Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 33
Filtrar
Más filtros

Banco de datos
Tipo del documento
Intervalo de año de publicación
1.
Small ; 20(29): e2310352, 2024 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-38368257

RESUMEN

Extensive research has focused on developing wide-bandgap metal compound-based passivating contacts as alternatives to conventional doped-silicon-layer-based passivating contacts to mitigate parasitic absorption losses in crystalline silicon (c-Si) solar cells. Herein, thermally-evaporated aluminum halides (AlX)-based electron-selective passivating contacts for c-Si solar cells are investigated. A low contact resistivity of 60.5 and 38.4 mΩ cm2 is obtained on the AlClx/n-type c-Si (n-Si) and AlFx/n-Si heterocontacts, respectively, thanks to the low work function of AlX. Power conversion efficiencies (PCEs) of 19.1% and 19.6% are achieved on proof-of-concept n-Si solar cells featuring a full-area AlClx/Al and AlFx/Al passivating contact, respectively. By further implementing an ultrathin SiO2 passivation interlayer and a pre-annealing treatment, the electron selectivity (especially the surface passivation) of AlX is significantly enhanced. Accordingly, a remarkable PCE of 21% is achieved on n-Si solar cells featuring a full-area SiO2/AlFx/Al rear contact. AlFx-based electron-selective passivating contacts exhibit good thermal stability up to ≈400 °C and better long-term environmental stability. This work demonstrates the potential of AlFx-based electron-selective passivating contact for solar cells.

2.
Small ; 19(45): e2304478, 2023 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-37420322

RESUMEN

Aluminum nanocrystals are emerging as a promising alternative to silver and gold for various applications ranging from plasmonic functionalities to photocatalysis and as energetic materials. Such nanocrystals often exhibit an inherent surface oxidation layer, as aluminum is highly reactive. Its controlled removal is challenging but required, as it can hinder the properties of the encaged metal. Herein, two wet-chemical colloidal approaches toward the surface coating of Al nanocrystals, which afford control over the surface chemistry of the nanocrystals and the oxide thickness, are presented. The first approach utilizes oleic acid as a surface ligand by its addition toward the end of the Al nanocrystals synthesis, and the second approach is the post-synthesis treatment of Al nanocrystals with NOBF4 , in a "wet" colloidal-based approach, which is found to etch and fluorinate the surface oxides. As surface chemistry is an important handle for controlling materials' properties, this research paves a path for manipulating Al nanocrystals while promoting their utilization in diverse applications.

3.
Bioorg Med Chem ; 60: 116687, 2022 04 15.
Artículo en Inglés | MEDLINE | ID: mdl-35278818

RESUMEN

The Al18F labeling method is a relatively new approach that allows radiofluorination of biomolecules such as peptides and proteins in a one-step procedure and in an aqueous solution. However, instability of the complex of [AlF]2+ with hexadentate chelator NOTA may attribute to the disassociation of free 18F- and [Al18F]2+ and accumulation in bone. In this study, we designed and synthesized a new bifunctional pentadentate AlF-chelator p-SCN-PhPr-NODA as well as its nitro form p-NO2-PhPr-NODA. Chelator p-NO2-PhPr-NODA exhibited increased Al (III) complexation kinetics determined by AA III complexation kinetic studies and stronger coordination ability towards [AlF]2+ according to DFT calculation studies in comparison with hexadentate chelator NOTA. As a proof of concept, bifunctional chelator p-SCN-PhPr-NODA was furthermore conjugated to a PSMA targeting moiety Glu-urea-Lys to form NODA-PrPh-GuL. The conjugated peptide showed acceptable radiochemical yield (12.5-16.4%) and efficiency with an excellent radiochemical purity (∼100% after SPE purification) in Al18F labeling. The labeled peptide exhibited good in vitro stability and significant specificity for PSMA. Biodistribution study and MicroPET scan in healthy Kun Ming mice with the labeled peptide were performed and demonstrated excellent in vivo stability of Al18F-labeled construct. In general, the successful application of the new bifunctional chelator in labeling dipeptide Glu-urea-Lys with Al18F could facilitate its possibility in conjugating with other peptides for PET imaging with enhanced in vivo stability, thus providing better in vivo performances.


