共查询到20条相似文献,搜索用时 15 毫秒
1.
Sin Yuin Yeo Mariska de Smet Sander Langereis Luce Vander Elst Robert N. Muller Holger Grüll 《生物化学与生物物理学报:生物膜》2014
Temperature-sensitive liposomes (TSLs) loaded with doxorubicin (Dox), and Magnetic Resonance Imaging contrast agents (CAs), either manganese (Mn2 +) or [Gd(HPDO3A)(H2O)], provide the advantage of drug delivery under MR image guidance. Encapsulated MRI CAs have low longitudinal relaxivity (r1) due to limited transmembrane water exchange. Upon triggered release at hyperthermic temperature, the r1 will increase and hence, provides a means to monitor drug distribution in situ. Here, the effects of encapsulated CAs on the phospholipid bilayer and the resulting change in r1 were investigated using MR titration studies and 1H Nuclear Magnetic Relaxation Dispersion (NMRD) profiles. Our results show that Mn2 + interacted with the phospholipid bilayer of TSLs and consequently, reduced doxorubicin retention capability at 37 °C within the interior of the liposomes over time. Despite that, Mn2 +-phospholipid interaction resulted in higher r1 increase, from 5.1 ± 1.3 mM− 1 s− 1 before heating to 32.2 ± 3 mM− 1 s− 1 after heating at 60 MHz and 37 °C as compared to TSL(Gd,Dox) where the longitudinal relaxivities before and after heating were 1.2 ± 0.3 mM− 1 s− 1 and 4.4 ± 0.3 mM− 1 s− 1, respectively. Upon heating, Dox was released from TSL(Mn,Dox) and complexation of Mn2 + to Dox resulted in a similar Mn2 + release profile. From 25 to 38 °C, r1 of [Gd(HPDO3A)(H2O)] gradually increased due to increase transmembrane water exchange, while no Dox release was observed. From 38 °C, the release of [Gd(HPDO3A)(H2O)] and Dox was irreversible and the release profiles coincided. By understanding the non-covalent interactions between the MRI CAs and phospholipid bilayer, the properties of the paramagnetic TSLs can be tailored for MR guided drug delivery. 相似文献
2.
Debabrata Chatterjee Ayon Sengupta Susan Basak Debasish Bhattacharyya 《Inorganica chimica acta》2005,358(10):2960-2965
Reaction of [RuIII(hedtra)(H2O)] (hedtra = N-hydroxyethylethylenediaminetriacetate) with thio-amino acids, L (L = cysteine, N-acetylcysteine, glutathione and penicilamine), was studied kinetically. Kinetic studies were performed at different concentrations of reactants, pH and temperature. Based on the kinetic results, it is suggested that the formation of S-bound substituted product takes place in a rapid ligand dependent rate determining step. Kinetic data and activation parameters are accounted for operation of an associative mechanism and discussed in reference to the data reported earlier for edta4− (ethylenediaminetetraacetate) complex of ruthenium(III). Results of cysteine protease inhibition studies revealed that inhibition activities of Ru-pac complexes are enzyme specific. 相似文献
3.
J. P. Hannan S. B. Whittaker S. L. Davy U. C. Kühlmann A. J. Pommer A. M. Hemmings R. James C. Kleanthous G. R. Moore 《Protein science : a publication of the Protein Society》1999,8(8):1711-1713
Ni2+ affinity columns are widely used for protein purification, but they carry the risk that Ni2+ ions may bind to the protein, either adventitiously or at a physiologically important site. Dialysis against ethylenediaminetetraacetic acid (EDTA) is normally used to remove metal ions bound adventitiously to proteins; however, this approach does not always work. Here we report that a bacterial endonuclease, the DNase domain of colicin E9, binds Ni2+ acquired from Ni2+ affinity columns, and appears to bind [Ni(EDTA)(H2O)n]2- at low ionic strength. NMR was used to detect the presence of both Ni2+ coordinated to amino acid side chains and [Ni(EDTA)(H2O)N]2-. Dialysis against > or =0.2 M NaCl was required to remove the [Ni(EDTA)(H2O)n]2-. The NMR procedure we have used to characterize the presence of Ni2+ and [Ni(EDTA)(H2O)n]2- should be applicable to other proteins where there is the possibility of binding paramagnetic metal ions that are present to expedite protein purification. In the present case, the binding of Ni2+ seems likely to be physiologically relevant, and the NMR data complement recent X-ray crystallographic evidence concerning the number of histidine ligands to bound Ni2+. 相似文献
4.
