Dilatometric studies of the phase transitions of sodium potassium tartrate tetrahydrate (RS)

Temperature dependence of the thermal expansion coefficients of Rochelle salt (RS) crystals for the basic crystallographic directions have been measured in the temperature range from 100 K to 308 K by an air-capacitor dilatometer. Anomalies of thermal expansion coefficients at about 210 K and 153 K have been observed, besides these corresponding to known ferroelectric phase transitions at the temperatures of 255 and 297 K.     

Chronic Activation of AMPK Induces Mitochondrial Biogenesis through Differential Phosphorylation and Abundance of Mitochondrial Proteins in Dictyostelium discoideum

Mitochondrial biogenesis is a highly controlled process that depends on diverse signalling pathways responding to cellular and environmental signals. AMP-activated protein kinase (AMPK) is a critical metabolic enzyme that acts at a central control point in cellular energy homeostasis. Numerous studies have revealed the crucial roles of AMPK in the regulation of mitochondrial biogenesis; however, molecular mechanisms underlying this process are still largely unknown. Previously, we have shown that, in cellular slime mould Dictyostelium discoideum, the overexpression of the catalytic α subunit of AMPK led to enhanced mitochondrial biogenesis, which was accompanied by reduced cell growth and aberrant development. Here, we applied mass spectrometry-based proteomics of Dictyostelium mitochondria to determine the impact of chronically active AMPKα on the phosphorylation state and abundance of mitochondrial proteins and to identify potential protein targets leading to the biogenesis of mitochondria. Our results demonstrate that enhanced mitochondrial biogenesis is associated with variations in the phosphorylation levels and abundance of proteins related to energy metabolism, protein synthesis, transport, inner membrane biogenesis, and cellular signalling. The observed changes are accompanied by elevated mitochondrial respiratory activity in the AMPK overexpression strain. Our work is the first study reporting on the global phosphoproteome profiling of D. discoideum mitochondria and its changes as a response to constitutively active AMPK. We also propose an interplay between the AMPK and mTORC1 signalling pathways in controlling the cellular growth and biogenesis of mitochondria in Dictyostelium as a model organism.     

Urease immobilized on aminated butyl acrylate-ethylenedimethacrylate copolymer

Urease was covalently immobilized on a new acrylic enzyme carrier: aminated butyl acrylate-ethylenedimethacrylate copolymer. The enzyme retained 56% of its original activity. The properties of the free and immobilized urease were determined and compared. The Michaelis constant was found to be higher for the immobilized urease than for the free one, while maximum reaction rate was lower for the immobilized enzyme. The stability of urease against change in pH was considerably improved by the immobilization. The immobilized urease showed very good storage stability and reusability. Resistance of the enzyme against heat inactivation at 70°C, however, was not found to be improved.     

Alternative oxidase in the branched mitochondrial respiratory network: an overview on structure, function, regulation, and role

Plants and some other organisms including protists possess a complex branched respiratory network in their mitochondria. Some pathways of this network are not energy-conserving and allow sites of energy conservation to be bypassed, leading to a decrease of the energy yield in the cells. It is a challenge to understand the regulation of the partitioning of electrons between the various energy-dissipating and -conserving pathways. This review is focused on the oxidase side of the respiratory chain that presents a cyanide-resistant energy-dissipating alternative oxidase (AOX) besides the cytochrome pathway. The known structural properties of AOX are described including transmembrane topology, dimerization, and active sites. Regulation of the alternative oxidase activity is presented in detail because of its complexity. The alternative oxidase activity is dependent on substrate availability: total ubiquinone concentration and its redox state in the membrane and O2 concentration in the cell. The alternative oxidase activity can be long-term regulated (gene expression) or short-term (post-translational modification, allosteric activation) regulated. Electron distribution (partitioning) between the alternative and cytochrome pathways during steady-state respiration is a crucial measurement to quantitatively analyze the effects of the various levels of regulation of the alternative oxidase. Three approaches are described with their specific domain of application and limitations: kinetic approach, oxygen isotope differential discrimination, and ADP/O method (thermokinetic approach). Lastly, the role of the alternative oxidase in non-thermogenic tissues is discussed in relation to the energy metabolism balance of the cell (supply in reducing equivalents/demand in energy and carbon) and with harmful reactive oxygen species formation.     

