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1.
This work investigates the thermal decomposition of magnesian kutnahorite, which belongs to the dolomite group.The DTA curve measured in static air using a small amount of sample (5.0 mg) is quite different from those published previously. This difference might be due to the effect of a self-generated CO2 atmosphere.In a CO2 flow of 100 ml min?1, magnesian kutnahorite decomposes in four steps. Mg-kutnahorite → CaCO3 + Mg2MnO4 + Mn3O4 + MgO → CaCO3 + CaMnO3 + MgO → CaCO3 + CaMnO3 + Ca2MnO4 + MgO → CaMnO3 + Ca2MnO4 + MgO + CaO.However, in a mixed gas flow of CO2 at 95 ml min?1 and CO at 5 ml min?1, it decomposes, like dolomite, in two steps. Mg-kutnahorite → CaCO3 + (Mg,Mn) → (Ca, Mn)O + (Mg,Mn).It has been found that the equilibrium redistribution of Mn between (Ca, Mn) and (Mg, Mn) is achieved at the second decomposition step. This is supported by theoretical considerations.Consequently, when the O2 partial pressure in the atmosphere is low enough to keep Mn in a bivalent state, the Mn bearing dolomite group mineral decomposes in a similar manner to dolomite itself. 相似文献
2.
Differentiation of neuronal cells has been shown to accelerate stress-induced cell death, but the underlying mechanisms are not completely understood. Here, we find that early and sustained increase in cytosolic ([Ca2+]c) and mitochondrial Ca2+ levels ([Ca2+]m) is essential for the increased sensitivity to staurosporine-induced cell death following neuronal differentiation in PC12 cells. Consistently, pretreatment of differentiated PC12 cells with the intracellular Ca2+-chelator EGTA-AM diminished staurosporine-induced PARP cleavage and cell death. Furthermore, Ca2+ overload and enhanced vulnerability to staurosporine in differentiated cells were prevented by Bcl-XL overexpression. Our data reveal a new regulatory role for differentiation-dependent alteration of Ca2+ signaling in cell death in response to staurosporine. 相似文献
3.
Xiuyan Wan Hui Zhong Wei Pan Yanhua Li Yuanyuan Chen Na Li Bo Tang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14272-14277
Dihydroartemisinin (DHA) has attracted increasing attention as an anticancer agent. However, using DHA to treat cancer usually depends on the synergistic effects of exogenous components, and the loss of DHA during delivery reduces its effectiveness in cancer therapy. Reported herein is a programmed release nanoplatform of DHA to synergistically treat cancer with a Fe‐TCPP [(4,4,4,4‐(porphine‐5,10,15,20‐tetrayl) tetrakis(benzoic acid)] NMOF (nanoscale MOF) having a CaCO3 mineralized coating, which prevents DHA leakage during transport in the bloodstream. When the nanoplatform arrives at the tumor site, the weakly acidic microenvironment and high concentration of glutathione (GSH) trigger DHA release and TCPP activation, enabling the synergistic Fe2+‐DHA‐mediated chemodynamic therapy, Ca2+‐DHA‐mediated oncosis therapy, and TCPP‐mediated photodynamic therapy. In vivo experiments demonstrated that the nanoplatform showed enhanced anticancer efficiency and negligible toxicity. 相似文献
4.
Light Irradiation of Mouse Spermatozoa: Stimulation of In Vitro Fertilization and Calcium Signals 总被引:2,自引:0,他引:2
Natalie Cohen Rachel Lubart Sara Rubinstein Haim Breitbart 《Photochemistry and photobiology》1998,68(3):407-413
Irradiation of mouse spermatozoa by 630 nm He-Ne laser was found to enhance the intracellular calcium levels and fertilizing potential of these cells. The effect of light on calcium transport and on fertilization rate was abrogated in the absence of Ca2+during the irradiation time, indicating that the effect of light is Ca2+dependent. The stimulatory effect of light on Ca2+uptake was abolished in the presence of a voltage-dependent Ca2+-channel inhibitor nifedipine, indicating the involvement of a plasma membrane voltage-dependent Ca2+channel. Furthermore, the stimulatory effect of light was completely inhibited by the mitochondrial uncoupler FCCP, indicating that laser irradiation might affect the mitochondrial Ca2+transport mechanisms. A causal association between laser irradiation, reactive oxygen species (ROS) generation and sperm function was indicated by studies with ROS scavengers, superoxide dismutase (SOD) and catalase, and exogenous hydrogen peroxide. The SOD treatment, which enhanced H2O2 production, resulted in increased Ca2+uptake and enhanced fertilization rate. On the other hand, catalase, which decomposes H2O2, impaired the light-induced stimulation in Ca2+uptake and the fertilization rate. Taken together, the data suggest that H2O2 might be involved in the irradiation effects, and indeed laser irradiation enhances the production of H2O2, by spermatozoa. These results indicate that the effect of 630 nm He-Ne laser irradiation is mediated through the generation of H2O2 by the spermatozoa and that this effect plays a significant role in the augmentation of the sperm cells' capability to fertilize metaphase H-arrested eggs in vitro. 相似文献
5.