The organometallic complex pentamethylcyclopentadienyl rhodium 2,2′-bipyridin ([Cp∗Rh(bpy)(H2O)]2+) was applied as regeneration catalyst for cytochrome C (CytC). Direct reduction of CytC-bound FeIII was achieved in this model system pointing towards a potential usefulness of this concept to promote cell-free P450 catalysis. In addition, controlled in situ provision with hydrogen peroxide was performed using [Cp∗Rh(bpy)(H2O)]2+ resulting in improved CytC-catalyzed sulfoxidation of thioanisol This work represents the first step towards the direct-[Cp∗Rh(bpy)(H2O)]2+ catalyzed regeneration of P450 monooxygenases and peroxidases. 相似文献
5.
Vincent Mutel Geo Adam Sylvie Chaboz John A. Kemp Agnés Klingelschmidt Jürg Messer Jürgen Wichmann Thomas Woltering John Grayson Richards 《Journal of neurochemistry》1998,71(6):2558-2564
Abstract: [(2S,2′R,3′R)-2-(2′,3′-[3H]Dicarboxycyclopropyl)glycine ([3H]DCG IV) binding was characterized in vitro in rat brain cortex homogenates and rat brain sections. In cortex homogenates, the binding was saturable and the saturation isotherm indicated the presence of a single binding site with a KD value of 180 ± 33 nM and a Bmax of 780 ± 70 fmol/mg of protein. The nonspecific binding, measured using 100 µM LY354740, was <30%. NMDA, AMPA, kainate, l (?)-threo-3-hydroxyaspartic acid, and (S)-3,5-dihydroxyphenylglycine were all inactive in [3H]DCG IV binding up to 1 mM. However, several compounds inhibited [3H]DCG IV binding in a concentration-dependent manner with the following rank order of potency: LY341495 = LY354740 > DCG IV = (2S,1′S,2′S)-2-(2-carboxycyclopropyl)glycine > (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid > (2S,1′S,2′S)-2-methyl-2-(2-carboxycyclopropyl)glycine > l -glutamate = ibotenate > quisqualate > (RS)-α-methyl-4-phosphonophenylglycine = l (+)-2-amino-3-phosphonopropionic acid > (S)-α-methyl-4-carboxyphenylglycine > (2S)-α-ethylglutamic acid > l (+)-2-amino-4-phosphonobutyric acid. N-Acetyl-l -aspartyl-l -glutamic acid inhibited the binding in a biphasic manner with an IC50 of 0.2 µM for the high-affinity component. The binding was also affected by GTPγS, reducing agents, and CdCl2. In parasagittal sections of rat brain, a high density of specific binding was observed in the accessory olfactory bulb, cortical regions (layers 1, 3, and 4 > 2, 5, and 6), caudate putamen, molecular layers of the hippocampus and dentate gyrus, subiculum, presubiculum, retrosplenial cortex, anteroventral thalamic nuclei, and cerebellar granular layer, reflecting its preferential (perhaps not exclusive) affinity for pre- and postsynaptic metabotropic glutamate mGlu2 receptors. Thus, the pharmacology, tissue distribution, and sensitivity to GTPγS show that [3H]DCG IV binding is probably to group II metabotropic glutamate receptors in rat brain. 相似文献
6.
Haruaki Ninomiya Reiko Fukunaga Takashi Taniguchi Motohatsu Fujiwara Shun Shimohama Masakuni Kameyama 《Journal of neurochemistry》1990,54(2):526-532
We studied [3H]N-[1-(2-thienyl)cyclohexyl]-3,4-piperidine [( 3H]TCP) binding to human frontal cortex obtained at autopsy from 10 histologically normal controls and eight histopathologically verified cases with Alzheimer-type dementia (ATD). Extensively washed membrane preparations were used to minimize the effects of endogenous substances. In ATD frontal cortex, the total concentration (Bmax) of [3H]TCP binding sites was significantly reduced by 40-50%. The apparent dissociation constant (KD) values showed no significant change. The reduction in binding capacity was also apparent in Triton X-100-treated membrane preparations, and there was a linear correlation between the number of [3H]TCP binding sites and that of N-methyl-D-aspartate (NMDA)-sensitive [3H]glutamate binding sites. [3H]TCP binding sites spared in ATD brains retained the affinity for the ligand and the reactivity to NMDA, L-glutamate, and glycine. These results suggest that the primary change in NMDA receptor-ion channel complex in ATD brains is the reduction of its number, possibly reflecting the loss of neurons bearing these receptor complexes, and that the functional linkage within the receptor complexes spared in ATD brains remains normal. 相似文献
7.
