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1.
Curcumin Attenuates Cr(VI)‐Induced Ascites and Changes in the Activity of Aconitase and F1F0 ATPase and the ATP Content in Rat Liver Mitochondria
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Wylly Ramsés García‐Niño Cecilia Zazueta Edilia Tapia José Pedraza‐Chaverri 《Journal of biochemical and molecular toxicology》2014,28(11):522-527
Occupational and environmental exposure to potassium dichromate (K2Cr2O7), a hexavalent chromium compound, can result in liver damage associated with oxidative stress and mitochondrial dysfunction. The purpose of this study was to evaluate the effect of the antioxidant curcumin (400 mg/kg b.w.) on the K2Cr2O7‐induced injury, with special emphasis on ascitic fluid accumulation and oxidative phosphorylation mitochondrial enzymes and the adenosine triphosphate (ATP) levels in isolated mitochondria from livers of rats treated with K2Cr2O7 (15 mg/kg b.w.). Thus, curcumin attenuated the ascites generation, prevented the decrease in the activities of aconitase and F1F0 ATPase, and maintained the ATP levels. The activity of complex II was not completely reestablished by curcumin, whereas complexes III and IV activities were unchanged. 相似文献
2.
Kehkashan Parveen 《Chemico-biological interactions》2009,181(3):343-1557
Environmental and occupational exposure to chromium compounds, especially hexavalent chromium [Cr(VI)], is widely recognized as a potential nephrotoxic in humans and animals. Its toxicity is associated with overproduction of free radicals, which induces oxidative damage. Recent evidence indicates that Pycnogenol® (PYC), French maritime pine bark extract, exhibits antioxidant potential and protects against various oxidative stressors. The aim of the present study was to examine the modulating impacts of PYC on potassium dichromate (K2Cr2O7)-induced oxidative damage and nephrotoxicity in rats. Male Wistar rats were divided into four groups. The first group was control, the second group was control plus pre-treated with PYC (10 mg/kg, body weight; in saline; intraperitoneally; once daily for 3 weeks) as drug control and the third group was saline pre-treated plus treated with a single injection of K2Cr2O7 (15 mg/kg, body weight; in saline; intraperitoneally) as toxicant group. The fourth group was PYC pre-treated plus K2Cr2O7 injected. Forty-eight hours after K2Cr2O7-treatment, blood was drawn for estimation of renal injury markers in serum. Rats were then sacrificed, and their kidneys were dissected for biochemical and histopathological assays. K2Cr2O7-treated rats showed significant increases in markers of renal injury in serum, including blood urea nitrogen (BUN), serum creatinine (Scr), and alkaline phosphatase (ALP), which were significantly (P < 0.05) decreased by PYC pre-treatment. Moreover, prophylactic pre-treatment of rats with PYC significantly (P < 0.05) ameliorated increased thiobarbituric reactive substances (TBARS), malonaldehyde (MDA) and protein carbonyl (PC), and decreased levels of glutathione (GSH) and catalase activity in the kidney homogenate of K2Cr2O7-treated rats. These results were also supported and confirmed with histopathological findings. The study suggests that PYC is effective in preventing K2Cr2O7-induced oxidative mediated nephrotoxicity, but more studies are needed to confirm the effects of PYC as a nephroprotective agent. 相似文献
3.
