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PubMed2003

Optimizing detection sensitivity on surface-enhanced Raman scattering of transition-metal electrodes with confocal Raman microscopy.

Some points on how to improve the detection sensitivity of confocal Raman microscopy for the study of surface-enhanced Raman scattering (SERS) of transition-metal electrodes are discussed, including the careful design of the spectroelectrochemical cell, proper selection of the thickness of the solution layer, the binning of charge-coupled device (CCD) pixels, and appropriate setting of the notch filter. Various roughening methods for the Pt, Rh, Fe, Co, and Ni electrode surfaces have been introduced in order to obtain SERS-active surfaces. It has been shown that the appropriate roughening procedure and the optimizing performance of the confocal Raman microscope are the two most important factors to directly generate and observe SERS on net transition-metal electrodes.

Electrochemistry↗
PubMed2003

Effect of Mn2+, Co2+, Ni2+, and Cu2+ on horseradish peroxidase: activation, inhibition, and denaturation studies.

The effects of transition metal ions (M2+) such as Mn2+, Co2+, Ni2+, and Cu2+ on the functional and structural stabilities of horseradish peroxidase (HRP) were investigated with respect to reversible chemical denaturation, Michaelis-Menten kinetics, chemical modification and time-dependent catalytic activity. Conformational Gibbs free energy (deltaGo(H2O)) as a structural stability criterion and transition concentrations of metal ions ([M2+] 1/2) were estimated using a two-state chemical denaturation model. Activation and inhibitory concentration ranges for each metal ion were specified by the steady-state enzyme kinetics. Results of a pH-profile method confirmed by chemical modification indicate that a histidine residue interacts in the activation concentration range, whereas carboxylic residues (Asp and Glu) contribute to interaction in the inhibitory concentration range. Incubation of the enzyme with the metal ion at activation concentration leads to long-term functional stability of peroxidase. Thus, such metal ions as potent effectors induced the enhancement of conformational and functional stabilities of horseradish peroxidase.

Cobalt↗
PubMed2002

Alleviation of the two-cell block of ICR mouse embryos by polyaminocarboxylate metal chelators.

The present study was undertaken to examine the effects of various transition metal ion chelators, both polyaminocarboxylates (including nitrilotriacetate (NTA), ethylenediaminediacetate (EDDA), ethyleneglycolbistetraacetate (EGTA), ethylenediaminetetraacetate (EDTA) and diethylenetriaminepentaacetate (DTPA)) and non-polyaminocarboxylates (dipicolinic acid and deferoxamine), on the development in vitro of one-cell ICR strain mouse embryos to the four-cell and blastocyst stages. The order of stability constants of polyaminocarboxylates for transition metal ions such as zinc, copper and iron is as follows: NTA < or = EDDA < EGTA < EDTA < DTPA. Addition of 10 or 100 micromol polyaminocarboxylates x l(-1) to the medium significantly enhanced the development of most one-cell embryos (66-88%) beyond the two-cell stage compared with that (< 25%) in medium without polyaminocarboxylates. Although EDDA, EDTA and DTPA at 10 micromol x l(-1) induced the development of most one-cell embryos to the four-cell stage and beyond, a higher concentration (100 micromol x l(-1)) of NTA and EGTA was required to obtain a similar result. Therefore, the ability of polyaminocarboxylates to overcome the two-cell block is not correlated with their potency to chelate transition metal ions. In contrast, the non-polyaminocarboxylates dipicolinic acid and deferoxamine, at 10 and 100 micromol x l(-1), did not have the same effect. Taken together, the results indicate that the ability of polyaminocarboxylates to overcome the two-cell block in embryo development is due to some common feature or features other than the ability to chelate transition metal ions.

Animals↗
PubMed2006

Vascular effects of ambient pollutant particles and metals.

