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1.
P. Köpf-Maier H. Köpf E. W. Neuse 《Journal of cancer research and clinical oncology》1984,108(3):336-340
Summary The antitumor activity of a series of iron complexes, i.e., of ferrocene [Cp2Fe], of tetrachloroferrates(III) [R4N]+[FeCl4]-, and of ferricenium complexes [Cp2Fe]+X- (X-=[FeCl4]-, 1/2[Cl3FeOFeCl3]2-, [H5Mo7O24]-·2H2O, [2,4,6-(NO2)3C6H2O]-, or [CCl3COO]-·2 CCl3COOH) was investigated against EAT in CF1 mice. Whereas ferrocene and the ammonium tetrachloroferrates(III) did not show recognizable tumor-inhibiting activity, such activity was exhibited by the water-soluble, salt-like ferricenium complexes; the best antineoplastic properties, with optimum cure rates of 100%, were found for ferricenium picrate and ferricenium trichloroacetate.The ferricenium compounds are the first iron complexes for which antineoplastic activity has now been shown. They represent a new type of antitumor agent insofar as they differ fundamentally from known inorganic and organometallic antitumor agents (a) by their ionic, salt-like character, which is responsible for their high water solubility, and (b) by the absence of a cis-dihalometal moiety; this moiety has been recognized as important for the intracellular action of other known inorganic cytostatics.Abbreviations Cp
C5H5, cyclopentadienyl ring ligand
- EAT
Ehrlich ascites tumor
- IP
intraperitoneal(ly)
- p.t.t.
post transplantationem tumoris
Supported by the Fonds der Chemischen Industrie and by Council, University of the Witwatersrand 相似文献
2.
Blue copper proteins: Synthesis, spectra, and structures of CuN(3)(SR) and CuN(3)(SR) active site analogues
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Thompson JS Marks TJ Ibers JA 《Proceedings of the National Academy of Sciences of the United States of America》1977,74(8):3114-3118
The reaction of Cu(SR) or [Cu(SR)][ClO4] derivatives (SR = p-nitrobenzenethiolate or O-ethylcysteinate) with potassium hydrotris(3,5-dimethyl-1-pyrazolyl)borate produces redox pairs of the stoichiometry CuIN3(SR) and CuIIN3(SR). These complexes are well-defined synthetic approximations to the proposed N3S binding sites of blue (type 1) copper electron transfer proteins. The compounds were investigated by a variety of chemical and spectral (optical, resonance Raman, and electron paramagnetic resonance) techniques; the complex K[Cu(hydrotris(3,5-dimethyl-1-pyrazolyl)borate)(p- NO2C6H4S]-2 acetone was also studied by single-crystal x-ray diffraction methods. The spectrochemical characteristics of the CuIIN3(SR) species are in large part similar to the native system and thus provide some perspective regarding the origin of the unique type 1 spectral parameters and electron transfer properties. 相似文献
3.
Dooshaye Moonshiram Vatsal Purohit Javier J. Concepcion Thomas J. Meyer Yulia Pushkar 《Materials》2013,6(2):392-409
Water oxidation is critically important for the development of energy solutions based on the concept of artificial photosynthesis. In order to gain deeper insight into the mechanism of water oxidation, the catalytic cycle for the first designed water oxidation catalyst, cis,cis-[(bpy)2(H2O)RuIIIORuIII(OH2)(bpy)2]4+ (bpy is 2,2-bipyridine) known as the blue dimer (BD), is monitored in D2O by combined application of stopped flow UV-Vis, electron paramagnetic resonance (EPR) and resonance Raman spectroscopy on freeze quenched samples. The results of these studies show that the rate of formation of BD[4,5] by Ce(IV) oxidation of BD[3,4] (numbers in square bracket denote oxidation states of the ruthenium (Ru) centers) in 0.1 M HNO3, as well as further oxidation of BD[4,5] are slower in D2O by 2.1–2.5. Ce(IV) oxidation of BD[4,5] and reaction with H2O result in formation of an intermediate, BD[3,4]′, which builds up in reaction mixtures on the minute time scale. Combined results under the conditions of these experiments at pH 1 indicate that oxidation of BD[3,4]′ is a rate limiting step in water oxidation with the BD catalyst. 相似文献
4.