Otacilio C. Moreira 《BBA》2005,1708(3):411-419
The bidentate complex of ATP with Cr3+, CrATP, is a nucleotide analog that is known to inhibit the sarcoplasmic reticulum Ca2+-ATPase and the Na+,K+-ATPase, so that these enzymes accumulate in a conformation with the transported ion (Ca2+ and Na+, respectively) occluded from the medium. Here, it is shown that CrATP is also an effective and irreversible inhibitor of the plasma membrane Ca2+-ATPase. The complex inhibited with similar efficiency the Ca2+-dependent ATPase and the phosphatase activities as well as the enzyme phosphorylation by ATP. The inhibition proceeded slowly (T1/2 = 30 min at 37 °C) with a Ki = 28 ± 9 μM. The inclusion of ATP, ADP or AMPPNP in the inhibition medium effectively protected the enzyme against the inhibition, whereas ITP, which is not a PMCA substrate, did not. The rate of inhibition was strongly dependent on the presence of Mg2+ but unaltered when Ca2+ was replaced by EGTA. In spite of the similarities with the inhibition of other P-ATPases, no apparent Ca2+ occlusion was detected concurrent with the inhibition by CrATP. In contrast, inhibition by the complex of La3+ with ATP, LaATP, induced the accumulation of phosphoenzyme with a simultaneous occlusion of Ca2+ at a ratio close to 1.5 mol/mol of phosphoenzyme. The results suggest that the transport of Ca2+ promoted by the plasma membrane Ca2+-ATPase goes through an enzymatic phospho-intermediate that maintains Ca2+ ions occluded from the media. This intermediate is stabilized by LaATP but not by CrATP. 相似文献
4.
Testa F Mastronicola D Cabelli DE Bordi E Pucillo LP Sarti P Saraiva LM Giuffrè A Teixeira M 《Free radical biology & medicine》2011,51(8):1567-1574
Unlike superoxide dismutases (SODs), superoxide reductases (SORs) eliminate superoxide anion (O2•−) not through its dismutation, but via reduction to hydrogen peroxide (H2O2) in the presence of an electron donor. The microaerobic protist Giardia intestinalis, responsible for a common intestinal disease in humans, though lacking SOD and other canonical reactive oxygen species-detoxifying systems, is among the very few eukaryotes encoding a SOR yet identified. In this study, the recombinant SOR from Giardia (SORGi) was purified and characterized by pulse radiolysis and stopped-flow spectrophotometry. The protein, isolated in the reduced state, after oxidation by superoxide or hexachloroiridate(IV), yields a resting species (Tfinal) with Fe3+ ligated to glutamate or hydroxide depending on pH (apparent pKa = 8.7). Although showing negligible SOD activity, reduced SORGi reacts with O2•− with a pH-independent second-order rate constant k1 = 1.0 × 109 M− 1 s− 1 and yields the ferric-(hydro)peroxo intermediate T1; this in turn rapidly decays to the Tfinal state with pH-dependent rates, without populating other detectable intermediates. Immunoblotting assays show that SORGi is expressed in the disease-causing trophozoite of Giardia. We propose that the superoxide-scavenging activity of SOR in Giardia may promote the survival of this air-sensitive parasite in the fairly aerobic proximal human small intestine during infection. 相似文献
5.
Uncoupling of oxidative phosphorylation by curcumin: Implication of its cellular mechanism of action
Han Wern Lim 《Biochemical and biophysical research communications》2009,389(1):187-41984
Curcumin is a phytochemical isolated from the rhizome of turmeric. Recent reports have shown curcumin to have antioxidant, anti-inflammatory and anti-tumor properties as well as affecting the 5′-AMP activated protein kinase (AMPK), mTOR and STAT-3 signaling pathways. We provide evidence that curcumin acts as an uncoupler. Well-established biochemical techniques were performed on isolated rat liver mitochondria in measuring oxygen consumption, F0F1-ATPase activity and ATP biosynthesis. Curcumin displays all the characteristics typical of classical uncouplers like fccP and 2,4-dinitrophenol. In addition, at concentrations higher than 50 μM, curcumin was found to inhibit mitochondrial respiration which is a characteristic feature of inhibitory uncouplers. As a protonophoric uncoupler and as an activator of F0F1-ATPase, curcumin causes a decrease in ATP biosynthesis in rat liver mitochondria. The resulting change in ATP:AMP could disrupt the phosphorylation status of the cell; this provides a possible mechanism for its activation of AMPK and its downstream mTOR and STAT-3 signaling. 相似文献
6.