Asunto(s)
Radioisótopos de Flúor , Dióxido de Nitrógeno , Animales , Línea Celular Tumoral , Quelantes/química , Radioisótopos de Flúor/química , Marcaje Isotópico/métodos , Cinética , Ligandos , Ratones , Péptidos/química , Tomografía de Emisión de Positrones/métodos , Distribución Tisular , Urea
4.
J Labelled Comp Radiopharm ; 64(8): 346-352, 2021 06 30.
Artículo en Inglés | MEDLINE | ID: mdl-34050679

RESUMEN

We report herein an efficient and fully automated protocol for the radiosynthesis of [18 F]FAPI-74, a new positron emission tomography (PET) radiopharmaceutical for in vivo detection of the fibroblast activation protein. [18 F]FAPI-74 was synthesized via a rapid [18 F]aluminum fluoride coordination reaction, which was first developed on the flexible GE TRACERLab FX2N (FXN) platform and later translated to the cassette-based module Trasis AllInOne (AIO). The results obtained with both modules were comparable in terms of yield and reproducibility. Automation of [18 F]FAPI-74 radiosynthesis on the FXN was carried out in 35 min with a radiochemical yield (RCY) of 18.5 ± 2.5% (n = 5, relative to starting [18 F]fluoride). Method transfer to the AIO platform following minor optimizations allowed for the production of [18 F]FAPI-74 in an isolated RCY of 20 ± 2.5% [n = 3] with an overall synthesis time of 40 min. The radiochemical purity was greater than 95% for [18 F]FAPI-74, obtained from both modules. Overall, the protocol reliably provides a sterile and pyrogen-free good manufacturing practice (GMP) compliant product of [18 F]FAPI-74 suitable for clinical PET imaging.


Asunto(s)
Compuestos de Aluminio , Fluoruros
5.
Beilstein J Org Chem ; 16: 2623-2635, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33133293

RESUMEN

The hydrofluorocarbon 245 isomers, 1,1,1,3,3-pentafluoropropane, 1,1,1,2,2- pentafluoropropane, and 1,1,1,2,3-pentafluoropropane (HFC-245fa, HFC-245cb, and HFC-245eb) were activated through C-F bond activations using aluminium chlorofluoride (ACF) as a catalyst. The addition of the hydrogen source Et3SiH is necessary for the activation of the secondary and tertiary C-F bonds. Multiple C-F bond activations such as hydrodefluorinations and dehydrofluorinations were observed, followed by hydroarylation and Friedel-Crafts-type reactions under mild conditions.

6.
Molecules ; 24(16)2019 Aug 07.
Artículo en Inglés | MEDLINE | ID: mdl-31394799

RESUMEN

Due to its ideal physical properties, fluorine-18 turns out to be a key radionuclide for positron emission tomography (PET) imaging, for both preclinical and clinical applications. However, usual biomolecules radiofluorination procedures require the formation of covalent bonds with fluorinated prosthetic groups. This drawback makes radiofluorination impractical for routine radiolabeling, gallium-68 appearing to be much more convenient for the labeling of chelator-bearing PET probes. In response to this limitation, a recent expansion of the 18F chemical toolbox gave aluminum [18F]fluoride chemistry a real prominence since the late 2000s. This approach is based on the formation of an [18F][AlF]2+ cation, complexed with a 9-membered cyclic chelator such as NOTA, NODA or their analogs. Allowing a one-step radiofluorination in an aqueous medium, this technique combines fluorine-18 and non-covalent radiolabeling with the advantage of being very easy to implement. Since its first reports, [18F]AlF radiolabeling approach has been applied to a wide variety of potential PET imaging vectors, whether of peptidic, proteic, or small molecule structure. Most of these [18F]AlF-labeled tracers showed promising preclinical results and have reached the clinical evaluation stage for some of them. The aim of this report is to provide a comprehensive overview of [18F]AlF labeling applications through a description of the various [18F]AlF-labeled conjugates, from their radiosynthesis to their evaluation as PET imaging agents.


