Breast cancer proteomics by laser capture microdissection, sample pooling, 54-cm IPG IEF, and differential iodine radioisotope detection

The presence of progesterone receptor (PR) in estrogen receptor (ER)-positive breast cancer is associated with a good prognosis, and indicates that tumors are likely to respond to tamoxifen. However, ER+/PR- tumors respond less well. To reveal the potential molecular mechanism of this phenomenon, we sought to identify differential protein abundances between invasive ductal carcinoma cells from cryopreserved ER+/PR+ and ER+/PR- mammary tumor specimens. Because current proteomics methods are hampered in the examination of most primary human tumor samples by the extreme tissue heterogeneity, we used laser capture microdissection (LCM) to isolate tumor cells and developed a sample pooling strategy to analyze small sample protein lysates. Proteins from LCM-harvested tumors were pooled into four sub-pools from each condition of three tumors/sub-pool, and proteins from respective paired sub-pools were co-electrophoresed by 2-DE using 54-cm IEF over pH 4-9. Abundance ratios were accurately quantified by a differential multiplex radioactive ProteoTope method at low attomole levels ( approximately 3.6 microg protein per labeling reaction, <180 ng per multiplex protein sample per 54-cm gel). Applying this approach, differentially displayed proteins were identified by MS using comigrating non-radioactively labeled tumor proteins. They include decreased cytochrome b5 and transgelin, and more abundant CRABP-II, cyclophilin A, Neudesin, and hemoglobin in ER+/PR+ tumors versus ER+/PR- providing a possible explanation for differential susceptibility against tamoxifen as a result of deregulated cytochrome b5-dependent metabolism. This study demonstrates the potential of ProteoTope and LCM to enable extremely sensitive and precise differential analyses from well-defined primary clinical specimen.     

Graphs for which the least eigenvalue is minimal, I

Let G be a connected graph whose least eigenvalue λ(G) is minimal among the connected graphs of prescribed order and size. We show first that either G is complete or λ(G) is a simple eigenvalue. In the latter case, the sign pattern of a corresponding eigenvector determines a partition of the vertex set, and we study the structure of G in terms of this partition. We find that G is either bipartite or the join of two graphs of a simple form.     

Q-integral graphs with edge-degrees at most five

We consider the problem of determining the Q-integral graphs, i.e. the graphs with integral signless Laplacian spectrum. We find all such graphs with maximum edge-degree 4, and obtain only partial results for the next natural case, with maximum edge-degree 5.     

Prediction of excess molar volumes of binary mixtures of organic compounds from refractive indices

The excess molar volumes of 51 binary mixtures containing diverse groups of organic compounds: alcohols (methanol, ethanol, propan-1-ol, butan-1-ol, pentan-1-ol, hexan-1-ol, and heptan-1-ol), (cyclo-) alkanes (hexane, heptane, octane, nonane, decane, undecane, dodecane, and cyclohexane), esters (diethyl carbonate and ethyl chloroacetate), aromatics (o-xylene, m-xylene, p-xylene, and ethylbenzene), ketones (acetone), and ethers (anisole), were predicted from the refractive index data, using three types of equations coupled with several different mixing rules for refractive index calculations: the Lorentz-Lorenz, Dale-Gladstone, Eykman, Arago-Biot, Newton, and the Oster. These systems were chosen since they belong to different classes of organic species forming molecular interactions and intermolecular forces during mixing resulting in positive or negative, smaller or larger deviations from ideal behaviour. The obtained results were analysed in terms of the applied equation and mixing rule, the nature of compounds of the mixtures and the influence of alkyl chain length of the alkane or alcohol molecule. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

Spectral simulation and interpretation of LiZn and LiCd blue-green emission

Magnetic hyperfine interaction constants (A factors) have been determined for nine levels in the 4d5s and 4d5p configurations of the Y⁺ ion by Doppler-free saturation spectroscopy and level crossing spectroscopy in a sputtered vapour.     

The analysis of hardening of metal materials

There has been researched the interdependence of the process of microalloying, thermomechanical treatment and obtained mechanical characteristics of steel and AIMgSi alloys. There have been analyzed the hardening mechanisms of the mentioned alloys in correlation with grade, speed and temperature of strain. The achieved effects of alloys hardening are the consequences of combined operations of grain raffination, precipitation of dispersing particles of microalloying elements and increased density of dislocation.     

Perturbations of the Dushman Reaction with Piroxicam: Experimental and Model Calculations

Perturbation of the Bray? Liebhafsky non‐oscillating subsystem (mixture of KIO₃ and H₂SO₄), i.e., Dushman reaction (DR), by piroxicam (PX), was observed in an open reactor, i.e., in the continuously fed well‐stirred tank reactor (CSTR). Monitoring the response of DR to perturbations by different concentrations of PX allows developing a simple procedure for quantitative determination of this analyte in both bulk drug and pharmaceutical preparation (injection). A tentative perturbation mechanism of PX action on the DR matrix, based on a kinetic scheme that was suggested by Agreda et al., is proposed. The PX reactivity in DR has been generally related to the reaction of PX with hypoiodous acid (HIO) present in the matrix.     

Review of the thermodynamic and transport properties of EuBr<Subscript>2</Subscript>–RbBr binary system

Differential Scanning Calorimetry was used to study phase equilibrium in EuBr₂–RbBr binary system. It was established that this system includes two eutectics and three stoichiometric compounds. First of them, Rb₂EuBr₄, decomposes peritectically at 778 K. Second one, RbEuBr₃, undergoes the solid–solid phase transition at 732 K and melts incongruently at 852 K. Third compound, RbEu₂Br₅, melts congruently at 888 K. The composition and temperature values of eutectics were determined as x(EuBr₂) = 0.316; T _eut = 776 K and x(EuBr₂) = 0.797; T _eut = 859 K. Mixing enthalpy was measured by direct calorimetry on the whole composition range. The minimum of the mixing enthalpy occurs around the composition x(EuBr₂) ≈ 0.4. The electrical conductivity of liquid mixtures was also investigated over the whole composition range and measured down to temperatures below solidification. The specific conductance (liquid phase) plotted against the mole fraction of EuBr₂ shows a broad minimum at x(EuBr₂) ~ 0.6. The activation energy for conductivity changes with temperature. Results obtained are discussed in terms of possible complex formation.