E. Katsarou A. Kolstad N. Hadjiliadis E. Sletten 《Journal of inorganic biochemistry》1998,70(3-4):265-269
The metal binding properties of trans-Cl2Pd(glyglyOH)2 and trans-Cl2Pd(glynvalOH)2 towards the oligonucleotide dodecamer [d(CGCGAATTCGCG)]2 duplex, have been studied by 1D and 2D 1H NMR spectroscopy. A selective binding of the metal with G4, followed by G2 was observed with both complexes. This indicates that an intrastrand GNG(G2C3G4)(N7-N7) chelation of Pd(II) with the dodecamer duplex may have taken place. The Pd(II)-duplex interaction is less aggressive with trans-Cl2Pd(glynvalOH)2, than with trans-Cl2Pd(glyglyOH)2. NOE connectivities in the first case show a through space hydrophobic ligand–ligand interaction of the dipeptide and oligonucleotide protons. 相似文献
8.
T. S. Selvamuniandy N. Mohamed S. M. Mansor N. K. Nair V. Navaratnam 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1997,700(1-2):209-213
A selective and sensitive HPLC assay for the quantitative determination of a new antifilarial drug, 6,4′-bis-(2-imidazolinylhydrazone)-2-phenylimidazo[1,2-a]pyridine (CDR 101) is described. After extraction from plasma and blood, CDR 101 was analysed using a C18 Nucleosil ODS column (250×4.6 mm, 5 μm particle size) and mobile phase of acetonitrile-0.05 M ammonium acetate adjusted to pH 3.0, with UV detection at 318 nm. The mean recoveries of CDR 101 in plasma and blood over a concentration range of 25–500 ng/ml were 95.5±2.01% and 83.3±1.87%, respectively. The within-day and day-to-day coefficient of variations for plasma were 3.23-6.21% and 2.59-9.90%, respectively, those for blood were 2.59-5.92% and 2.89-6.82%, respectively. The minimum detectable concentration for CDR 101 was 1 ng/ml in plasma and 2.5 ng/ml in whole blood. This method was found to be suitable for clinical pharmacokinetic studies. 相似文献
9.
《Inorganica chimica acta》2004,357(8):2324-2330
The reactions of Me(Ph)SnCl2 and Et(Ph)SnCl2 with 2,6-diacetylpyridine bis(thiosemicarbazone) (H2DAPTSC) afforded the complexes [Me(Ph)Sn(HDAPTSC)]Cl · 1.25MeOH (1) and [Et(Ph)Sn(H2DAPTSC)]Cl2 · MeOH · H2O (2), respectively. Single-crystal X-ray crystallography showed that in both complexes the ligand, monodeprotonated in 1 and neutral in 2, is S(1),S(2),N(3),N(4),N(5)-coordinated, and the coordination geometry around the metal can be described as a distorted pentagonal bipyramid with the aryl and alkyl groups in axial positions. 1H and 119Sn NMR studies of solution in DMSO suggest that 2 dissociates completely in this solvent, while 1 evolves to the new complex [Me(Ph)Sn(DAPTSC)], with release of H2DAPTSC and Me(Ph)SnCl2. These conclusions were also supported by conductivity measurements. 相似文献
10.