Asunto(s)
Aluminio/química , Quelantes , Radioisótopos de Flúor/química , Radioisótopos de Galio/química , Marcaje Isotópico , Animales , Biomarcadores , Quelantes/química , Compuestos de Flúor/química , Humanos , Imagen Molecular/métodos , Estructura Molecular , Péptidos/química , Tomografía de Emisión de Positrones/métodos , Conformación Proteica
7.
Molecules ; 23(2)2018 Jan 31.
Artículo en Inglés | MEDLINE | ID: mdl-29385091

RESUMEN

Amino acid residues 283-297 from sialic acid-binding immunoglobulin-like lectin 9 (Siglec-9) form a cyclic peptide ligand targeting vascular adhesion protein-1 (VAP-1). VAP-1 is associated with the transfer of leukocytes from blood to tissues upon inflammation. Therefore, analogs of Siglec-9 peptide are good candidates for visualizing inflammation non-invasively using positron emission tomography (PET). Gallium-68-labeled 1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid (DOTA)-conjugated Siglec-9 has been evaluated extensively for this purpose. Here, we explored two alternative strategies for radiolabeling Siglec-9 peptide using a 1,4,7-triazacyclononane-triacetic acid (NOTA)-chelator to bind [68Ga]Ga or [18F]AlF. The radioligands were evaluated by in vivo PET imaging and ex vivo γ-counting of turpentine-induced sterile skin/muscle inflammation in Sprague-Dawley rats. Both tracers showed clear accumulation in the inflamed tissues. The whole-body biodistribution patterns of the tracers were similar.


Asunto(s)
Antígenos CD , Radioisótopos de Flúor , Isótopos de Galio , Compuestos Heterocíclicos , Marcaje Isotópico/métodos , Tomografía de Emisión de Positrones/métodos , Lectinas Similares a la Inmunoglobulina de Unión a Ácido Siálico , Animales , Antígenos CD/química , Antígenos CD/farmacología , Compuestos Heterocíclicos/química , Compuestos Heterocíclicos/farmacología , Compuestos Heterocíclicos con 1 Anillo , Ratas , Ratas Sprague-Dawley , Lectinas Similares a la Inmunoglobulina de Unión a Ácido Siálico/química , Lectinas Similares a la Inmunoglobulina de Unión a Ácido Siálico/farmacología
8.
Angew Chem Int Ed Engl ; 56(45): 14227-14231, 2017 11 06.
Artículo en Inglés | MEDLINE | ID: mdl-28925536

RESUMEN

The solution structure of AlMe2 F and its reactivity with a prototypical ansa-metallocene have been investigated by advanced NMR techniques, in an attempt to indirectly shed some light on the structure and working principles of methylalumoxane (MAO) mixtures in olefin polymerization. In solution, AlMe2 F gives rise to a complex equilibrium of oligomeric species, including a heterocubane [(Me2 Al)4 F4 ] tetramer, resembling the behavior of MAO. This complex mixture reacts with (ETH)ZrMe2 (ETH=rac-[ethylenebis(4,5,6,7-tetrahydro-1-indenyl)]) to afford [(ETH)ZrMeδ+ (µ-F)(AlMe2 F)n AlMe3δ- ] inner-sphere ion pairs through successive insertions/deinsertions of AlMe2 F units into the Zr⋅⋅⋅(µ-F) bond.

9.
Luminescence ; 30(6): 878-82, 2015 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-25620581

RESUMEN

Results on optically stimulated luminescence (OSL) in LiCaAlF6:Eu(2+) are reported. Continuous wave OSL signal as recorded using blue (470 nm) stimulation was found to be ~31% that of standard phosphor lithium magnesium phosphate. The rate of OSL depletion for standard phosphor lithium magnesium phosphate is only three times less as compared with that of LiCaAlF6:Eu(2+). Strong photoluminescence (PL) in the near ultraviolet region is observed for LiCaAlF6:Eu(2+) with the characteristic Eu(2+) emission at 369 nm for 254 nm excitation. The thermoluminescence (TL) glow peak for LiCaAlF6:Eu(2+) was observed at around 180°C. The glow peak was about six times more intense compared with the dosimetric peak of the well known thermoluminescence dosimetric (TLD) phosphor LiF-TLD 100. Thus this phosphor deserves much more attention than it has received until now and may be useful as a dosimetric material in radiation dosimetry.