Pretreatment of polypropylene films for following technological processes,part 2: The use of low temperature plasma method

The surface of polypropylene (PP) films was activated by RF plasma method with the use different gases: argon, air, water vapor, and acetic acid vapor. Plasma was diagnosed based on spectra emitted by gas plasma using the method of optical emission spectroscopy. The effectiveness of these processing gases during plasma treatment was analyzed. The effects of PP activation were assessed with the use of IR‐ATR absorption spectroscopy, X‐ray photoelectron spectroscopy, atomic force microscopy, and the analysis of the surface free energy components based on liquid contact angle. The activation of PP surface by plasma treatment resulted in the increased energy of PP surface layer to the extent being dependent on the type of processing gases and in the formation of new chemical groups on it. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Immunological identification of the alternative oxidase of Acanthamoeba castellanii mitochondria

The exchange energy in the long-range near-dissociation region is analyzed for the ground electronic states of homo- and heteronuclear alkali diatomic molecules. The analysis is based on the use of the functional form Ae-ar to represent this exchange term. A period effect is observed in the values of both parameters and the exponent parameter a appears to approach an asymptotic limit for the heavier molecules. The results obtained in this study also suggest that some care must be taken in using even this function to represent the exchange energy. Copyright 1997 Academic Press. Copyright 1997Academic Press     

Linoleic acid-induced activity of plant uncoupling mitochondrial protein in purified tomato fruit mitochondria during resting, phosphorylating, and progressively uncoupled respiration

An uncoupling protein was recently discovered in plant mitochondria and demonstrated to function similarly to the uncoupling protein of brown adipose tissue. In this work, green tomato fruit mitochondria were purified on a self-generating Percoll gradient in the presence of 0.5% bovine serum albumin to deplete mitochondria of endogenous free fatty acids. The uncoupling protein activity was induced by the addition of linoleic acid during the resting state, and in the progressively uncoupled state, as well as during phosphorylating respiration in the presence of benzohydroxamic acid, an inhibitor of the alternative oxidase and with succinate (+ rotenone) as oxidizable substrate. Linoleic acid strongly stimulated the resting respiration in fatty acid-depleted mitochondria but had no effect on phosphorylating respiration, suggesting no activity of the uncoupling protein in this respiratory state. Progressive uncoupling of state 4 respiration decreased the stimulation by linoleic acid. The similar respiratory rates in phosphorylating and fully uncoupled respiration in the presence and absence of linoleic acid suggested that a rate-limiting step on the dehydrogenase side of the respiratory chain was responsible for the insensitivity of phosphorylating respiration to linoleic acid. Indeed, the ADP/O ratio determined by ADP/O pulse method was decreased by linoleic acid, indicating that uncoupling protein was active during phosphorylating respiration and was able to divert energy from oxidative phosphorylation. Moreover, the respiration rates appeared to be determined by membrane potential independently of the presence of linoleic acid, indicating that linoleic acid-induced stimulation of respiration is due to a pure protonophoric activity without any direct effect on the electron transport chain.     

A Proposed Molecular Mechanism of High-Dose Vitamin D3 Supplementation in Prevention and Treatment of Preeclampsia

A randomized prospective clinical study performed on a group of 74 pregnant women (43 presenting with severe preeclampsia) proved that urinary levels of 15-F_2t-isoprostane were significantly higher in preeclamptic patients relative to the control (3.05 vs. 2.00 ng/mg creatinine). Surprisingly enough, plasma levels of 25-hydroxyvitamin D₃ in both study groups were below the clinical reference range with no significant difference between the groups. In vitro study performed on isolated placental mitochondria and placental cell line showed that suicidal self-oxidation of cytochrome P450scc may lead to structural disintegration of heme, potentially contributing to enhancement of oxidative stress phenomena in the course of preeclampsia. As placental cytochrome P450scc pleiotropic activity is implicated in the metabolism of free radical mediated arachidonic acid derivatives as well as multiple Vitamin D₃ hydroxylations and progesterone synthesis, we propose that Vitamin D₃ might act as a competitive inhibitor of placental cytochrome P450scc preventing the production of lipid peroxides or excess progesterone synthesis, both of which may contribute to the etiopathogenesis of preeclampsia. The proposed molecular mechanism is in accord with the preliminary clinical observations on the surprisingly high efficacy of high-dose Vitamin D₃ supplementation in prevention and treatment of preeclampsia.