共查询到20条相似文献,搜索用时 31 毫秒
1.
Chandrasekar Balachandran Kenta Yokoi Kana Naito Jebiti Haribabu Yuichi Tamura Masakazu Umezawa Koji Tsuchiya Toshitada Yoshihara Seiji Tobita Shin Aoki 《Molecules (Basel, Switzerland)》2021,26(22)
In our previous paper, we reported that amphiphilic Ir complex–peptide hybrids (IPHs) containing basic peptides such as KK(K)GG (K: lysine, G: glycine) (e.g., ASb-2) exhibited potent anticancer activity against Jurkat cells, with the dead cells showing a strong green emission. Our initial mechanistic studies of this cell death suggest that IPHs would bind to the calcium (Ca2+)–calmodulin (CaM) complex and induce an overload of intracellular Ca2+, resulting in the induction of non-apoptotic programmed cell death. In this work, we conduct a detailed mechanistic study of cell death induced by ASb-2, a typical example of IPHs, and describe how ASb-2 induces paraptotic programmed cell death in a manner similar to that of celastrol, a naturally occurring triterpenoid that is known to function as a paraptosis inducer in cancer cells. It is suggested that ASb-2 (50 µM) induces ER stress and decreases the mitochondrial membrane potential (ΔΨm), thus triggering intracellular signaling pathways and resulting in cytoplasmic vacuolization in Jurkat cells (which is a typical phenomenon of paraptosis), while the change in ΔΨm values is negligibly induced by celastrol and curcumin. Other experimental data imply that both ASb-2 and celastrol induce paraptotic cell death in Jurkat cells, but this induction occurs via different signaling pathways. 相似文献
2.
Aging is a biological process characterized by a progressive functional impairment which is associated with increased susceptibility to a variety of diseases. The main purpose of this study is to understand the gender-based relationship between human aging and activities of two erythrocyte membranes bound enzymes, Ca++-ATPase and Na+/K+-ATPase. Ca++-ATPase and Na+/K+-ATPase activities were determined as per the previous reports. Statistical differences were analyzed with Student’s t test. Our results show a significant (p?<?0.0001) decrease in the Ca++-ATPase and Na+/K+-ATPase activities in males and females as a function of age. We also correlate the activities of ATPases with total antioxidant capacity of the plasma in term of ferric reducing ability of plasma values. The Ca++-ATPase and Na+/K+-ATPase activities positively correlated with ferric reducing ability of plasma value. No significant differences in the ATPase activity between males and females were observed. Decreased activity of Ca++-ATPase and Na+/K+-ATPase during human aging may be due to increased free radical generation which leads to oxidative stress and alter the erythrocyte membrane transport function and other activities. Our results emphasize the need to establish age-dependent reference values for membrane bound enzymes in studies involving its role in different disease conditions. 相似文献
3.
《中国化学快报》2021,32(12):3954-3961
Using nanoparticle-based drug delivery systems as enhancers is a robust strategy for transdermal delivery; however, the mechanisms by which these systems promote transdermal penetration are still unclear. Here, we fabricated a dual-labeled nano drug delivery system that allows discrete visualization of both the drug and the nanoparticle carrier. To comprehensively examine its potential mechanism, we investigated its effects on human epidermal keratinocyte HaCaT cells, including changes in cell membrane potential, intracellular Ca2+ concentration, and Ca2+-ATPase activity. P-glycoprotein (P-gp) expression in nanoparticle-treated human dermal microvascular endothelial cells was detected by western blotting and immunofluorescence. Furthermore, the transdermal absorption and biodistribution of the dual-labeled nanoparticles were deeply investigated by skin permeability study in vitro and in vivo using fluorescence microscopy and in vivo imaging, respectively. In addition to reducing membrane potential, increasing the intracellular Ca2+ concentration, and decreasing Ca2+-ATPase activity, our results indicate that the dual-labeled nanoparticles can downregulate P-gp to promote transdermal absorption. Fluorescence and in vivo imaging visually demonstrated that the nanoparticle delivery system penetrated into the dermis through the stratum corneum. All these results indicate that this dual-labeled nano delivery system provides a new method for future in-depth visual explorations of transdermal drug delivery mechanisms. 相似文献
4.