Emily M.S. Hopwood Duale AhmedSusan M. Aitken 《Biochimica et Biophysica Acta - Proteins and Proteomics》2014,1844(2):465-472
Cystathionine γ-lyase (CGL) catalyzes the hydrolysis of l-cystathionine (l-Cth), producing l-cysteine (l-Cys), α-ketobutyrate and ammonia, in the second step of the reverse transsulfuration pathway, which converts l-homocysteine (l-Hcys) to l-Cys. Site-directed variants substituting residues E48 and E333 with alanine, aspartate and glutamine were characterized to probe the roles of these acidic residues, conserved in fungal and mammalian CGL sequences, in the active-site of CGL from Saccharomyces cerevisiae (yCGL). The pH optimum of variants containing the alanine or glutamine substitutions of E333 is increased by 0.4–1.2 pH units, likely due to repositioning of the cofactor and modification of the pKa of the pyridinium nitrogen. The pH profile of yCGL-E48A/E333A resembles that of Escherichia coli cystathionine β-lyase. The effect of substituting E48, E333 or both residues is the 1.3–3, 26–58 and 124–568-fold reduction, respectively, of the catalytic efficiency of l-Cth hydrolysis. The Kml-Cth of E333 substitution variants is increased ~ 17-fold, while Kml-OAS is within 2.5-fold of the wild-type enzyme, indicating that residue E333 interacts with the distal amine moiety of l-Cth, which is not present in the alternative substrate O-acetyl-l-serine. The catalytic efficiency of yCGL for α,γ-elimination of O-succinyl-l-homoserine (kcat/Kml-OSHS = 7 ± 2), which possesses a distal carboxylate, but lacks an amino group, is 300-fold lower than that of the physiological l-Cth substrate (kcat/Kml-Cth = 2100 ± 100) and 260-fold higher than that of l-Hcys (kcat/Kml-Hcys = 0.027 ± 0.005), which lacks both distal polar moieties. The results of this study suggest that the glutamate residue at position 333 is a determinant of specificity. 相似文献
7.
Mohd. Rashid Khan Shabeena Siddiqui Kehkashan Parveen Saleem Javed Sandhya Diwakar Waseem A. Siddiqui 《Chemico-biological interactions》2010,186(2):228-238
Industrial and occupational exposure to chromium compounds, particularly hexavalent chromium (Cr(VI))-containing compounds are often known to cause acute renal injury (ARI) in humans and animals. Its nephrotoxicity is associated with an increased formation of reactive oxygen species and lipid peroxidation in renal tissue. Recent studies suggest that antioxidants of the vitamin E family have protective effects against metal toxicity. Tocotrienols are known to have greater antioxidant activity than tocopherols and protect more efficiently against some free radical-related diseases than does tocopherols. In the present study, ARI induced by potassium dichromate (K2Cr2O7) has been used as a model to investigate the possible nephroprotective effect of tocotrienol-rich fraction (TRF) from palm oil. Wistar male rats having an average body weight (bw) of 210 g were divided into four groups. The first group was taken as control and injected with vehicle alone while the second group was drug control and ingested with TRF (200 mg/kg, bw, orally, once daily for 21 days); the third group served as toxicant and was pre-treated with saline, followed by a single subcutaneous (SC) injection of K2Cr2O7 (15 mg/kg bw). The fourth group was pre-treated with TRF and subsequently injected with K2Cr2O7 (same dose as for the third group). Renal functions, oxidative and nitrosative stress were evaluated on days 0, 1, 2, 4, 7, 11 and 14 after treatment with K2Cr2O7. The results revealed altered proximal tubular function; decreased glomerular filtration accompanied by oxidative damage 48 h after exposure to dichromate; while in the TRF-treated group proximal reabsorptive function, glomerular function and the cellular redox status were sustained. These results were further supported and confirmed by histological findings. The study suggests that TRF is effective in preventing K2Cr2O7-induced acute renal injury, but more studies are needed to confirm the effects of TRF as a nephroprotective agent. 相似文献
8.
