Decomposing Magnetic Dark-Field Contrast in Spin Analyzed Talbot-Lau Interferometry: A Stern-Gerlach Experiment without Spatial Beam Splitting.

We have recently shown how a polarized beam in Talbot-Lau interferometric imaging can be used to analyze strong magnetic fields through the spin dependent differential phase effect at field gradients. While in that case an adiabatic spin coupling with the sample field is required, here we investigate a nonadiabatic coupling causing a spatial splitting of the neutron spin states with respect to the external magnetic field. This subsequently leads to no phase contrast signal but a loss of interferometer visibility referred to as dark-field contrast. We demonstrate how the implementation of spin analysis to the Talbot-Lau interferometer setup enables one to recover the differential phase induced to a single spin state. Thus, we show that the dark-field contrast is a measure of the quantum mechanical spin split analogous to the Stern-Gerlach experiment without, however, spatial beam separation. In addition, the spin analyzed dark-field contrast imaging introduced here bears the potential to probe polarization dependent small-angle scattering and thus magnetic microstructures.

Thermodynamics parameters for binding of halogenated benzotriazole inhibitors of human protein kinase CK2α.

The interaction of human CK2α (hCK2α) with nine halogenated benzotriazoles, TBBt and its analogues representing all possible patterns of halogenation on the benzene ring of benzotriazole, was studied by biophysical methods. Thermal stability of protein-ligand complexes, monitored by calorimetric (DSC) and optical (DSF) methods, showed that the increase in the mid-point temperature for unfolding of protein-ligand complexes (i.e. potency of ligand binding to hCK2α) follow the inhibitory activities determined by biochemical assays. The dissociation constant for the ATP-hCK2α complex was estimated with the aid of microscale thermophoresis (MST) as 4.3±1.8 µM, and MST-derived dissociation constants determined for halogenated benzotriazoles, when converted according to known ATP concentrations, perfectly reconstruct IC50 values determined by the biochemical assays. Ligand-dependent quenching of tyrosine fluorescence, together with molecular modeling and DSC-derived heats of unfolding, support the hypothesis that halogenated benzotriazoles bind in at least two alternative orientations, and those that are efficient hCK2α inhibitors bind in the orientation which TBBt adopts in its complex with maize CK2α. DSC-derived apparent heat for ligand binding (ΔΔHbind) is driven by intermolecular electrostatic interactions between Lys68 and the triazole ring of the ligand, as indicated by a good correlation between ΔΔHbind and ligand pKa. Overall results, additionally supported by molecular modeling, confirm that a balance of hydrophobic and electrostatic interactions contribute predominantly (~40 kJ/mol), relative to possible intermolecular halogen/hydrogen bonding (less than 10 kJ/mol), in binding of halogenated benzotriazoles to the ATP-binding site of hCK2α. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases.

Thermodynamic parameters for binding of some halogenated inhibitors of human protein kinase CK2.

The interaction of human CK2α with a series of tetrabromobenzotriazole (TBBt) and tetrabromobenzimidazole (TBBz) analogs, in which one of the bromine atoms proximal to the triazole/imidazole ring is replaced by a methyl group, was studied by biochemical (IC50) and biophysical methods (thermal stability of protein-ligand complex monitored by DSC and fluorescence). Two newly synthesized tri-bromo derivatives display inhibitory activity comparable to that of the reference compounds, TBBt and TBBz, respectively. DSC analysis of the stability of protein-ligand complexes shows that the heat of ligand binding (Hbind) is driven by intermolecular electrostatic interactions involving the triazole/imidazole ring, as indicated by a strong correlation between Hbind and ligand pKa. Screening, based on fluorescence-monitored thermal unfolding of protein-ligand complexes, gave comparable results, clearly identifying ligands that most strongly bind to the protein. Overall results, additionally supported by molecular modeling, confirm that a balance of hydrophobic and electrostatic interactions contribute predominantly, relative to possible intermolecular halogen bonding, in binding of the ligands to the CK2α ATP-binding site.

Tem-per-ature dependence in Bragg edge neutron transmission measurements.

A systematic study has been carried out to investigate the neutron transmission signal as a function of sample tem-per-ature. In particular, the experimentally de-ter-mined wavelength-dependent neutron attenuation spectra for a martensitic steel at tem-per-atures ranging from 21 to 700°C are com-pared with simulated data. A theoretical description that includes the Debye-Waller factor in order to describe the tem-per-ature influence on the neutron cross sections was im-plemented in the nxsPlotter software and used for the simulations. The analysis of the attenuation coefficients at varying tem-per-atures shows that the missing contributions due to elastic and inelastic scattering can be clearly distinguished: while the elastically scattered intensities decrease with higher tem-per-atures, the inelastically scattered intensities increase, and the two can be separated from each other by analysing unique sharp features in the form of Bragg edges. This study presents the first systematic approach to qu-antify this effect and can serve as a basis , for example, to correct measurements taken during in situ heat treatments, in many cases being a prerequisite for obtaining qu-anti-fiable results.

Design and synthesis of CK2 inhibitors.

A series of new polybrominated benzimidazoles and benzotriazoles has been synthesized and their influence on the activity of protein kinase CK2 was evaluated. It was revealed that the most active inhibitors are those with methyl or ethyl substituent at benzene ring, namely 5,6,7-tribromo-4-methyl-1H-benzotriazole (38, IC(50) 0.51 µM) and 5,6,7-tribromo-4-ethyl-1H-benzotriazole (40, IC(50) 0.16 µM). The derivatives with large aromatic or heterocyclic substituents connected to benzimidazole or benzotriazole scaffold appeared to be less potent inhibitors.