Monica Averna Alessandro A. Casazza Antonino Martines Marco Pedrazzi Alice Franchi Roberta De Tullio 《Natural product research》2019,33(10):1449-1455
We are reporting in the present study that molecules extracted from olive pomace prevent cell death induced by Ca2+-overloading in different cell types. Exposure of cells to these molecules counteracts the Ca2+-induced cell damages by reducing the activation of the Ca2+-dependent protease calpain, acting possibly through the modification of the permeability to Ca2+ of the plasma membrane. The purification step by RP-HPLC suggests that effective compound(s), differing from the main biophenols known to be present in the olive pomace extract, could be responsible for this effect. Our observations suggest that bioactive molecules present in the olive pomace could be potential candidates for therapeutic applications in pathologies characterised by alterations of intracellular Ca2+ homeostasis. 相似文献
5.
Amerigo Beneduci Giuseppe Chidichimo Giuseppe Dardo Gabriele Pontoni 《Analytica chimica acta》2011,(2):186
A method to obtain high reproducibility of 1H NMR chemical shift of peaks of biofluid metabolites, by simple acidification with HCl is evaluated. Biofluid 1H NMR analysis is indeed spoiled by a strong chemical shift dependence of metabolite peaks on parameters such as ionic strength, concentration of some earth alkali cations and, mostly, on pH of samples. The resulting chemical shift variations, as large as 0.1 ppm, generate misalignments of homogeneous peaks, artifacts and misinterpretations.Reproducible alignment is essential in 1H NMR based metabonomics, where peak misalignments prevent even very wide bins (i.e., 0.04 ppm, as elsewhere proposed) from being used to integrate spectral data for multivariate statistical analysis. Here is demonstrated that routine acidification with HCl to 1.2 ≤ pH ≤ 2.0 ensures highly reproducible peak alignment of urine 1H NMR spectra. In this respect, simple inspection of citrate peaks in the urine can be used to measure pH, as it will be extensively discussed, in that at such low pH they show no dependency on other urine components as reported at higher pH. Under these conditions, in as many as 493 urine samples, in which concentrations of Ca2+, Mg2+, K+, Na+, Cl−, phosphate, and creatinine and ionic strength measured by means of well standardized conventional procedures, showed very wide ranges, peaks align within a SD always lower than 0.002 ppm, thus allowing the use of integration bins at least five times narrower than 0.04 ppm. 相似文献
6.
Neelum Gul Qazi Arif-ullah Khan Sumra Wajid Abbasi Fawad Ali Shah Faisal Rasheed Fawad Ali Syed Shams ul Hassan Simona Bungau 《Molecules (Basel, Switzerland)》2022,27(18)
This present study aimed to delineate Rumex hastatus D. Don crude extract (Rh.Cr), n-Hexane, ethyl acetate, aqueous fractions (Rh.n-Hex, Rh.ETAC, Rh.Aq) and rutin for antidiarrheal, antisecretory effects, anti-spasmodic, gastrointestinal transient time, anti H. pylori, antiulcer effects, and toxicology. The preliminary phytochemical analysis of Rumex hastatus showed different phytoconstituents and shows different peaks in GC-MC chromatogram. Rumex hastatus crude extract (Rh.Cr), fractions, and rutin attributed dose-dependent (50–300 mg/kg) protection (0–100%) against castor oil-induced diarrhea and dose-dependently inhibited intestinal fluid secretions in mice. They decreased the distance traversed by charcoal in the gastrointestinal transit model in rats. In rabbit jejunum preparations, Rh.Cr and Rh.ETAC caused a concentration-dependent relaxation of both spontaneous and K+ (80 mM)-induced contractions at a similar concentration range, whereas Rh.n-Hex, rutin, and verapamil were relatively potent against K+-induced contractions and shifted the Ca2+ concentration–response curves (CRCs) to the right, Rh.Cr (0.3–1 mg/mL) and Rh.ETAC (0.1–0.3 mg/mL) shifted the isoprenaline-induced inhibitory CRCs to the left. Rh.n-Hex, Rh.ETAC and rutin showed anti-H. pylori effect, also shows an inhibitory effect against H+/K+-ATPase. Rumex hastatus showed gastroprotective and antioxidant effects. Histopathological evaluation showed improvement in cellular architecture and a decrease in the expression of inflammatory markers such as, cyclooxygenase (COX-2), tumor necrosis factor (TN,F-α) and phosphorylated nuclear factor kappa B (p-NFƙB), validated through immunohistochemistry and ELISA techniques. In RT-PCR it decreases H+/K+-ATPase mRNA levels. Rumex hastatus was found to be safe to consume up to a dose of 2000 mg/kg in a comprehensive toxicity profile. Docking studies revealed that rutin against H+/K+-ATPase pump and voltage-gated L-type calcium channel showed E-values of −8.7 and −9.4 Kcal/mol, respectively. MD simulations Molecular Mechanics Poisson Boltzmann surface area and molecular mechanics Generalized Born surface area (MMPBSA/GBSA) findings are consistent with the in-vitro, in-vivo and docking results. 相似文献
7.
