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At least 649 records · Page 36Linked to original sources
PubMed2002

The three-dimensional structure of the gallium complex of azoverdin, a siderophore of Azomonas macrocytogenes ATCC 12334, determined by NMR using residual dipolar coupling constants.

In iron-deficient conditions, Azomonas macrocytogenes ATCC 12334 excretes a fluorescent siderophore called azoverdin, which is composed of a six-amino-acid peptide chain linked to a chromophore. Azoverdin chelates iron(III) very strongly, solubilizing it and transporting it back into the cells using an outer-membrane receptor. This compound is related to the pyoverdins, the peptidic siderophores of Pseudomonas, but differs in the site on the chromophore at which the peptide is covalently linked. This feature identifies azoverdin as a member of a new class of pyoverdins: the isopyoverdins. We report the three-dimensional structure of azoverdin-Ga(III) in solution. The use of orientational constraints obtained from the measurement of residual dipolar couplings using samples dissolved in a liquid crystalline medium allowed us to define the absolute configuration of the metal complex, which is Delta. The structure is characterized by a U-shape adopted by the peptide chain, with the N(delta)-acetyl-N(delta)-hydroxyornithine side chains adopting extended conformations in order to chelate the gallium ion. This conformation leaves a large open space permitting access to the gallium ion. The structural consequences of the particular isopyoverdin chemical structure are discussed in the context of the three-dimensional structures of other pyoverdins.

Gallium↗
PubMed2003

Metalloantimalarials: targeting of P. falciparum strains with novel iron(III) and gallium(III) complexes of an amine phenol ligand.

Emergence of chloroquine (CQ)-resistant Plasmodium falciparum strains necessitates discovery of potent and inexpensive antimalarial drugs. The high cost of new drugs negatively impacts their access and distribution in the regions of the world with scarce economic resources. While exploring structure-activity relationships, using gallium(III) as a surrogate marker for iron(III), we found cationic, and moderately hydrophobic, compounds, [[1,12-bis(2-hydroxy-3-ethyl-benzyl)-1,5,8,12-tetraazadodecane]metal(III)](+) (metal = Fe(III) and Ga(III); [Fe-3-Eadd](+), 3; [Ga-3-Eadd](+), 4), that possessed antimalarial activity. Crystal structure analyses revealed octahedral geometry for these complexes. The RP-HPLC analysis, after incubation in PBS or HEPES buffer (pH 7.4) at 37 degrees C for 3 days, detected only parental compounds thereby providing evidence for stability under physiological conditions. Both 3 and 4 demonstrated promising half-maximum inhibitory concentration (IC(50)) values of approximately 80 and 86 nM in the CQ-sensitive HB-3 line, respectively. However, both 3 and 4 were found to possess elevated IC(50) values of 2.5 and 0.8 microM, respectively, in the CQ-resistant Dd2 line, thus displaying preferential cytotoxicity toward the CQ-sensitive HB3 line. In cultured parasites, 3 and 4 targeted hemozoin formation. Thus, these compounds acted similarly to chloroquine with regard to action and resistance, despite the lack of structural similarity to quinolines. Finally, similarity in coordination chemistry, stability, and antimalarial cytotoxicity profiles indicated that gallium(III) ion can serve as a template for iron(III) in structure elucidation of active molecules in solution.

Amines↗
PubMed2004

Synthesis, structure, and molecular dynamics of gallium complexes of schizokinen and the amphiphilic siderophore acinetoferrin.