J.D. Líbano-Soares 《生物化学与生物物理学报:生物膜》2008,1778(5):1316-1323
In a previous paper we showed that bradykinin (BK), interacting with its B2 receptor, inhibits proximal tubule Na+-ATPase activity but does not change (Na+ + K+)ATPase activity. The aim of this paper was to investigate the molecular mechanisms involved in B2-mediated modulation of proximal tubule Na+-ATPase by BK. To abolish B1 receptor-mediated effects, all experiments were carried out in the presence of (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Leu), des-Arg9-[Leu8]-BK (DALBK), a specific antagonist of B1 receptor. A dual effect on the Na+-ATPase activity through the B2 receptor was found: short incubation times (1-10 min) stimulate the enzyme activity; long incubation times (10-60 min) inhibit it. The stimulatory effect of BK is mediated by activation of phosphoinositide-specific phospholipase C β (PI-PLCβ)/protein kinase C (PKC); its inhibitory action is mediated by Ca2+-independent phospholipase A2 (iPLA2). Prior activation of the PI-PLCβ/PKC pathway is required to activate the iPLA2-mediated inhibitory phase. These results reveal a new mechanism by which BK can modulate renal sodium excretion: coupling between B2 receptor and activation of membrane-associated iPLA2. 相似文献
9.
John R. Hadcock David A. Griffith Phillip A. Carpino Shawn C. Black Denise Gautreau Diane M. Hargrove Dennis O. Scott 《Biochemical and biophysical research communications》2010,394(2):366-371
Cannabinoid CB1 receptor antagonists exhibit pharmacologic properties favorable for the treatment of metabolic disease. CP-945,598 (1-[9-(4-chlorophenyl)-8-(2-chlorophenyl)-9H-purin-6-yl]-4-ethylamino piperidine-4-carboxylic acid amide hydrochloride) is a recently discovered selective, high affinity, competitive CB1 receptor antagonist that inhibits both basal and cannabinoid agonist-mediated CB1 receptor signaling in vitro and in vivo. CP-945,598 exhibits sub-nanomolar potency at human CB1 receptors in both binding (Ki = 0.7 nM) and functional assays (Ki = 0.2 nM). The compound has low affinity (Ki = 7600 nM) for human CB2 receptors. In vivo, CP-945,598 reverses four cannabinoid agonist-mediated CNS-driven responses (hypo-locomotion, hypothermia, analgesia, and catalepsy) to a synthetic cannabinoid receptor agonist. CP-945,598 exhibits dose and concentration-dependent anorectic activity in two models of acute food intake in rodents, fast-induced re-feeding and spontaneous, nocturnal feeding. CP-945,598 also acutely stimulates energy expenditure in rats and decreases the respiratory quotient indicating a metabolic switch to increased fat oxidation. CP-945,598 at 10 mg/kg promoted a 9%, vehicle adjusted weight loss in a 10 day weight loss study in diet-induced obese mice. Concentration/effect relationships combined with ex vivo brain CB1 receptor occupancy data were used to evaluate efficacy in behavioral, food intake, and energy expenditure studies. Together, these in vitro, ex vivo, and in vivo data indicate that CP-945,598 is a novel CB1 receptor competitive antagonist that may further our understanding of the endocannabinoid system. 相似文献
10.
