PubMed Health⌕ Search

Biomedical subjects

Z Gross

Publications and source records attributed to Z Gross.

At least 19 recordsLinked to original sources
PubMed2001

Chromium corroles in four oxidation States.

We have isolated and characterized chromium complexes of 5,10,15-tris(pentafluorophenyl)corrole [(tpfc)H(3)] (1) in four oxidation states: [(tpfc(*))CrO][SbCl(6)] (6); [(tpfc)CrO] (2); [(tpfc)CrO][Cp(2)Co] (4); and [(tpfc)Cr(py)(2)] (3). Complex 6 was prepared both by electrochemical and chemical oxidation of 2; its formulation as a Cr(V)O ligand-radical species is based on UV-visible absorption as well as EPR measurements. Cobaltocene reduction of 2 gave 4; it was identified as a diamagnetic d(2) Cr(IV)O complex from its sharp (1)H NMR spectrum. Reaction of 2 with triphenylphosphine yielded a chromium(III) corrole, [(tpfc)Cr(OPPh(3))(2)] (5). Owing to its air sensitivity, 5 could not be isolated in the absence of excess OPPh(3). The structure of the Cr(III) bis-pyridine complex (3) was determined by X-ray crystallography (Cr-N distances: 1.926-1.952 A, pyrrole; 2.109, 2.129 A, pyridine).

Journal Article↗
PubMed2001

What is the difference between the manganese porphyrin and corrole analogues of cytochrome P450's compound I?

Density functional calculations on oxo-manganese complexes of corrole (1) and porphyrin (2 and 3) show a fundamental difference. The ground state of I is the singlet manganese(V) state, 1A(MnV), in which corrole is a closed shell. In contrast, 2 and 3 have high-spin manganese(IV) states, 1A1u and 3A2u respectively. This difference and the state ordering for each system are rationalized based on the competition between the intrinsic tendency of manganese to prefer high-spin electronic configurations, vis-à-vis the general tendency to prefer double occupancy in the low-lying orbitals. The outcome of this competition is determined primarily by the identity of the macrocycle, corrole versus porphyrin. Corrole with a small cavity holds the MnO moiety with a high off-plane displacement, and thereby prefers the low-spin state. On the other hand, porphyrin with the wider cavity holds the MnO moiety closer to the plane, and thereby prefers high-spin states.

Cytochrome P-450 Enzyme System↗
PubMed2001

Highly selective chlorosulfonation of tris(pentafluorophenyl)corrole as a synthetic tool for the preparation of amphiphilic corroles and metal complexes of planar chirality.

[reaction: see text]. The chlorosulfonation of tris(pentafluorophenyl)corrole proceeds with an extremely high selectivity as to afford one out of 139 possible isomers in very high yield. The bis-chlorosulfonated corrole is an excellent precursor to the planar-chirality (triphenylphosphine)cobalt(III) complex (fully characterized by X-ray crystallography) and to the amphiphilic bis-sulfonic acid derivative, both the first of their kind.

Cobalt↗
PubMed2001

Synthesis and structural characterization of a novel covalently-bound corrole dimer.

The (triphenylphosphine)cobalt(III) complex (2) of 5,10,15-tris(pentafluorophenyl)corrole (1) is shown to be an valuable precursor to complexes that have not been fully characterized previously. In contrast to other cobalt corroles, aromatic amines can be substituted for the triphenylphosphine in 2 to form six-coordinate bis(amine)cobalt(III) complexes. This is demonstrated by spectroscopic methods and by X-ray crystallography of the bis-pyridine complex 4, the first of its kind. While 2 and 4 and even their one-electron oxidized complexes are stable, a spontaneous dimerization of the corrole takes place in the absence of strongly bound ligands. The bis-cobalt complex of the novel corrole dimer 6 was fully characterized by spectroscopic methods and X-ray crystallography.

Cobalt↗
PubMed2001

Synthesis and characterization of germanium, tin, phosphorus, iron, and rhodium complexes of tris(pentafluorophenyl)corrole, and the utilization of the iron and rhodium corroles as cyclopropanation catalysts.

The germanium(IV), tin(IV). and phosphorus(v) complexes of tris(pentafluorophenyl)corrole were prepared and investigated by electrochemistry for elucidation of the electrochemical HOMO-LUMO gap of the corrole and the spectroscopic characteristics of the corrole pi radical cation. This information was found to be highly valuable for assigning the oxidation states in the various iron corroles that were prepared. Two iron corroles and the rhodium(I) complex of an N-substituted corrole were fully characterized by X-ray crystallography and all the transition metal corroles were examined as cyclopropanation catalysts. All iron (except the NO-ligated) and rhodium corroles are excellent catalysts for cyclopropanation of styrene, with the latter displaying superior selectivities. An investigation of the effect of the oxidation state of the metal and its ligands leads to the conclusion that for iron corroles the catalytically active form is iron(III), while all accesible oxidation states of rhodium are active.

