Optical analysis of RE3+ (RE = Nd or Er):B2O3–P2O5–CaF2–ZnO–(Li2O/Na2O/K2O) glasses

Calcium boro fluoro zinc phosphate glasses modified using alkali oxide and doped with Nd³⁺ and Er³⁺ ions with the chemical composition of 69.5 (B₂O₃) + 10 (P₂O₅) + 10 (CaF₂) + 5 (ZnO) + 5 (Na₂O/Li₂O/K₂O) + 0.5 (Er₂O₃/Nd₂O₃) were prepared using a conventional melt quenching technique. The results of X-ray diffraction patterns indicated the amorphous nature of all the prepared glasses. The visible–near-infrared red (NIR) absorption spectra of these glasses were analyzed systematically. The NIR emission spectra of Er³⁺ and Nd³⁺:calcium boro fluoro zinc phosphate glasses showed prominent emission bands at 1536 nm (⁴I_13/2→⁴I_15/2) and 1069 nm (⁴F_3/2→⁴I_11/2) respectively with λ_exci = 514.5 nm (Ar⁺ laser) as the excitation source.     

Fe3O4/ 生物可降解复合材料研究

磁性氧化铁纳米粒子因具有尺寸小、低毒性和超顺磁性等特点,已经引起了生物化工、医药工业领域的广泛关注。生物可降解高分子材料是生物医用高分子研究中最活跃的领域之一,已广泛用于外科手术缝合线,植入体材料及药物释放载体等。将Fe3O4和生物可降解高分子材料进行复合,可以扩大两者的应用范围,达到理想的治疗效果,并有望开创临床治疗的新时代。本文介绍了磁性四氧化三铁粒子的化学制备方法,包括共沉淀法、溶胶-凝胶法、微乳液法,并对各种方法的优缺点进行了比较;重点阐述了磁性壳聚糖,磁性聚乳酸,磁性PEG,磁性PCL复合材料的制备,及它们在酶的固定化、磁靶向药物及基因载体等医学领域的应用,显示了Fe3O4/生物可降解复合材料在医学领域的广阔应用前景;最后对复合材料走向临床应用所面临的问题及发展前景进行了讨论。     

Optical Magnetic Resonances in Subwavelength Ag–MgF2–Ag Grating Structures

Optical magnetic responses were demonstrated in subwavelength Ag–MgF₂–Ag grating structures for transverse magnetic-polarized light. The subwavelength Ag–MgF₂–Ag grating structures were fabricated using e-beam lithography followed by a lift-off process. By fixing the Ag–MgF₂–Ag strip dimension, the effect of the stripe width on the magnetic resonances was compared for two different grating pitches. With further reduced grating pitch, we pushed the optical magnetic resonances to near UV (deep blue). Numerical simulations confirmed our experimental observations and were in good agreement with the experimental results.     

Fe–O versus O–O bond cleavage in reactive iron peroxide intermediates of superoxide reductase

It is generally accepted that the catalytic cycles of superoxide reductases (SORs) and cytochromes P450 involve a ferric hydroperoxo intermediate at a mononuclear iron center with a coordination sphere consisting of four equatorial nitrogen ligands and one axial cysteine thiolate trans to the hydroperoxide. However, although SORs and P450s have similar intermediates, SORs selectively cleave the Fe–O bond and liberate peroxide, whereas P450s cleave the O–O bond to yield a high-valent iron center. This difference has attracted the interest of researchers, and is further explored here. Meta hybrid DFT (M06-2X) results for the reactivity of the putative peroxo/hydroperoxo reaction intermediates in the catalytic cycle of SORs were found to indicate a high-spin preference in all cases. An exploration of the energy profiles for Fe–O and O–O bond cleavage in all spin states in both ferric and ferrous models revealed that Fe–O bond cleavage always occurs more easily than O–O bond cleavage. While O–O bond cleavage appears to be thermodynamically and kinetically unfeasible in ferric hydrogen peroxide complexes, it could occur as a minor (significantly disfavored) side reaction in the interaction of ferrous SOR with hydrogen peroxide.     

FeS2 nanosheets–H2O2–NaHCO3 chemiluminescence method for procaine hydrochloride determination

FeS₂ nanosheets (NSs) were produced and exploited as a new catalyst for a chemiluminescence (CL) reaction. The characterization of FeS₂ NSs was performed using spectroscopic methods. In this regard, transmission electron microscopy images showed that FeS₂ NSs have a length of ~0.5–1 μm. The direct optical band gap energy of FeS₂ NSs was found to be 3.45 eV. Prepared FeS₂ NSs were used to catalyze the NaHCO₃–H₂O₂ CL reaction. It was found that procaine hydrochloride (PCH) could reduce the intensity of the FeS₂ NSs–NaHCO₃–H₂O₂ CL reaction so, with increasing PCH concentrations, the intensity of light emission decreased. Therefore, a simple and sensitive method was introduced to measure PCH with a linear range expanded from 1.00 × 10⁻⁶ to 1.00 × 10⁻³ mol L⁻¹ and an 8.32 × 10⁻⁷ mol L⁻¹ limit of detection. Studies related to the effect of foreign species and reaction mechanisms were performed. The application of the approach was verified by quantifying the PCH in the injection.     