The synthesis and calcium-selective chromogenic ion binding properties of benzothiazolium derivative of calix[4]arene are described. The merocyanine-type ionophore derived from calix[4]arene-diamide showed selective chromogenic properties toward Ca2+ ions in aqueous methanol. The compound showed significant Ca2+ ion dependent changes in UV-vis spectral properties in the presence of other physiologically important metal ions (Na+, K+, and Mg2+). The pH sensitive chromogenic behavior also suggests that the compound can be used as a sensitive pH indicator around pH 6.5. 相似文献
8.
Oxidative stress leads to protein degeneration or mitochondrial dysfunction, causing neuronal cell death. Glutamate is a neurotransmitter that nerve cells use to send signals. However, the excess accumulation of glutamate can cause excitotoxicity in the central nervous system. In this study, we deciphered the molecular mechanism of catechin-mediated neuroprotective effect on glutamate-induced oxidative stress in mouse hippocampal neuronal HT22 cells. Cellular antioxidant activity was determined using the 1,1-diphenyl-picryl hydrazyl (DPPH) assay and 2′,7′-dichlorodihydrofluorescein diacetate (DCFDA) staining. Furthermore, the levels of intracellular calcium (Ca2+) as well as nuclear condensation and protein expression related to neuronal damage were assessed. All five catechins (epigallocatechin gallate, gallocatechin gallate (GCG), gallocatechin, epicatechin gallate, and epicatechin) showed strong antioxidant effects. Among them, GCG exhibited the highest neuroprotective effect against glutamate excitotoxicity and was used for further mechanistic studies. The glutamate-induced increase in intracellular Ca2+ was reduced after GCG treatment. Moreover, GCG reduced nuclear condensation and the phosphorylation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinases (JNK) involved in cell death. The neuroprotective effect of GCG against glutamate-induced oxidative stress in HT22 cells was attributed to the reduction in intracellular free radicals and Ca2+ influx and also the inhibition of phosphorylation of ERK and JNK. Furthermore, the antioxidant effect of GCG was found to be likely due to the inhibition of phosphorylation of ERK and JNK that led to the effective suppression of neurocytotoxicity caused by glutamate in HT22 cells. 相似文献
9.
Tet Htut Soe Tomotaka Nanjo Kazunori Watanabe Takashi Ohtsuki 《Photochemistry and photobiology》2019,95(6):1395-1402
The inefficient endosomal escape of drugs or macromolecules is a major obstacle to achieving successful delivery to therapeutic targets. An efficient approach to circumvent this barrier is photochemical internalization (PCI), which uses light and photosensitizers for endosomal escape of the delivered macromolecules. The PCI mechanism is related to photogenerated singlet oxygen, but the mechanism is still unclear. In this study, we examined the relation of PCI to heat, pH and Ca2+ ions using cell penetrating peptide (CPP)‐cargo‐photosensitizer (Alexa546 or Alexa633) conjugates. A cell temperature changing experiment demonstrated that heat (thermal mechanism) does not significantly contribute to the photoinduced endosomal escape. Inhibition of V‐ATPase proton pump activity and endosomal pH upregulation indicated that PCI‐mediated endosomal escape needs endosomal acidification prior to photoirradiation. Imaging of the CPP‐cargo‐photosensitizer and Ca2+ ions during photostimulation showed that intracellular calcium increase is not the cause of the endosomal escape of the complex. The increment is mainly due to Ca2+ influx. These findings show the importance of extra‐ and intracellular milieu conditions in the PCI mechanism and enrich our understanding of PCI‐related changes in cell. 相似文献
10.