T. Marchini N. Magnani V. D'Annunzio D. Tasat R.J. Gelpi S. Alvarez P. Evelson 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
It has been suggested that mitochondrial function plays a central role in cardiovascular diseases associated with particulate matter inhalation. The aim of this study was to evaluate this hypothesis, with focus on cardiac O2 and energetic metabolism, and its impact over cardiac contractility.Methods
Swiss mice were intranasally instilled with either residual oil fly ash (ROFA) (1.0 mg/kg body weight) or saline solution. After 1, 3 or 5 h of exposure, O2 consumption was evaluated in heart tissue samples. Mitochondrial respiration, respiratory chain complexes activity, membrane potential and ATP content and production rate were assessed in isolated mitochondria. Cardiac contractile reserve was evaluated according to the Langendorff technique.Results
Three hours after ROFA exposure, tissue O2 consumption was significantly decreased by 35% (from 1180 ± 70 to 760 ± 60 ng-at O/min g tissue), as well as mitochondrial rest (state 4) and active (state 3) respiration, by 30 and 24%, respectively (control state 4: 88 ± 5 ng-at O/min mg protein; state 3: 240 ± 20 ng-at O/min mg protein). These findings were associated with decreased complex II activity, mitochondrial depolarization and deficient ATP production. Even though basal contractility was not modified (control: 75 ± 5 mm Hg), isolated perfused hearts failed to properly respond to isoproterenol in ROFA-exposed mice. Tissue O2 consumption rates positively correlated with cardiac contractile state in controls (r2 = 0.8271), but not in treated mice (r2 = 0.1396).General Significance
The present results show an impaired mitochondrial function associated with deficient cardiac contractility, which could represent an early cardiovascular alteration after the exposure to environmental particulate matter. 相似文献11.
Calmodulin (CaM) binding to the intracellular C-terminal tail (CTT) of the cardiac L-type Ca2+ channel (CaV1.2) regulates Ca2+ entry by recognizing sites that contribute to negative feedback mechanisms for channel closing. CaM associates with CaV1.2 under low resting [Ca2+], but is poised to change conformation and position when intracellular [Ca2+] rises. CaM binding Ca2+, and the domains of CaM binding the CTT are linked thermodynamic functions. To better understand regulation, we determined the energetics of CaM domains binding to peptides representing pre-IQ sites A1588, and C1614 and the IQ motif studied as overlapping peptides IQ1644 and IQ′1650 as well as their effect on calcium binding. (Ca2+)4-CaM bound to all four peptides very favorably (Kd ≤ 2 nM). Linkage analysis showed that IQ1644-1670 bound with a Kd ~ 1 pM. In the pre-IQ region, (Ca2+)2-N-domain bound preferentially to A1588, while (Ca2+)2-C-domain preferred C1614. When bound to C1614, calcium binding in the N-domain affected the tertiary conformation of the C-domain. Based on the thermodynamics, we propose a structural mechanism for calcium-dependent conformational change in which the linker between CTT sites A and C buckles to form an A-C hairpin that is bridged by calcium-saturated CaM. 相似文献
12.
To elucidate the physiological mechanism of chilling stress mitigated by cinnamic acid (CA) pretreatment, a cucumber variety (Cucumis sativus cv. Jinchun no. 4) was pretreated with 50 μM CA for 2 d and was then cultivated at two temperatures (15/8 and 25/18 °C) for 1 d. We investigated whether exogenous CA could protect cucumber plantlets from chilling stress (15/8 °C) and examined whether the protective effect was associated with the regulation of antioxidant enzymes and lipid peroxidation. At 2 d, exogenous CA did not influence plant growth, but induced the activities of some antioxidant enzymes, including superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), guaiacol peroxidase (GPX, EC 1.11.1.7), glutathione peroxidase (GSH-Px, EC 1.6.4.2) and ascorbate peroxidase (APX, EC 1.11.1.11) in cucumber leaves, and it also elevated the contents of reduced glutathione (GSH) and ascorbate (AsA). When CA was rinsed and the CA-pretreated seedlings were exposed to different temperatures, the antioxidant activities in leaves at 3 d had undergone additional change. Chilling increased the activities of CAT, GSH-PX, APX, GSH and AsA in leaves, but the combination of CA pretreatment and chilling enhanced the antioxidant activities even more. Moreover, chilling inhibited plant growth and increased the contents of malonaldehyde (MDA), superoxide radical (O2−) and hydrogen peroxide (H2O2) in cucumber leaves, and the stress resulted in 87.5% of the second leaves being withered. When CA pretreatment was combined with the chilling stress, we observed alleviated growth inhibition and decreased contents of MDA, H2O2 and O2− in comparison to non-pretreated stressed plants, and found that the withered leaves occurred at a rate of 25.0%. We propose that CA pretreatment increases antioxidant enzyme activities in chilling-stressed leaves and decreases lipid peroxidation to some extent, enhancing the tolerance of cucumber leaves to chilling stress. 相似文献
13.