Strength Analysis and Stress-Strain Deformation Behavior of 3 mol% Y-TZP and 21 wt.% Al2O3-3 mol% Y-TZP.

The mechanical behavior of 3 mol% Y2O3-ZrO2 ceramic and 21 wt.% Al2O3-3 mol% Y2O3-ZrO2 ceramic composite with submicron grain size was studied. Mechanical properties, such as hardness, Young's modulus, four-point bending strength, and fracture toughness of both materials were measured. Linear stress-strain deformation behavior of both 3 mol% Y2O3-ZrO2 and 21 wt.% Al2O3-3 mol% Y2O3-ZrO2 was observed in flexure, both at room temperature and at 400 °C. A small deviation from linear elastic deformation was detected in 21 wt.% Al2O3-3 mol% Y2O3-ZrO2 ceramic composite when loaded above a stress of 1500 MPa. Therefore, it was concluded that only elastic deformation occurred at low stresses upon loading, which exclude the presence of domain switching in zirconia upon bending under the loading conditions of this study.

In situ diagnostics of the crystal-growth process through neutron imaging: application to scintillators.

Neutrons are known to be unique probes in situations where other types of radiation fail to penetrate samples and their surrounding structures. In this paper it is demonstrated how thermal and cold neutron radiography can provide time-resolved imaging of materials while they are being processed (e.g. while growing single crystals). The processing equipment, in this case furnaces, and the scintillator materials are opaque to conventional X-ray interrogation techniques. The distribution of the europium activator within a BaBrCl:Eu scintillator (0.1 and 0.5% nominal doping concentrations per mole) is studied in situ during the melting and solidification processes with a temporal resolution of 5-7 s. The strong tendency of the Eu dopant to segregate during the solidification process is observed in repeated cycles, with Eu forming clusters on multiple length scales (only for clusters larger than ∼50 µm, as limited by the resolution of the present experiments). It is also demonstrated that the dopant concentration can be quantified even for very low concentration levels (∼0.1%) in 10 mm thick samples. The interface between the solid and liquid phases can also be imaged, provided there is a sufficient change in concentration of one of the elements with a sufficient neutron attenuation cross section. Tomographic imaging of the BaBrCl:0.1%Eu sample reveals a strong correlation between crystal fractures and Eu-deficient clusters. The results of these experiments demonstrate the unique capabilities of neutron imaging for in situ diagnostics and the optimization of crystal-growth procedures.

Flexible sample environment for high resolution neutron imaging at high temperatures in controlled atmosphere.

High material penetration by neutrons allows for experiments using sophisticated sample environments providing complex conditions. Thus, neutron imaging holds potential for performing in situ nondestructive measurements on large samples or even full technological systems, which are not possible with any other technique. This paper presents a new sample environment for in situ high resolution neutron imaging experiments at temperatures from room temperature up to 1100 °C and/or using controllable flow of reactive atmospheres. The design also offers the possibility to directly combine imaging with diffraction measurements. Design, special features, and specification of the furnace are described. In addition, examples of experiments successfully performed at various neutron facilities with the furnace, as well as examples of possible applications are presented. This covers a broad field of research from fundamental to technological investigations of various types of materials and components.

Efficacy and mechanism of anti-tumor action of new potential CK2 inhibitors toward glioblastoma cells.

Malignant gliomas are highly resistant to current therapeutic approaches due to genetic alterations rendering them resistant to cell death. CK2, a ubiquitous and constitutively active serine/threonine kinase, frequently elevated in tumors, contributes to enhanced cell proliferation and resistance to apoptosis. Inhibition of CK2 expression or treatment with inhibitors of CK2 affected survival or induced apoptosis in various cancer cells. Here we compared cytotoxic effects of well-known and new CK2 inhibitors: 4,5,6,7-tetrabromo-1H-benzotriazole (TBB), 4,5,6,7-tetrabromo-1H-benzimidazole (TBI), 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole (DMAT), the related 3-(4,5,6,7-tetrabromo-1H-benzimidazol-1-yl)propan-1-ol (MB001), 3-(4,5,6,7-tetrabromo-1H-1,2,3-benzotriazol-1-yl) propan-1-ol (MB002), 3-(4,5,6,7-tetrabromo-2H-1,2,3-benzotriazol-2-yl)propan-1-ol (MB003) and also structurally similar to above compounds pentabromobenzylisothiourea (ZKK1) and its derivatives (ZKK2-8) on cultured malignant glioma cells. TBI, ZKK1 and MB001-3 were more effective than TBB in inducing growth arrest and cell death in glioma cells. TBI and ZKK1 strongly induced apoptotic death involving caspase 3 and 7 activation followed by PARP cleavage. DMAT strongly upregulated the expression of cytotoxic ligand and its receptor Fas. Structural modifications of ZKK1 largely affected its efficacy: exchange of Br- to Cl- or F-substituents on the pentabromophenyl ring and inclusion of the bulky N-phenyl substituent in thiourea fragment of ZKK1 diminished cytotoxic activity, while N-substitution with short alkyl groups or an allyl group had opposite effects. Interestingly, TBI at moderate dose did not affect viability of non-transformed astrocytes, suggesting some specificity toward tumor cells in cytotoxic action. TBI, DMAT and ZKK1-induced apoptosis associated with caspase cascade activation in human malignant glioblastoma cells with mutated PT53 and PTEN genes. The reported data demonstrate that suitably modified polybromobenzene molecules exhibit a significant cytotoxic potential towards malignant glioblastoma cells.