A new general synthesis of the citrate-based siderophores acinetoferrin (Af) and schizokinen (Sz) and their analogues is described. The molecular structure of gallium schizokinen, GaSz, was determined by combined (1)H NMR, Hartree-Fock ab initio calculations, DFT, and empirical modeling of vicinal proton NMR spin-spin couplings. The metal-coordination geometry of GaSz was determined from NOE contacts to be cis-cis with respect to the two chelating hydroxamates. One diaminopropane adopts a single chairlike conformation while another is a mixture of two ring pucker arrangements. Both amide hydrogens are internally hydrogen bonded to metal-ligating oxygen atoms. The acyl methyl groups are directed away from each other with an average planar angle of ca. 130 degrees. The kinetics of GaSz racemization were followed by selective, double spin-echo inversion-recovery (1)H NMR spectroscopy over the temperature range of 10-45 degrees C. The racemization proceeds by a multistep mechanism that is proton independent between pD 5 and 12 (k(0) = 1.47 (0.15 s(-1))) and acid catalyzed below pD 4 (k(1) = 2.25 (0.15) x 10(4) M(-1) s(-1)). The activation parameters found for the two sequential steps of the proton independent pathway were DeltaH(++) = 25 +/- 3 kcal M(-1), DeltaS(++) = 25 +/- 7 cal M(-1) K(-1) and DeltaH(++) = 17.1 +/- 0.2 kcal M(-1), DeltaS(++) = 0.3 +/- 2.7 cal M(-1) K(-1). The first step of the proton-independent mechanism was assigned to the dissociation of the carboxyl group. The second step was assigned to complex racemization. The proton-assisted step was assigned to a complete dissociation of the alpha-hydroxy carboxyl group at pD < 4. The ab initio modeling of gallium acinetoferrin, GaAf, and analogues derived from the structure of GaSz has shown that the pendant trans-octenoyl fragments are oriented in opposite directions with the average planar angle of ca. 130 degrees. This arrangement prevents GaAf from adopting a phospholipid-like structural motif. Significantly, iron siderophore complex FeAf was found to be disruptive to phospholipid vesicles and is considerably more hydrophilic than Af, with an eight-fold smaller partition coefficient.

Acinetobacter↗
PubMed2006

Quantitative adsorption and local structures of gallium(III) at the water-alpha-FeOOH interface.

The adsorption of Ga(III) at the water-alpha-FeOOH (goethite) interface has been investigated by means of quantitative adsorption experiments, extended X-ray absorption fine structure (EXAFS) spectroscopy, and surface complexation modeling. Under the conditions studied, pH range 3-11 and surface coverages of 0.9-3.2 micromol/m2, Ga(III) was found to adsorb strongly to alpha-FeOOH, and the surface species were more resistant toward hydrolysis and formation of soluble Ga(OH)4- than either solid gallium hydroxides or soluble polynuclear complexes. The EXAFS measurements revealed the presence of octahedral Ga(III) complexes at the water-alpha-FeOOH interface, with practically no structural variations as a function of pH or total gallium concentration. Analysis of the first coordination shell required an anharmonic model indicating a distorted geometry of the GaO6 octahedra, with mean Ga-O distances at 1.96-1.98 angstroms. A method based on the continuous Cauchy wavelet transforms (CCWT) was used to identify backscattering atoms in the higher coordination shells. This analysis indicated predominately Fe backscattering, and the quantitative data fitting resulted in three Ga-Fe paths at 3.05, 3.2, and 3.55 angstroms, which correspond to two edge-sharing and one corner-sharing linkage, respectively. The collective results from EXAFS spectroscopy showed that Ga(III) adsorbs to Fe equivalent sites at the surface alpha-FeOOH as an extension of the rows of Fe octahedra in the bulk structure. This interpretation was further corroborated by a Ga-Fe-Fe multiple scattering path at 6.13 angstroms. The quantitative adsorption and proton data were modeled using a surface complexation formalism based on a 1 pK(a) constant capacitance model. In agreement with the EXAFS results, the model obtained included one predominating surface complex with the stoichiometry [triple bond]FeOGa(OH)2(-0.5) and the stability constant log beta(intr.) = -2.55 +/- 0.04 ([triple bond]FeOH(-0.5) + Ga3+ + 2H2O <--> [triple bond]FeOGa(OH)2(-0.5) + 3H+).

Adsorption↗
PubMed1998

The solution structure of a gallium-substituted putidaredoxin mutant: GaPdx C85S.

