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1.
Nucleic Acids Res ; 50(17): 10110-10122, 2022 09 23.
Artículo en Inglés | MEDLINE | ID: mdl-36107769

RESUMEN

Protein aggregates and abnormal proteins are toxic and associated with neurodegenerative diseases. There are several mechanisms to help cells get rid of aggregates but little is known on how cells prevent aggregate-prone proteins from being synthesised. The EBNA1 of the Epstein-Barr virus (EBV) evades the immune system by suppressing its own mRNA translation initiation in order to minimize the production of antigenic peptides for the major histocompatibility (MHC) class I pathway. Here we show that the emerging peptide of the disordered glycine-alanine repeat (GAr) within EBNA1 dislodges the nascent polypeptide-associated complex (NAC) from the ribosome. This results in the recruitment of nucleolin to the GAr-encoding mRNA and suppression of mRNA translation initiation in cis. Suppressing NAC alpha (NACA) expression prevents nucleolin from binding to the GAr mRNA and overcomes GAr-mediated translation inhibition. Taken together, these observations suggest that EBNA1 exploits a nascent protein quality control pathway to regulate its own rate of synthesis that is based on sensing the nascent GAr peptide by NAC followed by the recruitment of nucleolin to the GAr-encoding RNA sequence.


Asunto(s)
Infecciones por Virus de Epstein-Barr , Herpesvirus Humano 4 , Proteínas de Unión al ARN/metabolismo , Alanina , Antígenos Nucleares del Virus de Epstein-Barr/metabolismo , Glicina , Herpesvirus Humano 4/genética , Humanos , Péptidos/genética , Fosfoproteínas , Agregado de Proteínas , ARN Mensajero/genética , ARN Mensajero/metabolismo , Nucleolina
2.
BMC Public Health ; 24(1): 496, 2024 Feb 16.
Artículo en Inglés | MEDLINE | ID: mdl-38365671

RESUMEN

BACKGROUND: Prior to December 2022, there were no reports of reinfection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Shaanxi province, China. Since then, China has refined its strategy in response to coronaviruses. The purpose of this study was to determine the incidence of SARS-CoV-2 reinfections and its contributing factors, as well as to compare clinical characteristics between first and second episodes of infection in Shaanxi Province, China between December 2022 and February 2023. METHODS: We conducted a cross-sectional study using an epidemiological survey system and electronic questionnaires to investigate the incidence of SARS-CoV-2 reinfection among previously infected individuals during the epidemic wave owing to the Omicron variant that began in December 2022. A logistic regression model was used to determine those factors influencing SARS-CoV-2 reinfections. RESULTS: According to the virus variant that caused the first infection, the rate of reinfection for the Omicron variants was 1.28%, 1.96%, and 5.92% at 2-3 months, 4-5 months, and 7-9 months after the primary infection, respectively. The rate of reinfection for the Delta variants was 25.10% 11-12 months after the primary infection. Females, adults between 18 and 38 years and being a medical worker were associated with an increased risk of reinfection. Fever, cough, sore throat and fatigue were the four most common clinical symptoms during both first and second COVID-19 infections. CONCLUSIONS: In our study, the rate of SARS-CoV-2 reinfection increased over time during epidemic waves predominantly involving the Omicron variant in Shaanxi province, China. Large-scale infections are less likely in subsequent Omicron epidemic waves. Nevertheless, it is essential to continuously monitor cases of infection as well as continue surveillance for emerging SARS-CoV-2 variants.


Asunto(s)
COVID-19 , SARS-CoV-2 , Adulto , Femenino , Humanos , SARS-CoV-2/genética , COVID-19/epidemiología , Estudios Transversales , Reinfección/epidemiología , China/epidemiología
3.
BMC Med ; 21(1): 100, 2023 03 16.
Artículo en Inglés | MEDLINE | ID: mdl-36927437