Exposure to ambient pollutant particle (APP) is associated with increased cardiovascular morbidity and mortality. Recent evidence indicates that APP-induced vasoconstriction may be an important mechanism. APP constricts systemic arteries and increases blood pressure in human. APP decreases the diameter of pulmonary arterioles in animals. Intratracheal instillation of APP increases pulmonary artery resistance in isolated buffer-perfused lungs, and APP constricts isolated arterial rings. APP-induced vasoconstriction may be secondary to the release of inflammatory mediators from lung cells, which then activate vascular endothelial and smooth muscle cells. The vasoconstriction may also be caused by alterations in autonomic nervous system balance. Some soluble metals (e.g., vanadium) can produce acute vasoconstriction in in vitro and in vivo systems, and contribute to the systemic health effects of APP since they can more easily permeate the alveolar-capillary membrane than the whole particle. Both APP and its associated metals have been shown to enhance the release of endothelin 1 and reactive oxygen species, activate epithelial growth factor receptor and mitogen-activated protein kinases, and inhibit nitric oxide vasodilator activity. The vasoactive properties of APP and metals raised the possibility that patients with vascular diseases may be more susceptible to APP-induced adverse health effects, and that people who are regularly exposed to high amount of metals, e.g., vanadium contained in certain dietary and muscle-building regimens or in the air of boiler making plants, may have increased risk for vascular diseases. Understanding how metals induce vasoconstriction may lead to the development of novel vasodilator therapies for vascular diseases.

Air Pollutants↗
PubMed2004

Polyoxometalates: from inorganic chemistry to materials science.

Polyoxometalates have been traditionally the subject of study of molecular inorganic chemistry. Yet, these polynuclear molecules, reminiscent of oxide clusters, present a wide range of structures and with them ideal frameworks for the deployment of a plethora of useful magnetic, electroionic, catalytic, bioactive and photochemical properties. With this in mind, a new trend towards the application of these remarkable species in materials science is beginning to develop. In this review we analyze this trend and discuss two main lines of thought for the application of polyoxometalates as materials. On the one hand, there is their use as clusters with inherently useful properties on themselves, a line which has produced fundamental studies of their magnetic, electronic or photoelectrochemical properties and has shown these clusters as models for quantum-sized oxides. On the other hand, the encapsulation or integration of polyoxometalates into organic, polymeric or inorganic matrices or substrates opens a whole new field within the area of hybrid materials for harnessing the multifunctional properties of these versatile species in a wide variety of applications, ranging from catalysis to energy storage to biomedicine.

Electrochemistry↗
PubMed1993

Mechanisms of chromium carcinogenicity and toxicity.

Chromium, like many transition metal elements, is essential to life at low concentrations yet toxic to many systems at higher concentrations. In addition to the overt symptoms of acute chromium toxicity, delayed manifestations of chromium exposure become apparent by subsequent increases in the incidence of various human cancers. Chromium is widely used in numerous industrial processes, and as a result is a contaminant of many environmental systems. Chromium, in its myriad chemical forms and oxidation states, has been well studied in terms of its general chemistry and its interactions with biological molecules. However, the precise mechanisms by which chromium is both an essential metal and a carcinogen are not yet fully clear. The following review does not seek to embellish upon the proposed mechanisms of the toxic and carcinogenic actions of chromium, but rather provides a comprehensive review of these theories. The chemical nature of chromium compounds and how these properties impact upon the interactions of chromium with cellular and genetic targets, including animal and human hosts, are discussed.

Animals↗
PubMed2005

Amyloid-beta: acute-phase apolipoprotein with metal-binding activity.

In monomeric form, amyloid-beta (Abeta), an amphipatic 4 kDa peptide which plays a key role in the pathogenesis of Alzheimer's disease (AD), is associated with lipoproteins in biological fluids and possesses high affinity to transition metal ions; in addition, synthesis of Abeta is upregulated under acute phase conditions. These data suggest that Abeta can be regarded as a normal physiological component of lipoproteins and may represent an acute-phase apolipoprotein with metal-binding activity. Interaction with transition metal ions may cause aggregation of Abeta, leading to formation of oligomers. Such oligomerised Abeta may lose its normal biological functions and acquire deleterious activities. To be efficient, novel anti-AD therapies should target oligomeric forms of Abeta while preserving the monomeric form of the peptide.

