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1.
Artigo em Alemão | MEDLINE | ID: mdl-36149472

RESUMO

BACKGROUND AND AIM: People in Germany are very sensitive about their health data. The electronic health record (ePA) also raises questions about the patient's need for data sovereignty and acceptance. The possibility of selectively withholding data stored in the ePA from physicians who continue to treat the patient (opt-out) and the patient's prior knowledge of the ePA could influence the need for data sovereignty and acceptance of the ePA. The aim of this explorative study is to investigate these influences for three patient groups: "acute patients," "diabetes type 2 patients," and "palliative patients," as differences are expected between these groups. MATERIALS AND METHODS: From August to October 2019, a quantitative survey was conducted among 140 patients in the abovementioned groups. RESULTS: Of the respondents, 76.0% supported the selective opt-out option and stated that this would increase their willingness to participate in the ePA. Specifically, 81.1% of acute care patients, 80.6% of palliative care patients, and 65.6% of type 2 diabetes patients made this statement. Differences between groups were not significant. A general prior knowledge of the ePA was related to a higher need for data sovereignty - 43.2% of those who had never heard of the ePA rollout would occasionally hide their health data from other physicians, compared with 54.5% who knew of the rollout. DISCUSSION: Consideration of the data sovereignty needs of patients in the further establishment of the ePA is recommended. The selective opt-out option can contribute to acceptance. Knowledge of the ePA should be expanded, especially in the doctor-patient discussion, to enable an informed decision.


Assuntos
Diabetes Mellitus Tipo 2 , Registros Eletrônicos de Saúde , Humanos , Diabetes Mellitus Tipo 2/terapia , Alemanha , Cuidados Paliativos , Relações Médico-Paciente
2.
RNA ; 22(4): 571-82, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26873599

RESUMO

Coupling between transcription and RNA processing is key for gene regulation. Using live-cell photobleaching techniques, we investigated the factor TCERG1, which coordinates transcriptional elongation with splicing. We demonstrate that TCERG1 is highly mobile in the nucleoplasm and that this mobility is slightly decreased when it is associated with speckles. Dichloro-1-ß-D-ribofuranosylbenzimidazole (DRB) but not α-amanitin treatment reduced the mobility of TCERG1, which suggests interaction with paused transcription elongation complexes. We found that TCERG1 mobility is rapid at the transcription site (TS) of a reporter that splices post-transcriptionally and that TCERG1 is recruited to the active TS independent of the CTD of RNAPII, thus excluding phosphorylated CTD as a requirement for recruiting this factor to the TS. Importantly, the mobility of TCERG1 is reduced when the reporter splices cotranscriptionally, which suggests that TCERG1 forms new macromolecular complexes when splicing occurs cotranscriptionally. In this condition, spliceostatin A has no effect, indicating that TCERG1 rapidly binds and dissociates from stalled spliceosomal complexes and that the mobility properties of TCERG1 do not depend on events occurring after the initial spliceosome formation. Taken together, these data suggest that TCERG1 binds independently to elongation and splicing complexes, thus performing their coupling by transient interactions rather than by stable association with one or the other complexes. This finding has conceptual implications for understanding the coupling between transcription and RNA processing.


Assuntos
Splicing de RNA , Elongação da Transcrição Genética , Fatores de Elongação da Transcrição/fisiologia , Núcleo Celular/metabolismo , Genes Reporter , Células HEK293 , HIV-1/genética , Humanos , Transporte Proteico
3.
Microsc Microanal ; 29(Supplement_1): 1994-1995, 2023 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-37612918
4.
RNA ; 20(1): 1-8, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24255166

RESUMO

The HIV-1 Rev protein mediates export of unspliced and singly spliced viral transcripts by binding to the Rev response element (RRE) and recruiting the cellular export factor CRM1. Here, we investigated the recruitment of Rev to the transcription sites of HIV-1 reporters that splice either post- or cotranscriptionally. In both cases, we observed that Rev localized to the transcription sites of the reporters and recruited CRM1. Rev and CRM1 remained at the reporter transcription sites when cells were treated with the splicing inhibitor Spliceostatin A (SSA), showing that the proteins associate with RNA prior to or during early spliceosome assembly. Fluorescence recovery after photobleaching (FRAP) revealed that Rev and CRM1 have similar kinetics as the HIV-1 RNA, indicating that Rev, CRM1, and RRE-containing RNAs are released from the site of transcription in one single export complex. These results suggest that cotranscriptional formation of a stable export complex serves as a means to ensure efficient export of unspliced viral RNAs.