ObjectiveTo evaluate the antibacterial and antifungal effects of cadmium(II) complexes with hexamethyltetraazacyclotetradecadiene ligands.MethodsFive coordinated square pyramidal cadmium(II) complexes and six coordinated square octahedral cadmium(II) complexes have been synthesized by interaction of 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene (denoted by L.2HClO4) and C-chiral isomers of its saturated analogue (denoted by ‘teta’ and ‘tetb’) with different salts of Cd2+ ion [e.g. CdI2, Cd(NO3)2·6H2O, CdCl2·2H2O and Cd(ClO4)2·6H2O] in methanolic solution. Complexes of the ligands were investigated for antibacterial activity by disc diffusion method and antifungal effect by poisoned food technique.ResultsThe newly synthesized cadmium(II) complexes of the ligands were screened as potential antimicrobial agent against a number of medically important bacteria (Staphylococcus aureus, Bacillus cereus, Salmonella typhi, Shigella dysenteriae and Escherichia coli) and against two fungi (Candida albicans and Aspergillus aculeatus). The growth inhibiting activity of the ligands and complexes against bacteria and fungi were compared with the standard antibiotic ampicillin and commercially important antifungal agent, griseofulvin respectively. Among them some of the macrocyclic complexes were found to be more fungitoxic and antibacterial than the reference antifungal drug griseofulvin and antibacterial drug ampicillin respectively.ConclusionsHexamethyltetraazacyclotetradecadiene ligands and its complexes could be considered as very potential antibacterial and antifungal agent with further investigation. 相似文献
5.
Andrew T. Smith Wendy A. Doyle Pierre Dorlet Anabella Ivancich 《Proceedings of the National Academy of Sciences of the United States of America》2009,106(38):16084-16089
The surface oxidation site (Trp-171) in lignin peroxidase (LiP) required for the reaction with veratryl alcohol a high-redox-potential (1.4 V) substrate, was engineered into Coprinus cinereus peroxidase (CiP) by introducing a Trp residue into a heme peroxidase that has similar protein fold but lacks this activity. To create the catalytic activity toward veratryl alcohol in CiP, it was necessary to reproduce the Trp site and its negatively charged microenvironment by means of a triple mutation. The resulting D179W+R258E+R272D variant was characterized by multifrequency EPR spectroscopy. The spectra unequivocally showed that a new Trp radical [g values of gx = 2.0035(5), gy = 2.0027(5), and gz = 2.0022(1)] was formed after the [Fe(IV)=O Por•+] intermediate, as a result of intramolecular electron transfer between Trp-179 and the porphyrin. Also, the EPR characterization crucially showed that [Fe(IV)=O Trp-179•] was the reactive intermediate with veratryl alcohol. Accordingly, our work shows that it is necessary to take into account the physicochemical properties of the radical, fine-tuned by the microenvironment, as well as those of the preceding [Fe(IV)=O Por•+] intermediate to engineer a catalytically competent Trp site for a given substrate. Manipulation of the microenvironment of the Trp-171 site in LiP allowed the detection by EPR spectroscopy of the Trp-171•, for which direct evidence has been missing so far. Our work also highlights the role of Trp residues as tunable redox-active cofactors for enzyme catalysis in the context of peroxidases with a unique reactivity toward recalcitrant substrates that require oxidation potentials not realized at the heme site. 相似文献
6.