The Fe2S2 cluster of the ferredoxin putidaredoxin (Pdx) can be replaced by a single gallium ion, giving rise to a colorless, diamagnetic protein in which, apart from the metal binding site, the major structural features of the native ferredoxin are conserved. The solution structure of the C85S variant of gallium putidaredoxin (C85S GaPdx), in which a non-ligand cysteine is replaced by a serine, has been determined via multidimensional NMR methods using uniformly 15N, 13C labeled samples of C85S GaPdx. Stereospecific assignments of leucine and valine methyl resonances were made using 13C, 1H HSQC spectra obtained with fractionally 13C-labeled samples, and backbone dihedral angle restraints were obtained using a combination of two-dimensional J-modulated 15N, 1H HSQC and three-dimensional (HN)CO(CO)NH experiments. A total of 1117 NOE-derived distance restraints were used in the calculations, including 454 short range (i-j < or = 3), 456 long range (i-j > or = 4) interresidue restraints and 207 non-trivial intraresidue restraints. 97 phi and 55 chi 1 angular restraints were also included in the calculation of a family of 20 structures using a combined distance geometry-simulated annealing protocol. Most regions of the protein are well defined in the calculations, with an RMSD of 0.525 A for backbone atoms excluding the metal binding loop (residues 34-48) and the last three C-terminal residues (residues 103-106). Where comparison is possible, these regions show an increase in dynamic behavior over the native protein, as does the loop containing residues 74-76. Structural and dynamic differences between native Pdx and GaPdx are discussed in relation to charge and packing of the metal binding site.

Amino Acid Substitution↗
PubMed2004

Crystallographic alignment of high-density gallium nitride nanowire arrays.

Single-crystalline, one-dimensional semiconductor nanostructures are considered to be one of the critical building blocks for nanoscale optoelectronics. Elucidation of the vapour-liquid-solid growth mechanism has already enabled precise control over nanowire position and size, yet to date, no reports have demonstrated the ability to choose from different crystallographic growth directions of a nanowire array. Control over the nanowire growth direction is extremely desirable, in that anisotropic parameters such as thermal and electrical conductivity, index of refraction, piezoelectric polarization, and bandgap may be used to tune the physical properties of nanowires made from a given material. Here we demonstrate the use of metal-organic chemical vapour deposition (MOCVD) and appropriate substrate selection to control the crystallographic growth directions of high-density arrays of gallium nitride nanowires with distinct geometric and physical properties. Epitaxial growth of wurtzite gallium nitride on (100) gamma-LiAlO(2) and (111) MgO single-crystal substrates resulted in the selective growth of nanowires in the orthogonal [1\[Evec]0] and [001] directions, exhibiting triangular and hexagonal cross-sections and drastically different optical emission. The MOCVD process is entirely compatible with the current GaN thin-film technology, which would lead to easy scale-up and device integration.

Crystallization↗
PubMed2005

Setup of a scanning near field infrared microscope (SNIM): imaging of sub-surface nano-structures in gallium-doped silicon.

We have realized a scanning near-field infrared microscope in the 3-4 microm wavelength range. As a light source, a tunable high power continuous wave infrared optical parametric oscillator with an output power of up to 2.9 W in the 3-4 microm range has been set up. Using scanning near field infrared microscopy (SNIM) imaging we have been able to obtain a lateral resolution of < or =30 nm at a wavelength of 3.2 microm, which is far below the far-field resolution limit of lambda/2. Using this "chemical nanoscope" we could image a sub-surface structure of implanted gallium ions in a topographically flat silicon wafer giving evidence for a near-field contrast. The observed contrast is explained in terms of the effective infrared reflection as a function of the sub-surface gallium doping concentration. The future use of the setup for nm imaging in the chemically important OH, N-H and C-H stretching vibration is discussed.

Chemical Phenomena↗
PubMed1998

Giant cell granulamatous hypophysitis with remarkable uptake on Gallium-67 scintigraphy.

We treated a man with giant cell granulomatous hypophysitis with pituitary enlargement, as seen on magnetic resonance imaging. Endocrinological examination revealed panhypopituitarism and diabetes insipidus. Microscopic examination of the specimen obtained by transsphenoidal pituitary biopsy revealed a granulomatous lesion, composed of epitheliod cells, Langhans' multinucleated giant cells, lymphocytes and other chronic inflammatory cells. On whole body gallium-67 scintigraphy, there was extensive uptake in the pituitary gland. Gallium-67 scintigraphy may greatly aid in the diagnosis of granulomatous hypophysitis.