RESUMEN

BACKGROUND: A global plan has been set to end human deaths from dog-mediated rabies by 2030 ("Zero-by-30"), but whether it could be achieved in some countries, such as China, remains unclear. Although elimination strategies through post-exposure prophylaxis (PEP) use, dog vaccination, and patient risk assessments with integrated bite case management (IBCM) were proposed to be cost-effective, evidence is still lacking in China. We aim to evaluate the future burdens of dog-mediated human rabies deaths in the next decade and provide quantitative evidence on the cost-effectiveness of different rabies-control strategies in China. METHODS: Based on data from China's national human rabies surveillance system, we used decision-analytic modelling to estimate dog-mediated human rabies death trends in China till 2035. We simulated and compared the expected consequences and costs of different combination strategies of the status quo, improved access to PEP, mass dog vaccination, and use of IBCM. RESULTS: The predicted human rabies deaths in 2030 in China will be 308 (95%UI: 214-411) and remain stable in the next decade under the status quo. The strategy of improved PEP access alone could only decrease deaths to 212 (95%UI: 147-284) in 2028, remaining unchanged till 2035. In contrast, scaling up dog vaccination to coverage of 70% could eliminate rabies deaths by 2033 and prevent approximately 3,265 (95%UI: 2,477-3,687) extra deaths compared to the status quo during 2024-2035. Moreover, with the addition of IBCM, the "One Health" approach through mass dog vaccination could avoid unnecessary PEP use and substantially reduce total cost from 12.53 (95%UI: 11.71-13.34) to 8.73 (95%UI: 8.09-9.85) billion US dollars. Even if increasing the total costs of IBCM from 100 thousand to 652.10 million US dollars during 2024-2035, the combined strategy of mass dog vaccination and use of IBCM will still dominate, suggesting the robustness of our results. CONCLUSIONS: The combined strategy of mass dog vaccination and IBCM requires collaboration between health and livestock/veterinary sectors, and it could eliminate Chinese rabies deaths as early as 2033, with more deaths averted and less cost, indicating that adding IBCM could reduce unnecessary use of PEP and make the "One Health" rabies-control strategy most cost-effective.


Asunto(s)
Mordeduras y Picaduras , Rabia , Humanos , Perros , Animales , Rabia/epidemiología , Rabia/prevención & control , Rabia/veterinaria , Objetivos , Vacunación , Profilaxis Posexposición/métodos
4.
Amino Acids ; 54(2): 169-180, 2022 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-34837556

RESUMEN

The human Dietary Approaches to Stop Hypertension-Sodium Trial has shown that ß-aminoisobutyric acid (BAIBA) may prevent the development of salt-sensitive hypertension (SSHT). However, the specific antihypertensive mechanism remains unclear in the renal tissues of salt-sensitive (SS) rats. In this study, BAIBA (100 mg/kg/day) significantly attenuated SSHT via increased nitric oxide (NO) content in the renal medulla, and it induced a significant increase in NO synthesis substrates (L-arginine and malic acid) in the renal medulla. BAIBA enhanced the activity levels of total NO synthase (NOS), inducible NOS, and constitutive NOS. BAIBA resulted in increased fumarase activity and decreased fumaric acid content in the renal medulla. The high-salt diet (HSD) decreased fumarase expression in the renal cortex, and BAIBA increased fumarase expression in the renal medulla and renal cortex. Furthermore, in the renal medulla, BAIBA increased the levels of ATP, ADP, AMP, and ADP/ATP ratio, thus further activating AMPK phosphorylation. BAIBA prevented the decrease in renal medullary antioxidative defenses induced by the HSD. In conclusion, BAIBA's antihypertensive effect was underlined by the phosphorylation of AMPK, the prevention of fumarase's activity reduction caused by the HSD, and the enhancement of NO content, which in concert attenuated SSHT in SS rats.


