Beyond Sham and Cyanide: Opportunities for Studying the Alternative Oxidase in Plant Respiration Using Oxygen Isotope Discrimination.

1995 ◽  
Vol 22 (3) ◽  
pp. 487 ◽  
Author(s):  
SA Robinson ◽  
M Ribas-Carbo ◽  
D Yakir ◽  
L Giles ◽  
Y Reuveni ◽  
...  
Keyword(s):  
Gas Phase ◽  
Alternative Oxidase ◽  
Dark Respiration ◽  
Alternative Pathway ◽  
Phase System ◽  
A New Technique ◽  
Plant Respiration ◽  
Oxygen Isotope Discrimination ◽  
Pathway Flux

Discrimination against 18O during dark respiration forms the basis of a new technique for measuring- flux through the alternative pathway during plant respiration. This technique, first reported by Guy and coworkers, is the first to allow measurements of the alternative oxidase in vivo under steady-state conditions. Improvements to the technique have produced a gas-phase system which allows measurements of alternative pathway flux in intact tissues in less than an hour. The development and application of these techniques and the potential for future experiments are discussed in this review.

Calculation of the oxygen isotope discrimination factor for studying plant respiration

1999 ◽  
Vol 26 (8) ◽  
pp. 773 ◽  
Author(s):  
Beverley K. Henry ◽  
Owen K. Atkin ◽  
Graham D. Farquhar ◽  
David A. Day ◽  
A. Harvey Millar ◽  
...  
Keyword(s):  
Gas Phase ◽  
Reliable Method ◽  
Dark Respiration ◽  
Phase System ◽  
Discrimination Factor ◽  
Closed Chamber ◽  
Isotope Discrimination ◽  
Alternative Pathways ◽  
Plant Respiration ◽  
Oxygen Isotope Discrimination

Measurement of discrimination against 18O during dark respiration in plants is currently accepted as the only reliable method of estimating the partitioning of electrons between the cytochrome and alternative pathways. In this paper, we review the theory of the technique and its application to a gas-phase system. We extend it to include sampling effects and show that the isotope discrimination factor, D, is calculated as –dln(1 + δ)/dlnO*, where δ is isotopic composition of the substrate oxygen and O*=[O2]/[N2] in a closed chamber containing tissue respiring in the dark. It is not necessary to integrate the expression but, if the integrated form is used, the resultant regression should not be constrained through the origin. This is important since any error in D will have significant effects on the estimation of the flux of electrons through the two pathways.

In vivo cytochrome and alternative pathway respiration in leaves of Arabidopsis thaliana plants with altered alternative oxidase under different light conditions

2011 ◽  
Vol 34 (8) ◽  
pp. 1373-1383 ◽  
Author(s):  
IGOR FLOREZ-SARASA ◽  
JAUME FLEXAS ◽  
ALLAN G. RASMUSSON ◽  
ANN L. UMBACH ◽  
JAMES N. SIEDOW ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Alternative Oxidase ◽  
Alternative Pathway ◽  
Light Conditions

scholarly journals Cytochrome c Deficiency Differentially Affects the In Vivo Mitochondrial Electron Partitioning and Primary Metabolism Depending on the Photoperiod

Plants ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 444
Author(s):  
Igor Florez-Sarasa ◽  
Elina Welchen ◽  
Sofia Racca ◽  
Daniel H. Gonzalez ◽  
José G. Vallarino ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Tca Cycle ◽  
Day Length ◽  
Primary Metabolism ◽  
Stress Signaling ◽  
Alternative Pathways ◽  
Tca Cycle Intermediates ◽  
Growth Adaptation ◽  
Plant Respiration

Plant respiration provides metabolic flexibility under changing environmental conditions by modulating the activity of the nonphosphorylating alternative pathways from the mitochondrial electron transport chain, which bypass the main energy-producing components of the cytochrome oxidase pathway (COP). While adjustments in leaf primary metabolism induced by changes in day length are well studied, possible differences in the in vivo contribution of the COP and the alternative oxidase pathway (AOP) between different photoperiods remain unknown. In our study, in vivo electron partitioning between AOP and COP and expression analysis of respiratory components, photosynthesis, and the levels of primary metabolites were studied in leaves of wild-type (WT) plants and cytochrome c (CYTc) mutants, with reduced levels of COP components, under short- and long-day photoperiods. Our results clearly show that differences in AOP and COP in vivo activities between WT and cytc mutants depend on the photoperiod likely due to energy and stress signaling constraints. Parallel responses observed between in vivo respiratory activities, TCA cycle intermediates, amino acids, and stress signaling metabolites indicate the coordination of different pathways of primary metabolism to support growth adaptation under different photoperiods.