A new pyrene-containing fluorescent sensor has been synthesized from 2,3,3-trimethylindolenine. Spectroscopic and photophysical properties of sensor are presented. The large change in fluorescence intensity (I/I0 = 0.13) at 381 nm and affinity to Hg2+ over other cations such as K+, Na+, Ca2+, Mg2+, Pb2+, and Cu2+ make this compound a useful chemosensor for Hg2+ detection in hydrophilic media. The sensor (6.0 × 10−6 M) displays significant fluorescence quenching upon addition of Hg2+ in pH 7.4 HEPES buffer without excimer formation. Job’s plot analysis shows the binding stoichiometry to be 2:1 (host/guest). 相似文献
11.
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
12.
Najeeb Ur Rehman Mohd Nazam Ansari Abdul Samad Wasim Ahmad 《Molecules (Basel, Switzerland)》2022,27(4)
Fenchone is a bicyclic monoterpene found in a variety of aromatic plants, including Foeniculum vulgare and Peumus boldus, and is used in the management of airways disorders. This study aimed to explore the bronchodilator effect of fenchone using guinea pig tracheal muscles as an ex vivo model and in silico studies. A concentration-mediated tracheal relaxant effect of fenchone was evaluated using isolated guinea pig trachea mounted in an organ bath provided with physiological conditions. Sustained contractions were achieved using low K+ (25 mM), high K+ (80 mM), and carbamylcholine (CCh; 1 µM), and fenchone inhibitory concentration–response curves (CRCs) were obtained against these contractions. Fenchone selectively inhibited with higher potency contractions evoked by low K+ compared to high K+ with resultant EC50 values of 0.62 mg/mL (0.58–0.72; n = 5) and 6.44 mg/mL (5.86–7.32; n = 5), respectively. Verapamil (VRP) inhibited both low and high K+ contractions at similar concentrations. Pre-incubation of the tracheal tissues with K+ channel blockers such as glibenclamide (Gb), 4-aminopyridine (4-AP), and tetraethylammonium (TEA) significantly shifted the inhibitory CRCs of fenchone to the right towards higher doses. Fenchone also inhibited CCh-mediated contractions at comparable potency to its effect against high K+ [6.28 mg/mL (5.88–6.42, n = 4); CCh] and [6.44 mg/mL (5.86–7.32; n = 5); high K+]. A similar pattern was obtained with papaverine (PPV), a phosphodiesterase (PDE), and Ca2+ inhibitor which inhibited both CCh and high K+ at similar concentrations [10.46 µM (9.82–11.22, n = 4); CCh] and [10.28 µM (9.18–11.36; n = 5); high K+]. However, verapamil, a standard Ca2+ channel blocker, showed selectively higher potency against high K+ compared to CCh-mediated contractions with respective EC50 values of 0.84 mg/mL (0.82–0.96; n = 5) 14.46 mg/mL (12.24–16.38, n = 4). The PDE-inhibitory action of fenchone was further confirmed when its pre-incubation at 3 and 5 mg/mL potentiated and shifted the isoprenaline inhibitory CRCs towards the left, similar to papaverine, whereas the Ca2+ inhibitory-like action of fenchone pretreated tracheal tissues were authenticated by the rightward shift of Ca2+ CRCs with suppression of maximum response, similar to verapamil, a standard Ca2+ channel blocker. Fenchone showed a spasmolytic effect in isolated trachea mediated predominantly by K+ channel activation followed by dual inhibition of PDE and Ca2+ channels. Further in silico molecular docking studies provided the insight for binding of fenchone with Ca2+ channel (−5.3 kcal/mol) and K+ channel (−5.7), which also endorsed the idea of dual inhibition. 相似文献
13.
