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At least 127 records · Page 7Linked to original sources
PubMed2003

Systematic studies on pH-dependent transformations of dinuclear vanadium(V)-citrate complexes in aqueous solutions. A perspective relevance to aqueous vanadium(V)-citrate speciation.

Vanadium(V) involvement in interactions with physiological ligands in biological media prompted us to delve into the systematic pH-dependent synthesis, spectroscopic characterization, and perusal of chemical properties of arising aqueous vanadium(V)-citrate species in the requisite system. To this end, facile reactions led to dinuclear complexes (NH(4))(4)[V(2)O(4)(C(6)H(5)O(7))(2)].4H(2)O (1) and (NH(4))(6)[V(2)O(4)(C(6)H(4)O(7))(2)].6H(2)O (2). Complex 1 and 2 were characterized by elemental analysis, FT-IR and X-ray crystallography. Complex 1 crystallizes in the monoclinic space group C2/c with a=16.998(5) A, b=16.768(5) A, c=9.546(3) A, beta=105.22(1) degrees, V=2625(1) A(3), and Z=4. Complex 2 crystallizes in the triclinic space group P1;, with a=9.795(4) A, b=9.942(4) A, c=9.126(3) A, alpha=90.32(1) degrees, beta=111.69(1) degrees, gamma=108.67(1) degrees, V=774.5(5) A(3), and Z=1. The structures of 1 and 2 were consistent with the presence of a V(V)(2)O(2) core, to which citrate ligands of differing protonation state were bound in a coordination mode consistent with past observations. Ultimately, the aqueous pH dependent transformations of a series of three dinuclear complexes, 1, 2 and (NH(4))(2)[V(2)O(4)(C(6)H(6)O(7))(2)].2H(2)O (3), all isolated at pH values from 3 to 7.5, were explored and revealed an important interconnection among all species. Collectively, pH emerged as a determining factor of structural attributes in all three complexes, with the adjoining acid-base chemistry unfolding around the stable V(V)(2)O(2) core. The results point to the participation of all three species in aqueous vanadium(V)-citrate speciation, and may relate the site-specific protonations-deprotonations on the dinuclear complexes to potential biological processes involving vanadium(V) and physiological ligand targets.

Citrates↗
PubMed2005

pH-specific aqueous synthetic chemistry in the binary cadmium(II)-citrate system. Gaining insight into cadmium(II)-citrate speciation with relevance to cadmium toxicity.

The involvement of Cd(II) in toxic manifestations and pathological aberrations in lower and higher organisms entails interactions with low and high molecular mass biological targets. To understand the relevant chemistry in aqueous media, we have launched pH-dependent synthetic efforts targeting Cd(II) with the physiological ligand citric acid. Reactions of Cd(II) with citric acid upon the addition of NaOH at pH 2.5 and pyridine at pH 3 and the addition of ammonia at pH approximately 7 led to the new complexes [Cd3(C6H5O7)2(H2O)5] x H2O (1) and (NH4)[Cd(C6H5O7)(H2O)] x H2O (2), respectively. Complexes 1 and 2 were characterized by elemental analysis, spectroscopy (FT-IR and NMR), and X-ray crystallography. Complex 1 crystallizes in the monoclinic space group P2(1)/n, with a = 18.035(6) A, b = 10.279(4) A, c = 12.565(4) A, beta = 109.02(1) degrees, V = 2202(2) A3, and Z = 4. Complex 2 crystallizes in the monoclinic space group P2(1), with a = 9.686(4) A, b = 8.484(4) A, c = 7.035(3) A, beta = 110.28(1) degrees, V = 542.3(4) A3, and Z = 2. Complex 1 is a trinuclear assembly with the citrate ligand securing a stable metallacyclic ring around one Cd(II), with the terminal carboxylates spanning into the coordination sphere of two nearby Cd(II) ions. Complex 2 contains mononuclear units of Cd(II) bound by citrate in an overall coordination number of 8. In both 1 and 2, the participating citrates exhibit three different modes of coordination, thus projecting a distinct yet variable aqueous structural chemistry of Cd(II) with physiological substrates. The pH-dependent chemistry and its apparent structural diversity validate past solution speciation studies, projecting the existence of mononuclear species such as the one in the anion of 2. The spectroscopic and structural properties of 2 emphasize the significance of the information emerging from synthetic studies that otherwise would not have been revealed through conventional solution studies, while concurrently shedding light onto the linkage of the requisite chemistry with the potential biological toxicity of Cd(II).

