Mechanisms and dynamics of the metastable decay in Ar-2(+)

A detailed experimental as well as theoretical investigation of the properties of the metastable dissociation Ar-2(+)--\u3eAr++Ar is presented. The mass-analyzed ion kinetic energy (MIKE) scan technique has been performed using a three sector field mass spectrometer. The possible mechanisms of the metastability of Ar-2(+) have been examined and the observed decay process is assigned to the II(1/2)(u)--\u3eI(1/2)(g) bound to continuum radiative transition, in agreement with earlier work. The calculation of the theoretical shape of the kinetic energy release distribution of fragment ions allowed us to construct the theoretical MIKE peak and compare it with the raw experimental data. The accuracy of various sets of potential energy curves for Ar-2(+) is discussed, as well as the way of production of the metastable Ar-2(+)[II(1/2)(u)] electronic state by electron impact. Excellent agreement between the experimental data and theoretical model has been observed. (C) 2004 American Institute of Physics

Selective ALDH3A1 Inhibition by Benzimidazole Analogues Increase Mafosfamide Sensitivity in Cancer Cells

Aldehyde dehydrogenase enzymes irreversibly oxidize aldehydes generated from metabolism of amino acids, fatty acids, food, smoke, additives, and xenobiotic drugs. Cyclophosphamide is one such xenobiotic used in cancer therapies. Upon activation, cyclophosphamide forms an intermediate, aldophosphamide, which can be detoxified to carboxyphosphamide by aldehyde dehydrogenases (ALDH), especially ALDH1A1 and ALDH3A1. Consequently, selective inhibition of ALDH3A1 could increase chemosensitivity toward cyclophosphamide in ALDH3A1 expressing tumors. Here, we report detailed kinetics and structural characterization of a highly selective submicromolar inhibitor of ALDH3A1, 1-[(4-fluorophenyl)sulfonyl]-2-methyl-1H-benzimidazole (CB7, IC50 of 0.2 μM). CB7 does not inhibit ALDH1A1, ALDH1A2, ALDH1A3, ALDH1B1, or ALDH2 activity. Structural, kinetics, and mutagenesis studies show that CB7 binds to the aldehyde binding pocket of ALDH3A1. ALDH3A1-expressing lung adenocarcinoma and glioblastoma cell lines are sensitized toward mafosfamide (MF) treatment in the presence analogues of CB7, whereas primary lung fibroblasts lacking ALDH3A1 expression, are not

N,N-diethylaminobenzaldehyde (DEAB) as a substrate and mechanism-based inhibitor for human ALDH isoenzymes

N,N-diethylaminobenzaldehyde (DEAB) is a commonly used "selective" inhibitor of aldehyde dehydrogenase isoenzymes in cancer stem cell biology due to its inclusion as a negative control compound in the widely utilized Aldefluor assay. Recent evidence has accumulated that DEAB is not a selective inhibitory agent when assayed in vitro versus ALDH1, ALDH2 and ALDH3 family members. We sought to determine the selectivity of DEAB toward ALDH1A1, ALDH1A2, ALDH1A3, ALDH1B1, ALDH1L1, ALDH2, ALDH3A1, ALDH4A1 and ALDH5A1 isoenzymes and determine the mechanism by which DEAB exerts its inhibitory action. We found that DEAB is an excellent substrate for ALDH3A1, exhibiting a Vmax/KM that exceeds that of its commonly used substrate, benzaldehyde. DEAB is also a substrate for ALDH1A1, albeit an exceptionally slow one (turnover rate ∼0.03 min(-1)). In contrast, little if any turnover of DEAB was observed when incubated with ALDH1A2, ALDH1A3, ALDH1B1, ALDH2 or ALDH5A1. DEAB was neither a substrate nor an inhibitor for ALDH1L1 or ALDH4A1. Analysis by enzyme kinetics and QTOF mass spectrometry demonstrates that DEAB is an irreversible inhibitor of ALDH1A2 and ALDH2 with apparent bimolecular rate constants of 2900 and 86,000 M(-1) s(-1), respectively. The mechanism of inactivation is consistent with the formation of quinoid-like resonance state following hydride transfer that is stabilized by local structural features that exist in several of the ALDH isoenzymes

Structural and cation distribution analysis of Nickel-Copper/Nickel-Magnesium Substituted Lithium Ferrites

Lithium ferrite (Li0.5Fe2.5O4) shows significant promise in electrical and electronic engineering. It possesses a crystal spinel crystal structure denoted as AB2O4, with "A" and "B" representing specific tetrahedral and octahedral lattice sites respectively. Analysis of X-ray diffraction (XRD) patterns aligns well with the JCPDS card (no. 38-0259), confirming the spinel structure with the Fd3m space group. However, an additional peak at 211 in the basic lithium ferrite suggests a subtle Fd3m to the P4132 phase change with a minor secondary hematite phase. Investigating the cation distribution in these ferrites is crucial for further exploration of their magnetic and dielectric properties. These ferrites find widespread applications in microwave technology and magnetic and electric energy storage devices