Dr. Ryota Suwa Assoc. Prof. Masayuki Hatta Prof. Kazuhiko Ichikawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13656-13661
CaCO3‐saturated saline waters at pH values below 8.5 are characterized by two stationary equilibrium states: reversible chemical calcification/decalcification associated with acid dissociation, Ca2++HCO3??CaCO3+H+; and reversible static physical precipitation/dissolution, Ca2++CO32??CaCO3. The former reversible reaction was determined using a strong base and acid titration. The saturation state described by the pH/PCO2‐independent solubility product, [Ca2+][CO32?], may not be observed at pH below 8.5 because [Ca2+][CO32?]/([Ca2+][HCO3?]) ?1. Since proton transfer dynamics controls all reversible acid dissociation reactions in saline waters, the concentrations of calcium ion and dissolved inorganic carbon (DIC) were expressed as a function of dual variables, pH and PCO2. The negative impact of ocean acidification on marine calcifying organisms was confirmed by applying the experimental culture data of each PCO2/pH‐dependent coral polyp skeleton weight (Wskel) to the proton transfer idea. The skeleton formation of each coral polyp was performed in microspaces beneath its aboral ectoderm. This resulted in a decalcification of 14 weight %, a normalized CaCO3 saturation state Λ of 1.3 at PCO2 ≈400 ppm and pH ≈8.0, and serious decalcification of 45 % and Λ 2.5 at PCO2 ≈1000 ppm and pH ≈7.8. 相似文献
6.
Transparent thin films of calcium‐ion‐incorporated polymer composites were synthesized with calcium carbonate (CaCO3) and polymers such as poly(acrylic acid) (PAA), poly(ethylene glycol) (PEG), and methylcellulose. The homogeneous distribution of Ca2+ in the composite films was observed because of the high concentration of COO? groups along the PAA backbone for the complexation of Ca2+ ions. The optical transparency of the composites depends on the weight percentages of the three polymers and the molar concentration of CaCO3 in the composites. Maximum transparency was obtained for a composite film with a PAA/CaCO3 ratio of 9:1. The results indicated that methylcellulose improved the film‐forming capabilities and that PEG improved the transparency of the composites. All polymer complexes were characterized with X‐ray diffraction, fourier transfer infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, dynamic mechanical analysis, and optical transparency measurements. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4459–4465, 2004 相似文献
7.
Cheng‐Li YAO 《中国化学》2008,26(6):1075-1078
The biliary protein (BP) was isolated from pig bile by gel filtration. The interaction between Ca2+ and protein was measured by fluorescence spectra. The result showed that there was a strong coordination between biliary protein and Ca2+. The CaCO3 crystals obtained in systems with and without BP were characterized by scanning electron microscopy, Fourier transform infrared spectrography and powder X‐ray diffractometry. The possible formation mechanism of CaCO3 in biliary protein solution was discussed. 相似文献
8.
Greta Linden Lei Zhang Fabian Pieck Uwe Linne Dmitri Kosenkov Ralf Tonner Olalla Vzquez 《Angewandte Chemie (International ed. in English)》2019,58(37):12868-12873
We report the use of bioorthogonal reactions as an original strategy in photodynamic therapy to achieve conditional phototoxicity and specific subcellular localization simultaneously. Our novel halogenated BODIPY‐tetrazine probes only become efficient photosensitizers (ΦΔ≈0.50) through an intracellular inverse‐electron‐demand Diels–Alder reaction with a suitable dienophile. Ab initio computations reveal an activation‐dependent change in decay channels that controls 1O2 generation. Our bioorthogonal approach also enables spatial control. As a proof‐of‐concept, we demonstrate the feasibility of the selective activation of our dormant photosensitizer in cellular nuclei, causing cancer cell death upon irradiation. Thus, our dual biorthogonal, activatable photosensitizers open new venues to combat current limitations of photodynamic therapy. 相似文献
9.