Cadmium↗
PubMed1966

Citrate and the conversion of carbohydrate into fat. Citrate cleavage in obesity and lactation.

1. The specific activity of ATP citrate lyase is two to four times as great in livers of mice with hereditary obesity as in livers of their non-obese siblings. The enzyme activity in both types of mice can be reduced by starvation, and can be increased by refeeding starved animals. The specific activity of acetyl-CoA synthetase is approximately the same in both types of mice. 2. ATP citrate lyase of mammary gland of the rat undergoes large increases in activity after the onset of lactation. It declines rapidly upon weaning. 3. The changes in activity of ATP citrate lyase in obesity and lactation are consistent with the hypothesis that the enzyme supplies extramitochondrial acetyl-CoA for fatty acid synthesis.

Animals↗
PubMed1992

Red cell and platelet concentrates from blood collected into half-strength citrate anticoagulant: improved maintenance of red cell 2,3-diphosphoglycerate in half-citrate red cells.

This study confirms previous work suggesting equivalent in vitro properties in blood components prepared from donations collected into half-citrate preservative (HCPD) compared to components derived from donations collected into standard citrate-phosphate-dextrose (CPD) preservatives. In addition, red cell products harvested from HCPD donations showed significantly improved maintenance of pH over storage, and this was reflected in improved maintenance of intracellular 2,3-diphosphoglycerate (2,3-DPG). This effect was observed in whole blood and in red cells suspended in a phosphate-containing additive solution (Tuta AAS). Collection into HCPD also improved 2,3-DPG maintenance in red cell concentrates processed following an 18-hour hold at 22 degrees C. These improvements were less pronounced in red cells suspended in a non-phosphate-containing medium (Fenwal Adsol) in which a higher pH was maintained even in units collected in CPD. Platelets harvested from HCPD blood and suspended in plasma showed equivalent quality to platelets from standard donations. Some deterioration of platelet properties was observed when HCPD platelets were stored in a non-citrate synthetic medium. Together with data indicating improved coagulation factor stability, these results suggest that collection into HCPD improves stored blood quality and may also allow logistical benefits in blood component preparation.

2,3-Diphosphoglycerate↗
PubMed1982

Identification of citrate utilization transposon Tn3411 from a naturally occurring citrate utilization plasmid.

We have isolated a new transposon, Tn3411, encoding citrate-utilizing ability, from a naturally occurring citrate utilization (Cit) plasmid, pOH3001. Citrate transposon Tn3411 was transposed from pOH3001 to lambda b519 b515 cI857 S7 (abbreviated lambda bb) phage, and further from the resulting lambda bb:Tn3411 to a vector plasmid, pBR322, in recA-deficient strains. The Cit+ plasmids (pOH2 and pOH3) constructed by the integration of Tn3411 into pBR322 were examined by restriction endonuclease and heteroduplex analysis. The results obtained were as follows: (i) Tn3411 was 7.4 kilobases long and flanked by small inverted repeats, and it contained one more pair of inverted repeats at the opposite orientation in the internal region, thus making alternate repeats; and (ii) the Cit+ structure gene was located on the fragment (5.5 kilobases) between two SalI cleavage sites on Tn3411.

Bacteriophage lambda↗
PubMed1977

[Whole-body retention studies of 169Yb-citrate.--Estimation of radiation dose to humans from 169Yb-citrate (author's transl)].

For purpose of the estimation of the radiation dose to humans from 169Yb-citrate, the whole-body retention studies using five rats were carried out. Following intravenous administration of 169Yb-citrate, the whole-body activity was monitored for 40 days by the animal counter. The whole-body retention curve consisted of three components: the first with a 3.6 hours effective half-time, the second with an 154 hours effective half-time and the third with a 29.9 days effective half-time. Therefore it was assumed that 32% of the administered 169Yb-citrate clears from the kidney with a short biologic half-time (3.6hours), 18% remains in the liver and other soft tissues with a relatively long biologic half-time (194 hours) and 50% remains in the bone with a long biologic half-time (850 days). Based on these biological data and the MIRD Committe method, the average dose to the bone and whole-body were 20.8 rads/mCi and 4.5 rads/mCi respectively.