Qinru Sun Ning Jia Weixi Wang Hui JinJiehua Xu Haitao Hu 《Biochemical and biophysical research communications》2014
As one of the most important hallmarks of Alzheimer’s disease (AD), β-amyloid (Aβ) plays important roles in inducing reactive oxygen species (ROS) generation, mitochondrial dysfunction and apoptotic cell death in neurons. Curcumin extracted from the yellow pigments spice plant turmeric shows multiplied bioactivities such as antioxidant and anti-apoptosis properties in vitro and in vivo. In the present study, the neuroprotective effect of curcumin against Aβ25–35-induced cell death in cultured cortical neurons was investigated. We found that pretreatment of curcumin prevented the cultured cortical neurons from Aβ25–35-induced cell toxicity. In addition, curcumin improved mitochondrial membrane potential (ΔΨm), decreased ROS generation and inhibited apoptotic cell death in Aβ25–35 treated neurons. Furthermore, we found that application of curcumin activated the expression of SIRT1 and subsequently decreased the expression of Bax in the presence of Aβ25–35. The protective effect of curcumin was blocked by SIRT1 siRNA. Taken together, our results suggest that activation of SIRT1 is involved in the neuroprotective action of curcumin. 相似文献
14.
The dinickel(II) compound [Ni2(μ-OAc)2(OAc)2(μ-H2O)(asy·dmen)2]·2.5H2O, 1; undergoes facile reaction in a 1:2 molar ratio with benzohydroxamic acid (BHA) in ethanol to give the novel nickel(II) tetranuclear hydroxamate complex [Ni4(μ-OAc)3(μ-BA)3(asy·dmen)3][OTf]2·H2O, 2, in which the bridging acetates, bridging two nickel atoms in 1, undergo a carboxylate shift from the μ2-η1:η1 bridging mode of binding to the μ3-η1:η2 bridging three nickel atoms in the tetramer. The structure of complex 2 was determined by single-crystal X-ray crystallography. The two monodentate acetates, water and two bidentate bridging acetates of two moles of complex 1 are replaced by three monodentate bridging acetates and three benzohydroxamates. Three nickel atoms in the tetramer, Ni(2), Ni(3) and Ni(4) are in a N2O4 octahedral environment, while the fourth nickel atom Ni(1) is in an O(6) octahedral environment. The Ni-Ni separations are Ni(1)-Ni(2) = 3.108 Å, Ni(1)-Ni(3) = 3.104 Å and Ni(1)-Ni(4) = 3.110 Å, which are longer than previously studied in dinuclear urease inhibited models but shorter than in the nickel(II) tetrameric glutarohydroxamate complex [Ni4(μ-OAc)2(μ-gluA2)2(tmen)4][OTf]2, isolated and characterized previously in this laboratory. Magnetic studies of the tetrameric complex show that the four Ni(II) ions are ferromagnetically coupled, leading to a total ground spin state ST = 4. Three analogous tetranuclear nickel hydroxamates were prepared from AHA and BHA and the appropriate dinuclear complex with either sy·dmen or asy·dmen as capping ligands. 相似文献
15.