New photo-induced electron transfer (PET) probes OMOX and OBOX, carrying an additional binding site in the form of ‘oxadiazole nitrogen’ have been designed to evaluate binding interactions with biologically significant Li+, Na+, K+, Ca2+, Mg2+, and Zn2+ including environmentally toxic Ba2+ and Cd2+ using optical spectral techniques. While Li+, Na+, and K+ did not appreciably perturb either the absorption or emission spectra, Ba2+, Ca2+, Mg2+, Zn2+, and Cd2+ induced slight red shifts (2-8 nm) in the UV-visible spectra as well as pronounced chelation induced enhanced fluorescence (CHEF). Both OMOX and OBOX exhibited the highest CHEF in contact with the zinc ion, whereas Ba2+, Ca2+, Mg2+, and Cd2+ induced relatively less emission enhancements. OBOX, which is a poorer emitter (Φf=0.0062) than OMOX (Φf=0.015), showed highly promising 160-fold emission enhancement in the presence of Zn2+. Potential, therefore is available in OBOX to function as a selective luminescent ‘off-on’ sensor for Zn2+ in the presence of coordinatively competing Ba2+, Ca2+, Mg2+, and Cd2+ ions. 相似文献
14.
Sung-Yup Cho Jin-Haeng Lee Han-Dong Bae Eui Man Jeong Gi-Yong Jang Chai-Wan Kim Dong-Myung Shin Ju-Hong Jeon In-Gyu Kim 《Experimental & molecular medicine》2010,42(9):639-650
An abrupt increase of intracellular Ca2+ is observed in cells under hypoxic or oxidatively stressed conditions. The dysregulated increase of cytosolic Ca2+ triggers apoptotic cell death through mitochondrial swelling and activation of Ca2+-dependent enzymes. Transglutaminase 2 (TG2) is a Ca2+-dependent enzyme that catalyzes transamidation reaction producing cross-linked and polyaminated proteins. TG2 activity is known to be involved in the apoptotic process. However, the pro-apoptotic role of TG2 is still controversial. In this study, we investigate the role of TG2 in apoptosis induced by Ca2+-overload. Overexpression of TG2 inhibited the -induced apoptosis through suppression of caspase-3 and -9 activities, cytochrome c release into cytosol, and mitochondria membrane depolarization. Conversely, down-regulation of TG2 caused the increases of cell death, caspase-3 activity and cytochrome c in cytosol in response to Ca2+-overload. Western blot analysis of Bcl-2 family proteins showed that TG2 reduced the expression level of Bax protein. Moreover, overexpression of Bax abrogated the anti-apoptotic effect of TG2, indicating that TG2-mediated suppression of Bax is responsible for inhibiting cell death under Ca2+-overloaded conditions. Our findings revealed a novel anti-apoptotic pathway involving TG2, and suggested the induction of TG2 as a novel strategy for promoting cell survival in diseases such as ischemia and neurodegeneration. A23187相似文献
15.
Introduction: Safranal, which endows saffron its unique aroma, causes vasodilatation and has a hypotensive effect in animal studies, but the mechanisms of these effects are unknown. In this study, we investigated the mechanisms of safranal vasodilation. Methods: Isolated rat endothelium-intact or -denuded aortic rings were precontracted with phenylephrine and then relaxed with safranal. To further assess the involvement of nitric oxide, prostaglandins, guanylate cyclase, and phospholipase A2 in safranal-induced vasodilation, aortic rings were preincubated with L-NAME, indomethacin, methylene blue, or quinacrine, respectively, then precontracted with phenylephrine, and safranal concentration–response curves were established. To explore the effects of safranal on Ca2+ influx, phenylephrine and CaCl2 concentration–response curves were established in the presence of safranal. Furthermore, the effect of safranal on aortic rings in the presence of ouabain, a Na+-K+ ATPase inhibitor, was studied to explore the contribution of Na+/Ca2+ exchanger to this vasodilation. Results: Safranal caused vasodilation in endothelium-intact and endothelium-denuded aortic rings. The vasodilation was not eliminated by pretreatment with L-NAME, indomethacin, methylene blue, or quinacrine, indicating the lack of a role for NO/cGMP. Safranal significantly inhibited the maximum contractions induced by phenylephrine, or by CaCl2 in Ca2+-free depolarizing buffer. Safranal also relaxed contractions induced by ouabain, but pretreatment with safranal totally abolished the development of ouabain contractions. Discussion/Conclusion: Inhibition of Na+-K+ ATPase by ouabain leads to the accumulation of Na+ intracellularly, forcing the Na+/Ca2+ exchanger to work in reverse mode, thus causing a contraction. Inhibition of the development of this contraction by preincubation with safranal indicates that safranal inhibited the Na+/Ca2+ exchanger. We conclude that safranal vasodilation is mediated by the inhibition of calcium influx from extracellular space through L-type Ca2+ channels and by the inhibition of the Na+/Ca2+ exchanger. 相似文献
16.