A 28-electron reduced C2h-Mo-blue 34Ǻ outer ring diameter circular ring, [Mo142O429H10(H2O)49(CH3CO2)5(C2H5CO2)]30- (≡{Mo142(CH3CO2)5(C2H5CO2)}) comprising eight carboxylate-coordinated (with disorder) {Mo2} linkers and six defect pockets in two inner rings (four and three for each, respectively), reacts with La3+ in aqueous solutions at pH 3.5 to yield a 28-electron reduced elliptical Ci-Mo-blue ring of formula [Mo134O416H20(H2O)46{La(H2O)5}4{La(H2O)7}4{LaCl2(H2O)5}2]10- (≡{Mo134La10}), isolated as the Na10[Mo134O416H20(H2O)46{La(H2O)5}4{La(H2O)7}4{LaCl2(H2O)5}2]·144 H2O Na+ salt. The elliptical structure of {Mo134La10} showing 36 and 31 Å long and short axes for the outer ring diameters is attributed to four (A-D) modes of LaO9/LaO7Cl2 tricapped-trigonal-prismatic coordination (TTP) geometries. Two different LaO2(H2O)7 and one LaO2(H2O)2Cl2 TTP geometries (as A-C modes) for each of two inner rings result from the coordination of all three defect pockets of the inner ring for {Mo142(CH3CO2)5(C2H5CO2)}, and two LaO4(H2O)5 TTP geometries (as D mode) result from the displacement of two (acetate/propionate-coordinated) binuclear {Mo2} linkers with La3+ in each inner ring. The isothermal titration calorimetry (ITC) of the ring modification from circle to ellipsoid, showing the endothermic reaction of [La3+]/[{Mo142(CH3CO2)5(C2H5CO2)}] = 6/1 with ΔH = 22 kJ⋅mol-1, ΔS = 172 J⋅K-1⋅mol-1, ΔG = −28 kJ⋅mol-1, and K = 9.9 × 104 M-1 at 293 K, leads to the conclusion that the coordination of the defect pockets to La3+ precedes the replacement of the {Mo2} linkers with La3+. 139La- NMR spectrometry of the coordination of {Mo142(CH3CO2)5(C2H5CO2)} ring to La3+ is also discussed. 相似文献
7.
Smith SO Myers AB Pardoen JA Winkel C Mulder PP Lugtenburg J Mathies R 《Proceedings of the National Academy of Sciences of the United States of America》1984,81(7):2055-2059
Resonance Raman spectra of the BR568, BR548, K625, and L550 intermediates of the bacteriorhodopsin photocycle have been obtained in 1H2O and 2H2O by using native purple membrane as well as purple membrane regenerated with 14,15-13C2 and 12,14-2H2 isotopic derivatives of retinal. These derivatives were selected to determine the contribution of the C14—C15 stretch to the normal modes in the 1100- to 1400-cm-1 fingerprint region and to characterize the coupling of the C14—C15 stretch with the NH rock. Normal mode calculations demonstrate that when the retinal Schiff base is in the C[unk]N cis configuration the C14—C15 stretch and the NH rock are strongly coupled, resulting in a large (≈50-cm-1) upshift of the C14—C15 stretch upon deuteration of the Schiff base nitrogen. In the C[unk]N trans geometry these vibrations are weakly coupled and only a slight (<5-cm-1) upshift of the C14—C15 stretch is predicted upon N-deuteration. In BR568, the insensitivity of the 1201-cm-1 C14—C15 stretch to N-deuteration demonstrates that its retinal C[unk]N configuration is trans. The C14—C15 stretch in BR548, however, shifts up from 1167 cm-1 in 1H2O to 1208 cm-1 in 2H2O, indicating that BR548 contains a C[unk]N cis chromophore. Thus, the conversion of BR568 to BR548 (dark adaptation) involves isomerization about the C[unk]N bond in addition to isomerization about the C13[unk]C14 bond. The insensitivity of the native, [14,15-13C2]-, and [12,14-2H2]K625 and L550 spectra to N-deuteration argues that these intermediates have a C[unk]N trans configuration. Thus, the primary photochemical step in bacteriorhodopsin (BR568 → K625) involves isomerization about the C13[unk]C14 bond alone. The significance of these results for the mechanism of proton-pumping by bacteriorhodopsin is discussed. 相似文献
8.
Farrell FT Jones LE 《Proceedings of the National Academy of Sciences of the United States of America》1986,83(15):5364-5366
Among other results, we rationally calculate the algebraic K-theory of any discrete cocompact subgroup of a Lie group G, where G is either O(n, 1), U(n, 1), Sp(n, 1), or F4, in terms of the homology of the double coset space Γ\G/K, where K is a maximal cocompact subgroup of G. We obtain the formula Kn(ZΓ) [unk] [unk] [unk]i=0∞Hi(Γ\G/K; [unk]n-i), where [unk]j is a stratified system of Q vector spaces over Γ\G/K and the vector space [unk]j(ΓgK) corresponding to the double coset ΓgK is isomorphic to KJ(Z(Γ [unk] gKg-1)) [unk] Q. Note Γ [unk] gKg-1 is a finite subgroup of Γ. Earlier, a similar formula for discrete cocompact subgroups Γ of the group of rigid motions of Euclidean space was conjectured by F. T. Farrell and W. C. Hsiang and proven by F. Quinn. 相似文献
9.