Asunto(s)
Europio/química , Sustancias Luminiscentes/química , Partículas beta , Litio/química , Luminiscencia , Sustancias Luminiscentes/efectos de la radiación , Estroncio/química , Dosimetría Termoluminiscente/métodos , Difracción de Rayos X
10.
J Labelled Comp Radiopharm ; 57(4): 219-23, 2014 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-24408125

RESUMEN

Radiolabeled receptor-binding peptides and proteins have emerged as an important class of radiopharmaceuticals that have changed radionuclide imaging in clinical practice. Many strategies have been developed to radiolabel these peptide and proteins with fluorine-18. The majority of these methods is time-consuming and suffer from low yields. A more straightforward approach was proposed a few years ago, based on the chelation of aluminum fluoride by (1,4,7-triazacyclononane-1,4,7-triacetic acid). This approach has been optimized with regard to labeling yield and specific activity. In addition, crystallography studies have led to the design of optimized chelators. Subsequently, the Al(18) F technology is finding widespread use in labeling peptides and proteins. Various hapten peptides for pre-targeting studies have been labeled with Al(18) F, as well as αv ß3 integrin-binding peptides have been studied, and also larger peptides, such as exendin-4 and affibody molecules and heat-labile proteins have been labeled with Al(18) F. Here, we summarize the development, optimization, and applications of the Al(18) F labeling technology.


Asunto(s)
Compuestos de Aluminio/química , Fluoruros/química , Radioisótopos de Flúor , Marcaje Isotópico/métodos , Péptidos/química , Proteínas/química , Animales , Compuestos Heterocíclicos/química , Compuestos Heterocíclicos con 1 Anillo
11.
Chempluschem ; : e202400578, 2024 Oct 04.
Artículo en Inglés | MEDLINE | ID: mdl-39363715

RESUMEN

The Protein Data Bank (PDB) was scrutinized for the presence of noncovalent O···Al Triel Bonding (TrB) interactions, involving protein residues (e.g. GLU and GLN), adenosine/guanine diphosphate moieties (ADP and GDP), water molecules and two aluminum fluorides (AlF3 and AlF4-). The results were statistically analyzed, revealing a vast number of O···Al contacts in the active sites of phosphoryl transfer enzymes, with a marked directionality towards the Al σ-/π-hole. The physical nature of the TrBs studied herein was analyzed using Molecular Electrostatic Potential (MEP) maps, the Quantum Theory of Atoms in Molecules (QTAIM), the Non Covalent Interaction plot (NCIplot) visual index and Natural Bonding Orbital (NBO) studies. As far as our knowledge extends, it is the first time that O···Al TrBs are analyzed within a biological context, participating in protein trapping mechanisms related to phosphoryl transfer enzymes. Moreover, since they are involved in the stabilization of aluminum fluorides inside the protein's active site, we believe the results reported herein will be valuable for those scientists working in supramolecular chemistry, catalysis and rational drug design.

12.
Structure ; 32(10): 1834-1846.e3, 2024 Oct 03.
Artículo en Inglés | MEDLINE | ID: mdl-39106858

RESUMEN

Enzymes facilitating the transfer of phosphate groups constitute the most extensive protein families across all kingdoms of life. They make up approximately 10% of the proteins found in the human genome. Understanding the mechanisms by which enzymes catalyze these reactions is essential in characterizing the processes they regulate. Metal fluorides can be used as multifunctional tools to study these enzymes. These ionic species bear the same charge as phosphate and the transferring phosphoryl group and, in addition, allow the enzyme to be trapped in catalytically important states with spectroscopically sensitive atoms interacting directly with active site residues. The ionic nature of these phosphate surrogates also allows their removal and replacement with other analogs. Here, we describe the best practices to obtain these complexes, their use in NMR, X-ray crystallography, cryo-EM, and SAXS and describe a new metal fluoride, scandium tetrafluoride, which has significant anomalous signal using soft X-rays.


Asunto(s)
Fluoruros , Fluoruros/química , Fluoruros/metabolismo , Cristalografía por Rayos X , Microscopía por Crioelectrón , Modelos Moleculares , Dominio Catalítico , Humanos , Dispersión del Ángulo Pequeño , Difracción de Rayos X , Fosfotransferasas/metabolismo , Fosfotransferasas/química
13.
Environ Sci Pollut Res Int ; 31(18): 27388-27402, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38512573