Expression of HvHMA2 in tobacco modifies Zn–Fe–Cd homeostasis

HvHMA2 is a plasma membrane P_1B-ATPase from barley that functions in Zn/Cd root-to-shoot transport. To assess the usefulness of HvHMA2 for modifying the metal content in aerial plant parts, it was expressed in tobacco under the CaMV35S promoter. Transformation with HvHMA2 did not produce one unique pattern of Zn and Cd accumulation; instead it depended on external metal supply. Thus Zn and Cd root-to-shoot translocation was facilitated, but not at all applied Zn/Cd concentrations. Metal uptake was restricted in HvHMA2-transformed plants and the level in the shoot was not enhanced. It was shown that HvHMA2 localizes to the plasma membrane of tobacco cells, and overloads the apoplast with Zn, which could explain the overall decrease in metal uptake observed. Despite the lower levels in the shoot, HvHMA2 transformants showed increased Zn sensitivity. Moreover, introduction of HvHMA2 into tobacco interfered with Fe metabolism and Fe accumulation was modified in HvHMA2-transformants in a Zn- and Cd-concentration dependent manner. The results indicate that ectopic expression of the export protein HvHMA2 in tobacco interferes with tobacco metal Zn–Cd–Fe cross-homeostasis, inducing internal mechanisms regulating metal uptake and tolerance.     

Pi和PGA对玉米叶片PFK-2/FBPase-2的作用

Fructose-6-phosphate 2-kinase and fructose 2,6-bisphosphatase have been partially purified from maize leaves by PEG fractionadon and by chromatography on TSK-DEAE ion exchanger and Blue-Sepharose 4B. Fructose-6-phosphate 2-kinase was activated by phosphate and inhibited by 3-pnosphoglycerate. Furctose 2,6-bisphosphatase was inhibited by inorganic phosphate and fructose-6-phosphate.The observed pattern of reguladon suggests that systhesis and degradation of Fru-2,6-P_2 respond to changes in the concentration of effectors. An increase in the level of glycerate-3-phosphate or dihydroxyacetonephosphate will result in a decrease in the level of Fru-2,6-P_2. Conversely a rise in Fru-6-P concentration will lead to an increase in the Fru-2, 6-P_2 concentration.     

Thermoluminescence dosimetric attributes of Yb3+-doped BaO–ZnO–LiF–B2O3 glass material after Er3+ co-doping

Motivated by our previous study on Sm³⁺ ions as thermoluminescence (TL) sensitizers to the BaO–ZnO–LiF–B₂O₃–Yb₂O₃ glass system, in the current study we examined the effect of Er³⁺ ion co-doping on the TL characteristics of this glass system. The 4f–4f electronic transitions of the Er³⁺ and Yb³⁺ ions were confirmed via the optical absorption spectrum. Notably, the use of Yb³⁺–Er³⁺ ions failed to improve the TL intensity, sensitivity, and trap density. However, they enabled the glass system to function as an activator–quencher system. The linearity range and effective atomic number remained unaffected after co-doping. In addition, the problem of anomalous fading caused a remnant signal of just 58% after a week of storage of the Yb³⁺ monodoped glass. This was resolved by the optimum co-doping of Er³⁺ ions to achieve an 89% signal. The co-doping of Er³⁺ ions to the BaO–ZnO–LiF–B₂O₃–Yb₂O₃ glass system regulated its thermal stability and therefore supplemented its potential for radiation monitoring in food processing and retrospective dosimetry.     

Oligonucleotide-Mediated Au–Ag Core–Shell Nanoparticles

The bimetallic core–shell nanoparticles show unique plasmonic properties and their preparations and characterizations are currently under investigation. A new type of Au core–Ag shell (Au@Ag) nanoparticles is prepared by sandwiching the chemically attached Raman reporter molecules (RRMs) and a 12-base-long oligonucleotide between the 13 nm average size core-gold nanoparticles (AuNPs) and 9 nm and 21 nm average size of Ag shell. The synthesized Au@Ag nanoparticles are tested for their surface-enhanced Raman scattering (SERS) performance. It is found that the chemical attachment of the oligonucleotides along with the RRM improved the enhancement in Raman scattering more than one order of the magnitude with the Au@Ag nanoparticles with an average 9-nm shell thickness while the Au@Ag nanoparticles with 21 nm average shell thickness have poor SERS activity. A minimum enhancement factor of 1.0 × 10⁷ is estimated for the SERS active oligonucleotide-mediated Au@Ag nanoparticles. The approach may provide new routes for preparation of highly sensitive new generation of bimetallic core–shell nanoparticles.     