Effect of a Nonstationary Electric Current on the Oxide Melt–Gas Phase System

2018 ◽  
Vol 2018 (2) ◽  
pp. 197-200 ◽  
Author(s):  
S. A. Krasikov ◽  
B. T. Utelbaev ◽  
E. N. Suleimenov
Keyword(s):  
Electric Current ◽  
Gas Phase ◽  
Phase System ◽  
Oxide Melt

scholarly journals A discrete pathway for the transfer of intermembrane space proteins across the outer membrane of mitochondria

2014 ◽  
Vol 25 (25) ◽  
pp. 3999-4009 ◽  
Author(s):  
Agnieszka Gornicka ◽  
Piotr Bragoszewski ◽  
Piotr Chroscicki ◽  
Lena-Sophie Wenz ◽  
Christian Schulz ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Membrane ◽  
Alternative Pathway ◽  
Intermembrane Space ◽  
Outer Mitochondrial Membrane ◽  
Membrane Translocation ◽  
Tom Complex ◽  
Precursor Proteins ◽  
Core Components

Mitochondrial proteins are synthesized on cytosolic ribosomes and imported into mitochondria with the help of protein translocases. For the majority of precursor proteins, the role of the translocase of the outer membrane (TOM) and mechanisms of their transport across the outer mitochondrial membrane are well recognized. However, little is known about the mode of membrane translocation for proteins that are targeted to the intermembrane space via the redox-driven mitochondrial intermembrane space import and assembly (MIA) pathway. On the basis of the results obtained from an in organello competition import assay, we hypothesized that MIA-dependent precursor proteins use an alternative pathway to cross the outer mitochondrial membrane. Here we demonstrate that this alternative pathway involves the protein channel formed by Tom40. We sought a translocation intermediate by expressing tagged versions of MIA-dependent proteins in vivo. We identified a transient interaction between our model substrates and Tom40. Of interest, outer membrane translocation did not directly involve other core components of the TOM complex, including Tom22. Thus MIA-dependent proteins take another route across the outer mitochondrial membrane that involves Tom40 in a form that is different from the canonical TOM complex.

A Developed Numerical Method for Turbulent Unsteady Fluid Flow in Two-Phase Systems with Moving Interface

2017 ◽  
Vol 14 (06) ◽  
pp. 1750063 ◽  
Author(s):  
A. M. Hegab ◽  
S. A. Gutub ◽  
A. Balabel
Keyword(s):  
Numerical Model ◽  
Gas Phase ◽  
Level Set ◽  
The Body ◽  
Phase System ◽  
Computational Domain ◽  
Two Phase ◽  
Moving Interface ◽  
Level Set Function ◽  
Gas System

This paper presents the development of an accurate and robust numerical modeling of instability of an interface separating two-phase system, such as liquid–gas and/or solid–gas systems. The instability of the interface can be refereed to the buoyancy and capillary effects in liquid–gas system. The governing unsteady Navier–Stokes along with the stress balance and kinematic conditions at the interface are solved separately in each fluid using the finite-volume approach for the liquid–gas system and the Hamilton–Jacobi equation for the solid–gas phase. The developed numerical model represents the surface and the body forces as boundary value conditions on the interface. The adapted approaches enable accurate modeling of fluid flows driven by either body or surface forces. The moving interface is tracked and captured using the level set function that initially defined for both fluids in the computational domain. To asses the developed numerical model and its versatility, a selection of different unsteady test cases including oscillation of a capillary wave, sloshing in a rectangular tank, the broken-dam problem involving different density fluids, simulation of air/water flow, and finally the moving interface between the solid and gas phases of solid rocket propellant combustion were examined. The latter case model allowed for the complete coupling between the gas-phase physics, the condensed-phase physics, and the unsteady nonuniform regression of either liquid or the propellant solid surfaces. The propagation of the unsteady nonplanar regression surface is described, using the Essentially-Non-Oscillatory (ENO) scheme with the aid of the level set strategy. The computational results demonstrate a remarkable capability of the developed numerical model to predict the dynamical characteristics of the liquid–gas and solid–gas flows, which is of great importance in many civilian and military industrial and engineering applications.