A new lanthanum ethylenediaminetetraacetate (EDTA) coordination polymer, {[La(EDTA)(H2O)]2}n (EDTA3− = [(CH2N)2(CH2COOH)(CH2COO−)3]), was hydrothermally prepared from LaCl3 solution and ethylenediaminetetracetic acid at 448 K. The compound was characterized by elemental analysis, FTIR, TG-DTA, and X-ray crystallography. The structure consists of ladder-like chains of [La(EDTA)(H2O)]2 dimers bridged by O-C-O groups. Hydrothermal method successfully reduced the high number of La-aqua coordinations in known lanthanum EDTA to one giving rise to relatively compact structure. It has high thermal stability up to 550 K. Every EDTA ligand with COOH group is involved in eight La-O(N) bonds to three nine-coordinated La centers. 相似文献
11.
k-Binding and Degradation of [3 H]Dynorphin A (1–8) and [3 H]Dynorphin A (1–9) in Suspensions of Guinea Pig Brain Membranes 总被引:3,自引:0,他引:3
Maureen G. C. Gillan Linda E. Robson Alexander T. McKnight Hans W. Kosterlitz 《Journal of neurochemistry》1985,45(4):1034-1042
Following incubation of [3H]dynorphin A (1-8) and [3H]dynorphin A (1-9) with suspensions of guinea pig brain membranes, analysis of the supernatants by HPLC has shown that both peptides are degraded at 25 degrees C and at 0 degrees C. Bestatin and captopril reduce degradation at 0 degrees C but for a similar degree of protection at 25 degrees C arginine-containing dipeptides are also required. The effects of these peptidase inhibitors on the degradation profiles indicate that [3H]dynorphin A (1-8) has three main sites of cleavage: the Tyr1-Gly2, Arg6-Arg7, and Leu5-Arg6 bonds. With [3H]dynorphin A (1-9) as substrate the Arg7-Ile8 and Ile8-Arg9 bonds are also liable to cleavage. In binding assays, in contrast to the effects of peptidase inhibitors on the degradation of unbound [3H]dynorphin A (1-8) and [3H]dynorphin A (1-9), bestatin and captopril have little effect on the binding characteristics of the tritiated dynorphin A fragments at the kappa-site at 0 degrees C. However, at 25 degrees C binding is low in the absence of peptidase inhibitors. When binding at mu- and delta-sites is prevented, the maximal binding capacities of [3H]dynorphin A (1-8), [3H]dynorphin A (1-9), and [3H](-)-bremazocine at the kappa-site are similar; [3H]dynorphin A (1-9) has 5-10 times higher affinity for the kappa-site than [3H]dynorphin A (1-8). Comparison of the effects of peptidase inhibitors on unbound dynorphin A fragments with their effects in binding assays suggests that the bound peptides are protected from the action of peptidases. 相似文献
12.
Abstract: In the postmortem human brain (27 specimens of frontal cortex, Brodmann area 9), the specific binding of the antagonists [3H]RX 821002 (2-methoxyidazoxan) to α2A-adrenoceptors and that of [3H]idazoxan to l2-imidazo-line sites (a nonadrenoceptor mitochondrial site) were determined in parallel to study the effect of aging (range, 4–89 years) on both brain proteins. The density of α2A-adrenoceptors and age were negatively correlated (r=-0.71; p < 0.001). In contrast, the density of l2-imidazo-line sites was positively correlated with aging (r= 0.59; p < 0.005). The ratio of receptor densities (α2A/l2) also showed a marked negative correlation with age (r=-0.76; p < 0.001). In an age-selected group (range, 10–89 years), the density of monoamine oxidase (MAO)-B sites labeled by [3H]Ro 19–6327 (lazabemide) also showed a positive correlation with age (r= 0.80; p < 0.005). In these subjects, the density of l2-imidazoline sites correlated well with the density of MAO-B sites (r= 0.70; p < 0.005). The ratio of the density of these sites (MAO-B/l2) did not correlate with the age of the subject at death (r=-0.15). In the human frontal cortex, idazoxan displayed very low affinity (Ki= 89 μM) against the binding of [3H]Ro 19–6327 to MAO-B, which discounted a direct interaction of [3H]idazoxan with the active center of the enzyme and indicated that the l2-imidazoline site cannot be identified with MAO-B. However, l2-imidazoline sites and MAO-B show a clear coexpression not only in the human frontal cortex during the process of aging, but also in various brain regions of the human and rat brains. It is suggested that the l2-imidazoline site has a specific location on glial (astrocyte) cells. 相似文献
13.
A neutral four-coordinate CuIIN3O complex with Shiff base ligand, product of template assembling of two S-methylisothiosemicarbazide units with benzoylacetone and nitromalondialdehyde, was synthesized by two steps procedure via CuIIN2O2 chelate precursor and was fully characterized by elemental analysis, IR, UV-Vis, ESR spectra and magnetochemistry. X-ray analysis confirms its structural assignment. The assembling ligand assumes an acyclic structure of ‘4+1’ type where a non-bonding interaction between the metal and the amino group of one S-methylisothiosemicarbazide unit takes place. 相似文献
14.