Morphological analysis of Cu substituted Ni\Zn in Ni-Zn ferrites

Cu substituted Ni in Ni0.5-xCuxZn0.5Fe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) samples and Cu substituted Zn in Ni0.5Zn0.5−xCuxFe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) is synthesized using the sol-gel auto-combustion process. Recently, we have carried out their structural analysis using XRD and FTIR and found a cubic spinel structure. In this paper, we have studied their morphological and compositional structure with the help of a Scanning Electron Microscope (SEM) attached with an Energy Dispersive Spectrometer (EDS). The comparative study shows that the grain size of Cu substituted Ni is greater than Cu substituted Zn in Ni-Zn ferrite. These smaller grain-sized ferrites are preferred for many microstructural applications. Depending on the available magnetic field, sintering temperature, and atmosphere, they can have different nucleation, and hence their application mode is different. They can have a critical concentration that can tune their properties. The EDS attached with the SEM confirmed the proper composition of samples. BIBECHANA 18 (2) (2020) 80-8

Structural and cation distribution analysis of Nickel-Copper/Nickel-Magnesium Substituted Lithium Ferrites

Lithium ferrite (Li0.5Fe2.5O4) shows significant promise in electrical and electronic engineering. It possesses a crystal spinel crystal structure denoted as AB2O4, with "A" and "B" representing specific tetrahedral and octahedral lattice sites respectively. Analysis of X-ray diffraction (XRD) patterns aligns well with the JCPDS card (no. 38-0259), confirming the spinel structure with the Fd3m space group. However, an additional peak at 211 in the basic lithium ferrite suggests a subtle Fd3m to the P4132 phase change with a minor secondary hematite phase. Investigating the cation distribution in these ferrites is crucial for further exploration of their magnetic and dielectric properties. These ferrites find widespread applications in microwave technology and magnetic and electric energy storage devices

Morphological analysis of Cu substituted Ni\Zn in Ni-Zn ferrites

Cu substituted Ni in Ni0.5-xCuxZn0.5Fe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) samples and Cu substituted Zn in Ni0.5Zn0.5−xCuxFe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) is synthesized using the sol-gel auto-combustion process. Recently, we have carried out their structural analysis using XRD and FTIR and found a cubic spinel structure. In this paper, we have studied their morphological and compositional structure with the help of a Scanning Electron Microscope (SEM) attached with an Energy Dispersive Spectrometer (EDS). The comparative study shows that the grain size of Cu substituted Ni is greater than Cu substituted Zn in Ni-Zn ferrite. These smaller grain-sized ferrites are preferred for many microstructural applications. Depending on the available magnetic field, sintering temperature, and atmosphere, they can have different nucleation, and hence their application mode is different. They can have a critical concentration that can tune their properties. The EDS attached with the SEM confirmed the proper composition of samples. BIBECHANA 18 (2) (2020) 80-8

Cr3+ substitution effect on Co-Cu and Cu-Co nano ferrites on structural and morphological properties

The Cr3+ substituted Co-Cu (Co0.7Cu0.3Fe2-xCrxO4) and Cu-Co (Cu0.7Co0.3Fe2-xCrxO4) where x = 0.0, 0.05, 0.1, 0.15, 0.2 and 0.25 nano ferrite composite were prepared with the sol-gel approach. Their structural, dc electrical resistivity, and magnetic properties were analyzed. XRD shows the single-phase spinel ferrite. Adding Cr3+ ions decreases the lattice volume and the size of the crystallite respectively. FESEM images show non-spherical particles on a largely uniform surface shape with decreasing grain size on doping Cr3+. The FTIR pattern supports the XRD patterns for spinel ferrite

Correlation between the Magnetic and DC resistivity studies of Cu substituted Ni and Zn in Ni-Zn ferrites

Cu substituted Ni0.5-xCuxZn0.5Fe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) samples is synthesized using the sol-gel auto-combustion process. They have a cubic spinel structure with crystallite size in the range of 29.01–42.68 nm. The increment in the copper content increases the DC conductivity. The electrical resistivity decrease with an increase in the temperature i.e. it has a negative temperature coefficient with resistance similar to semiconductors. The remnant ratios R obtained from VSM show their isotropic nature forming single domain ferrimagnetic particles. The results are compared with Ni0.5CuxZn0.5-xFe2O4 (x = 0 to 0.25).  The resultant material Cu substituted Zn is more significant than that of Ni as indicated by its results and previous literature. BIBECHANA 19 (2022) 61-67

Cr3+ substitution effect on Co-Cu and Cu-Co nano ferrites on structural and morphological properties

The Cr3+ substituted Co-Cu (Co0.7Cu0.3Fe2-xCrxO4) and Cu-Co (Cu0.7Co0.3Fe2-xCrxO4) where x = 0.0, 0.05, 0.1, 0.15, 0.2 and 0.25 nano ferrite composite were prepared with the sol-gel approach. Their structural, dc electrical resistivity, and magnetic properties were analyzed. XRD shows the single-phase spinel ferrite. Adding Cr3+ ions decreases the lattice volume and the size of the crystallite respectively. FESEM images show non-spherical particles on a largely uniform surface shape with decreasing grain size on doping Cr3+. The FTIR pattern supports the XRD patterns for spinel ferrite