Mass spectrometric identification of mitochondrial oxidative phosphorylation subunits separated by two-dimensional blue-native polyacrylamide gel electrophoresis

Blue-native polyacrylamide gel electrophoresis is a powerful tool for the separation of intact membrane protein complexes mainly applied to the analysis of the enzymes of the mitochondrial oxidative phosphorylation system (OXPHOS). Combined with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), it reveals a two-dimensional pattern showing the individual subunits of the five OXPHOS multi-enzyme complexes. This pattern is useful in the diagnostic analysis of several diseases related to disorders in the oxidative phosphorylation system. However, in order to use this method for systematic diagnostic purposes and to be able to link disease with absence or reduced expression of specific subunits, an unambiguous identification of the individual subunits is necessary. In this study, we completed this task, implementing peptide mass fingerprinting and mass spectrometric sequence analysis. In the course of these analyses, we discovered a novel variant of a cytochrome c oxidase subunit VIc.     

The crossing function of a graph

The crossing function of a graphG with orientable genusn is defined as a mapping \(f:\{ \not 0,1, \ldots ,n\} \to \{ \not 0,1,2, \ldots \} \) for whichf(k)=cr _k (G) the crossing number ofG on the orientable surface of genusk. It is proved that any decreasing convex function \(f:\{ \not 0,1, \ldots ,n\} \to \{ \not 0,1,2, \ldots \} \) with \(f(n) = \not 0\) is the crossing function of some connected graph.     

Mechanism of Thermal Toluene Autoxidation

Aerobic oxidation of toluene (PhCH₃) is investigated by complementary experimental and theoretical methodologies. Whereas the reaction of the chain‐carrying benzylperoxyl radicals with the substrate produces predominantly benzyl hydroperoxide, benzyl alcohol and benzaldehyde originate mainly from subsequent propagation of the hydroperoxide product. Nevertheless, a significant fraction of benzaldehyde is also produced in primary PhCH₃ propagation, presumably via proton rather than hydrogen transfer. An equimolar amount of benzyl alcohol, together with benzoic acid, is additionally produced in the tertiary propagation of PhCHO with benzylperoxyl radicals. The “hot” oxy radicals generated in this step can also abstract aromatic hydrogen atoms from PhCH₃, and this results in production of cresols, known inhibitors of radical‐chain reactions. The very fast benzyl peroxyl‐initiated co‐oxidation of benzyl alcohol generates HO₂^. radicals, along with benzaldehyde. This reaction also causes a decrease in the overall oxidation rate, due to the fast chain‐terminating reaction of HO₂^. with the benzylperoxyl radicals, which causes a loss of chain carriers. Moreover, due to the fast equilibrium PhCH₂OOH+HO₂^.?PhCH₂OO^.+H₂O₂, and the much lower reactivity of H₂O₂ compared to PhCH₂OOH, the fast co‐oxidation of the alcohol means that HO₂^. gradually takes over the role of benzylperoxyl as principal chain carrier. This drastically changes the autoxidation mechanism and, among other things, causes a sharp decrease in the hydroperoxide yield.     

2‐(2‐Oxazolin‐2‐yl)benzene‐1,4‐diol: X‐ray and density functional theory studies

In the crystal structure of the title compound, C₉H₉NO₃, there are strong intra­molecular O—H⋯N and inter­molecular O—H⋯O hydrogen bonds which, together with weak inter­molecular C—H⋯O hydrogen bonds, lead to the formation of infinite chains of mol­ecules. The calculated inter­molecular hydrogen‐bond energies are −11.3 and −2.7 kJ mol⁻¹, respectively, showing the dominant role of the O—H⋯O hydrogen bonding. A natural bond orbital analysis revealed the electron contribution of the lone pairs of the oxazoline N and O atoms, and of the two hydr­oxy O atoms, to the order of the relevant bonds.     

Capillary zone electrophoresis in methanol: migration behavior and background electrolytes

Nonaqueous (NA) solutions are often used as background electrolytes (BGEs) and NA solvents are added to aqueous BGEs as organic modifiers in capillary zone electrophoresis (CZE), in order to optimize the separations. This can be tricky, however, because the pH* and pK* concepts may be totally different in NA solvents, whereas often less knowledge is available concerning phenomena, such as system zones, applying NA solvents. In this paper, the concepts of pH* and pK* are considered for methanol as a solvent and pK* values are determined for several components in mixtures of water and methanol. With a mathematical model, adapted for calculations in methanol, parameters are calculated describing the fronting or tailing character of peaks and the question of peaks or dips, and the existence of system zones is discussed for pure methanol as a solvent. These aspects are experimentally verified, applying BGEs useful for the separation of cationic species in the indirect UV mode. It can be concluded that the mathematical model developed for aqueous BGEs is applicable to BGEs in methanol, too, and that the behavior of BGEs in methanol is comparable with that in water concerning the fronting or tailing character of peaks and the question of peaks and dips, although the mobilities and pK values can change significantly.     

Theoretical modeling of the relationship between Young's modulus and formulation variables for segmented polyurethanes

We describe a new modeling approach to prediction of Young's modulus of segmented polyurethanes. This approach combines micromechanical models with thermodynamic considerations based on the theory of block copolymers. The resulting model predicts both the equilibrium morphology and the “ideal” Young's modulus of a segmented polyurethane polymer as a function of its formulation (hard segment chemical structure, hard segment weight fraction, soft segment equivalent weight) and temperature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2123–2135, 2007     

Cardinality of retracts of monounary algebras

For an uncountable monounary algebra (A, f) with cardinality κ it is proved that (A, f) has exactly 2_κ retracts. The case when (A, f) is countable is also dealt with. This work was suported by the the Slovak VEGA Grant No. 1/3003/06. This work was supported by Science and Technology Assistance Agency under the contract No. APVT-20-004104.     

Pseudo‐merohedrally twinned tetra­kis­(1H‐imidazole‐κN3)bis­(N‐nitro­cyanamidato‐κN)copper(II)

Crystals of the title complex, [Cu(CN₃O₂)₂(C₃H₄N₂)₄], the structure of which has been determined by single‐crystal X‐ray diffraction at 304 K, appear to be pseudo‐merohedrally twinned. Transformation to a monoclinic C‐centred cell was necessary in order to derive the twin law. Twin refinement in a triclinic unit cell significantly reduced the R value. The asymmetric unit of the triclinic cell consists of one mol­ecule in a general position and two half entities with the Cu atom on a centre of inversion. The coordination of the Cu atom is quasi‐octa­hedral, with four imidazole N‐atom donors in the equatorial plane and two cyano N atoms from the N‐nitro­cyanamidate anion in axial positions. Owing to symmetry in the centrosymmetric mol­ecules, the trans imidazole ligands are parallel, while those in the non‐centrosymmetric mol­ecule make angles of 22.8 (2) and 77.9 (2)°.