Under biotic/abiotic stresses, the red alga Kappaphycus alvarezii reportedly releases massive amounts of H2O2 into the surrounding seawater. As an essential redox signal, the role of chloroplast-originated H2O2 in the orchestration of overall antioxidant responses in algal species has thus been questioned. This work purported to study the kinetic decay profiles of the redox-sensitive plastoquinone pool correlated to H2O2 release in seawater, parameters of oxidative lesions and antioxidant enzyme activities in the red alga Kappaphycus alvarezii under the single or combined effects of high light, low temperature, and sub-lethal doses of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), which are inhibitors of the thylakoid electron transport system. Within 24 h, high light and chilling stresses distinctly affected the availability of the PQ pool for photosynthesis, following Gaussian and exponential kinetic profiles, respectively, whereas combined stimuli were mostly reflected in exponential decays. No significant correlation was found in a comparison of the PQ pool levels after 24 h with either catalase (CAT) or ascorbate peroxidase (APX) activities, although the H2O2 concentration in seawater (R = 0.673), total superoxide dismutase activity (R = 0.689), and particularly indexes of protein (R = 0.869) and lipid oxidation (R = 0.864), were moderately correlated. These data suggest that the release of H2O2 from plastids into seawater possibly impaired efficient and immediate responses of pivotal H2O2-scavenging activities of CAT and APX in the red alga K. alvarezii, culminating in short-term exacerbated levels of protein and lipid oxidation. These facts provided a molecular basis for the recognized limited resistance of the red alga K. alvarezii under unfavorable conditions, especially under chilling stress. 相似文献
16.
Pradip K. Tarafdar 《生物化学与生物物理学报:生物膜》2010,1798(5):872-13717
Recent studies show that O-acylethanolamines (OAEs), structural isomers of the putative stress-fighting lipids, namely N-acylethanolamines (NAEs), can be derived from NAEs and are present in biological membranes under physiological conditions. In view of this, we have synthesized O-stearoylethanolamine (OSEA) as a representative OAE and investigated its phase behavior and crystal structure. The thermotropic phase transitions of OSEA dispersed in water and in 150 mM NaCl were characterized using calorimetric, spectroscopic, turbidimetric and X-ray diffraction studies. These studies have revealed that when dispersed in water OSEA undergoes a cooperative phase transition centered at 53.8 °C from an ordered gel phase to a micellar structure whereas in presence of 150 mM NaCl the transition temperature increases to 55.8 °C and most likely the bilayer structure is retained above the phase transition. O-Stearoylethanolamine crystallized in the orthorhombic space group P212121 with four symmetry-related molecules in the unit cell. Single-crystal X-ray diffraction studies show that OSEA molecules adopt a linear structure with all-trans conformation in the acyl chain region. The molecules are organized in a tail-to-tail fashion, similar to the arrangement in a bilayer membrane. These studies are relevant to understanding the role of salt on the phase properties of this new class of lipids. 相似文献
17.
Yakov M. Milgrom 《BBA》2010,1797(10):1768-1774
The effect of inorganic phosphate (Pi) on uni-site ATP binding and hydrolysis by the nucleotide-depleted F1-ATPase from beef heart mitochondria (ndMF1) has been investigated. It is shown for the first time that Pi decreases the apparent rate constant of uni-site ATP binding by ndMF1 3-fold with the Kd of 0.38 ± 0.14 mM. During uni-site ATP hydrolysis, Pi also shifts equilibrium between bound ATP and ADP + Pi in the direction of ATP synthesis with the Kd of 0.17 ± 0.03 mM. However, 10 mM Pi does not significantly affect ATP binding during multi-site catalysis. 相似文献
18.
Hickok JR Sahni S Shen H Arvind A Antoniou C Fung LW Thomas DD 《Free radical biology & medicine》2011,51(8):1558-1566
It is well established that nitric oxide (•NO) reacts with cellular iron and thiols to form dinitrosyliron complexes (DNIC). Little is known, however, regarding their formation and biological fate. Our quantitative measurements reveal that cellular concentrations of DNIC are proportionally the largest of all •NO-derived adducts (900 pmol/mg protein, or 45-90 μM). Using murine macrophages (RAW 264.7), we measured the amounts, and kinetics, of DNIC assembly and disappearance from endogenous and exogenous sources of •NO in relation to iron and O2 concentration. Amounts of DNIC were equal to or greater than measured amounts of chelatable iron and depended on the dose and duration of •NO exposure. DNIC formation paralleled the upregulation of iNOS and occurred at low physiologic •NO concentrations (50-500 nM). Decreasing the O2 concentration reduced the rate of enzymatic •NO synthesis without affecting the amount of DNIC formed. Temporal measurements revealed that DNIC disappeared in an oxygen-independent manner (t1/2 = 80 min) and remained detectable long after the •NO source was removed (> 24 h). These results demonstrate that DNIC will be formed under all cellular settings of •NO production and that the contribution of DNIC to the multitude of observed effects of •NO must always be considered. 相似文献
19.