RESUMEN

In aluminum electrolysis, the iron-rich cover material is formed on the cover material and the steel rod connecting the carbon anode. Due to the high iron content in the iron-rich cover material, it differs from traditional cover material and thus requires harmless recycling and treatment. A process was proposed and used in this study to recovery F, Al, and Fe elements from the iron-rich cover material. This process involved aluminum sulfate solution leaching for fluorine recovery and alkali-acid synergistic leaching for α-Al2O3 and Fe2O3 recovery were obtained. The optimal leaching rates for F, Na, Ca, Fe, and Si were 93.92, 96.25, 94.53, 4.48, and 28.87%, respectively. The leaching solution and leaching residue were obtained. The leaching solution was neutralized to obtain the aluminum hydroxide fluoride hydrate (AHFH, AlF1.5(OH)1.5·(H2O)0.375). AHFH was calcined to form a mixture of AlF3 and Al2O3 with a purity of 96.14%. The overall recovery rate of F in the entire process was 92.36%. Additionally, the leaching residue was sequentially leached with alkali and acid to obtain the acid leach residue α-Al2O3. The pH of the acid-leached solution was adjusted to produce a black-brown precipitate, which was converted to Fe2O3 under a high-temperature calcination, and the recovery rate of Fe in the whole process was 94.54%. Therefore, this study provides a new method for recovering F, Al, and Fe in iron-rich cover material, enabling the utilization of aluminum hazardous waste sources.


Asunto(s)
Óxido de Aluminio , Aluminio , Electrólisis , Compuestos Férricos , Fluoruros , Compuestos Férricos/química , Aluminio/química , Fluoruros/química , Óxido de Aluminio/química , Hierro/química , Compuestos de Aluminio/química , Reciclaje
14.
J Inorg Biochem ; 246: 112267, 2023 09.
Artículo en Inglés | MEDLINE | ID: mdl-37329775

RESUMEN

Theranostic and personalized medicine are blooming strategies to improve oncologic patients' health care and facilitate early treatment. While 18F-radiochemistry for theranostic application is attractive due to its imaging properties, combining diagnosis by positron emission tomography (PET) via aluminum-fluoride-18 and ß- therapy with lutetium-177 is relevant. Nevertheless, it requires the use of two different chelating agents, which are NOTA and DOTA for aluminum-fluoride-18 and lutetium-177 radiolabeling, respectively. To overcome this issue, we propose herein the synthesis of a new hybrid chelating agent named NO2A-AHM, which can be labeled with different types of emitters (ß+, ß- and γ) using the mismatched Al18F/177Lu pair. NO2A-AHM, is based on a hydrazine moiety functionalized by a NOTA cycle, a chelating arm, and a linker with a maleimide function. This design is chosen to increase the flexibility and allow the formation of 5 up to 7 coordination bonds with metal ions. Moreover, this agent can be coupled to targeting moieties containing a thiol function, such as peptides, to increase selectivity towards specific cancer cells. Experimental complexation and computational chemistry studies are performed to confirm the capacity of our chelating agent to label both aluminum-fluoride and lutetium using molecular modeling approaches at Density Functional Theory (DFT) level. The proof of concept of the ability of NO2A-AHM to complex both aluminum-fluoride-18, for PET imaging applications, and lutetium-177 for radiotherapy has shown encouraging results which is prominent for the development of a fully consistent theranostic approach.


Asunto(s)
Quelantes , Fluoruros , Humanos , Quelantes/química , Aluminio/química , Tomografía de Emisión de Positrones , Línea Celular Tumoral
15.
ISA Trans ; 133: 285-301, 2023 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-35811160

RESUMEN

The aluminum fluoride (AF) addition in aluminum electrolysis process (AEP) can directly influence the current efficiency, energy consumption, and stability of the process. This paper proposes an optimization scheme for AF addition based on pruned sparse fuzzy neural network (PSFNN), aiming at providing an optimal AF addition for aluminum electrolysis cell under normal superheat degree (SD) condition. Firstly, a Gaussian mixture model (GMM) is introduced to identify SD conditions in which the operating modes of AEP are unknown. Then, PSFNN is proposed to establish the AF addition model under normal SD condition identified by GMM. Specifically, a sparse regularization term is designed in loss function of PSFNN to extract the sparse representation from nonlinear process data. A structure optimization strategy based on enhanced optimal brain surgeon (EOBS) algorithm is proposed to prune redundant neurons in the rule layer. Mini-batch gradient descent and AdaBound optimizer are then introduced to optimize the parameters of PSFNN. Finally, the performance is confirmed on the simulated Tennessee Eastman process (TEP) and real-world AEP. Experimental results demonstrate that the proposed scheme provides a satisfactory performance.