Herbicide resistance in Chlamydomonas reinhardtii results from a mutation in the chloroplast gene for the 32-kilodalton protein of photosystem II 总被引:11,自引:1,他引:10
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Erickson JM Rahire M Bennoun P Delepelaire P Diner B Rochaix JD 《Proceedings of the National Academy of Sciences of the United States of America》1984,81(12):3617-3621
We report the isolation and characterization of a uniparental mutant of Chlamydomonas reinhardtii that is resistant to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine). Such herbicides inhibit photosynthesis by preventing transfer of electrons in photosystem II from the primary stable electron acceptor Q to the secondary stable electron acceptor complex B, which is thought to contain a protein of 32 kDa and a bound quinone. It has been proposed that herbicide binding to the 32-kDa protein alters the B complex so that electron transfer from Q is prohibited. Both whole and broken-cell preparations of the mutant alga show a resistance to the effects of herbicide on electron transfer from Q to B, as measured by fluorescence-induction kinetics. In the absence of herbicide, mutant cells exhibit a slower rate of Q to B electron transfer than do wild-type cells. The 32-kDa protein from wild-type cells, but not mutant cells, binds azido[14C]atrazine at 0.1 μM. We have isolated psbA, the chloroplast gene for the 32-kDa protein, from both wild-type and herbicide-resistant algae and sequenced the coding regions of the gene that are contained in five exons. The only difference between the exon nucleotide sequences of the wild-type and mutant psbA is a single T-A to G-C transversion. This mutation results in a predicted amino acid change of serine in the wild-type protein to alanine in the mutant. We suggest that this alteration in the 32-kDa protein is the molecular basis for herbicide resistance in the C. reinhardtii mutant. 相似文献
10.
Lin X Hu X Concepcion JJ Chen Z Liu S Meyer TJ Yang W 《Proceedings of the National Academy of Sciences of the United States of America》2012,109(39):15669-15672
Water oxidation is a linchpin in solar fuels formation, and catalysis by single-site ruthenium complexes has generated significant interest in this area. Combining several theoretical tools, we have studied the entire catalytic cycle of water oxidation for a single-site catalyst starting with [RuII(tpy)(bpm)(OH2)]2+ (i.e., [RuII-OH2]2+; tpy is 2,2′∶6′,2′′-terpyridine and bpm is 2,2′-bypyrimidine) as a representative example of a new class of single-site catalysts. The redox potentials and pKa calculations for the first two proton-coupled electron transfers (PCETs) from [RuII-OH2]2+ to [RuIV = O]2+ and the following electron-transfer process to [RuV = O]3+ suggest that these processes can proceed readily in acidic or weakly basic conditions. The subsequent water splitting process involves two water molecules, [RuV = O]3+ to generate [RuIII-OOH]2+, and H3O+ with a low activation barrier (∼10 kcal/mol). After the key O---O bond forming step in the single-site Ru catalysis, another PECT process oxidizes [RuIII-OOH]2+ to [RuIV-OO]2+ when the pH is lower than 3.7. Two possible forms of [RuIV-OO]2+, open and closed, can exist and interconvert with a low activation barrier (< 7 kcal/mol) due to strong spin-orbital coupling effects. In Pathway 1 at pH = 1.0, oxygen release is rate-limiting with an activation barrier ∼12 kcal/mol while the electron-transfer step from [RuIV-OO]2+ to [RuV - OO]3+ becomes rate-determining at pH = 0 (Pathway 2) with Ce(IV) as oxidant. The results of these theoretical studies with atomistic details have revealed subtle details of reaction mechanisms at several stages during the catalytic cycle. This understanding is helpful in the design of new catalysts for water oxidation. 相似文献
11.