Jorunn Sletten Miguel Julve Francesc Lloret Isabel Castro Gunther Seitz Klaus Mann 《Inorganica chimica acta》1996,250(1-2):219-225
The first crystal and molecular structure of a transition metal complex containing 1,2-dithiocroconate (1,2-dtcr, dianion of 1,2-dimercaptocylopent-1-ene-3,4,5-trione), [Cu(bpca)(H2O)]2[Cu(1,2-dtcr)2]·2H2O (where bpca is the bis(2-pyrdidylcarbonyl)amide anion), has been determined by single crystal X-ray diffraction methods. The compound crystallizesin the monoclinic syste, space group P21/c, with a = 11.661(3), b = 20.255(6), c = 8.265(3) Å, ß = 107.26(2)° and Z = 2. The structure is formally built of [Cu(1,2-dtcr)2]2− and [Cu(bpca)(H2O)]+ ions and water of hydration. The copper atom of the anion is situated at a crystallographic inversion centre, bonded to four sulfur atoms in a planar, approximately square arrangement. In the cation the copper equatorial plane is formed by the three nitrogen atoms of the bpca ligand and a water oxygen atom. In addition there is a very weak axial bond to one of the sulfur atoms of a 1,2-dtcr ligand in the anion. Through these latter weak bonds each anion is connected to, and sandwiched between, two cations, resulting in neutral, trinuclear, centrosymmetric formula units. The triple-decker molecules are arranged in stacks along the crystallographic a-axis creating close contacts between the terminal copper atoms and bpca groups of the neighbouring molecules. This intermolecular interaction is, however, too weak to define the structure as a chain compound. The distance between adjacent copper atoms within the trinuclear unit is 4.189(1) Å, while the shortest intra-stack metal-metal separation between terminal copper atoms is 5.281(1) Å. Variable-temperature magnetic susceptibility measurements in the temperature r.2–140 K reveal that a Curie law is followed; with three non-interacting copper(II) ions in the formula unit. 相似文献
15.
Shuna Sun Xiaohua LiGuanxin Zhang Huimin MaDeqing Zhang Zhijuan Bao 《Biochimica et Biophysica Acta (BBA)/General Subjects》2006
Singlet oxygen (1O2) has been shown to play an important role in salivary defense system, but its generation process and level from human saliva remain uncertain due to the lack of a reliable detection method. We have previously reported 4,4′(5′)-bis[2-(9-anthryloxy)ethylthio]tetrathiafulvalene (BAET) as a novel chemiluminescence probe for 1O2. In this work, the probe is successfully used to characterize H2O2-dependent generation of 1O2 from saliva in real time. However, the yield of 1O2 is found to be very low, for example, being about 0.13 nmol from 200 μL saliva in the presence of 1 mM of hydrogen peroxide over a 5-s reaction period. The result is also compared with that obtained with another 1O2 probe 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-a]pyrazin-3-one (CLA), demonstrating that, besides 1O2, the other reactive oxygen species such as hydroxyl radical may also be involved in the reaction of saliva with H2O2. Furthermore, the present study shows that the selectivity of BAET for 1O2 is much higher than that of CLA and thus BAET is highly suited for the detection of 1O2 in the presence of other reactive oxygen species in biological systems. 相似文献
16.
Ruthenium complexes with one dipyrido[3,2-a:2′-3′-c]phenazine (dppz) ligand, e.g. [Ru(phen)2(dppz)]2+ (phen = phenanthroline), shows strong binding to double helical DNA and are well-known DNA “light-switch” molecules. We have here investigated four new [Ru(phen)2(dppz)]2+ derivatives with different bulky quaternary ammonium substituents on the dppz ligand to find relationships between molecular structure and intercalation kinetics, which is considered to be of importance for antitumor applicability. Linear dichroism spectroscopy shows that the enantiomers of the new complexes exhibit very similar binding geometries (intercalation of dppz moiety between adjacent DNA base pairs) as the enantiomers of the parent [Ru(phen)2(dppz)]2+ complex. Absorption spectra and luminescence properties provide further evidence for a final intercalative binding mode which has to be reached by threading of a bulky moiety between the strands of the DNA. Δ-enantiomers of all the new complexes show much slower association and dissociation kinetics than that of a reference complex without a cationic substituent. Kinetics were not very different whether the bulky quaternary group was derived from hexamethylene tetramine or 1,4-diazabicyclo-(2,2,2)octane (DABCO) or whether it had one or two positive charges. However, a complex in which the hexamethylene tetramine substituent is attached via a phenyl group showed a lowered association rate, in addition to an improved quantum yield of luminescence. A second positive charge on the DABCO substituent resulted in a much slower dissociation rate, suggesting that the distance from the Ru-centre and the amount of charge are both important for threading intercalation kinetics. 相似文献
17.