Adult↗
PubMed1987

[False-positive findings of 67-gallium scintigraphy in staging/restaging of malignant lymphoma].

Gallium scintigraphy has been an established method for the diagnosis of malignant lymphomas for some years. If properly interpreted, the value of the method is not necessarily reduced by the lack of tumour specificity and the well known property of 67Ga to accumulate in inflammatory and granulomatous conditions. A retrospective analysis of 123 patients with malignant lymphomas showed false positive 67Ga scintigrams in 7%. These cases demonstrate the spectrum of possible errors. 'False positives' were all those localised areas of uptake which were due to some pathological condition which was not lymphomatous. All the positive gallium findings could be elucidated by clinical, radiological and histological investigations.

False Positive Reactions↗
PubMed1971

Antitumor activity and toxicity of salts of inorganic group 3a metals: aluminum, gallium, indium, and thallium.

The toxicity and antitumor activity of salts of the Group IIIa metals aluminum, gallium, indium, and thallium were determined. With the (lethal dose)(50) as a measure, the decreasing order of toxicity was TlCl(3) >/= In(NO(3))(3) > Ga(NO(3))(3) > Al(NO(3))(3). All four metals exhibited antitumor activity, but when the tumor was inoculated by a route different from that of the drug, only Ga(+3) and, to a lesser extent, In(+3) inhibited tumor growth. Ga(NO(3))(3) was found to inhibit the growth of three out of four rodent solid tumors. Gallium therefore has potential therapeutic usefulness for treatment of solid tumors in man.

Aluminum↗
PubMed2004

Port-A catheter-associated Nocardia bacteremia detected by gallium inflammation scan: a case report and literature review.

Central venous catheter-associated Nocardia bacteremia is rarely reported. We present the case of a 48-y-old male with a history of advanced T-cell lymphoma who suffered from recurrent fever and persistent Gram-positive bacillus bacteremia. Port-A catheter-associated Nocardia bacteremia was diagnosed on the basis of the clinical response to removal of the catheter and the finding of increased gallium uptake, along with the Port-A catheter presented in the gallium inflammation scan.

Anti-Bacterial Agents↗
PubMed1989

Dissolution of crystalline gallium arsenide in aqueous solutions containing complexing agents.

Crystalline gallium arsenide (GaAs) was found to dissolve in an aqueous solution containing the inorganic anions, chloride, sulfate, bicarbonate, monohydrogen phosphate, and dihydrogen phosphate, and the organic anions, acetate and citrate. The aqueous solution was made up to resemble lung fluid (Gamble solution) and was maintained at a pH of 7.4. The concentrations of arsenic (As) and gallium (Ga) in solution and the As-GA ratio on the surface of the GaAs increased continuously as the time of contact with the aqueous solution increased. X-ray photoelectron spectroscopic studies of the GaAs surface, at various time intervals, showed that As migrated to the surface and was oxidized to a species resembling As2O3 and, finally, was dissolved. The zinc present in the crystalline GaAs also migrated to the surface.

Arsenic↗
PubMed1986

Use of technetium-99m methylene diphosphonate and gallium-67 citrate scans after intraarticular injection of Staphylococcus aureus into knee joints of rabbits with chronic antigen-induced arthritis.

Numerous clinical studies have questioned the ability of radionuclide scans to differentiate septic from aseptic joint inflammation. A clinical study may not be able to document an underlying disease process or duration of infection and, thus, may make conclusions about the accuracy of scan interpretations open to debate. In this study, the Dumonde-Glynn model of antigen-induced arthritis in rabbits was used as the experimental model to study technetium and gallium scans in Staphylococcus aureus infection of arthritic and normal joints. Gallium scans were negative in normal rabbits, usually negative in antigen-induced arthritis, but positive in septic arthritis. The bone scan was usually negative in early infection but positive in late septic arthritis, a finding reflecting greater penetration of bacteria into subchondral bone because of the underlying inflammatory process.