Monika Kalinowska Ewelina Gobiewska Liliana Mazur Hanna Lewandowska Marek Pruszyski Grzegorz
widerski Marta Wyrwas Natalia Pawluczuk Wodzimierz Lewandowski 《Materials》2021,14(12)
The Mg(II) and heterometallic Mn(II)/Na(I) complexes of isoferulic acid (3-hydroxy-4-methoxycinnamic acid, IFA) were synthesized and characterized by infrared spectroscopy FT-IR, FT-Raman, electronic absorption spectroscopy UV/VIS, and single-crystal X-ray diffraction. The reaction of MgCl2 with isoferulic acid in the aqueous solutions of NaOH resulted in synthesis of the complex salt of the general formula of [Mg(H2O)6]⋅(C10H9O4)2⋅6H2O. The crystal structure of this compound consists of discrete octahedral [Mg(H2O)6]2+ cations, isoferulic acid anions and solvent water molecules. The hydrated metal cations are arranged among the organic layers. The multiple hydrogen-bonding interactions established between the coordinated and lattice water molecules and the functional groups of the ligand stabilize the 3D architecture of the crystal. The use of MnCl2 instead of MgCl2 led to the formation of the Mn(II)/Na(I) complex of the general formula [Mn3Na2(C10H7O4)8(H2O)8]. The compound is a 3D coordination polymer composed of centrosymmetric pentanuclear subunits. The antioxidant activity of these compounds was evaluated by assays based on different antioxidant mechanisms of action, i.e., with •OH, DPPH• and ABTS•+ radicals as well as CUPRAC (cupric ions reducing power) and lipid peroxidation inhibition assays. The pro-oxidant property of compounds was measured as the rate of oxidation of Trolox. The Mg(II) and Mn(II)/Na(I) complexes with isoferulic acid showed higher antioxidant activity than ligand alone in DPPH (IFA, IC50 = 365.27 μM, Mg(II) IFA IC50 = 153.50 μM, Mn(II)/Na(I) IFA IC50 = 149.00 μM) and CUPRAC assays (IFA 40.92 μM of Trolox, Mg(II) IFA 87.93 μM and Mn(II)/Na(I) IFA 105.85 μM of Trolox; for compounds’ concentration 10 μM). Mg(II) IFA is a better scavenger of •OH than IFA and Mn(II)/Na(I) IFA complex. There was no distinct difference in ABTS•+ and lipid peroxidation assays between isoferulic acid and its Mg(II) complex, while Mn(II)/Na(I) complex showed lower activity than these compounds. The tested complexes displayed only slight antiproliferative activity tested in HaCaT human immortalized keratinocyte cell line within the solubility range. The Mn(II)/Na(I) IFA (16 μM in medium) caused an 87% (±5%) decrease in cell viability, the Mg salt caused a comparable, i.e., 87% (±4%) viability decrease in a concentration of 45 μM, while IFA caused this level of cell activity attenuation (87% ± 5%) at the concentration of 1582 μM (significant at α = 0.05). 相似文献
12.
Hexanuclear rhenium complexes are promising candidates for use as antitumor drugs. However, to date, there has been no investigation into the nature of their binding to DNA. In this study, density functional theory (DFT) was used to examine the binding of [Re6Se8(OH)2(H2O)4] to the DNA purine base guanine. The geometrical structures of cluster-guanine adducts in water were modeled at the zero order regular approximation (ZORA)-PW91 level. Calculating the bond energies allowed us to compare the cis and trans forms of the cluster, and a possible manners of interaction between [Re6Se8(OH)2(H2O)3] clusters and DNA was obtained and explained. 相似文献
13.