scholarly journals In Vivo Experimental and Analytical Studies for Bevacizumab Diffusion Coefficient Measurement in the Rabbit Vitreous Humor

2020 ◽  
Author(s):  
Shuqi Zhang ◽  
Anita Penkova ◽  
Mark Humayun ◽  
Juan Carlos Martinez-Camarillo ◽  
Abegail C. Tadle ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Effective Diffusion ◽  
Drug Distribution ◽  
Vitreous Humor ◽  
Contour Method ◽  
Experimental Result ◽  
Coefficient Measurement ◽  
A New Technique ◽  
Best Fit

Abstract In order to measure the effective diffusion coefficient of Bevacizumab (Avastin, Genentech) in the vitreous humor, a new technique is developed based on the 'contour method' and in vivo OCT measurements. After injection of Bevacizumab-fluorescein conjugated compound solution into the rabbit eye, the contours of drug concentration distribution at the subsurface of injection were tracked over time. The 2D contours were extrapolated to 3D contours using reasonable assumptions and a numerically integrated analytical model was developed for the theoretical contours for the irregularly shaped drug distribution in the experimental result. By floating the diffusion coefficient, different theoretical contours were constructed and the least-squares best fit to the experimental contours was performed at each time point to get the best fit solution. The approach generated consistent diffusion coefficient values based on the experiments on four rabbit eyes over a period of 3 hours each, which gave , D=1.2±0.6×(?10?^(-6) ?cm?^2)/s and the corresponding theoretical contours matched well with the experimental contours. The quantitative measurement of concentration using OCT and fluorescein labeling gives a new approach for the "non-contact" in vivo drug distribution measurement within vitreous and other ocular tissues.

scholarly journals In Silico Investigation of Mitragynine and 7-Hydroxymitragynine Metabolism

2019 ◽  
Author(s):  
Taweetham Limpanuparb ◽  
Rattha Noorat ◽  
Yuthana Tantirungrotechai
Keyword(s):  
Gas Phase ◽  
In Silico ◽  
Metabolic Pathways ◽  
Experimental Studies ◽  
Medicinal Uses ◽  
Detection Techniques ◽  
Mass Spectrom ◽  
Gibbs Energies ◽  
In Silico Study

Abstract Objective: Mitragynine is the main active compound of Mitragyna speciose (Kratom in Thai). The understanding of mitragynine derivative metabolism in human body is required to develop effective detection techniques in case of drug abuse or establish an appropriate dosage in case of medicinal uses. This in silico study is based upon in vivo results in rat and human by Philipp et al. (J. Mass Spectrom., 2009, 44, 1249.) Results: The gas-phase structures of mitragynine, 7-hydroxymitragynine and their metabolites were obtained by quantum chemical method at B3LYP/6-311++G(d,p) level. Results in terms of standard Gibbs energies of reaction for all metabolic pathways are reported with solvation energy from SMD model. We found that 7-hydroxy substitution leads to changes in reactivity in comparison to mitragynine: position 17 is more reactive towards demethylation and conjugation to a glucuronide and position 9 is less reactive towards conjugation to a glucuronide. Despite the changes, position 9 is the most reactive for demethylation and position 17 is the most reactive for conjugation to a glucuronide for both mitragynine and 7-hydroxymitragynine. Our results suggest that 7-hydroxy substitution could lead to different metabolic pathways and raise an important question for further experimental studies of this more potent derivative.

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