Asunto(s)
Fumarato Hidratasa , Hipertensión , Ácidos Aminoisobutíricos , Animales , Presión Sanguínea , Suplementos Dietéticos , Fumarato Hidratasa/genética , Fumarato Hidratasa/metabolismo , Hipertensión/tratamiento farmacológico , Hipertensión/prevención & control , Ratas , Ratas Endogámicas Dahl
5.
Nucleic Acids Res ; 48(12): 6775-6787, 2020 07 09.
Artículo en Inglés | MEDLINE | ID: mdl-32453417

RESUMEN

Cell growth requires a high level of protein synthesis and oncogenic pathways stimulate cell proliferation and ribosome biogenesis. Less is known about how cells respond to dysfunctional mRNA translation and how this feeds back into growth regulatory pathways. The Epstein-Barr virus (EBV)-encoded EBNA1 causes mRNA translation stress in cis that activates PI3Kδ. This leads to the stabilization of MDM2, induces MDM2's binding to the E2F1 mRNA and promotes E2F1 translation. The MDM2 serine 166 regulates the interaction with the E2F1 mRNA and deletion of MDM2 C-terminal RING domain results in a constitutive E2F1 mRNA binding. Phosphorylation on serine 395 following DNA damage instead regulates p53 mRNA binding to its RING domain and prevents the E2F1 mRNA interaction. The p14Arf tumour suppressor binds MDM2 and in addition to preventing degradation of the p53 protein it also prevents the E2F1 mRNA interaction. The data illustrate how two MDM2 domains selectively bind specific mRNAs in response to cellular conditions to promote, or suppress, cell growth and how p14Arf coordinates MDM2's activity towards p53 and E2F1. The data also show how EBV via EBNA1-induced mRNA translation stress targets the E2F1 and the MDM2 - p53 pathway.


Asunto(s)
Factor de Transcripción E2F1/genética , Neoplasias/genética , Proteínas Proto-Oncogénicas c-mdm2/genética , Proteína p53 Supresora de Tumor/genética , Carcinogénesis/genética , Ciclo Celular/genética , Proliferación Celular/genética , Daño del ADN/genética , Genes Supresores de Tumor , Herpesvirus Humano 4/genética , Humanos , Neoplasias/virología , Oncogenes/genética , Fosforilación/genética , Dominios Proteicos/genética , Proteínas con Motivos de Reconocimiento de ARN/genética , ARN Mensajero/genética , Proteína p14ARF Supresora de Tumor/genética
6.
Int J Mol Sci ; 23(16)2022 Aug 18.
Artículo en Inglés | MEDLINE | ID: mdl-36012592

RESUMEN

DNA and RNA binding proteins (DRBPs) are a broad class of molecules that regulate numerous cellular processes across all living organisms, creating intricate dynamic multilevel networks to control nucleotide metabolism and gene expression. These interactions are highly regulated, and dysregulation contributes to the development of a variety of diseases, including cancer. An increasing number of proteins with DNA and/or RNA binding activities have been identified in recent years, and it is important to understand how their activities are related to the molecular mechanisms of cancer. In addition, many of these proteins have overlapping functions, and it is therefore essential to analyze not only the loss of function of individual factors, but also to group abnormalities into specific types of activities in regard to particular cancer types. In this review, we summarize the classes of DNA-binding, RNA-binding, and DRBPs, drawing particular attention to the similarities and differences between these protein classes. We also perform a cross-search analysis of relevant protein databases, together with our own pipeline, to identify DRBPs involved in cancer. We discuss the most common DRBPs and how they are related to specific cancers, reviewing their biochemical, molecular biological, and cellular properties to highlight their functions and potential as targets for treatment.


Asunto(s)
Neoplasias , Proteínas de Unión al ARN , ADN , Proteínas de Unión al ADN/metabolismo , Humanos , Neoplasias/genética , Neoplasias/metabolismo , ARN/genética , Proteínas de Unión al ARN/metabolismo
7.
Nucleic Acids Res ; 47(7): 3257-3271, 2019 04 23.
Artículo en Inglés | MEDLINE | ID: mdl-30828720

RESUMEN

A large number of signalling pathways converge on p53 to induce different cellular stress responses that aim to promote cell cycle arrest and repair or, if the damage is too severe, to induce irreversible senescence or apoptosis. The differentiation of p53 activity towards specific cellular outcomes is tightly regulated via a hierarchical order of post-translational modifications and regulated protein-protein interactions. The mechanisms governing these processes provide a model for how cells optimize the genetic information for maximal diversity. The p53 mRNA also plays a role in this process and this review aims to illustrate how protein and RNA interactions throughout the p53 mRNA in response to different signalling pathways control RNA stability, translation efficiency or alternative initiation of translation. We also describe how a p53 mRNA platform shows riboswitch-like features and controls the rate of p53 synthesis, protein stability and modifications of the nascent p53 protein. A single cancer-derived synonymous mutation disrupts the folding of this platform and prevents p53 activation following DNA damage. The role of the p53 mRNA as a target for signalling pathways illustrates how mRNA sequences have co-evolved with the function of the encoded protein and sheds new light on the information hidden within mRNAs.