Animals↗
PubMed1991

A phase II trial of gallium nitrate (NSC #15200) in previously treated ovarian carcinoma. A Gynecologic Oncology Group Study.

Twenty-six evaluable patients with advanced or recurrent epithelial ovarian cancer were treated with 750 mg/m2 of gallium nitrate every three weeks. All patients had prior cisplatin chemotherapy. One patient had a complete response (3.8%), two patients had partial responses (7.7%), and six patients had stable disease (23.1%). The 95% upper confidence bound for response is 27.2%. The major toxicity was nausea and vomiting which was modest, and anemia, which was moderate to severe. Myelosuppression was minimal. Gallium nitrate has modest activity in previously treated patients with epithelial ovarian cancer.

Adult↗
PubMed1998

Vinblastine, ifosfamide, gallium nitrate, and filgrastim in platinum- and paclitaxel-resistant ovarian cancer: a phase II study.

The authors performed a phase II trial of the VIG regimen (vinblastine, ifosfamide, and gallium nitrate) in patients who had advanced ovarian cancer who were refractory to cisplatin and/or carboplatin and whose disease had progressed after paclitaxel-based therapy. This was a heavily pretreated population, with five patients having received two to three prior chemotherapy regimens and six patients having received more than six prior chemotherapy regimens, with an average of 21 therapy cycles per patient. Fourteen patients were treated with vinblastine, 0.08 mg/kg intravenously on days 1 and 2; ifosfamide, 900 mg/m2 intravenously on days 1 through 5 with standard mesna uroprotection; and gallium nitrate administered as a continuous intravenous infusion at 225 mg/m2 per 24 hours x 120 hours. Granulocyte colony-stimulating factor (G-CSF) was administered subcutaneously at 5 microg/kg/day beginning on day 7 until day 13. Five of 14 patients achieved a partial response for an overall response rate of 36% (95% confidence interval, 14%-68%). The median response duration was 14 weeks. Toxicity was primarily hematologic, with anemia and leukopenia being most significant. There were no treatment-related deaths. Further evaluation of this regimen in a less heavily pretreated population is warranted.

Aged↗
PubMed2001

Unexplained systemic symptoms and Gallium-67--guided decisions.

Over 3 months, a healthy man developed prominent systemic symptoms that defied investigation. Physical examination was noncontributory, and extensive studies revealed only a marked acute-phase response associated with increased serum IL-6 levels. A whole body Gallium-67 scan was crucial in diagnosis, directing attention to high uptake in the left paraspinal and psoas muscles. Open surgical excision biopsy was performed, guided by intraoperative use of a gamma-probe. Removed tissue was diagnosed as diffuse, large B-cell non-Hodgkin lymphoma of muscle (stage IE), a rare extranodal lymphoma. Cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) therapy was given, and the patient became asymptomatic with normal blood tests and was thought to be in remission. However, a repeat Gallium-67 scan revealed recurrent multifocal disease and salvage chemotherapy was instituted. A 47,XXY karyotype (Klinefelter syndrome) was later identified, possibly associated with the lymphoma.

Agriculture↗
PubMed1979

Gallium scan: clue to diagnosis of starch peritonitis.

A patient with starch peritonitis was given a gallium scan which showed diffuse uptake in the abdomen and intense uptake in a noninfected incision six weeks after surgery. The accumulation of gallium in a noninfected surgical incision later than one week after surgery, accompanied by diffuse abdominal uptake, may indicate the presence of starch peritonitis.

Abdomen↗
PubMed1981

Gallium imaging in cancer of the esophagus.

Ga-67-citrate scintigraphy was used in 17 patients with carcinoma of the esophagus as part of the preoperative evaluation. Intense concentration in the primary site was associated with an extensive tumor. In all patients but one in whom resection was attempted, the tumors were found to be unresectable. Gallium scintigraphy diaphragm and in the left supraclavicular fossa. Of special interest were three patients in whom esophagoscopy and contrast radiography suggested a benign stricture. All had intense concentration of gallium at the esophagogastric junction, an indication that proved to be carcinoma.

Adenocarcinoma↗