S. Umeki 《Annals of hematology》1994,68(6):267-277
Summary Professional phagocytes, neutrophils, possess a unique membrane-associated NADPH-oxidase system, dormant in resting cells, which becomes activated upon exposure to the appropriate stimuli and catalyzes the one-electron reduction of molecular oxygen to superoxide, O
2
–
. Oxidase activation involves the assembly, in the plasma membrane, of membrane-bound and cytosolic constituents of the oxidase system, which are disassembled in the resting state. The oxidase system consists of two plasma membrane-bound components; low-potential cytochromeb
558, which is composed of two subunits of 22-kDa, and 91-kDa, and a possible flavoprotein related to the electron transport between NADPH and cytochromeb
558. Recent reports have indicated that FAD-binding sites of the oxidase are contained in cytochromeb
558. At least two cytosolic components, 67-kDa protein and a phosphorylated 47-kDa protein, are known to translocate to the plasma membrane, ensuring assembly of an active O
2
–
-generating NADPH-oxidase system. It is the purpose of this review to focus on recent data concerning electron transfer mechanisms of the activated neutrophil NADPH-oxidase complex and molecular pathology of chronic granulomatous disease. 相似文献
14.
Lidija Kaniaj Pavla enjug Damir Paji Luka Pavi Kreimir Mol
anov Marijana Juri 《Materials》2020,13(23)
One-dimensional (1D) oxalate-bridged homometallic {[Mn(bpy)(C2O4)]·1.5H2O}n (1) (bpy = 2,2’-bipyridine) and heterodimetallic {[CrCu3(bpy)3(CH3OH)(H2O)(C2O4)4][Cu(bpy)Cr(C2O4)3]·CH2Cl2·CH3OH·H2O}n (2) coordination polymers, as well as the three-dimensional (3D) heterotrimetallic {[CaCr2Cu2(phen)4(C2O4)6]·4CH3CN·2H2O}n (3) (1,10-phenanthroline) network, have been synthesized by a building block approach using a layering technique, and characterized by single-crystal X-ray diffraction, infrared (IR) and impedance spectroscopies and magnetization measurements. During the crystallization process partial decomposition of the tris(oxalato)chromate(III) happened and 1D polymers 1 and 2 were formed. The antiferromagnetic interactions between the manganese(II) ions were mediated by oxalate ligands in the chain [Mn(bpy)(C2O4)]n of 1, with intra-chain super-exchange interaction 𝐽 = (−3.134 ± 0.004) K; magnetic interaction between neighbouring chains is negligible making this system closer than other known Mn-chains to the ideal 1D Heisenberg antiferromagnet. Compound 2 comprises a 1D coordination anion [Cu(bpy)Cr(C2O4)3]nn− (Cr2–Cu4) with alternating [Cr(C2O4)3]3− and [Cu(bpy)]2+ units mutually bridged through the oxalate group. Another chain (Cr1–Cu3) is similar, but involves a homodinuclear unit [Cu(bpy)(H2O)(µ-C2O4)Cu(bpy)(CH3OH)]2+ (Cu1–Cu2) coordinated as a pendant group to a terminal oxalate oxygen. Magnetic measurements showed that the Cu1−Cu2 cationic unit is a strongly coupled antiferromagnetic dimer, independent from the other magnetic ions within ferromagnetic chains Cr1–Cu3 and Cr2–Cu4. A 3D polymer {[CaCr2Cu2(phen)4(C2O4)6]·4CH3CN·2H2O}n (3) comprising three different metal centers (Ca2+, Cr3+ and Cu2+) oxalate-bridged, contains Ca2+ atoms as nodes connected with four Cr3+ atoms through oxalate ligands. The network thus formed can be reduced to an underlying graph of diamondoid (dia) or (66) topology. Magnetization of 3 shows the ferromagnetic oxalate-bridged dimers [CuIICrIII], whose mutual interaction could possibly originate through the spin polarization of Ca2+ orbitals. Compounds 1 and 3 exhibit lower electrical conductivity at room temperature (RT) in comparison to compound 2. 相似文献
15.