Animals↗
PubMed2004

pH-specific synthesis of a dinuclear vanadium(V)-peroxo-citrate complex in aqueous solutions: pH-dependent linkage, spectroscopic and structural correlations with other aqueous vanadium(V)-peroxo-citrate and non-peroxo species.

Aqueous reactions of V2O5 or VCl3 in the presence of the physiological citric acid and hydrogen peroxide, in a pH specific fashion, afforded a new vanadium(V)-peroxo-citrate material isolated in a pure crystalline form. Elemental analysis pointed to the molecular formulation (NH4)6[V(V)2O2(O2)2(C6H4O7)2].4.5H2O (1). Complex 1 was further characterized by UV-vis, FT-IR, and X-ray crystallography. Compound 1 crystallizes in the monoclinic space group C2/c with a = 12.391(5) A, b = 15.737(7) A, c = 17.102(7) A, beta = 110.84(1) degrees, V = 3117(1) A3, and Z = 4. The structure of the anionic assembly consists of a planar V(V)2O2 core with two fully deprotonated citrates bound to it through the central carboxylate and alkoxide moieties as well as one of the terminal carboxylate groups. The presence of one peroxide group attached to each vanadium(V) renders the geometry around each metal center pentagonal bipyramidal. Key structural and spectroscopic features of 1 correlate with those seen in the peroxo congener and low-pH analogue (NH4)2[V(V)2O2(O2)2(C6H6O7)2].2H2O (3), in which all terminal carboxylate groups are protonated. In solution, simple pH-dependent transformation of 1 to 3 attests to their participation in the requisite speciation and potentiates the presence of other similar peroxo analogues not yet isolated and characterized. The reactivity of 1 through transformation reactions, yielding a plethora of well-characterized species, establishes a linkage among various species with the same or different vanadium oxidation states. Collectively, the data reflect soluble forms of vanadium with peroxide and citrate that contribute to the requisite pH-dependent distribution of that metal ion and likely influence biological processes.

Journal Article↗
PubMed1997

Low polymorphonuclear cell degranulation during citrate anticoagulation: a comparison between citrate and heparin dialysis.

INTRODUCTION: Haemodialysis (HD)-induced bio-incompatibility includes alterations in both cellular elements and humoral factors. As far as polymorphonuclear (PMN) cells are concerned, an increase in both adhesion and degranulation has been reported. However, whereas increased PMN adherence and aggregation is highly linked with early transient complement activation, degranulation seems a continuous process, independent from the formation of complement degradation products. In the process of cell activation, including PMN degranulation, divalent cations (Ca2+) appear to play a pivotal role. As regionally administering citrate creates an almost Ca(2+)-free environment within the dialyser, it is tempting to speculate that Ca2+ dependent phenomena of bio-incompatibility, originating within the dialyser, can be attenuated by substituting conventional heparin for citrate. METHODS: Therefore, both anticoagulation modalities were compared in 10 stable patients, undergoing haemodialysis (HD) treatment with cellulose-triacetate membranes (CTA) only. Apart from the intracellular granule products myeloperoxidase (MPO) and lactoferrin (LF), the classical parameters of bio-incompatibility, peripheral blood neutropenia and complement activation, were measured. RESULTS: Analysis of MPO and LF gradients across the dialyser (concentration in efferent line-concentration in afferent line) suggested that degranulation is an early process, that occurs mainly within the extracorporeal circuit. Citrate abolished the release of MPO almost completely, whereas LF release was partially inhibited. Neither neutropenia, nor complement activation could be correlated with the occurrence of degranulation. CONCLUSIONS: HD-induced PMN degranulation seems largely independent from complement activation, but primarily reliant on Ca2+, at least in the case of CTA membranes.

Adult↗
PubMed2004

Comparison of ranitidine bismuth citrate, tetracycline and metronidazole with ranitidine bismuth citrate and azithromycin for the eradication of Helicobacter pylori in patients resistant to PPI based triple therapy.