Asunto(s)
ARN Mensajero/genética , Estrés Fisiológico/genética , Proteína p53 Supresora de Tumor/genética , Regiones no Traducidas 3'/genética , Regiones no Traducidas 5'/genética , Animales , Humanos , Ligandos , Unión Proteica , Proteínas Proto-Oncogénicas c-mdm2/metabolismo , Riboswitch/genética
8.
Biochem J ; 476(21): 3401-3411, 2019 11 15.
Artículo en Inglés | MEDLINE | ID: mdl-31652301

RESUMEN

Allosteric changes imposed by post-translational modifications regulate and differentiate the functions of proteins with intrinsic disorder regions. HDM2 is a hub protein with a large interactome and with different cellular functions. It is best known for its regulation of the p53 tumour suppressor. Under normal cellular conditions, HDM2 ubiquitinates and degrades p53 by the 26S proteasome but after DNA damage, HDM2 switches from a negative to a positive regulator of p53 by binding to p53 mRNA to promote translation of the p53 mRNA. This change in activity is governed by the ataxia telangiectasia mutated kinase via phosphorylation on serine 395 and is mimicked by the S395D phosphomimetic mutant. Here we have used different approaches to show that this event is accompanied by a specific change in the HDM2 structure that affects the HDM2 interactome, such as the N-termini HDM2-p53 protein-protein interaction. These data will give a better understanding of how HDM2 switches from a negative to a positive regulator of p53 and gain new insights into the control of the HDM2 structure and its interactome under different cellular conditions and help identify interphases as potential targets for new drug developments.


Asunto(s)
Proteínas de la Ataxia Telangiectasia Mutada/metabolismo , Mutación Missense , Proteínas Proto-Oncogénicas c-mdm2/química , Proteínas Proto-Oncogénicas c-mdm2/metabolismo , Regulación Alostérica , Secuencias de Aminoácidos , Proteínas de la Ataxia Telangiectasia Mutada/genética , Humanos , Fosforilación , Unión Proteica , Proteínas Proto-Oncogénicas c-mdm2/genética , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismo
9.
Wei Sheng Yan Jiu ; 47(2): 250-295, 2018 Mar.
Artículo en Zh | MEDLINE | ID: mdl-29903278

RESUMEN

OBJECTIVE: To investigate the status of pesticides residues in vegetables, fruits, edible mushrooms and tea bags in Shaanxi Province. METHODS: Ten cities in Shaanxi Province were selected as monitoring area, pesticides residues in food were detected by gas chromatograph-mass spectrometry. RESULTS: The total detection rate of pesticide residues was 15. 60%( 159/1019). The detection rate of pesticides in vegetables, fruits, edible mushrooms and tea bag was 18. 64%, 15. 00%, 4. 68% and23. 63%, respectively. The detection rate of organophosphorus, carbamate, pyrethroid and organochlorine was 7. 36%, 6. 48%, 8. 34% and 5. 79%, respectively. Methyl parathion, parathion, omethoate, cyhalothrin, cyhalothrin and cypermethrin were still overused in the vegetables, and the total exceeding rate was 1. 51%. CONCLUSION: The pesticides in food were detected in Shaanxi Province, but the total of exceeding standard is below the national level.