Donald WA Leib RD O'Brien JT Holm AI Williams ER 《Proceedings of the National Academy of Sciences of the United States of America》2008,105(47):18102-18107
A gaseous nanocalorimetry approach is used to investigate effects of hydration and ion identity on the energy resulting from ion–electron recombination. Capture of a thermally generated electron by a hydrated multivalent ion results in either loss of a H atom accompanied by water loss or exclusively loss of water. The energy resulting from electron capture by the precursor is obtained from the extent of water loss. Results for large-size-selected clusters of Co(NH3)6(H2O)n3+ and Cu(H2O)n2+ indicate that the ion in the cluster is reduced on electron capture. The trend in the data for Co(NH3)6(H2O)n3+ over the largest sizes (n ≥ 50) can be fit to that predicted by the Born solvation model. This agreement indicates that the decrease in water loss for these larger clusters is predominantly due to ion solvation that can be accounted for by using a model with bulk properties. In contrast, results for Ca(H2O)n2+ indicate that an ion–electron pair is formed when clusters with more than ≈20 water molecules are reduced. For clusters with n = ≈20–47, these results suggest that the electron is located near the surface, but a structural transition to a more highly solvated electron is indicated for n = 47–62 by the constant recombination energy. These results suggest that an estimate of the adiabatic electron affinity of water could be obtained from measurements of even larger clusters in which an electron is fully solvated. 相似文献
16.
New Schiff base complexes [Cu2(HL1)(L1)(N3)3]∙2H2O (1) and [Cu2L2(N3)2]∙H2O (2) were synthesized. The crystal structures of 1 and 2 were determined by single-crystal X-ray diffraction analysis. The HL1 ligand results from the condensation of salicylaldehyde and 1-(2-aminoethyl)piperazine, while a new organic ligand, H2L2, was formed by the dimerization of HL1 via a coupling of two piperazine rings of HL1 on a carbon atom coming from DMF solvent. The dinuclear building units in 1 and 2 are linked into complex supramolecular networks through hydrogen and coordination bondings, resulting in 2D and 1D architectures, respectively. Single-point and broken-symmetry DFT calculations disclosed negligible singlet–triplet splittings within the dinuclear copper fragments in 1 and 2. Catalytic studies showed a remarkable activity of 1 and 2 towards cyclohexane oxidation with H2O2 in the presence of nitric acid and pyridine as promoters and under mild conditions (yield of products up to 21%). Coordination compound 1 also acts as an active catalyst in the intermolecular coupling of cyclohexane with benzamide using di-tert-butyl peroxide (tBuOOtBu) as a terminal oxidant. Conversion of benzamide at 55% was observed after 24 h reaction time. By-product patterns and plausible reaction mechanisms are discussed. 相似文献
17.
A mononuclear complex [MoOCl4(H2O)]− readily forms a metal−metal bonded {Mo2O4}2+ core. A high content of pyridine in the reaction mixture prevents further aggregation of dinuclear cores into larger clusters and a neutral, dinuclear complex with the [Mo2O4Cl2(Py)4] composition is isolated as a product. Solid state structures of two compounds containing this complex, [Mo2O4Cl2(Py)4]·2.25Py (1) and [Mo2O4Cl2(Py)4]·1.5PyHCl (2), were investigated by X-ray crystallography. 相似文献
18.
Henk Everaars Guus A. de Waard Roel S. Driessen Ibrahim Danad Peter M. van de Ven Pieter G. Raijmakers Adriaan A. Lammertsma Albert C. van Rossum Paul Knaapen Niels van Royen 《JACC: Cardiovascular Interventions》2018,11(20):2044-2054
Objectives
This study sought to compare Doppler flow velocity reserve (CFRDoppl) and thermodilution-derived coronary flow reserve (CFRthermo) head-to-head with the gold standard for quantification of myocardial perfusion, [15O]H2O positron emission tomography (PET).Background
Coronary flow reserve (CFR) is an important parameter for assessing coronary vascular function. To date, 2 techniques are available for invasive assessment of CFR: Doppler flow velocity and thermodilution. Although these techniques have been compared with each other, neither has been compared with [15O]H2O PET perfusion imaging.Methods
CFR was assessed in 98 vessels of 40 consecutive stable patients with suspected coronary artery disease. Patients underwent [15O]H2O PET, followed by invasive angiography in conjunction with simultaneous measurements of fractional flow reserve, CFRDoppl, and CFRthermo. Both normal and obstructed arteries were included.Results
The quality of Doppler flow velocity traces was significantly lower than that of thermodilution curves (p < 0.001). A moderate correlation was observed between CFRDoppl and CFRthermo (r = 0.59; p < 0.001). CFRDoppl correlated well with PET-derived CFR (CFRPET) (r = 0.82; p < 0.001). In contrast, the correlation between CFRthermo and CFRPET was only modest (r = 0.55; p < 0.001). This difference in correlation with CFRPET was significant (t = 4.9; df = 95; p < 0.001). Bland-Altman analysis revealed a tendency of CFRthermo to overestimate flow reserve at higher values.Conclusions
Coronary flow reserve, determined using Doppler flow velocity, has superior agreement with [15O]H2O PET in comparison with CFRthermo. 相似文献19.