Huanhuan Fan Dr. Zilong Zhao Guobei Yan Prof. Xiaobing Zhang Dr. Chao Yang Hongmin Meng Zhuo Chen Hui Liu Prof. Weihong Tan 《Angewandte Chemie (International ed. in English)》2015,54(16):4801-4805
DNAzymes hold promise for gene‐silencing therapy, but the lack of sufficient cofactors in the cell cytoplasm, poor membrane permeability, and poor biostability have limited the use of DNAzymes in therapeutics. We report a DNAzyme–MnO2 nanosystem for gene‐silencing therapy. MnO2 nanosheets adsorb chlorin e6‐labelled DNAzymes (Ce6), protect them from enzymatic digestion, and efficiently deliver them into cells. The nanosystem can also inhibit 1O2 generation by Ce6 in the circulatory system. In the presence of intracellular glutathione (GSH), MnO2 is reduced to Mn2+ ions, which serve as cofactors of 10–23 DNAzyme for gene silencing. The release of Ce6 generates 1O2 for more efficient photodynamic therapy. The Mn2+ ions also enhance magnetic resonance contrast, providing GSH‐activated magnetic resonance imaging (MRI) of tumor cells. The integration of fluorescence recovery and MRI activation provides fluorescence/MRI bimodality for monitoring the delivery of DNAzymes. 相似文献
10.
Motivated by the need for new phosphors of white light emitting diode (WLED) application, Ca0.95Nb2 O6:Eu3+0.05 phosphors were synthesized by high temperature solid‐state reaction. Increasing the content of doped‐Eu3+ and adding the co‐activator Bi3+ to improve the photoluminescence (PL) intensity of Ca1?xNb2 O6Eu3+x phosphors were investigated in detail. The effects of Eu3+ were better than that of Bi3+ on the PL intensity of Ca1?xNb2 O6Eu3+x phosphors. Compared with Y2O2 S:0.05Eu3+ the Ca0.70Nb2 O6:Eu3+0.03 phosphor could be excited efficiently by UV (395 nm) light and emit the red light at 614 nm with line spectra, which were coupled well with the characteristic emission from UV‐Near UV LED. The CIE (International Commission on Illumination) chromaticity coordinates (x?0.654, y?0.348) of Ca0.70Nb2O6:Eu3+0.03 were close to the NTSC (National Television Standard Committee) standard values. Therefore Ca0.70Nb2 O6:Eu3+0.03 might find application to UV‐Near UV InGaN chip‐based white light emitting diodes, which is further proved by the LED fabrication with the Ca0.70Nb2 O6:Eu3+0.03 phosphor. 相似文献
11.
A general method to find the rate constant and particle self-diffusion coefficient is suggested for a heterogeneous isotopic exchange reaction which is controlled by surface mass reaction or controlled by a combination of surface mass reaction and intraparticle diffusion. The values of the kinetic parameter, ξ1 (ratio of the forward surface mass reaction rate to the intraparticle diffusion rate), particle self-diffusion coefficient D and rate constant k are obtained by the proposed method for the isotopic exchange reaction systems CaCO3(s)/Ca2+(aq) and CaC2O4(s)/Ca2+(aq). 相似文献
12.
Chunqiu Zhang Tiezheng Pan Prof. Christian Salesse Dongmei Zhang Lu Miao Liang Wang Yuzhou Gao Jiayun Xu Prof. Zeyuan Dong Prof. Quan Luo Prof. Junqiu Liu 《Angewandte Chemie (International ed. in English)》2014,53(49):13536-13539
A Ca2+‐responsive artificial selenoenzyme was constructed by computational design and engineering of recoverin with the active center of glutathione peroxidase (GPx). By combining the recognition capacity for the glutathione (GSH) substrate and the steric orientation of the catalytic selenium moiety, the engineered selenium‐containing recoverin exhibits high GPx activity for the catalyzed reduction of H2O2 by glutathione (GSH). Moreover, the engineered selenoenzyme can be switched on/off by Ca2+‐induced allosterism of the protein recoverin. This artificial selenoenzyme also displays excellent antioxidant ability when it was evaluated using a mitochondrial oxidative damage model, showing great potential for controlled catalysis in biomedical applications. 相似文献
13.