BACKGROUND/AIMS: Helicobacter pylori is the most common infectious disease all over the world. Ten to twenty percent of the patients remain infected despite treatment with proton pump inhibitors (PPIs), amoxicillin and clarithromycin. We compared PPI, bismuth, tetracycline and metronidazole with ranitidine bismuth citrate, tetracycline and metronidazole in cases resistant to PPIs-based triple therapies. METHODS: The study included 52 patients who underwent a triple therapy with PPI, clarithromycin and amoxicillin for 14 days between September 2001 and December 2002, and were found to be resistant to the therapy. They were randomized to take ranitidine bismuth citrate (Rb) 400 mg twice a day, tetracycline (T) 1 g twice a day and metronidazole (M) 500 mg three times a day for 14 days (RbTM), or ranitidine bismuth citrate (Rb) 400 mg twice a day for 14 days and azithromycin (A) 500 mg once a day for 7 days (RbA). Four weeks after the treatment, endoscopies were repeated, and patients were assessed with respect to changes in symptoms. When H. pylori was negative on histological analysis and urease test, eradication was achieved. RESULTS: A total of 52 patients, 32 females and 20 males with a mean age of 49+/-12 years, were included in the study. Eradication was achieved in 15 (28%) out of 52 patients in total. There was a significant difference between RbA and RbTM groups (p=0.01). In fact, H. pylori was eradicated in 3 (12%) out of 25 patients in the RbA group, whereas it was eradicated in 12 (44.4%) out of 27 patients in the RbTM group. Symptom scores significantly improved in both groups after the treatment, though there was not a significant difference between the groups (p=0.705). CONCLUSIONS: Triple therapy including azithromycin does not seem to be a good choice in cases resistant to the first line therapies; however, a similarly lower rate of eradication was achieved with the quadruple therapy proposed. Therefore, different treatment schemes should be applied in resistant patients, and further studies are needed as well.

Adult↗
PubMedDate not supplied

The effect of citrate and other compounds on PMN incubated in vitro: further studies on the site and mechanism of action of citrate.

Polymorphonuclear leukocytes (PMN) are important in corneal disease because of their role as effector cells in inflammation and ulceration. The favorable effect of citrate on corneal ulceration appears to result from inhibition of the PMN. Citrate does not enter the cells but chelates Ca2+ in the extracellular fluid and may promote a loss of some intracellular Ca2+. Isocitrate is the only tricarboxylic acid cycle intermediate that inhibits PMN, also by Ca2+ chelation. When isobutylcyanoacrylate is polymerized, a substance, probably formaldehyde, inhibitory to PMN, continuously leeches from the plastic. Although acetylcysteine has been reported to inhibit collagenase in vitro it has a direct effect of enhancing the respiratory burst and possibly degranulation of PMN stimulated by opsonized zymosan. Dexamethasone had no effect on PMN stimulation while prednisolone was partially inhibitory at high concentrations. Indomethacin exerts an inhibitory effect on all parameters of PMN stimulation. These studies clarify the site and mechanism of citrate action as well as show the importance of knowing the effect of drugs on the PMN.

Acetylcysteine↗
PubMed1985

Placenta, embryo, and tumor uptake of 67Ga-citrate and 59Fe-citrate.

The uptake of gallium citrate Ga67 and ferrous citrate Fe59 was studied in pregnant rats with or without a 4-dimethylamino-stilben(DS)-induced sarcoma tumor. The liver and placenta of the mother concentrated 67Ga, while the uptake of 67Ga in the embryo was minimal. However, the embryo showed higher concentrations of 59Fe. Preloading with iron did not affect the 67Ga uptake of the placenta, but increased the uptake in the blood and liver of the mother. With regard to 59Fe uptake, iron loading only affected the embryo liver. Tumors and the placenta showed a similar 67Ga uptake but a different incorporation of 59Fe. The probable mechanisms involved are discussed.

Animals↗
PubMed1985

Experimental pulmonary fibrosis induced by trisodium citrate and acid-citrate-dextrose.