Mechanism of O2−- and H2O2-induced stimulation of sugar transport in mouse fibroblast BALB/3T3 cells

Xanthine/xanthine oxidase and H₂O₂ stimulated sugar transport. Application of superoxide dismutase and catalase to the cells showed an inhibitory effect on these agent-stimulated sugar transports. Addition of amiloride and 4-acetamide-4′-isothiocyanostilbene-2,2′-disulfonic acid (SITS), which abolish the cytoplasmic alkalinization, inhibited the stimulation of sugar transport by xanthine/xanthine oxidase in the presence of catalase. The calmodulin antagonists, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) and trifluoperazine inhibited H₂O₂-stimulated sugar transport. These results suggest that O₂⁻ stimulates sugar transport in an intracellular pH-dependent manner and that H₂O₂ stimulates sugar transport in a calcium-calmodulin-dependent manner. These mechanisms may be involved in sugar-transport stimulation in mouse fibroblast BALB/3T3 cells by the tumor-promoting phorbol ester phorbol-12,13-dibutyrate and insulin, since the stimulatory effects of these agents were inhibited by scavengers of oxygen radicals.     

The McClure and Weiss models of Fe–O2 bonding for oxyhemes, and the HbO2 + NO reaction

For the Fe–O₂(S = 0) linkages of oxyhemes, valence bond (VB) structures are re-presented for the McClure [Fe^II(S = 1) + O₂(S = 1)], Pauling–Coryell [Fe^II(S = 0) + O₂*(S = 0)], and Weiss [Fe^III(S = ½) + O₂ ^?(S = ½)] models of bonding. The VB structures for the McClure and Weiss models are of the increased-valence type, with more electrons participating in bonding than occur in their component Lewis structures. The Fe–O bond number and O–O bond order for the McClure structure are correlated with measured Fe–O and O–O bond lengths for oxymyoglobin. Back-bonding from O ₂ ^? to Fe^III of the Weiss structure gives a restricted form of the McClure structure. The McClure and Weiss increased-valence structures are used to provide VB formulations of mechanisms for the oxyhemoglobin + NO reaction. The products of these two formulations are Hb⁺ and NO₃ ^? (where Hb is hemoglobin) and Hb⁺ and OONO^?, respectively. Because Hb⁺ and NO₃ ^? are the observed products, they provide an experimental procedure for distinguishing the McClure and Weiss models. It is also shown that the same type of agreement between McClure-type theory and experiment occurs for oxycoboglobin + NO, cytochrome P450 monooxygenases, and related hydrogen atom transfer reactions. In the appendices, the results of density functional theory and multireference molecular orbital calculations for oxyhemes are related to one formulation of the increased-valence wavefunction for the McClure model, and theory is presented for the calculation of approximate weights for the Lewis structures that are components of the McClure increased-valence structure.     

Dynamic relocation of the TORC1–Gtr1/2–Ego1/2/3 complex is regulated by Gtr1 and Gtr2

TORC1 regulates cellular growth, metabolism, and autophagy by integrating various signals, including nutrient availability, through the small GTPases RagA/B/C/D in mammals and Gtr1/2 in budding yeast. Rag/Gtr is anchored to the lysosomal/vacuolar membrane by the scaffold protein complex Ragulator/Ego. Here we show that Ego consists of Ego1 and Ego3, and novel subunit Ego2. The ∆ego2 mutant exhibited only partial defects both in Gtr1-dependent TORC1 activation and Gtr1 localization on the vacuole. Ego1/2/3, Gtr1/2, and Tor1/Tco89 were colocalized on the vacuole and associated puncta. When Gtr1 was in its GTP-bound form and TORC1 was active, these proteins were preferentially localized on the vacuolar membrane, whereas when Gtr1 was in its GDP-bound form, they were mostly localized on the puncta. The localization of TORC1 to puncta was further facilitated by direct binding to Gtr2, which is involved in suppression of TORC1 activity. Thus regulation of TORC1 activity through Gtr1/Gtr2 is tightly coupled to the dynamic relocation of these proteins.     