Assuntos
HIV-1/metabolismo , Carioferinas/metabolismo , Complexos Multiproteicos/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Transcrição Gênica/fisiologia , Produtos do Gene rev do Vírus da Imunodeficiência Humana/metabolismo , Processamento Alternativo/fisiologia , Sítios de Ligação , Células Cultivadas , HIV-1/genética , Humanos , Complexos Multiproteicos/genética , Ligação Proteica , Multimerização Proteica , Estabilidade Proteica , RNA Viral/genética , RNA Viral/metabolismo , Proteína Exportina 1
5.
Phys Chem Chem Phys ; 17(28): 18278-81, 2015 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-26123655

RESUMO

We investigate the resistivity switching in individual Ag-TCNQ wires with on/off-ratios of up to 10(3). Raman and soft X-ray absorption microspectroscopy studies disclose reverse charge transfer. Quantifying of the fraction of neutral TCNQ within the switched material yields values up to 22.3%. These findings expedite the understanding of the switching process in Ag-TCNQ nanowires.

6.
J Cell Sci ; 125(Pt 11): 2709-20, 2012 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-22393237

RESUMO

Nuclear primary microRNA (pri-miRNA) processing catalyzed by the DGCR8-Drosha (Microprocessor) complex is highly regulated. Little is known, however, about how microRNA biogenesis is spatially organized within the mammalian nucleus. Here, we image for the first time, in living cells and at the level of a single microRNA cluster, the intranuclear distribution of untagged, endogenously-expressed pri-miRNAs generated at the human imprinted chromosome 19 microRNA cluster (C19MC), from the environment of transcription sites to single molecules of fully released DGCR8-bound pri-miRNAs dispersed throughout the nucleoplasm. We report that a large fraction of Microprocessor concentrates onto unspliced C19MC pri-miRNA deposited in close proximity to their genes. Our live-cell imaging studies provide direct visual evidence that DGCR8 and Drosha are targeted post-transcriptionally to C19MC pri-miRNAs as a preformed complex but dissociate separately. These dynamics support the view that, upon pri-miRNA loading and most probably concomitantly with Drosha-mediated cleavages, Microprocessor undergoes conformational changes that trigger the release of Drosha while DGCR8 remains stably bound to pri-miRNA.


Assuntos
Cromossomos Humanos Par 19/genética , Impressão Genômica/genética , MicroRNAs/genética , Família Multigênica/genética , Proteínas/metabolismo , Ribonuclease III/metabolismo , Linhagem Celular Tumoral , Núcleo Celular/genética , Sobrevivência Celular , Regulação da Expressão Gênica , Loci Gênicos/genética , Proteínas de Fluorescência Verde/metabolismo , Humanos , Cinética , MicroRNAs/metabolismo , Modelos Biológicos , Ligação Proteica , Estrutura Terciária de Proteína , Transporte Proteico , Proteínas/química , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA , Proteínas Recombinantes de Fusão/metabolismo , Ribonuclease III/química , Transcrição Gênica
7.
Nucleic Acids Res ; 40(2): 775-86, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21948796

RESUMO

Cellular micro(mi)RNAs are able to recognize viral RNAs through imperfect micro-homologies. Similar to the miRNA-mediated repression of cellular translation, this recognition is thought to tether the RNAi machinery, in particular Argonaute 2 (AGO2) on viral messengers and eventually to modulate virus replication. Here, we unveil another pathway by which AGO2 can interact with retroviral mRNAs. We show that AGO2 interacts with the retroviral Group Specific Antigen (GAG) core proteins and preferentially binds unspliced RNAs through the RNA packaging sequences without affecting RNA stability or eliciting translation repression. Using RNAi experiments, we provide evidences that these interactions, observed with both the human immunodeficiency virus 1 (HIV-1) and the primate foamy virus 1 (PFV-1), are required for retroviral replication. Taken together, our results place AGO2 at the core of the retroviral life cycle and reveal original AGO2 functions that are not related to miRNAs and translation repression.