Feng Hong Olivia A. John Yi-Ying Wu David P. Wilson Jonathan E. Baker 《Journal of molecular biology》2009,390(5):879-173
A current popular model to explain phosphorylation of smooth muscle myosin (SMM) by myosin light-chain kinase (MLCK) proposes that MLCK is bound tightly to actin but weakly to SMM. We found that MLCK and calmodulin (CaM) co-purify with unphosphorylated SMM from chicken gizzard, suggesting that they are tightly bound. Although the MLCK:SMM molar ratio in SMM preparations was well below stoichiometric (1:73 ± 9), the ratio was ∼ 23-37% of that in gizzard tissue. Fifteen to 30% of MLCK was associated with CaM at ∼ 1 nM free [Ca2+]. There were two MLCK pools that bound unphosphorylated SMM with Kd ∼ 10 and 0.2 μM and phosphorylated SMM with Kd ∼ 20 and 0.2 μM. Using an in vitro motility assay to measure actin sliding velocities, we showed that the co-purifying MLCK-CaM was activated by Ca2+ and phosphorylation of SMM occurred at a pCa50 of 6.1 and at a Hill coefficient of 0.9. Similar properties were observed from reconstituted MLCK-CaM-SMM. Using motility assays, co-sedimentation assays, and on-coverslip enzyme-linked immunosorbent assays to quantify proteins on the motility assay coverslip, we provide strong evidence that most of the MLCK is bound directly to SMM through the telokin domain and some may also be bound to both SMM and to co-purifying actin through the N-terminal actin-binding domain. These results suggest that this MLCK may play a role in the initiation of contraction. 相似文献
20.
Marzieh Ghasemi Mahnaz Azarnia Mansoor Jamali Ghadireh Mirabolghasemi Shahram Nazarian Mohammad Mehdi Naghizadeh Majid Rajabi Yaser Tahamtani 《Tissue & cell》2014
Inflammation and oxidation are two important factors in the pathogenesis of liver. Ephedra pachyclada (EP) is a traditional medical herb that has anti-inflammatory and anti-oxidant activities. During this study, anti-oxidant activities of the EP extract was measured in vitro by 2,2′- diphenyl-1-picrylhydrazyl (DPPH) and β-Carotene bleaching assays. Then, we examined possible in vivo hepatoprotective effects of EP extract on mouse models of carbon tetrachloride (CCl4)-induced chronic and acute liver failure. To produce mouse models of chronic and acute liver injuries, male SW1 mice were interaperitoneally injected with 1 ml/kg body weight (bw) CCl4 biweekly for 42 days and a single dose of 2 ml/kg bw, respectively. In the experimental groups, mouse models were treated with low (140 mg/kg bw) and high (1400 mg/kg bw) doses of the EP extract. Olive oil and water treated mice were considered as controls during model derivation and EP extract treatment respectively. The results showed the antioxidant activity of EP extract and a significant reduction of all parameters of CCl4-induced liver injury such as relative liver weight, necrosis, fibrosis, inflammation, and serum aspartate transaminase (AST) and alanine aminotransferase (ALT) in mouse models of acute and chronic liver injury treated with EP extract. Therefore, EP induces its hepatoprotective effects probably by suppressing oxidative stress and inhibit inflammation in the liver and is able to protect the liver against CCl4-induced acute and chronic injuries. 相似文献