Acute-Phase Proteins↗
PubMed2002

Oxygen-dependent and -independent regulation of HIF-1alpha.

Hypoxia-inducible factor-1 (HIF-1) is composed of HIF-1alpha and HIF-1beta, and is a master regulator of oxygen homeostasis, playing critical roles in physiological and pathological processes. Normally, the formation and transcriptional activity of HIF-1 depend on the amount of HIF-1alpha, and the expression of HIF-1alpha is tightly controlled by the cellular oxygen tension. Recent progress in the study of its regulation mechanism provided clues as to how HIF-1alpha is regulated by oxygen. It appears that HIF-1alpha is not regulated only by the oxygen tension, but also by various other stimuli, such as transition metals, nitric oxide, reactive oxygen species, growth factors, and mechanical stresses. In this review, we summarize the oxygen-dependent and -independent regulation of HIF-1alpha, and the respective physiological and pathological meanings.

Animals↗
PubMed1999

Assessment and collaboration: Key elements in comprehensive and cohesive transition planning.

The relatively recent study of adolescent transitions into adulthood has compiled little consensus on exemplary practices or theoretical models. Despite this, transition planning teams are mandated to develop plans that result in successful achievement of adult roles. This task is predicated upon choosing appropriate assessments, and assembling them into a comprehensive and cohesive transition profile through collaboration among transition team members. States have provided broad guidelines or frameworks but few offer detailed listings of domains to address in the planning process. This article addresses some of the major issues team members face and identifies strategies for their successful resolution.

Journal Article↗
PubMed2002

New transition-metal-dependent DNAzymes as efficient endonucleases and as selective metal biosensors.

Like proteins and RNA molecules, many DNA molecules have now been shown to catalyze a variety of reactions and are thus called DNAzymes. With limited building blocks, DNAzymes need to recruit other cofactors in order to match other enzymes in terms of reaction diversity and catalytic efficiency. Several unique properties make transition-metal ions an ideal choice of cofactor for DNAzymes. Indeed, new DNAzymes that bind transition-metal ions with high affinity and selectivity have been obtained through the use of a powerful combinatorial biology tool called in vitro selection. This accomplishment now makes it possible to obtain different classes of metallo-DNAzymes in the laboratory within a short period of time. It also offers a rare opportunity to compare and contrast structural and functional properties of metal-binding sites in proteins and in DNAzymes. The resulting transition-metal-dependent DNAzymes have displayed high activity toward cleavage of DNA and RNA and thus hold promise for their biochemical and pharmaceutical applications. Finally, the use of DNAzymes as a new class of highly sensitive and selective biosensors for metal ions has been demonstrated recently.

Base Sequence↗
PubMedDate not supplied

Transition metal ions significantly decrease phospholipase C activity degrading phosphatidylinositol-4,5-bisphosphate in the brain cortex.

Highly reactive transition metals, such as copper and iron play an obligatory role in generating of reactive oxygen species (ROS). Many neurodegenerative diseases including Alzheimer's disease (AD) and Parkinson's disease (PD) show increased accumulation of these metals. Phosphoinositide metabolism is altered in neurodegenerative diseases. In the present study, we examined the effect of CuSO(4) and FeCl(2) on phospholipase C (PLC) activity degrading phosphatidylinositol-4,5-bisphosphate (PIP(2)) and phosphatidylinositol (PI) in synaptic plasma membranes (SPM) from the rat brain cortex. We report that 25 microM CuSO(4) and FeCl(2) decreased PIP(2)-PLC activity by 60% and 75%, respectively. However, both compounds had no effect on PI-PLC activity. These data indicated that exclusively PIP(2)-PLC is sensitive to transition metal ions. We suggest that chelators of these metals may protect brain against alteration of phosphoinositide metabolism and might be beneficial in the treatment of neurodegenerative diseases.