Asunto(s)
Análisis de los Alimentos , Contaminación de Alimentos/análisis , Frutas/química , Residuos de Plaguicidas/análisis , Plaguicidas/efectos adversos , Verduras/química , Humanos
10.
Chemistry ; 23(41): 9857-9871, 2017 Jul 21.
Artículo en Inglés | MEDLINE | ID: mdl-28498613

RESUMEN

A series of AlNa bimetallic ammonium metal formate frameworks (AlNa AMFFs) have been prepared by employing various ammoniums from NH4+ to large linear polyammoniums. The series consists of six perovskites of (412 ⋅63 ) topology for mono-ammoniums, two chiral (49 ⋅66 ) frameworks incorporating polyethylene ammoniums, two niccolites with (412 ⋅63 )(49 ⋅66 ) topology containing diammoniums, and two layered compounds made of 2D (4,4) AlNa formate sheets intercalated by small diammoniums. The first ten compounds present the structural hierarchy of (412 ⋅63 )m (49 ⋅66 )n framework topologies for (m, n)=(1, 0), (0, 1), and (1, 1), respectively, in parallel to the homometallic AMFFs for divalent metals. The symmetry lowering, asymmetric formate bridges, and different hydrogen-bonding strengths appeared in the bimetallic structures owing to the different charge and size of Al3+ and Na+ seemingly inhibits the occurrence of phase transitions for more than half the AlNa AMFFs within the series, and the bimetallic members undergoing phase transitions show different transition behaviors and dielectric properties compared with the homometallic analogs. Anisotropic/negative/zero thermal expansions of the materials could be rationally attributed to the librational motion, or flip movement between different sites, of the ammonium cations, and the coupled change of AlNa formate frameworks. The thermal and IR spectroscopic properties have also been investigated.

11.
J Sci Food Agric ; 97(3): 868-874, 2017 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-27197789

RESUMEN

BACKGROUND: Crude camellia seed oil is rich in free fatty acids, which must be removed to produce an oil of acceptable quality. In the present study, we reduced the free fatty acid content of crude camellia seed oil by lipophilization of epicatechin with these free fatty acids in the presence of Candida antarctica lipase B (Novozym 435), and this may enhance the oxidative stability of the oil at the same time. RESULTS: The acid value of crude camellia seed oil reduced from 3.7 to 2.5 mgKOH g-1 after lipophilization. Gas chomatography-mass spectrometry analysis revealed that epicatechin oleate and epicatechin palmitate were synthesized in the lipophilized oil. The peroxide, p-anisidine, and total oxidation values during heating of the lipophilized oil were much lower than that of the crude oil and commercially available camellia seed oil, suggesting that lipophilized epicatechin derivatives could help enhance the oxidative stability of edible oil. CONCLUSION: The enzymatic process to lipophilize epicatechin with the free fatty acids in crude camellia seed oil described in the present study could decrease the acid value to meet the quality standards for commercial camellia seed oil and, at the same time, obtain a new edible camellia seed oil product with good oxidative stability. © 2016 Society of Chemical Industry.


Asunto(s)
Antioxidantes/metabolismo , Camellia sinensis/química , Catequina/metabolismo , Ácidos Grasos no Esterificados/metabolismo , Proteínas Fúngicas/metabolismo , Lipasa/metabolismo , Aceites de Plantas/química , Semillas/química , Antioxidantes/análisis , Antioxidantes/química , Catequina/análogos & derivados , Catequina/análisis , Catequina/química , China , Grasas Insaturadas en la Dieta/análisis , Grasas Insaturadas en la Dieta/metabolismo , Enzimas Inmovilizadas/metabolismo , Ácidos Grasos no Esterificados/análisis , Ácidos Grasos no Esterificados/química , Manipulación de Alimentos , Calidad de los Alimentos , Cromatografía de Gases y Espectrometría de Masas , Calor/efectos adversos , Interacciones Hidrofóbicas e Hidrofílicas , Ácidos Oléicos/análisis , Ácidos Oléicos/química , Ácidos Oléicos/metabolismo , Oxidación-Reducción , Palmitatos/análisis , Palmitatos/química , Palmitatos/metabolismo , Solubilidad
12.
Chemistry ; 22(18): 6199-203, 2016 Apr 25.
Artículo en Inglés | MEDLINE | ID: mdl-26892832

RESUMEN

A niccolite series of [bnH2 (2+) ][M(HCOO)3 ]2 (bnH2 (2+) =1,4-butyldiammonium) shows four kinds of metal-dependent phase transitions, from high temperature para-electric phases to low-temperature ferro-, antiferro-, glass-like, and para-electric phases. The conformational flexibility of bnH2 (2+) and the different size, mass, and bonding character of the metal ion lead to various disorder-order transitions of bnH2 (2+) in the lattice and relevant framework modulations, thus different phase transitions and dielectric responses. The magnetic members display a coexistence or combination of electric and magnetic orderings in the low-temperature region.