Assuntos
Proteínas Argonautas/metabolismo , Produtos do Gene gag/metabolismo , Interferência de RNA , RNA Viral/metabolismo , Retroviridae/genética , Linhagem Celular , HIV-1/genética , Humanos , MicroRNAs/metabolismo , Biossíntese de Proteínas , RNA Mensageiro/metabolismo , Retroviridae/fisiologia , Vírion/metabolismo , Replicação Viral
8.
Cytometry A ; 83(9): 876-89, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23847177

RESUMO

To quantify more precisely and more reliably diffusion and reaction properties of biomolecules in living cells, a novel closed description in 3D of both the bleach and the post-bleach segment of fluorescence recovery after photobleaching (FRAP) data acquired at a point, i.e., a diffraction-limited observation area, termed point FRAP, is presented. It covers a complete coupled reaction-diffusion scheme for mobile molecules undergoing transient or long-term immobilization because of binding. We assess and confirm the feasibility with numerical solutions of the differential equations. By applying this model to free EYFP expressed in HeLa cells using a customized confocal laser scanning microscope that integrates point FRAP and fluorescence correlation spectroscopy (FCS), the applicability is validated by comparison with results from FCS. We show that by taking diffusion during bleaching into consideration and/or by employing a global analysis of series of bleach times, the results can be improved significantly. As the point FRAP approach allows to obtain data with diffraction-limited positioning accuracy, diffusion and binding properties of the exon-exon junction complex (EJC) components REF2-II and Magoh are obtained at different localizations in the nucleus of MCF7 cells and refine our view on the position-dependent association of the EJC factors with a maturating mRNP complex. Our findings corroborate the concept of combining point FRAP and FCS for a better understanding of the underlying diffusion and binding processes.


Assuntos
Recuperação de Fluorescência Após Fotodegradação/métodos , Espectrometria de Fluorescência/métodos , Proteínas de Bactérias/química , Linhagem Celular Tumoral , Células HeLa , Histonas/química , Humanos , Proteínas Luminescentes/química , Células MCF-7 , Ligação Proteica , Proteínas Recombinantes de Fusão/química
9.
Acta Crystallogr E Crystallogr Commun ; 79(Pt 11): 1067-1071, 2023 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-37936864

RESUMO

In the crystal structures of the formamide monosolvate (1a) and the n-propanol/H2O solvate/hydrate (1b) of the title compound, C38H50N4O3 (1), the tripodal host mol-ecule adopts a conformation in which the substituents attached to the central benzene ring are arranged in an alternating order above and below the ring plane. As a result of the different nature of the involved guest species, the crystal components in 1a create a three-dimensional supra-molecular architecture, while the crystal structure of 1b consists of two-dimensional supra-molecular aggregates extending parallel to the crystallographic ab plane.

10.
J Cell Sci ; 123(Pt 12): 2085-93, 2010 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-20519584

RESUMO

Numerous non-coding RNAs are known to be involved in the regulation of gene expression. In this work, we analyzed RNAs that co-immunoprecipitated with human RNA polymerase II from mitotic cell extracts and identified U1 small nuclear RNA (snRNA) as a major species. To investigate a possible splicing-independent recruitment of U1 snRNA to transcription units, we established cell lines having integrated a reporter gene containing a functional intron or a splicing-deficient construction. Recruitment of U snRNAs and some splicing factors to transcription sites was evaluated using fluorescence in situ hybridization (FISH) and immunofluorescence. To analyze imaging data, we developed a quantitative procedure, 'radial analysis', based on averaging data from multiple fluorescence images. The major splicing snRNAs (U2, U4 and U6 snRNAs) as well as the U2AF65 and SC35 splicing factors were found to be recruited only to transcription units containing a functional intron. By contrast, U1 snRNA, the U1-70K (also known as snRNP70) U1-associated protein as well as the ASF/SF2 (also known as SFRS1) serine/arginine-rich (SR) protein were efficiently recruited both to normally spliced and splicing-deficient transcription units. The constitutive association of U1 small nuclear ribonucleoprotein (snRNP) with the transcription machinery might play a role in coupling transcription with pre-mRNA maturation.