Chao Wang Fengjuan Cao Yudi Ruan Xiaodan Jia Wenyao Zhen Xiue Jiang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(29):9951-9955
The generation of singlet oxygen (1O2) during photodynamic therapy is limited by the precise cooperation of light, photosensitizer, and oxygen, and the therapeutic efficiency is restricted by the elevated glutathione (GSH) levels in cancer cells. Herein, we report that an ultrathin two‐dimensional metal–organic framework of Cu‐TCPP nanosheets (TCPP=tetrakis(4‐carboxyphenyl)porphyrin) can selectively generate 1O2 in a tumor microenvironment. This process is based on the peroxidation of the TCPP ligand by acidic H2O2 followed by reduction to peroxyl radicals under the action of the peroxidase‐like nanosheets and Cu2+, and their spontaneous recombination reaction by the Russell mechanism. In addition, the nanosheets can also deplete GSH. Consequently, the Cu‐TCPP nanosheets can selectively destroy tumor cells with high efficiency, constituting an attractive way to overcome current limitations of photodynamic therapy. 相似文献
14.
Haizhen Ding Fangfang Ren Peifei Liu Yushuo Feng Xiaoqian Ma Zhiyang Shen Qianqian Shi Mengjiao Xu Wenle Li Prof. Hongmin Chen 《Angewandte Chemie (International ed. in English)》2023,62(44):e202311549
Both hydrogen (H2) and copper ions (Cu+) can be used as anti-cancer treatments. However, the continuous generation of H2 molecules and Cu+ in specific sites of tumors is challenging. Here we anchored Cu2+ on carbon photocatalyst (Cu@CDCN) to allow the continuous generation of H2 and hydrogen peroxide (H2O2) in tumors using the two-electron process of visible water splitting. The photocatalytic process also generated redox-active Cu-carbon centers. Meanwhile, the Cu2+ residues reacted with H2O2 (the obstacle to the photocatalytic process) to accelerate the two-electron process of water splitting and cuprous ion (Cu+) generation, in which the Cu2+ residue promoted a pro-oxidant effect with glutathione through metal-reducing actions. Both H2 and Cu+ induced mitochondrial dysfunction and intracellular redox homeostasis destruction, which enabled hydrogen therapy and cuproptosis to inhibit cancer cell growth and suppress tumor growth. Our research is the first attempt to integrate hydrogen therapy and cuproptosis using metal-enhanced visible solar water splitting in nanomedicine, which may provide a safe and effective cancer treatment. 相似文献
15.
A new ratiometric fluorescent sensor ( 1 ) for Cu2+ based on 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) with di(2‐picolyl)amine (DPA) as ion recognition subunit has been synthesized and investigated in this work. The binding abilities of 1 towards different metal ions such as alkali and alkaline earth metal ions (Na+, K+, Mg2+, Ca2+) and other metal ions ( Ba2+, Zn2+, Cd2+, Fe2+, Fe3+, Pb2+, Ni2+, Co2+, Hg2+, Ag+) have been examined by UV‐vis and fluorescence spectroscopies. 1 displays high selectivity for Cu2+ among all test metal ions and a ~10‐fold fluorescence enhancement in I582/I558 upon excitation at visible excitation wavelength. The binding mode of 1 and Cu2+ is a 1:1 stoichiometry determined via studies of Job plot, the nonlinear fitting of the fluorometric titration and ESI mass. 相似文献
16.
Dr. Li Ma Dr. William W. Y. Lam Dr. Po‐Kam Lo Dr. Kai‐Chung Lau Prof. Tai‐Chu Lau 《Angewandte Chemie (International ed. in English)》2016,55(9):3012-3016
Although FeO42? (ferrate(IV)) is a very strong oxidant that readily oxidizes water in acidic medium, at pH 9–10 it is relatively stable (<2 % decomposition after 1 h at 298 K). However, FeO42? is readily activated by Ca2+ at pH 9–10 to generate O2. The reaction has the following rate law: d[O2]/dt=kCa[Ca2+][FeO42?]2. 18O‐labeling experiments show that both O atoms in O2 come from FeO42?. These results together with DFT calculations suggest that the function of Ca2+ is to facilitate O–O coupling between two FeO42‐ions by bridging them together. Similar activating effects are also observed with Mg2+ and Sr2+. 相似文献
17.