16.
Biomolecules ; 12(10)2022 09 22.
Artículo en Inglés | MEDLINE | ID: mdl-36291554

RESUMEN

The P-loop fold nucleoside triphosphate (NTP) hydrolases (also known as Walker NTPases) function as ATPases, GTPases, and ATP synthases, are often of medical importance, and represent one of the largest and evolutionarily oldest families of enzymes. There is still no consensus on their catalytic mechanism. To clarify this, we performed the first comparative structural analysis of more than 3100 structures of P-loop NTPases that contain bound substrate Mg-NTPs or their analogues. We proceeded on the assumption that structural features common to these P-loop NTPases may be essential for catalysis. Our results are presented in two articles. Here, in the first, we consider the structural elements that stimulate hydrolysis. Upon interaction of P-loop NTPases with their cognate activating partners (RNA/DNA/protein domains), specific stimulatory moieties, usually Arg or Lys residues, are inserted into the catalytic site and initiate the cleavage of gamma phosphate. By analyzing a plethora of structures, we found that the only shared feature was the mechanistic interaction of stimulators with the oxygen atoms of gamma-phosphate group, capable of causing its rotation. One of the oxygen atoms of gamma phosphate coordinates the cofactor Mg ion. The rotation must pull this oxygen atom away from the Mg ion. This rearrangement should affect the properties of the other Mg ligands and may initiate hydrolysis according to the mechanism elaborated in the second article.


Asunto(s)
Dominio AAA , Nucleósido-Trifosfatasa , Nucleósido-Trifosfatasa/química , Nucleósido-Trifosfatasa/metabolismo , Hidrólisis , Nucleósidos , Adenosina Trifosfatasas/metabolismo , GTP Fosfohidrolasas/metabolismo , Adenosina Trifosfato/metabolismo , ADN , ARN , Fosfatos/metabolismo , Proteínas AAA/metabolismo , Oxígeno/metabolismo
17.
FEBS J ; 288(2): 582-599, 2021 01.
Artículo en Inglés | MEDLINE | ID: mdl-32352209

RESUMEN

Human guanylate-binding protein 1 (hGBP-1) shows a dimer-induced acceleration of the GTPase activity yielding GDP as well as GMP. While the head-to-head dimerization of the large GTPase (LG) domain is well understood, the role of the rest of the protein, particularly of the GTPase effector domain (GED), in dimerization and GTP hydrolysis is still obscure. In this study, with truncations and point mutations on hGBP-1 and by means of biochemical and biophysical methods, we demonstrate that the intramolecular communication between the LG domain and the GED (LG:GED) is crucial for protein dimerization and dimer-stimulated GTP hydrolysis. In the course of GTP binding and γ-phosphate cleavage, conformational changes within hGBP-1 are controlled by a chain of amino acids ranging from the region near the nucleotide-binding pocket to the distant LG:GED interface and lead to the release of the GED from the LG domain. This opening of the structure allows the protein to form GED:GED contacts within the dimer, in addition to the established LG:LG interface. After releasing the cleaved γ-phosphate, the dimer either dissociates yielding GDP as the final product or it stays dimeric to further cleave the ß-phosphate yielding GMP. The second phosphate cleavage step, that is, the formation of GMP, is even more strongly coupled to structural changes and thus more sensitive to structural restraints imposed by the GED. Altogether, we depict a comprehensive mechanism of GTP hydrolysis catalyzed by hGBP-1, which provides a detailed molecular understanding of the enzymatic activity connected to large structural rearrangements of the protein. DATABASE: Structural data are available in RCSB Protein Data Bank under the accession numbers: 1F5N, 1DG3, 2B92.


Asunto(s)
Proteínas de Unión al GTP/química , Guanosina Difosfato/química , Guanosina Trifosfato/química , Dominios y Motivos de Interacción de Proteínas , Sitios de Unión , Biocatálisis , Clonación Molecular , Cristalografía por Rayos X , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Unión al GTP/genética , Proteínas de Unión al GTP/metabolismo , Expresión Génica , Vectores Genéticos/química , Vectores Genéticos/metabolismo , Guanosina 5'-O-(3-Tiotrifosfato)/química , Guanosina 5'-O-(3-Tiotrifosfato)/metabolismo , Guanosina Difosfato/metabolismo , Guanosina Trifosfato/metabolismo , Humanos , Cinética , Modelos Moleculares , Mutación , Unión Proteica , Conformación Proteica en Hélice alfa , Conformación Proteica en Lámina beta , Multimerización de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Especificidad por Sustrato
18.
Appl Radiat Isot ; 162: 109199, 2020 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-32501233