In this work, we synthesised and characterised three novel fluorescence macrocyclic sensors containing optically active dansyl groups. The studies for the interaction of the synthesised compounds with various mental ions (Li+, Na+, K+, Ag+, Mg2+, Ca2+, Ba2+, Pb2+, Zn2+, Co2+, Cd2+, Hg2+, Ni2+, Cu2+, Mn2+, Cr3+, Al3+, Fe3+) were performed by fluorescence titration, Job’s plot, ESI-MS and DFT calculations. The results showed that the sensors 1a–1c displayed selective recognition for Cu2+ and Fe3+ ions and formed stoichiometry 1:1 complex through PET mechanism in DMSO/H2O solution (1:1, v/v, pH 7.4 of HEPES). The binding constant (K) and detection limit were calculated. 相似文献
17.
Federica Carnamucio Claudia Foti Massimiliano Cordaro Ottavia Giuffr 《Molecules (Basel, Switzerland)》2022,27(17)
Metronidazole (MNZ) is an antibiotic widely used for the treatment of various infectious diseases and as an effective pesticide agent for the cultivation of chickens and fish. Its high resistance to purification processes and biological activity has led to the classification of MNZ as an emerging contaminant. A speciation study, aimed to define the acid-base properties of MNZ and its interaction with Ca2+, commonly present in natural waters, is reported. The protonation constants of MNZ, as well as the formation constant value of Ca2+-MNZ species, were obtained by potentiometric titrations in an aqueous solution, using NaCl as background salt at different ionic strengths (0.15, 0.5, 1 mol L−1) and temperature (15, 25 and 37 °C) conditions. The acid-base behavior and the complexation with Ca2+ were also investigated by 1H NMR and UV-Vis titrations, with results in very good agreement with the potentiometric ones. The dependence of the formation constants on the ionic strength and temperature was also determined. The sequestering ability of MNZ towards Ca2+ was defined by the empirical parameter pL0.5 at different pH and temperature values. The speciation of MNZ simulating sea water conditions was calculated. 相似文献
18.
19.
A new fluorescent Ca2+ indicator STDln-AM for detecting [Ca2+], transients in cultured smooth muscle cells is presented. By making a comparison, the difference between STDln and fluo-3
is discussed in detail. Using the new Ca2+ indicator, the mechanism of 5-hydroxytryptamino (5-HT) induced intracellular calcium dynamics in stomach fundus smooth muscle
cells (SFSMC) of rats is investigated. It is shown that in contrast with fluo-3, STDln is uniformly distributed in the cytosolic
compartment but excluded from the nucleus, when it is transfected into cells. This feature makes it a real cytosol Ca2+ indicator and can reflect changes of cytosol [Ca2+] more accurately than that of fluo-3. In addition, STDln responds to the [Ca2+], transients more sensitive and faster than fluo-3. The results also show that, the L-type Ca2+ channel inhibitor Mn9202 and the PLC inhibitor Compound 48/80 can significantly inhibit the [Ca2+], elevation induced by 5-HT, while the PKC inhibitor D-Sphingosine can enhance the effect of 5-HT. The results suggest that
5-HT acts by the way of 5-HT2 receptors on SFSMC, then through 5-HT2 receptors coupled IP3/Ca2+ and GC/PKC double signal transduction pathways to make Ca2+ release from intracellular Ca2+ stores and Ca2+ influx possibly through L-type calcium channels. 相似文献
20.
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