Gehlenite, Ca2Al[AlSiO7], has melilite‐type structure with space group . It contains two topologically distinct positions coordinated tetrahedrally by oxygen. One is completely occupied by Al3+, whereas the other one contains Al3+ and Si4+. Normally, the Al3+ molar fraction in the second tetrahedrally coordinated position does not exceed xAl = 0.5, i.e. the so‐called Loewenstein‐rule is obeyed. In this contribution the structural variations in the melilite‐type compounds of the compositions LaxCa2?xAl[Al1+xSi1?xO7], EuxCa2?xAl[Al1+xSi1?xO7] and ErxCa2?xAl[Al1+xSi1?xO7] are discussed. All members of the solid solution except the end‐members violate Loewenstein's rule. Rietveld refinements against X‐ray powder diffraction patterns confirm that the compounds have space group , without changes in the Wyckoff‐positions of the ions compared to gehlenite. 相似文献
18.
Sophie H. Dale Mark R. J. Elsegood 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(12):m540-m542
The reaction of CaCO3 with isophthalic acid in water yields nonaaquapenta‐μ‐isophthalato‐pentacalcium octahydrate, {[Ca5(C8H4O4)5(H2O)9]·8H2O}n, a complex polymeric one‐dimensional column structure bearing metal–carboxylate bonds and Ca‐bound terminal and bridging water molecules, in addition to hydrogen‐bonded water molecules of crystallization. The asymmetric unit comprises half of the formula unit, with one Ca2+ ion located on a twofold axis, and contains 16 unique strong O—H⋯O hydrogen bonds, some of which link the columns together. 相似文献
19.
Yaping Huang Qiang Shen Weiping Sui Meili Guo Ying Zhao Dujin Wang Duanfu Xu 《Colloid and polymer science》2007,285(6):641-647
An amphiphilic derivative of carboxymethylchitosan (CMCS), (2-hydroxyl-3-butoxyl)propyl-CMCS (HBP-CMCS), was used as an organic
additive in the precipitation process of calcium carbonate (CaCO3). HBP-CMCS molecules can interact with calcium ions, the functional groups of which act as active sites for the nucleation
and crystallization of CaCO3. Simultaneously, HBP-CMCS molecule also functionalizes as a colloidal stabilizer to prohibit the sedimentation of the grown
CaCO3 crystals, depending upon the molar ratio of the initial Ca2+ ions to the repeat units of HBP-CMCS molecules. The combination investigations of scanning electron microscopy, X-ray diffraction,
and Fourier transform infrared spectroscopy on the precipitated CaCO3 crystals proved that concentrations of HBP-CMCS and Ca2+ exert great influence on the crystallization habit of CaCO3, such as the nucleation, growth, morphology, crystal form, etc. The formation of the peanut-shaped CaCO3 particles suggests the template effect of HBP-CMCS molecules on the aggregation behavior of CaCO3 nanocrystals. 相似文献
20.
Minfeng Huo Liying Wang Linlin Zhang Chenyang Wei Yu Chen Jianlin Shi 《Angewandte Chemie (International ed. in English)》2020,59(5):1906-1913
Sustained tumor oxygenation is of critical importance during type‐II photodynamic therapy (PDT), which depends on the intratumoral oxygen level for the generation of reactive oxygen species. Herein, the modification of photosynthetic cyanobacteria with the photosensitizer chlorin e6 (ce6) to form ce6‐integrated photosensitive cells, termed ceCyan, is reported. Upon 660 nm laser irradiation, sustained photosynthetic O2 evolution by the cyanobacteria and the immediate generation of reactive singlet oxygen species (1O2) by the integrated photosensitizer could be almost simultaneously achieved for tumor therapy using type‐II PDT both in vitro and in vivo. This work contributes a conceptual while practical paradigm for biocompatible and effective PDT using hybrid microorganisms, displaying a bright future in clinical PDT by microbiotic nanomedicine. 相似文献