Galangin ameliorates cardiac remodeling via the MEK1/2–ERK1/2 and PI3K–AKT pathways

Cardiac remodeling is associated with inflammation and apoptosis. Galangin, as a natural flavonol, has the potent function of regulating inflammation and apoptosis, which are factors related to cardiac remodeling. Beginning 3 days after aortic banding (AB) or Sham surgery, mice were treated with galangin for 4 weeks. Cardiac remodeling was assessed according to echocardiographic parameters, histological analyses, and hypertrophy and fibrosis markers. Our results showed that galangin administration attenuated cardiac hypertrophy, dysfunction, and fibrosis response in AB mice and angiotensin II-treated H9c2 cells. The inhibitory action of galangin in cardiac remodeling was mediated by MEK1/2–extracellular-regulated protein kinases 1/2 (ERK1/2)–GATA4 and phosphoinositide 3-kinase (PI3K)–protein kinase B (AKT)–glycogen synthase kinase 3β (GSK3β) activation. Furthermore, we found that galangin inhibited inflammatory response and apoptosis. Our findings suggest that galangin protects against cardiac remodeling through decreasing inflammatory responses and apoptosis, which are associated with inhibition of the MEK1/2–ERK1/2–GATA4 and PI3K–AKT–GSK3β signals.     

Thermodynamics of pyrope–majorite,Mg3Al2Si3O12–Mg4Si4O12, solid solution from atomistic model calculations

Static lattice energy calculations, based on empirical pair potentials have been performed for a large set of different structures with compositions between pyrope and majorite, and with different states of order of octahedral cations. The energies have been cluster expanded using pair and quaternary terms. The derived ordering constants have been used to constrain Monte–Carlo simulations of temperature-dependent properties in the ranges of 1073–3673 K and 0–20 GPa. The free energies of mixing have been calculated using the method of thermodynamic integration. At zero pressure the cubic/tetragonal transition is predicted for pure majorite at 3300 K. The transition temperature decreases with the increase of the pyrope mole fraction. A miscibility gap associated with the transition starts to develop at about 2000 K and x _maj = 0.8, and widens with the decrease in temperature and the increase in pressure. Activity–composition relations in the range of 0–20 GPa and 1073–2673 K are described with the help of a high-order Redlich–Kister polynomial.     

Fe3O4 and bimetal–organic framework Zn/Mg composite peroxide-like catalyze luminol chemiluminescence for specific measurement of atropine in Datura plant

Atropine (AT) is an anticholinergic drug. AT is abundantly in Datura plant seeds. Fe₃O₄@Zn/Mg MOF (Fe₃O₄@MOF) composite was synthesized. The compound had a high peroxidase-like activity in a chemiluminescence (CL) reaction. Addition of AT quenched CL. The linear range and limit of detection were 5–600 μg L⁻¹ and 2 × 10⁻² μg L⁻¹. This method is fast, reversible, and selective, without biodegradability effects, high accuracy, and precision for measuring AT in the Datura plant.     

Fe3O4磁性纳米粒子在生物医学领域的应用

Fe_3O_4磁性纳米粒子由于其良好的磁学性能,被广泛应用到了化学、生物、物理、环境保护等各个领域。尤其是在生物医学领域中的应用越来越受到研究者的关注。由于其所具有的优秀的超顺磁性性质,Fe_3O_4磁性纳米粒子可以作为造影剂,增强核磁共振成像的对比度和成像效果;也可以结合到纳米载药系统内用于药物的靶向输送;也可以包埋到蛋白内部用于蛋白的磁性分离;也可以用于基因治疗,提高靶细胞的转染效率;由于其在近红外光的作用下具有很好的光热转换效果,使温度升高,展现出的良好热疗效果,Fe_3O_4磁性纳米粒子又可以用于癌细胞的热疗。本文针对其在该领域中作为药物的靶向传递,蛋白的磁分离,核磁共振成像,热疗,以及基因治疗的载体等方面的研究应用进行了系统性的总结,阐述了Fe_3O_4磁性纳米粒子在生物医学领域中各种应用进展和优势。     

硅烷化试剂修饰Fe3O4磁性微粒的研究进展

磁性微粒作为一种新型的功能材料,已经在生物分离、生物医学和环境工程等领域得到了广泛的应用.作者对硅烷化试剂修饰的Fe3O4磁性微粒的制备方法以及硅烷化试剂修饰的Fe3O4磁性微粒在各个领域的最新应用进展进行了评述,引用文献62篇.     

Proton magnetic resonance studies of 7 Fe ferredoxins: Lower potential of the [4 Fe–4 S] redox center than the [3 Fe–3 S] cluster

Two types of iron-sulfur clusters, [3 Fe–3 S] and [4 Fe–4 S], were identified by ¹H-NMR in ferredoxins from Thermus thermophilus, Mycobacterium smegmatis and Pseudomonas ovalis. The [4 Fe–4 S] clusters always showed the redox couples which had potentials lower than that of the [3 Fe–3 S] clusters.