Thermally induced changes in reconstituted and membranous cytochrome c oxidase

1979 ◽  
Vol 57 (3) ◽  
pp. 238-249 ◽  
Author(s):  
A. S. Denes ◽  
N. Z. Stanacev
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Spin Label ◽  
Liquid Crystalline ◽  
Spectral Characteristics ◽  
Temperature Dependent ◽  
Scanning Calorimetry ◽  
Thermally Induced ◽  
Lipid Protein Interaction ◽  
Induced Changes

The Arrhenius plots of electron transport activity in cytochrome c oxidase reconstituted with well-defined phospholipids have been shown to display a change in slope at 20–25 °C regardless of the chemical nature of the incorporated lipid. In native membranous cytochrome c oxidase, the discontinuity in Arrhenius activity plot occurred at 16–18 °C. These temperature breaks were found to correlate with changes in spin-label mobilities but not with the bulk lipid transition observed by differential scanning calorimetry. Temperature-dependent reciprocal equilibrium between the immobilized and fluid pools is demonstrated. It is suggested that the changes in kinetic and spin-label spectral characteristics in cytochrome c oxidase membranes are related very likely to a lipid-protein interaction prompted by a thermally induced change in the physical state of the lipids that does not involve a gel to liquid crystalline transition.

scholarly journals Temperature-dependent nanomechanics and topography of bacteriophage T7

2018 ◽  
Author(s):  
Zsuzsanna Vörös ◽  
Gabriella Csík ◽  
Levente Herényi ◽  
Miklós Kellermayer
Keyword(s):  
Structural Changes ◽  
Mechanical Stability ◽  
Genetic Material ◽  
Heat Inactivation ◽  
Infectious Agents ◽  
Temperature Dependent ◽  
Thermally Induced ◽  
Partial Denaturation ◽  
Induced Changes ◽  
T7 Bacteriophage

AbstractViruses are nanoscale infectious agents which may be inactivated by heat treatment. Although heat inactivation is thought to be caused by the release of genetic material from the capsid, the thermally-induced structural changes in viruses are little known. Here we measured the heat-induced changes in the properties of T7 bacteriophage particles exposed to two-stage (65 °C and 80 °C) thermal effect by using AFM-based nanomechanical and topographical measurements. We found that exposure to 65 °C caused the release of genomic DNA due to the loss of the capsid tail which leads to a destabilization of the T7 particles. Further heating to 80 °C surprisingly led to an increase in mechanical stability due to partial denaturation of the capsomeric proteins kept within the global capsid arrangement.

scholarly journals Mechanically and Thermally Induced Degradation and Modification of Cereal Biopolymers during Grinding

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 448 ◽  
Author(s):  
Sabina Paulik ◽  
Mario Jekle ◽  
Thomas Becker
Keyword(s):  
Mechanical Stress ◽  
Structural Modification ◽  
Wheat Starch ◽  
Water Addition ◽  
Scanning Calorimetry ◽  
Hydration Properties ◽  
Thermally Induced ◽  
Induced Changes ◽  
The Impact ◽  
Main Factor

It is presumed that structural and functional alterations of biopolymers, which occur during grinding, are caused by a mechanical modification of polymers. As a result, thermally induced changes of flours are neglected. In this study, the impact of thermo-mechanical stress (TMS), as occurring during general grinding procedures, was further differentiated into thermal stress (TS) and mechanical stress (MS). For TS, native wheat flour, as well as the purified polymers of wheat—starch and gluten—were heated without water addition up to 110 ∘ C. Isolated MS was applied in a temperature-controlled ultra-centrifugal grinder (UCG), whereby thermal and mechanical treatment (TMS) was simultaneously performed in a non-cooled UCG. TS starch (110 ∘ C) and reference starch did not show differences in starch modification degree (2.53 ± 0.24 g/100 g and 2.73 ± 0.15 g/100 g, AACC 76-31), gelatinization onset (52.44 ± 0.14 ∘ C and 52.73 ± 0.27 ∘ C, differential scanning calorimetry (DSC)) and hydration properties (68.9 ± 0.8% dm and 75.8 ± 3.0%, AACC 56-11), respectively. However, TS led to an elevated gelatinization onset and a rise of water absorption of flours (Z-kneader) affecting the processing of cereal-based dough. No differences were visible between MS and TMS up to 18,000 rpm regarding hydration properties (65.0 ± 2.0% dm and 66.5 ± 0.3% dm, respectively). Consequently, mechanical forces are the main factor controlling the structural modification and functional properties of flours during grinding.

scholarly journals Discotic Mesophases of the Hexakis(alkylsulfono)benzene Series: Characterization by Differential Scanning Calorimetry, Optical Microscopy and Nuclear Magnetic Resonance Spectroscopy

1984 ◽  
Vol 39 (7) ◽  
pp. 950-956 ◽  
Author(s):  
K. Praefcke ◽  
W. Poules ◽  
B. Scheuble ◽  
R. Poupko ◽  
Z. Luz
Keyword(s):  
Nmr Spectra ◽  
Liquid Crystalline ◽  
Alkyl Chain ◽  
Columnar Structure ◽  
Resonance Spectroscopy ◽  
Temperature Dependent ◽  
Scanning Calorimetry ◽  
Strong Magnetic Fields ◽  
Benzene Series ◽  
Quadrupolar Splittings

Members of the Hexakis(alkylsulfono)benzene series 4, containing 7 to 15 carbon atoms per alkyl chain (4 c-k), exhibit one and possibly several liquid crystalline discotic mesophases. The mesophases are uniaxial and most probably have a columnar structure. Their anisotropic magnetic susceptibility is negative and in sufficiently strong magnetic fields they align with the director perpendicular to the field direction. Deuterium NMR spectra of C6D6 dissolved in the mesophases exhibit quadrupolar splittings which are strongly temperature dependent. In analogy with the conventional discotics this suggests the presence of multiple solvation sites for solute molecules.

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