Animals↗
PubMed2004

[Electron spectra of chemical assembly mesoporous MCM-41 with transition metal complexes].

In the paper the complexes of metal cobalt(III), manganese(III), iron(III) and copper(II) with Schiff-base N,N-ethylenebis(salicylideneaminnato) have been synthesized and characterized. The nanosized porous material MCM-41 has been functionalized by the modification of the internal pore surface with gamma-aminopropyl and was assembled by the modification groups with metal complex of Schiff-base. These metal complexes and functionalized nanosized porous materials were charcterized by XRD, IR and UV-Vis. It is indicated by spectral analysis that the synthesized nanosized porous materials have been confirmed to be MCM-41 with hexagon bores, and the gamma-aminopropyls have been bonded on their internal pore surface. And the complexes of metal cobalt(III), manganese(III), iron(III) and copper(II) with Schiff-base N,N-ethylenebis(salicylideneaminnato) were assembled into MCM-41. The IR spectra of these samples show that there were characteristic absorptions of the amino and the Schiff base groups, and the absorption of amino shifted to longer wavelength.

Cobalt↗
PubMed2004

[Preparation and spectra of the complexes of the first series transition metals with diphenic acid].

The ligand diphenic acid has been synthesized and the corresponding complexes of transition metal Co, Ni and Mn with diphenic acid have been prepared and characterized by the elementary analysis, IR spectra and ultraviolet-visible spectra. The results of IR show that the vas and vs of -CO2- in the complexes are lower than those of ligand diphenic acid, which can be explained by the coordinating between metal and ligand. In addition, compared with the complex IR spectra, the IR spectra of ligand became complicated due to the ligand polymerization through hydrogen bond. The UV-Vis spectra show that the ligand has three absorption peaks at 288, 273 and 270 nm, respectively, and these are slightly shifted in the complexes. Because the metal d-d absorption is weak, only in Co(C14H8O4) x 2H2O there is a d-d absorption at 537 nm.

Biphenyl Compounds↗
PubMed1997

[Resonance Raman spectra of transition metal Mn(III), Fe(III), Rh(III), Pd(II) porphyrin complexes].

The resonance Raman spectra of Mn(III), Rh(III), Fe(III), Pd(II) protoporphyrin IX-dimethylester (PP) and tetra-phenylporphyrin (TPP) complexes were reported. The difference of their structure-sensitive band frequency was a result of the interaction of different metal ions' outer d electrons with the electrons of the porphyrin ring. As well the effects of different porphyrin rings and their substituts on the structure-sensitive bands were discussed in this paper.

Iron↗
PubMed1987

Bronchial granular cell tumor. Presentation of three cases with tissue culture and ultrastructural study.

Three granular cell tumors, two arising from the bronchi and one from the trachea, are described. Two of the cases were studied by tissue culture and electron microscopy of the original tumor tissue and the cultivated cells. The granular cells grew actively in culture and showed a specific pattern in vitro different from tumors of fibrohistiocytic and schwannian origin. Ultrastructural examination of the newly grown cells allowed follow-up of the progressive cytoplasmic granulation of cells, with a transition from elements with an ultrastructural morphology consistent with the "early granular cells" described in tumor tissue in previous studies to fully developed mature granular cells.

Adult↗
PubMedDate not supplied

[Mathematical models in epidemiology: Study on viral hepatitis in Italy (author's transl)].

In this paper a mathematical approach to the epidemics is proposed. The method is based upon a model able to describe any time-depending phenomena using the following elements: "class", "transition" and "related probability". The solution of the differential equations describing the model are obtained: first, by numerical techniques; second, by a Montecarlo simulation method. Deterministic and stochastic solutions which have been obtained, by applying the model to the study of viral hepatitis in Italy during 1960--1970, have been compared each other, to improve the model itself.

Carrier State↗