A single intrapulmonary injection of 3.8% trisodium citrate and acid-citrate-dextrose (ACD) into rabbits results in extensive degeneration and necrosis of alveolar pneumocytes, including the type II pneumocyte, and of bronchiolar or bronchial epithelial cells. Subsequently, the alveoli and alveolar ducts collapse, and the septa and ductal walls adhere to each other, accompanied by the proliferation of interstitial fibroblasts. These fibroblasts produce fibrous connective tissue which is followed by pulmonary fibrosis in 1 week. Epithelial regeneration, especially that resulting from the proliferation of immature type II pneumocytes, occurs around the periphery of the fibrous lesions. The synthesis and release of large amounts of surfactant materials by the proliferated type II pneumocytes may induce the surfactant materials to reopen the air spaces of the collapsed and adhesive alveoli. By 4 weeks those fibrous areas in the pathological lungs become smaller and/or appear normal. These results suggest that this is a useful experimental animal model for pulmonary fibrosis, and that epithelial cells, especially type II pneumocytes, are associated with both the induction of and the recovery from the disorder; in the early stage, interference by reepithelization resulting from type II pneumocyte proliferation may elicit the proliferation of fibroblasts, and in later stages, reepithelization and surfactant synthesis by newly proliferated type II pneumocytes may permit the reopening of collapsed and adhesive air spaces.

Animals↗
PubMed1992

Proton uptake accompanies formation of the ternary complex of citrate synthase, oxaloacetate, and the transition-state analog inhibitor, carboxymethyl-CoA. Evidence that a neutral enol is the activated form of acetyl-CoA in the citrate synthase reaction.

Citrate synthase complexes with the transition-state analog inhibitor, carboxymethyl-CoA (CM-CoA), are believed to mimic those with the activated form of acetyl-CoA. The X-ray structure [Karpusas, M., Branchaud, B., & Remington, S.J. (1990) Biochemistry 29, 2213] of the ternary complex of the enzyme, oxaloacetate, and CMCoA has been used as the basis for a proposal that a neutral enol of acetyl-CoA is that activated form. Since the inhibitor carboxyl has a pKa of 3.90, analogy with an enolic acetyl-CoA intermediate leads to the prediction that a proton should be taken up from solution upon formation of the analog complex so that the transition-state analog carboxyl is protonated when bound. We have obtained evidence in solution for this proposal by comparing the isoelectric points and the pH dependence of the dissociation constants of the ternary complexes of the pig heart enzyme with the neutral ground-state analog inhibitor, acetonyl-CoA (KCoA), and the anionic transition-state analog inhibitor (CMCoA) and by studying the NMR spectra of the transition-state analog complexes of allosteric (Escherichia coli) and nonallosteric (pig heart) enzymes. The pH dependence of the dissociation constant of the ground-state analog indicates no proton uptake, while that for the transition-state analog indicates that 0.55 +/- 0.04 proton is taken up when the analog binds to the citrate synthase-oxaloacetate binary complex. The overall charges of ternary complexes of the pig heart enzyme with the transition-state and ground-state analog inhibitors are the same, as monitored by their isoelectric points.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetyl Coenzyme A↗
PubMed2003

A new dinuclear Ti(IV)-peroxo-citrate complex from aqueous solutions. Synthetic, structural, and spectroscopic studies in relevance to aqueous titanium(IV)-peroxo-citrate speciation.

The wide use of titanium in applied materials has prompted pertinent studies targeting the requisite chemistry of that metal's biological interactions. In order to understand such interactions as well as the requisite titanium aqueous speciation, we launched investigations on the synthesis and spectroscopic and structural characterization of Ti(IV) species with the physiological citric acid. Aqueous reactions of TiCl(4) with citric acid in the presence of H(2)O(2) and neutralizing ammonia afforded expediently the red crystalline material (NH(4))(4)[Ti(2)(O(2))(2)(C(6)H(4)O(7))(2)].2H(2)O (1). Complex 1 was further characterized by UV-vis, FT-IR, FT- and laser-Raman, NMR, and finally by X-ray crystallography. Compound 1 crystallizes in the monoclinic space group P2(1)/n, with a = 10.360(4) A, b = 10.226(4) A, c = 11.478(6) A, beta = 107.99(2) degrees, V = 1156.6(9) A(3), and Z = 2. The X-ray structure of 1 reveals a dinuclear anionic complex containing a Ti(IV)(2)O(2) core. In that central unit, two fully deprotonated citrate ligands are coordinated to the metal ions through their carboxylate moieties in a monodentate fashion. The central alkoxides serve as bridges to the two titanium ions. Also attached to the Ti(IV)(2)O(2) core are two peroxo ligands each bound in a side-on fashion to the respective metal ions. NH(4)(+) ions neutralize the 4- charge of the anion in 1, further contributing to the stability of the derived lattice through H-bond formation. The structural similarities and differences with congener vanadium(V)-peroxo-citrate complexes may point out potential implications in the chemistry of titanium with physiological ligands, when the former is present in a biologically relevant medium.