13.
Inorg Chem ; 55(20): 10075-10082, 2016 Oct 17.
Artículo en Inglés | MEDLINE | ID: mdl-27366822

RESUMEN

A series of isostructural hydrazinium lanthanide (Ln) formate framework compounds of [NH2NH3][Ln(HCOO)4] for Ln3+ ions from Tb3+ to Lu3+ and Y3+ have been successfully prepared by utilizing NH2NH3+. The compounds crystallize in orthorhombic polar space group Pca21, with cell parameters at 180 K of a = 18.2526(7)-18.1048(5) Å, b = 6.5815(2)-6.5261(2) Å, c = 7.6362(3)-7.5044(2) Å, and V = 917.33(6)-886.67(4) Å3, showing the effect of lanthanide contraction. The compounds possess polar perovskite-like structures incorporating the hydrazinium cations in the cavities of the NaCl-like framework, in which the Ln3+ ions in a bicapped trigonal prism are connected by anti-anti and syn-anti formate groups. The N-H···Oformate hydrogen-bonding interactions are between the hydrazinium cations and the anionic framework. One anti-anti formate group is frustrated by the competitive N-H···Oformate hydrogen-bonding interactions. It thus twists or flips upon warming, resulting in large anisotropic thermal expansion and negative thermal expansion below 180 K. A comparison with the transition metal and magnesium analogues revealed that the structural compactness, tighter binding of the hydrazinium cation by the framework, and symmetrically better match between the framework and ammonium cation for Ln compounds could inhibit the occurrence of phase transition in the series. The IR spectroscopic, thermal, and magnetic properties are investigated.

14.
Artículo en Zh | MEDLINE | ID: mdl-30130036

RESUMEN

Objective: To analyze the malaria situation in Shaanxi Province during 2005-2014, in the aim of providing reference for improving malaria elimination strategies and measures. Methods: Data on malaria control and malaria epidemic reports during 2005-2014 were collected, and analysis was made on prevalence and regional distribution of malaria, species of plasmodium, diagnosis of patients, and sources of imported malaria. Results: Four hundred and fifty three cases of malaria were reported in Shaanxi Province during 2005-2014, consisting of 73 local cases (16.1%) and 380 imported cases (83.9%) of which 141 were falciparum malaria (37.1%, 141/380). Three patients died and they all were imported cases of falciparum malaria. No indigenous infection had been reported since 2011. Most of the cases were laboratory-confirmed(71.5%, 324/453). The falciparum malaria cases accounted for 31.1%(141/453) of all the cases, and they all were imported cases. No cases of quartan malaria and ovale malaria were reported. The 73 indigenous cases distributed in 25 districts (counties) of 7 cities, including 3 cities in South Shaanxi (Shangluo, Hanzhong, Ankang)(61.6%, 45/73) and four cities in Central Shaanxi (Xi'an, Weinan, Xianyang, Baoji) (38.4%, 28/73). The imported cases showed an increasing trend from 24 in 2005 to 59 in 2014. The 380 imported cases were mainly from over 20 countries in Africa (72.6%, 276/380), with top sources of Angola (64 cases), Cameroon (26), Ghana (24), and Equatorial Guinea (23) accounting for 36.0% ( 137/380). The median of interval from onset to diagnosis was 5 d. The cases were mainly reported by clinical medical institutions (87.6%, 397/453), only 7.5% (34/453) were reported by disease control institutions. Conclusion: No indigenous cases have been reported since 2011, but the imported malaria cases show a trend of increase with a major source of Africa.