The reaction of with Co(dmgBF2)2(H2O)2 in 1.0 M HClO4/LiClO4 was found to be first-order in both reactants and the [H+] dependence of the second-order rate constant is given by k2obs = b/[H+], b at 25 °C is 9.23 ± 0.14 × 102 s−1. The [H+] dependence at lower temperatures shows some saturation effect that allowed an estimate of the hydrolysis constant for as Ka = 9.5 × 10−3 M at 10 and 15 °C. Marcus theory and the known self-exchange rate constant for Co(OH2)5OH2+/+ were used to estimate an electron self-exchange rate constant of k22 = 1.7 × 10−4 M−1 s−1 for . 相似文献
18.
Di-μ-azido-bis[azido(2-aminopyridine)aquo]dicopper(II), [Cu(2-ampy)(N3)2(H2O)]2, was synthesized and characterized by X-ray crystallography. The crystals are triclinic, space group P, with a = 7.142(1), b = 7.812(1), c = 9.727(1) Å, a = 96.52(1), β = 95.52(1), γ = 113.47(1)°, and Z = 1. The structure was refined to RF = 0.030 for 1960 observed MoKα diffractometer data. The dimeric molecule, which possesses a crystallographic inversion center, contains both terminal and μ(1)-bridging azido groups. Each copper(II) atom is further coordinated by a 2-aminopyridine ligand (via its ring N atom) and a water molecule to give a distorted square pyramid, with the metal atom raised by 0.17 Å above the N4 basal plane [CuN (ring) = 2.001(2), CuN (azide) = 1.962(3)–2.018(2) Å] towards the apical aquo ligand [CuO = 2.371(2) Å]. Each water molecule forms an intramolecular O?HN (amine) acceptor hydrogen bond, and is linked by two OH?N (terminal azide) intermolecular donor hydrogen bonds to adjacent dimeric complexes to yield a layer structure parallel to (001). Infrared and electronic spectral data are presented and discussed. 相似文献
19.
20.
The reaction of lead(II) nitrate with trisodium citrate Na3(C6H5O7) in a 1:22.5 ratio at pH 4.8 provides crystals of {Na(H2O)3}[Pb5(H2O)3(C6H5O7)3(C6H6O7)]·9.5H2O (1). The structure of 1 is two-dimensional and exhibits five distinct Pb(II) sites and four different modes of citrate bonding. The five lead sites all display hemidirected coordination geometries, that is, irregular distribution of neighboring oxygen atoms resulting in obvious gaps in the coordination spheres. Consequently, the lead coordination geometries exhibit proximal bonding to a number of oxygen donors, as well as distal interactions with nearest neighbors. The coordination numbers vary from 8 to 10, with ‘5+3’, ‘5+4’, ‘6+4’ and ‘7+3’ coordination modes where the first number refers to the proximal ligands and the second to the distal set. The four crystallographically distinct citrate groups include three with deprotonated carboxylate groups (C6H5O7)3− and one with a single protonated carboxyl group (C6H6O7)2. The citrate ligands bridge 3, 5, 7 and 7 lead sites. Three of the citrate groups exhibit tridentate chelation coordination to a lead site through two carboxylate oxygen donors and the hydroxyl groups. One citrate group projects an uncoordinated -OH group and a pendant protonated carboxyl group into the interlamellar domain. This latter carboxyl group coordinates to a sodium cation, which exhibits five coordinate geometry defined by three aqua ligands and the carbonyl oxygen of the -CO2H groups in the basal plane and a citrate -OH donor in the apical position. 相似文献