Assuntos
Células/metabolismo , RNA Polimerase II/metabolismo , Splicing de RNA , Ribonucleoproteína Nuclear Pequena U1/metabolismo , Transcrição Gênica , Linhagem Celular , Células/citologia , Células HeLa , Humanos , Hibridização in Situ Fluorescente , Microscopia de Fluorescência por Excitação Multifotônica , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Ligação Proteica , RNA Polimerase II/genética , RNA Nuclear Pequeno/metabolismo , Proteínas de Ligação a RNA , Ribonucleoproteína Nuclear Pequena U1/genética , Fatores de Processamento de Serina-Arginina
11.
Acta Crystallogr E Crystallogr Commun ; 78(Pt 8): 825-828, 2022 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-35974834

RESUMO

In the crystal structure of the title compound, C30H50N4O4, the two bis-(hy-droxy-eth-yl)amino moieties and the 2,4-di-methyl-pyridinyl-amino unit of the mol-ecule are located on one side of the central benzene ring, while the ethyl substituents are oriented in the opposite direction. The dihedral angle between the planes of the aromatic rings is 73.6 (1)°. The conformation of the mol-ecule is stabilized by intra-molecular O-H⋯O (1.86-2.12 Å) and C-H⋯N (2.40, 2.54 Å) hydrogen bonds. Dimers of inversion-related mol-ecules represent the basic supra-molecular entities of the crystal structure. They are further connected via O-H⋯O hydrogen bonding into undulating layers extending parallel to the crystallographic bc plane. Inter-layer inter-action is accomplished by weak C-H⋯π contacts.

12.
Geobiology ; 20(3): 363-376, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35212124

RESUMO

Fossilized tree resin, or amber, commonly contains fossils of animals, plants and microorganisms. These inclusions have generally been interpreted as hollow moulds or mummified remains coated or filled with carbonaceous material. Here, we provide the first report of calcified and silicified insects in amber from the mid-Cretaceous Kachin (Burmese) amber. Data from light microscopy, scanning electron microscopy (SEM), energy-dispersive and wavelength-dispersive X-ray spectroscopy (EDX and WDX), X-ray micro-computed tomography (Micro-CT) and Raman spectroscopy show that these Kachin fossils owe their preservation to multiple diagenetic mineralization processes. The labile tissues (e.g. eyes, wings and trachea) mainly consist of calcite, chalcedony and quartz with minor amounts of carbonaceous material, pyrite, iron oxide and phyllosilicate minerals. Calcite, quartz and chalcedony also occur in cracks as void-filling cements, indicating that the minerals formed from chemical species that entered the fossil inclusions through cracks in the resin. The results demonstrate that resin and amber are not always closed systems. Fluids (e.g. sediment pore water, diagenetic fluid and ground water) at different burial stages have chances to interact with amber throughout its geological history and affect the preservational quality and morphological fidelity of its fossil inclusions.


Assuntos
Âmbar , Quartzo , Âmbar/química , Animais , Carbonato de Cálcio , Fósseis , Insetos , Microtomografia por Raio-X
13.
RNA ; 15(5): 862-76, 2009 May.
Artigo em Inglês | MEDLINE | ID: mdl-19324961

RESUMO

The exon-exon junction complex (EJC) forms via association of proteins during splicing of mRNA in a defined manner. Its organization provides a link between biogenesis, nuclear export, and translation of the transcripts. The EJC proteins accumulate in nuclear speckles alongside most other splicing-related factors. We followed the establishment of the EJC on mRNA by investigating the mobility and interactions of a representative set of EJC factors in vivo using a complementary analysis with different fluorescence fluctuation microscopy techniques. Our observations are compatible with cotranscriptional binding of the EJC protein UAP56 confirming that it is involved in the initial phase of EJC formation. RNPS1, REF/Aly, Y14/Magoh, and NXF1 showed a reduction in their nuclear mobility when complexed with RNA. They interacted with nuclear speckles, in which both transiently and long-term immobilized factors were identified. The location- and RNA-dependent differences in the mobility between factors of the so-called outer shell and inner core of the EJC suggest a hypothetical model, in which mRNA is retained in speckles when EJC outer-shell factors are missing.


Assuntos
Splicing de RNA , RNA Mensageiro/metabolismo , Animais , Linhagem Celular Tumoral , Núcleo Celular/metabolismo , Citoplasma/metabolismo , Éxons , Humanos , Modelos Moleculares , RNA Mensageiro/química
14.
J Cell Biol ; 172(3): 373-81, 2006 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-16431928

RESUMO

The bimolecular fluorescence complementation (BiFC) assay, which allows the investigation of interacting molecules in vivo, was applied to study complex formation between the splicing factor Y14 and nuclear export factor 1 (NXF1), which evidence indicates are functionally associated with nuclear mRNA. Y14 linked to the COOH terminus of yellow fluorescent protein (YFP; YC-Y14), and NXF1 fused to the NH2 terminus of YFP (YN-NXF1) expressed in MCF7 cells yielded BiFC upon specific binding. Fluorescence accumulated within and around nuclear speckles, suggesting the involvement of speckles in mRNA processing and export. Accordingly, BiFC depended on transcription and full-length NXF1. Coimmunoprecipitation of YC-Y14 with YN-NXF1, NXF1, Y14, and RNA indicated that YC-Y14 and YN-NXF1 functionally associate with RNA. Fluorescence recovery after photobleaching and fluorescence loss in photobleaching revealed that roughly half of the accumulated BiFC complexes were immobile in vivo. This immobile fraction was readily depleted by adenosine triphosphate (ATP) administration in permeabilized cells. These results suggest that a fraction of RNA, which remains in the nucleus for several hours despite its association with splicing and export proteins, accumulates in speckles because of an ATP-dependent mechanism.


Assuntos
Núcleo Celular/metabolismo , Proteínas de Transporte Nucleocitoplasmático/metabolismo , Mapeamento de Interação de Proteínas , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/metabolismo , Transporte Ativo do Núcleo Celular/efeitos dos fármacos , Trifosfato de Adenosina/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Linhagem Celular Tumoral , Permeabilidade da Membrana Celular/efeitos dos fármacos , Núcleo Celular/efeitos dos fármacos , Digitonina/farmacologia , Recuperação de Fluorescência Após Fotodegradação , Humanos , Espaço Intranuclear/metabolismo , Cinética , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Mutação/genética , Proteínas Nucleares/metabolismo , Proteínas de Transporte Nucleocitoplasmático/genética , Ligação Proteica , RNA Polimerase II/antagonistas & inibidores , Proteínas de Ligação a RNA/genética , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Ribonucleoproteínas/metabolismo , Fatores de Processamento de Serina-Arginina , Azida Sódica/farmacologia , Transfecção
15.
Proc Natl Acad Sci U S A ; 105(25): 8513-8, 2008 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-18559857

RESUMO

Collagens are integral structural proteins in animal tissues and play key functional roles in cellular modulation. We sought to discover collagen model peptides (CMPs) that would form triple helices and self-assemble into supramolecular fibrils exhibiting collagen-like biological activity without preorganizing the peptide chains by covalent linkages. This challenging objective was accomplished by placing aromatic groups on the ends of a representative 30-mer CMP, (GPO)(10), as with l-phenylalanine and l-pentafluorophenylalanine in 32-mer 1a. Computational studies on homologous 29-mers 1a'-d' (one less GPO), as pairs of triple helices interacting head-to-tail, yielded stabilization energies in the order 1a' > 1b' > 1c' > 1d', supporting the hypothesis that hydrophobic aromatic groups can drive CMP self-assembly. Peptides 1a-d were studied comparatively relative to structural properties and ability to stimulate human platelets. Although each 32-mer formed stable triple helices (CD) spectroscopy, only 1a and 1b self-assembled into micrometer-scale fibrils. Light microscopy images for 1a depicted long collagen-like fibrils, whereas images for 1d did not. Atomic force microscopy topographical images indicated that 1a and 1b self-organize into microfibrillar species, whereas 1c and 1d do not. Peptides 1a and 1b induced the aggregation of human blood platelets with a potency similar to type I collagen, whereas 1c was much less effective, and 1d was inactive (EC(50) potency: 1a/1b >> 1c > 1d). Thus, 1a and 1b spontaneously self-assemble into thrombogenic collagen-mimetic materials because of hydrophobic aromatic interactions provided by the special end-groups. These findings have important implications for the design of biofunctional CMPs.


Assuntos
Colágenos Fibrilares/química , Peptídeos/química , Trombina/metabolismo , Biomimética , Dicroísmo Circular , Colágenos Fibrilares/metabolismo , Humanos , Interações Hidrofóbicas e Hidrofílicas , Microscopia de Força Atômica , Modelos Moleculares , Peptídeos/síntese química , Trombina/química
16.
Micron ; 143: 103029, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33581473

RESUMO

Due to the specific vacuum requirements for scanning electron microscopy (SEM), the Raman microscope has to operate in vacuum in a correlative Raman-SEM, which is a type of microscope combination that has recently increased in popularity. This works considers the implications of conducting Raman microscopy under vacuum, as opposed to operating in ambient air, the standard working regime of this technique. We show that the performance of the optics of the Raman microscope are identical in both conditions, but laser beam-sample interactions, such as fluorescent bleaching and beam damage, might be different due to the lack of oxygen in vacuum. The bleaching of the fluorescent background appears to be mostly unaffected by the lack of oxygen, except when very low laser powers are used. Regarding laser-beam damage, organic samples are more sensitive in vacuum than in air, whereas no definite verdict is possible for inorganic samples. These findings have practical implications for the application of correlative Raman-SEM, as low laser powers, or in extreme cases cryo-methods, need to be used for organic samples that appear only moderately beam sensitive under usual ambient air.

17.
J Hazard Mater ; 374: 447-458, 2019 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-31075536

RESUMO

Asbestos consists in natural minerals crystallized in a specific habit and possessing in particular properties. In the case of Naturally Occurring Asbestos, usual methods applied to the identification of mineral fibers and the determination of their possible asbestiform nature seems not efficient, especially in the case of mineral fibers included in mineral matrix. We present a new in-situ method based on the use of confocal Raman-in-SEM imaging implemented in a Scanning Electron Microscope as an efficient method for in-situ mineralogy. The limitation of conventional methods is discussed. We applied 2D-Raman imaging to the identification of sub-micrometric fibers included in different mineral matrix. We were able to identify actinolite fibers down to 400 nm in diameter, included in feldspar, quartz and/or calcite matrix. Moreover, Confocal Raman allows the collection of 3D data that would provide access to critical information on the morphology of the amphibole fibers in the volume, such as aspect ratio, fibers distribution and amphibole volume fraction. We performed this method on various examples of rocks containing actinolite fibers of mean structural formula is: Na0,04-0,12 Mg2,79-3,73 Al0,29-0,58 K0,01 Ca1,79-1,98 Mn0,01-0,09 Fe2+0,99-1,91 Fe3+Si7,64-7,73 O22(OH)2. We demonstrated that coupling confocal Raman imaging and SEM is a new and efficient in-situ method for identification and morphological characterization of amphibole fibers.