Asunto(s)
Malaria , China , Epidemias , Humanos , Plasmodium , Prevalencia
15.
Angew Chem Int Ed Engl ; 55(6): 2097-100, 2016 Feb 05.
Artículo en Inglés | MEDLINE | ID: mdl-26709724

RESUMEN

The compound [CH3 CH2 NH3][Cu(HCOO)3] undergoes a phase transition at 357 K, from a perovskite to a diamond structure, by heating. The backward transition can be driven by pressure at room temperature but not cooling under ambient or lower pressure. The rearrangement of one long copper-formate bond, the switch of bridging-chelating mode of the formate, the alternation of N-H⋅⋅⋅O H-bonds, and the flipping of ethylammonium are involved in the transition. The strong N-H⋅⋅⋅O H-bonding probably locks the metastable diamond phase. The two phases display magnetic and electric orderings of different characters.

16.
Angew Chem Int Ed Engl ; 54(38): 11093-6, 2015 Sep 14.
Artículo en Inglés | MEDLINE | ID: mdl-26245518

RESUMEN

The A-site mixed-ammonium solid solutions of metal-organic perovskites [(NH2 NH3 )x (CH3 NH3 )1-x ][Mn(HCOO)3 ] (x=1.00-0.67) exhibit para- to ferroelectric diffuse phase transitions with lowered transition temperatures from x=1.00 to 0.67. These properties are due to the decreased framework distortion and polarization in their low temperature ferroelectric phases caused by the increased CH3 NH3 (+) concentration.

17.
Chemistry ; 20(48): 15872-83, 2014 Nov 24.
Artículo en Inglés | MEDLINE | ID: mdl-25303719

RESUMEN

We present here the compound [NH4][Cu(HCOO)3], a new member of the [NH4][M(HCOO)3] family. The Jahn-Teller Cu(2+) ion leads to a distorted 4(9)⋅6(6) chiral Cu-formate framework. In the low-temperature (LT) orthorhombic phase, the Cu(2+) is in an elongated octahedron, and the NH4⁺ ions in the framework channel are off the channel axis. From 94 to 350 K the NH4⁺ ion gradually approaches the channel axis and the related modulation of the framework and the hydrogen-bond system occurs. The LT phase is simple antiferroelectric (AFE). The material becomes hexagonal above 355 K. In the high-temperature (HT) phase, the Cu(2+) octahedron is compressed, and the NH4⁺ ions are arranged helically along the channel axis. Therefore, the phase transition is one from LT simple AFE to HT helical AFE. The temperature-dependent structure evolution is accompanied by significant thermal and dielectric anomalies and anisotropic thermal expansion, due to the different status of the NH4⁺ ions and the framework modulations, and the structure-property relationship was established based on the extensive variable-temperature single-crystal structures. The material showed long range ordering of antiferromagnetism (AFM), with low dimensional character and a Néel temperature of 2.9 K. Therefore, within the material AFE and AFM orderings coexist in the low-temperature region.

18.
Inorg Chem ; 53(16): 8708-16, 2014 Aug 18.
Artículo en Inglés | MEDLINE | ID: mdl-25072411

RESUMEN

We report an ammonium uranyl formate framework of formula [(C2H5)4N][U2O4(HCOO)5], prepared by using components of tetraethylammonium, uranyl, and formate. The compound possesses a layered structure of anionic uranyl-formate wavy sheets and intercalated (C2H5)4N(+) cations. The sheet consists of pentagonal bipyramidal uranyl cations connected by equatorial anti-anti and anti-syn HCOO(-) bridges, and it has a topology of 3(3)·4(3)·5(4) made of edge-sharing square and triangle grids. The high-temperature (HT) phase belongs to the chiral but nonpolar tetragonal space group P42(1)m. In the structure, one HCOO(-) is 2-fold disordered, showing a flip motion between the two anti-syn orientations. On cooling, this flip motion slowed and finally froze, leading to a phase transition at ∼200 K. The low-temperature (LT) structure is monoclinic and polar in space group P2(1); the cations shift, and the layers slide. Especially, the concerted and net shifts of the ammonium cations toward the -b direction, with respect to the anionic sheets, result in an estimated spontaneous polarization of 0.86 µC cm(-2) in LT. The phase transition is thus para- to ferro-electric, in Aizu notation 42mF2, accompanied by significant, anisotropic dielectric anomalies, with a quite significant thermal hysteresis. Variable-temperature luminescent spectroscopy and differential scanning calorimetry confirmed the transition and provided further information. The structure-property relationship is established.