Citrates↗
PubMed2006

Citrate, in collaboration with a guanidinium ion, as a generator of cubane-like complexes with a range of metal cations: synthesis, structures, and magnetic properties of [C(NH2)3]8[(M(II))4(cit)4].8H2O (M = Mg, Mn, Fe, Co, Ni, and Zn; cit = Citrate).

Aqueous reaction mixtures containing citric acid, guanidinium carbonate, and a range of metal cations (Mg2+, Mn2+, Fe2+, Co2+, Ni2+, and Zn2+) at room temperature give crystalline products of composition [C(NH2)3]8[(M(II))4(cit)4].8H2O (cit = citrate). In all cases, the crystals are suitable for single-crystal X-ray diffraction studies, which reveal that the compounds are isostructural (space group P4(2)/n; a approximately 16.2 A, and c approximately 11.5 A). As was intended, cubane-like [M4(cit)4]8- complex anions are present. The individual citrate units are chiral, but each cubane unit contains two of one hand and two of the other, related around an S4 axis. The cubane units are involved in no less than 40 H-bonding interactions with guanidinium cations and lattice water molecules. Detailed susceptibility and magnetization studies show that the intracluster magnetic coupling within the Mn(II), Fe(II), Co(II), and Ni(II) cubanes is very weak in all cases with J values of -0.82, -0.43, and -0.09 cm(-1) for the Mn, Fe, and Co species, respectively. A two-J model gave the best agreement with the susceptibility and high-field magnetization data for the Ni(II) case, over the whole temperature range studied, and the sign of the parameters, J12 = -0.3 cm(-1) and J13 = +2.97 cm(-1), correlated with the two Ni-(mu3-O)-Ni angles observed in the cluster structure. All members of the 3d-block [M4(cit)4]8- family have spin ground states, ST, of zero, with the higher ST levels just a few reciprocal centimeters away in energy.

Cations↗
PubMed1979

Haemodynamic consequences of citrate infusion in the anaesthetized dog: comparison between two citrate solutions and the influence of beta blockade.

We have compared the effects of a solution of acid--citrate--dextrose (ACD) with those of a solution of citrate--phosphate--dextrose (CPD), infused at equal rates, on blood calcium ion concentration and different indices of haemodynamic performance in 17 dogs. The influence of beta adrenergic blockade on these changes was examined. The effects of ACD and CPD were studied in five dogs and were similar. Peripheral vascular changes were the principal cause of arterial hypotension. In six dogs, propranolol 0.5 mg kg-1 intensified the hypocalcaemia-induced left ventricular dysfunction.

Animals↗
PubMed1975

Intracellular pH (pHi) of red cells stored in acid citrate dextrose medium. Effects of temperature and citrate anions.

The intracellular pH (pHi) of red cells stored in acid citrate dextrose (ACD) medium was estimated by the 5,5'-dimethyloxazoldine,-2,4-dione (DMO) method. The initial pHi at 4degrees was about 7.6 and was higher than the extracellular pH (pHe) at 4degrees. During storage, both pHi and pHe decreased, but the former was always higher than the latter and the former decreased more slowly than the latter. The high pHi of ACD blood was a results of the temperature at which the pHe and the pHi were measured (4degrees) and the presence of citrate anions in the medium, and could be explained by application of the Donnan-Gibbs equilibrium. ATP and 2,3-diphosphoglycerate (DPG) were well-maintained in heparinized blood when it was acidified and pHe and pHi at 4degrees were both about 7.4, which suggests that improvement of blood preservation may be attained by suitable adjustment of the pHi and pHe of the blood.

Adenosine Triphosphate↗