RESUMEN

Several methods have been developed to label compounds with 18F. However, in general these are laborious and require a multistep synthesis. A method based on the chelation of 18F-aluminum fluoride ([18F]AlF) by 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) was developed recently. The present work was aimed to radiolabel hexavalent lactoside (NOTA-HL) by [18F]AlF method for PET imaging of asialoglycoprotein receptor (ASGPR). METHODS: hexavalent lactoside was conjugated with the NOTA chelate and labeled with 18F in a one-pot method. The labeling procedure was investigated with different amounts of NOTA-HL and aluminum concentration. Radiochemical yield and radiochemical purity were determined by radio-TLC and radio-HPLC respectively. In vitro stability study of [18F]AlF-HL were carried out. PET/CT imaging of normal mice injected with [18F]AlF-NOTA-HL was performed. RESULTS: The Radiochemical yield of [18F]AlF-NOTA-HL was higher with more precursor and optimal Al+ concentration. The radiochemical purity of labeled product was >95% after purified by Sep-Pak cartridge to remove unbound [18F]AlF. The radiolabeling, including purification, was performed in 30 min [18F]AlF-NOTA-HL exhibited good in vitro stability. PET studies in normal mice revealed high specific accumulation of activity in the liver. CONCLUSION: NOTA-HL could be labeled rapidly and efficiently with aqueous 18F using AlF method. [18F]AlF-NOTA-HL would provide another efficient approach for PET imaging of ASGPR.


Asunto(s)
Receptor de Asialoglicoproteína/metabolismo , Radioisótopos de Flúor/administración & dosificación , Glicósidos/química , Animales , Humanos , Ratones , Tomografía Computarizada por Tomografía de Emisión de Positrones
19.
Polymers (Basel) ; 11(12)2019 Dec 04.
Artículo en Inglés | MEDLINE | ID: mdl-31817124

RESUMEN

Mullite whiskers were novelty prepared via pressure field assisted polycondensation nonaqueous precipitation method. The precipitate phase transition in heating process, phase compositions and microstructure of samples calcined at different temperatures, effect of pressure field on precursors polycondensation and AlF3 amount on sample morphology, the structure and the growth mechanism of whiskers were investigated. The results indicate that pressure field caused by kettle treatment promotes the polycondensation reaction between AlF3 and tetraethyl orthosilicate (TEOS), the excess aluminum fluoride coordinates with the precipitate skeleton of the =Al-O-Si≡, which brings about the low mullitization temperature (900 °C). The sample prepared with the optimal amount of aluminum fluoride (1.3 of the theoretical amount) calcined at 1100 °C presents high yield and aspect ratio (>15, 100 nm in diameter) of mullite whiskers. Growth of whiskers prepared via pressure field assisted polycondensation nonaqueous precipitation method is attributed to a vapor-solid (VS) mechanism with the inducement of screw. These mullite whiskers with the structure of multi-needle whiskers connected in the same center can be distributed evenly in epoxy resin, which greatly improves the mechanical properties of epoxy resin.

20.
Materials (Basel) ; 12(19)2019 Sep 30.
Artículo en Inglés | MEDLINE | ID: mdl-31574919

RESUMEN

This study aims to investigate the shear bonding strength (SBS) and thermal cycling effect of orthodontic brackets bonded with fluoride release/rechargeable LiAl-F layered double hydroxide (LDH-F) contained dental orthodontic resin. 3% and 5% of LDH-F nanopowder were gently mixed to commercial resin-based adhesives Orthomite LC (LC, LC3, LC5) and Transbond XT (XT, XT3). A fluoroaluminosilicate modified resin adhesive Transbond color change (TC) was selected as a positive control. Fifteen brackets each group were bonded to bovine enamel and the SBS was tested with/without thermal cycling. The adhesive remnant index (ARI) was evaluated at 20× magnification. The fluoride-releasing/rechargeability and cytocompatibility were also evaluated. The SBS of LC, LC3, and LC5 were significantly higher than XT and TC. After thermal cycling, the SBS of LC, LC3, and LC5 did not decrease and was significantly higher than TC. The changes of ARI scores indicate that failure occurred not only cohesive but also semi-cohesive fracture. The 30 days accumulated daily fluoride release of LC3, LC5, and TC without recharge are higher than 300 µg/cm2. The LDH-F contained resin adhesive possesses higher SBS compared to positive control TC. Fluoride release and the rechargeable feature can be achieved for preventing enamel demineralization without cytotoxicity.

SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA