previous phase diagram investigations. The isothermal section at 700 °C describes phase equilibria only in the complex Cu-rich part of the phase diagram. A new ternary compound τ was found in the region between (Al,Cu)-γ(1) and (Cu,Si)-γ and its solubility range was determined. The solubility of Al in κ-CuSi was found to be extremely high at 700 °C. In contrast, no ternary solubility in the ß-phase of Cu-Al was found, although this phase is supposed to form a complete solid solution according to previous phase diagram assessments. Two isopleths, at 10 and 40 at.% Si, were investigated by means of DTA and a partial ternary reaction scheme (Scheil diagram) was constructed, based on the current work and the latest findings in the binary systems Al-Cu and Cu-Si. The current study shows that the high temperature equilibria in the Cu-rich corner are still poorly understood and additional studies in this area would be favorable.

10.
Intermetallics (Barking) ; 19(11): 1737-1746, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27103761

RESUMO

The phase equilibria and reaction temperatures in the system Al-Cu were re-investigated by a combination of optical microscopy, powder X-ray diffraction (XRD) at ambient and elevated temperature, differential thermal analysis (DTA) and scanning electron microscopy (SEM). A full description of the phase diagram is given. The phase equilibria and invariant reactions in the Cu-poor part of the phase diagram could be confirmed. The Cu-rich part shows some differences in phase equilibria and invariant reactions compared to the known phase diagram. A two phase field was found between the high temperature phase η1 and the low temperature phase η2 thus indicating a first order transition. In the ζ1/ζ2 region of the phase diagram recent findings on the thermal stability could be widely confirmed. Contrary to previous results, the two phase field between δ and γ1 is very narrow. The results of the current work indicate the absence of the high temperature ß0 phase as well as the absence of a two phase field between γ1 and γ0 suggesting a higher order transition between γ1 and γ0. The structure of γ0 (I-43m, Cu5Zn8-type) was confirmed by means of high-temperature XRD. Powder XRD was also used to determine the structure of the high temperature phase η1-Al1-δCu. The phase is orthorhombic (space group Cmmm) and the lattice parameters are a = 4.1450(1) Å, b = 12.3004(4) Å and c = 8.720(1) Å; atomic coordinates are given.

11.
Intermetallics (Barking) ; 19(10-3): 1479-1488, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27087749

RESUMO

Cu-Si phase equilibria have been investigated at compositions greater than 72 at.% Cu by X-ray diffraction, optical and electronic microscopy, electron probe microanalysis and differential thermal analysis. The general aspects of the phase equilibria already reported in literature have been substantially confirmed, but selected composition ranges and the nature of a few invariant equilibria have been modified. In particular stability ranges of the ß, δ and η phases have been slightly modified as well as temperature and nature of the invariant equilibria related to the γ â‡„ Î´ transformation. Stability of the ɛ-(Cu15Si4) phase has been especially investigated concluding that it is thermodynamically stable but kinetically inhibited by nucleation difficulties which become especially effective when samples are synthesized in very high purity conditions. Crystal structure and composition ranges of the high temperature ß and δ phases, despite difficulties by the non-quenchability of these phases, have been investigated by different methods including high temperature XRD.

12.
Intermetallics (Barking) ; 19(12): 1919-1929, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27087751

RESUMO

The Al-Fe-Si system was studied for an isothermal section at 800 °C in the Al-rich part and at 900 °C in the Fe-rich part, and for half a dozen vertical sections at 27, 35, 40, 50 and 60 at.% Fe and 5 at.% Al. Optical microscopy and powder X-ray diffraction (XRD) was used for initial sample characterization, and Electron Probe Microanalysis (EPMA) and Scanning Electron Microscopy (SEM) of the annealed samples was used to determine the exact phase compositions. Thermal reactions were studied by Differential Thermal Analysis (DTA). Our experimental results are generally in good agreement with the most recent phase diagram versions of the system Al-Fe-Si. A new ternary high-temperature phase τ12 (cF96, NiTi2-type) with the composition Al48Fe36Si16 was discovered and was structurally characterized by means of single-crystal and powder XRD. The variation of the lattice parameters of the triclinic phase τ1 with the composition Al2+x Fe3Si3-x (-0.3 < x < 1.3) was studied in detail. For the binary phase FeSi2 only small solubility of Al was found in the low-temperature modification LT-FeSi2 (릧 ) but significant solubility in the high-temperature modification HT-FeSi2 (ζα ) (8.5 at.% Al). It was found that the high-temperature modification of FeSi2 is stabilized down to much lower temperature in the ternary, confirming earlier literature suggestions on this issue. DTA results in four selected vertical sections were compared with calculated sections based on a recent CALPHAD assessment. The deviations of liquidus values are significant suggesting the need for improvement of the thermodynamic models.

13.
Acta Crystallogr C ; 66(Pt 9): i87-8, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20814091

RESUMO

The crystal structure of iron dialuminide [Corby & Black (1973). Acta Cryst. B29, 2669-2677] has been redetermined on a single crystal synthesized from the elements by arc melting. The compound crystallizes in the triclinic space group P-1 with 19 atoms per unit cell, one Fe site being on an inversion centre. The crystal structure can be described as an inclusion-plus-deformation derivative of the orthorhombic YPd(2)Si structure type.

14.
J Mater Sci ; 55(24): 10796-10810, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32624620

RESUMO

The phase diagram of the Al-Cu-Zn ternary system was re-investigated experimentally. The current study was designed to contribute to a better description of those parts of the phase diagram, which are disputed in the current scientific literature. Mutual relations in the family of ternary intermetallic phases τ with cubic, rhombohedral and modulated structure at temperatures 400 °C and 550 °C were described. The phase relation between the γ and γ' phases was studied at different temperatures. A two-phase field between γ and γ' was observed below 400 °C, while the transition appears to be second order at higher temperatures. A vertical section between γ and γ' phases in Cu-Zn and Al-Cu and four isothermal sections at 400 °C, 550 °C, 700 °C and 820 °C, respectively, were constructed.

15.
Acta Crystallogr C Struct Chem ; 74(Pt 7): 863-869, 2018 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-29973426

RESUMO

A study of the ternary Rh-Mn-Bi phase diagram revealed the existence of two new ternary bismuthides, viz. hexarhodium pentamanganese octadecabismuthide (Rh6Mn5Bi18) and rhodium manganese tribismuthide (RhMnBi3). Their crystal structures represent new structure types. Rh6Mn5Bi18, with a Wyckoff sequence a f2 g2 i5, crystallizes in the tetragonal system (space group P42/mnm; Pearson symbol tP58), and RhMnBi3, with a Wyckoff sequence a c g i q, crystallizes in the orthorhombic system (Cmmm; oS20). In the Rh6Mn5Bi18 structure, the transition metal atoms are linked into ribbon-like structural units aligned along the [001] direction, whereas planar sheets are formed in RhMnBi3. In both crystal structures, the units formed by the transition metal atoms are enveloped by Bi atoms, which themselves form a loosely bound network. The linkage results in a layer structure for RhMnBi3, while in the case of Rh6Mn5Bi18, a three-dimensional network is formed; the latter, however, contains several areas where Bi...Bi distances suggest van der Waals interactions. Both phases under discussion have analogous structural motifs.

16.
Acta Crystallogr B ; 63(Pt 4): 551-60, 2007 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-17641424

RESUMO

The ternary compound Co(6)Al(11-x)Si(6+x) (epsilon phase) was prepared from the elements by arc melting and subsequent heat treatment, and then characterized by single-crystal X-ray diffraction (XRD), electron-probe microanalysis (EPMA), differential thermal analysis (DTA) and transmission electron microscopy (TEM). This new structure type consists of planar layers with the composition [Co(6)Al(10)Si(4)], which are penetrated by perpendicular (Si-Si-Al) chains. While the layers are well described by an orthorhombic model (space group Pnma, Pearson symbol oP46), the chains exhibit doubled periodicity, thus yielding a superstructure. Two alternative ordering models (space group Cmc2(1), oC184, and space group P2(1)/c, mP92) are presented and discussed based on XRD and TEM results. The (Si-Si-Al) chains are located in pentagonal antiprismatic ;channels' which reveal the similarity of the Co(6)Al(11-x)Si(6+x) structure to Al-rich transition-metal compounds such as Co(4)Al(13), Co(2)Al(5), Fe(4)Al(13), V(7)Al(45), V(4)Al(23) and VAl(10), which also exhibit this type of pentagonal ;channels' in their crystal structures. The phase shows only a very small homogeneity range.

17.
Inorg Chem ; 44(13): 4576-85, 2005 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-15962964

RESUMO

The title compound was detected and characterized during a systematic study of the Al-rich part of the Co-Al-Si system. The crystal structure was established via single-crystal X-ray diffraction. It represents a new type of structure of intermetallic compounds (Pearson symbol mC26, space group C2/m). The homogeneity range of the phase Co4Al(7+x)Si(2-x) (0.27(3) < or = x < or = 1.05(2)) and equilibria with neighboring phases were studied by electron probe microanalysis (EPMA) and X-ray powder diffraction. The lattice parameters of the compound were found to vary between Al-poor and Al-rich composition (a = 11.949(1)-12.042(1) A, b = 3.9986(4)-4.0186(4) A, c = 7.6596(8)-7.6637(9) A, and beta = 106.581(7)-106.140(7) degrees). A partial disorder caused by the Al/Si substitution in one of the five main group element positions was found, and different ordering models yielding different Al/Si occupation motifs and different distributions of interatomic distances are discussed in detail. Chemical bonding analysis with the electron localization function (ELF) reveals a covalently bonded Al/Si network and rather ionic interactions between Co and the network.

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