Journal Article↗
PubMed2001

High-valent corrole metal complexes.

This commentary concentrates on corrole complexes with the three metal ions that are most relevant to oxidation catalysis: chromium, manganese, and iron. Particular emphasis is devoted to the only recently introduced meso-triarylcorroles and a comparison with the traditionally investigated beta-pyrrole-substituted corroles. Based on a combination of spectroscopic methods, electrochemistry, and X-ray crystallography, it is concluded that in most high-valent metallocorroles the corrole is not oxidized. Both experimental (for (oxo)chromium(V) corrole) and computational (for (oxo)manganese(V) corrole) evidence indicate that the stabilization of high-valent metal ions by corroles originates from a combination of short metal-nitrogen bonds and large metal out-of-plane displacements in the corrole, which lead to quite unexpected interactions of the oxo-metal pi* orbitals with the in-plane orbitals of the corrole.

Corrinoids↗
PubMed2000

Structural, Electrochemical, and Photophysical Properties of Gallium(III) 5,10,15-Tris(pentafluorophenyl)corrole We acknowledge support of this research from the Fund for the Promotion of Research at the Technion (Z.G.), the National Science Foundation (H.B.G.), and the Danish Natural Science Research Council for financial support under grant No. 9800549 (J.B.). We also thank Dr. H. Weihe (University of Copenhagen) for access to computing facilities, and L. M. Henling (Beckman Institute) for assistance with the crystal structure determination.

Explore the source record for details and available documents.

Journal Article↗
PubMed2000

Porphyrin analogues as novel antagonists of fibroblast growth factor and vascular endothelial growth factor receptor binding that inhibit endothelial cell proliferation, tumor progression, and metastasis.

Fibroblast growth factors (FGFs) and vascular endothelial growth factor (VEGF) play a pivotal role in the multistep pathway of tumor progression, metastasis, and angiogenesis. We have identified a porphyrin analogue, 5,10,15,20-tetrakis(methyl-4-pyridyl)-21H,23H-porphine-tetra -p-tosylate salt (TMPP), as a potent inhibitor of FGF2 and VEGF receptor binding and activation. TMPP demonstrated potent inhibition of binding of soluble FGF receptor 1 (FGFR1) to FGF2 immobilized on heparin at submicromolar concentrations. TMPP inhibits binding of radiolabeled FGF2 to FGFR in a cell-free system as well as to cells genetically engineered to express FGFR1. Furthermore, TMPP also inhibits the binding of VEGF to its tyrosine kinase receptor in a dose-dependent manner. In an in vitro angiogenic assay measuring the extent of endothelial cell growth, tube formation, and sprouting, TMPP dramatically reduced the extent of the FGF2-induced endothelial cell outgrowth and differentiation. In a Lewis lung carcinoma model, mice receiving TMPP showed a marked inhibition of both primary tumor progression and lung metastases development, with nearly total inhibition of the metastatic phenotype upon alternate daily injections of TMPP at 25 microg/g of body mass. Finally, novel meso-pyridylium-substituted, nonsymmetric porphyrins, as well as a novel corrole-based derivative, with >50-fold increase in activity in vitro, had a significantly improved efficacy in blocking tumor progression and metastasis in vivo.

Animals↗
PubMed1999

N-Substituted Corroles: A Novel Class of Chiral Ligands.

Although known for almost 35 years, N-substituted corroles have only now been recognized as being chiral. Several examples of these species were prepared in a facile two-step synthesis and separated into their enantiomers by HPLC. The zinc(II) complex of the corrole shown schematically was also synthesized.

Journal Article↗
PubMed1995

Ectopic pregnancy. Nonsurgical, outpatient evaluation and single-dose methotrexate treatment.

Seventeen patients with suspected ectopic pregnancy (EP) were managed as outpatients with single-dose intramuscular methotrexate (MTX) in a community hospital. A nonsurgical method was utilized for evaluation based on transvaginal ultrasonography in combination with serum human chorionic gonadotropin (hCG) determination and performance of dilation and curettage (D&C). The mean pretreatment hCG concentration was 3,320.9 mIU/mL, with a range of 158-12,420. Sixteen of 17 (94.1%) patients responded successfully to therapy, with a mean duration until hCG resolution of 26.4 days (range, 12-55). One patient experienced rupture 14 days after treatment. One of 17 patients (5.9%) complained of increased abdominal pain six days after treatment and was managed without intervention. There were no reports of adverse effects from the chemotherapy. This study demonstrated that nonsurgical evaluation for presumed EP in carefully selected patients may be performed without D&C and managed safely and effectively with well-tolerated, single-dose, systemic MTX. Our approach was designed for community hospitals.