Conversion of prohistidine decarboxylase to histidine decarboxylase: Peptide chain cleavage by nonhydrolytic serinolysis 总被引:3,自引:0,他引:3
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Paul A. Recsei Quang K. Huynh Esmond E. Snell 《Proceedings of the National Academy of Sciences of the United States of America》1983,80(4):973-977
Unlabeled prohistidine decarboxylase and prohistidine decarboxylase containing L-[carboxyl-18O]serine or L-[hydroxyl-18O]serine were isolated in homogeneous form from mutant 3 of Lactobacillus 30a grown with the appropriately labeled serine. There was no randomization or redistribution of label during growth, isolation of the protein, or enzymatic hydrolysis and reisolation of the labeled amino acids. These proteins were used to show that during proenzyme activation, in which individual π subunits of the proenzyme are converted to α and β subunits of the active enzyme [Formula: see text] (in which π, α, and β subunits have the partial structures shown and Prv designates a pyruvoyl group), no 18O from H218O is incorporated into the newly formed carboxyl terminus (Ser-81) of the β chain, although no labilization of 18O from proenzyme labeled with L-[carboxyl-18O]serine occurred when the proenzyme was activated in H216O by the same procedures. The additional oxygen atom present in the carboxyl group of Ser-81 of the β subunit is transferred from the hydroxyl group of Ser-82 of the proenzyme during the activation reaction. The same result was obtained with wild-type enzyme formed intracellularly. Peptide bond cleavage during activation of the proenzyme thus proceeds by a hitherto unobserved direct or indirect “serinolysis” coupled to α,β-elimination at Ser-82 to yield the pyruvoyl group of the α subunit, rather than by hydrolysis. Possible mechanisms for the reaction are discussed briefly. 相似文献
20.
Energies and kinetics of radical pairs involving bacteriochlorophyll and bacteriopheophytin in bacterial reaction centers
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Shuvalov VA Parson WW 《Proceedings of the National Academy of Sciences of the United States of America》1981,78(2):957-961
Absorbance changes reflecting the formation of a transient radical-pair state, PF, were measured in reaction centers from Rhodopseudomonas sphaeroides under conditions that blocked electron transfer to a later carrier (a quinone, Q). The temperature dependence of the absorbance changes suggests that PF is an equilibrium mixture of two states, which appear to be mainly 1[P[unk]B[unk]] and 1[P[unk]H[unk]]. P is a bacteriochlorophyll dimer, B is a bacteriochlorophyll absorbing at 800 nm, and H is a bacteriopheophytin. In the presence of Q[unk], the energy of 1[P[unk]B[unk]] is about 0.025 eV above that of 1[P[unk]H[unk]], 1[P[unk]H[unk]] can decay to a triplet state, PR, which also is an equilibrium mixture of two states, separated by about 0.03 eV. The lower of these appears to be mainly a locally excited triplet state of P, 3P; the upper state contains a major contribution from a triplet charge-transfer state, 3[P[unk]B[unk]]. The temperature dependence of delayed fluorescence from PR indicates that 3P lies 0.40 eV below the excited singlet state, P*, which is about 0.05 eV above 1[P[unk]H[unk]]. The 1,3[P[unk]B[unk]] charge-transfer states thus appear to interact with the locally excited states of P and B to give singlet and triplet states that are separated in energy by about 0.35 eV. This is 106 times larger than the splitting between 1[P[unk]H[unk]] and 3[P[unk]H[unk]] and implies strong orbital overlap between P[unk] and B[unk]. This is consistent with recent picosecond studies which suggest that electron transfer from P* to B occurs within 1 ps and is followed in 4 to 10 ps by electron transfer from B[unk] to H. 相似文献