18.
Mater Sci Eng C Mater Biol Appl ; 98: 401-408, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30813041

RESUMO

Titanium and its alloys have been used as implant materials. Non-ideal osseointegration of the implant materials has facilitated the development of the bioactive coatings on the implant surfaces. In this work, the bioactive calcium silicate (CaSi) powder prepared in a green synthesis route was used to cover the surface of Ti implants by a facile electrospray deposition method. Post annealing in air was also applied to form the oxidation layer on the Ti surface with the aim of increasing the bond strength between the CaSi coating layer and Ti substrate. For the characterization of the coatings several analytical methods such as X-ray diffraction, scanning electron microscopy, secondary neutral mass spectrometry, and Raman-spectroscopy were used, in addition to the measurement of bond strength and corrosion resistance. The results indicated a uniform CaSi layer with a thickness of about 1 µm deposited on the Ti substrate. Annealing in the range of 700-900 °C in air resulted in the formation of rutile phase of TiO2; more importantly, annealing at 800 °C did not significantly affect the composition of the CaSi layer consisting of ß-Ca2SiO4. The bond strength between the coating layer and Ti substrate can be remarkably enhanced at an annealing temperature of 700 or 800 °C compared with the as-prepared coating without annealing. The annealed coatings had a better corrosion resistance than the as-prepared coating. It is concluded that the electrospray method associated with the post-annealing can be successfully used for the deposition of a CaSi layer with a defined structure and composition on titanium implants.


Assuntos
Compostos de Cálcio/química , Teste de Materiais/métodos , Silicatos/química , Titânio/química , Materiais Revestidos Biocompatíveis/química , Corrosão , Eletricidade , Técnicas Eletroquímicas , Espectrometria por Raios X , Temperatura , Difração de Raios X
19.
Ultramicroscopy ; 188: 48-51, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29549789

RESUMO

Site-specific preparation of specimens using focused ion beam instruments for transmission electron microscopy is at the forefront of targeting regions of interest for nanoscale characterization. Typical methods of pinpointing desired features include electron backscatter diffraction for differentiating crystal structures and energy-dispersive X-Ray spectroscopy for probing compositional variations. Yet there are situations, notably in the titanium dioxide system, where these techniques can fail. Differentiating between the brookite and anatase polymorphs of titania is either excessively laborious or impossible with the aforementioned techniques. However, due to differences in bonding structure, Raman spectroscopy serves as an ideal candidate for polymorph differentiation. In this work, a correlative approach utilizing Raman spectroscopy for targeted focused ion beam specimen preparation was employed. Dark field imaging and diffraction in the transmission electron microscope confirmed the region of interest located via Raman spectroscopy and demonstrated the validity of this new method. Correlative Raman spectroscopy, scanning electron microscopy, and focused ion beam is shown to be a promising new technique for identifying site-specific preparation of nanoscale specimens in cases where conventional approaches do not suffice.

20.
Ultramicroscopy ; 97(1-4): 229-37, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-12801675

RESUMO

We employed magnetic ACmode atomic force microscopy (MACmode AFM) as a novel dynamic force microscopy method to image surfaces of biological membranes in their native environments. The lateral resolution achieved under optimized imaging conditions was in the nanometer range, even when the sample was only weakly attached to the support. Purple membranes (PM) from Halobacterium salinarum were used as a test standard for topographical imaging. The hexagonal arrangement of the bacteriorhodopsin trimers on the cytoplasmic side of PM was resolved with 1.5nm lateral accuracy, a resolution similar to images obtained in contact and tapping-mode AFM. Human rhinovirus 2 (HRV2) particles were attached to mica surfaces via nonspecific interactions. The capsid structure and 2nm sized protein loops of HRV2 were routinely obtained without any displacement of the virus. Globular and filamentous structures on living and fixed endothelial cells were observed with a resolution of 5-20nm. These examples show that MACmode AFM is a favorable method in studying the topography of soft and weakly attached biological samples with high resolution under physiological conditions.


Assuntos
Membrana Celular/ultraestrutura , Microscopia de Força Atômica/métodos , Membrana Purpúrea/ultraestrutura , Capsídeo/ultraestrutura , Células Cultivadas , Endotélio/citologia , Halobacterium salinarum/ultraestrutura , Humanos , Magnetismo , Rhinovirus/ultraestrutura
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