19.
Chemosphere ; 358: 142220, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38710410

RESUMEN

Microplastics have become a prevalent environmental pollutant due to widespread release and production. Algae, as primary producers, play a crucial role in maintaining the ecological balance of freshwater environments. Despite reports on the inhibition of microalgae by microplastics, the size-dependent effects on microalgae and associated molecular mechanism remain poorly understood. This study investigates the impacts of three polystyrene micro/nano-plastics (PS-MNPs) with different sizes (100 nm, 350 nm, and 6 µm) and concentrations (25-200 mg/L) on Chlamydomonas reinhardtii (C. reinhardtii) throughout its growth period. Results reveal size- and concentration-dependent growth inhibition and induction of oxidative stress by PS-MNPs, with microalgae exhibiting increased vulnerability to smaller-sized and higher-concentration PS-MNPs. Proteomics analysis elucidates the size-dependent suppression of proteins involved in the photosynthesis process by PS-MNPs. Photosynthetic activity assays demonstrate that smaller PS-MNPs more significantly reduce chlorophyll content and the maximal photochemical efficiency of photosystem II. Finally, electron microscope and Western blot assays collectively confirm the size effect of PS-MNPs on microalgae growth is attributable to suppressed protein expression rather than shading effects. This study contributes to advancing our understanding of the intricate interactions between micro/nano-plastics and algae at the molecular level, emphasizing the efficacy of proteomics in dissecting the mechanistic aspects of microplastics-induced biological effects on environmental indicator organisms.


Asunto(s)
Chlamydomonas reinhardtii , Microplásticos , Fotosíntesis , Poliestirenos , Proteómica , Chlamydomonas reinhardtii/efectos de los fármacos , Chlamydomonas reinhardtii/metabolismo , Chlamydomonas reinhardtii/crecimiento & desarrollo , Poliestirenos/toxicidad , Poliestirenos/química , Microplásticos/toxicidad , Fotosíntesis/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Clorofila/metabolismo , Contaminantes Químicos del Agua/toxicidad , Microalgas/efectos de los fármacos , Plásticos/toxicidad , Tamaño de la Partícula , Complejo de Proteína del Fotosistema II/metabolismo
20.
Cell Death Differ ; 30(4): 1072-1081, 2023 04.
Artículo en Inglés | MEDLINE | ID: mdl-36813920

RESUMEN

Cellular stress conditions activate p53-dependent pathways to counteract the inflicted damage. To achieve the required functional diversity, p53 is subjected to numerous post-translational modifications and the expression of isoforms. Little is yet known how p53 has evolved to respond to different stress pathways. The p53 isoform p53/47 (p47 or ΔNp53) is linked to aging and neural degeneration and is expressed in human cells via an alternative cap-independent translation initiation from the 2nd in-frame AUG at codon 40 (+118) during endoplasmic reticulum (ER) stress. Despite an AUG codon in the same location, the mouse p53 mRNA does not express the corresponding isoform in either human or mouse-derived cells. High-throughput in-cell RNA structure probing shows that p47 expression is attributed to PERK kinase-dependent structural alterations in the human p53 mRNA, independently of eIF2α. These structural changes do not take place in murine p53 mRNA. Surprisingly, PERK response elements required for the p47 expression are located downstream of the 2nd AUG. The data show that the human p53 mRNA has evolved to respond to PERK-mediated regulation of mRNA structures in order to control p47 expression. The findings highlight how p53 mRNA co-evolved with the function of the encoded protein to specify p53-activities under different cellular conditions.


Asunto(s)
Estrés del Retículo Endoplásmico , Proteína p53 Supresora de Tumor , Humanos , Animales , Ratones , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Estrés del Retículo Endoplásmico/genética , eIF-2 Quinasa/genética , eIF-2 Quinasa/metabolismo , Procesamiento Proteico-Postraduccional , Isoformas de Proteínas/metabolismo
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