Adult↗
PubMed1995

Vincristine for refractory autoimmune thrombocytopenic purpura in pregnancy. A case report.

BACKGROUND: Autoimmune thrombocytopenic purpura is a common disease during pregnancy. Newborns of affected mothers commonly develop thrombocytopenia. Standard therapy consists of corticosteroids, hyperimmune gamma globulin and splenectomy. CASE: Severe autoimmune thrombocytopenic purpura was diagnosed in a 22-year-old woman, gravida 2, para 1, at 28 weeks' gestation. A sufficient response was obtained after vincristine was added to the treatment with corticosteroids, hyperimmune gamma globulin and danazole. A male infant weighing 2,545 g was delivered by cesarean section at 33.5 weeks' gestation. There were no maternal or fetal complications except for severe newborn thrombocytopenia, which resolved with medical therapy. CONCLUSION: Vincristine has been used in all trimesters of pregnancy, with favorable outcomes in most cases. This is the first reported case of successful vincristine treatment for autoimmune thrombocytopenic purpura in pregnancy. Vincristine, when carefully used, offers an option for unusually refractory cases of autoimmune thrombocytopenic purpura before delivery.

Adult↗
PubMed1986

Incorporation and modification of exogenous phosphatidylcholines by mycoplasmas.

The uptake and modification of exogenous phosphatidylcholine (PC) by several Mycoplasma and Spiroplasma species was investigated. While in most Mycoplasma species and in all Spiroplasma species tested the PC appears to be incorporated unchanged from the growth medium, the PC of M. gallisepticum, M. pulmonis, and M. pneumoniae was disaturated PC, apparently formed by modification of 1-saturated-2-unsaturated PC from the growth medium. The modification of the exogenous PC by M. gallisepticum was inhibited by chloramphenicol under conditions that did not affect de novo synthesis of phosphatidylglycerol. A low activity of an endogenous phospholipase A was detected in native M. gallisepticum membranes. The activity was markedly stimulated by treating the membranes with low concentrations of the nonionic detergents. The PC modification was affected by the fatty acid composition of the exogenous PC species. Diunsaturated, 1-saturated-2-unsaturated, and 1-unsaturated-2-saturated PCs were modified to various extents, whereas the disaturated dipalmitoyl PC (DPPC) was not. Both modified and unmodified PCs were incorporated by the cells, but the unmodified DPPC was incorporated at a lower rate and to a lesser extent. The possibility that the incorporation of DPPC into M. gallisepticum cells is associated with the formation of intracytoplasmic membranes is discussed.

Chloramphenicol↗
PubMed1986

Lipid interconversions in aging Mycoplasma capricolum cultures.

During the progression of Mycoplasma capricolum cultures from the early exponential to the stationary phase of growth, a decrease in the phospholipid-to-protein ratio and increases in both the unsaturated-to-saturated fatty acid ratio and the diphosphatidylglycerol (DPG)-to-phosphatidylglycerol (PG) ratio were found. The freedom of motion of spin-labeled fatty acids incorporated into the membrane remained unchanged throughout the growth cycle. The increase in DPG was almost stoichiometric with the decrease in PG. Furthermore, exogenous PG added to the medium was incorporated by the cells and partially converted to DPG. The DPG that was accumulated upon aging was always more unsaturated than the PG. This accumulation was enhanced in palmitic acid-poor media, but was inhibited even in aged cells when the cells were grown in palmitic acid-rich media, suggesting that the accumulation of DPG upon aging was associated with changes in the fatty acid composition of membrane lipids rather than with the transition of the cells from the exponential- to stationary-growth phase.

Bacterial Proteins↗
PubMed1984

Uptake and transbilayer distribution of phosphatidylcholines in Mycoplasma gallisepticum and their effect on cell morphology.

Mycoplasma gallisepticum cells grown in a serum-free medium incorporated large amounts of egg-phosphatidylcholine (Egg-PC), dioleoylphosphatidylcholine (DOPC) or dipalmitoylphosphatidylcholine (DPPC) added to the growth medium. Egg-PC and DOPC were incorporated at a high rate and to a large extent and were modified by the organisms, whereas DPPC was incorporated at a lower rate and to a lesser extent and was not modified by the cells. The lactoperoxidase-mediated radioiodination applied to study the transbilayer distribution of phosphatidylcholine (PC) in the membranes revealed that the PC in cells grown with DOPC is almost equally distributed in the outer and inner leaflets of M. gallisepticum membranes, while the PC in DPPC-grown cells is preferentially located in the outer leaflet and that in Egg-PC-grown cells is found in the inner leaflet. Thus, in Egg-PC- or DPPC-grown cells the equilibrium in structure and properties between the inner and outer leaflets is disturbed, resulting in dramatic effects on the morphology of M. gallisepticum cells.

Biological Transport↗