Slow passive diffusion of NAD+ between intact isolated plant mitochondria and suspending medium

Isolated potato (Solanum tuberosum) tuber mitochondria purified by isopycnic centrifugation in density gradients of Percoll were found to be highly intact, to be devoid of extramitochondrial contaminations and to retain a high rate of O2 consumption. When suspended in a medium that avoided rupture of the outer membrane, intact purified mitochondria progressively lost their NAD+ content by passive diffusion. This led to a slow decrease of oxoglutarate-dependent O2 consumption by isolated mitochondria. Addition of NAD+ to the medium restored the initial State-3 rate of oxoglutarate oxidation. The rate of NAD+ accumulation in the matrix space was concentration-dependent, exhibited Michaelis-Menten kinetics and was strongly inhibited by the analogue N-4-azido-2-nitrophenyl-4-aminobutyryl-NAD+.

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Changes in the proportions of two mitochondrial populations during the development of embryonic chick liver

Biochemical Journal ◽

10.1042/bj1230347 ◽

1971 ◽

Vol 123 (3) ◽

pp. 347-353 ◽

Cited By ~ 18

Author(s):

J. K. Pollak ◽

Maria Woog

Keyword(s):

Respiratory Control ◽

Mitochondrial Fraction ◽

Liver Mitochondria ◽

Progressive Increase ◽

Rat Liver Mitochondria ◽

Matrix Space ◽

The Matrix ◽

Phospholipid Ratio ◽

Two Populations ◽

Isopycnic Centrifugation

1. Two populations of morphologically intact mitochondria were isolated from embryonic, neonatal and adult chick liver by isopycnic centrifugation. 2. The protein/phospholipid ratio of the total mitochondrial fraction, the low-density mitochondria (B2, d1.176) and the high-density mitochondria (B3, d1.206) did not differ significantly. 3. During development there is a marked increase in the B2 fraction in relation to the B3 fraction. 4. Cytochrome oxidase and malate dehydrogenase activities as well as respiratory control increased during the embryonic development of the chick, though their rates of increase were not correlated. 5. In the three different embryonic stages that were investigated, as well as in the neonatal and adult chick, the protein/lipid as well as the protein/phospholipid ratio stayed constant and showed no progressive increase, as had been previously reported. 6. It was shown that forces greater than 18400gav. for 2h have to be used before chick liver mitochondria reach isopycnic equilibrium. 7. As for rat liver mitochondria, the constant protein/phospholipid ratio of the B2 and B3 fractions and their apparent morphological intactness leads one to conclude that the matrix space of B2 mitochondria is inaccessible to sucrose, whereas B3 mitochondria possess an inner membrane that is permeable to sucrose.

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Regulation of malate oxidation in plant mitochondria. Response to rotenone and exogenous NAD+

Biochemical Journal ◽

10.1042/bj2080703 ◽

1982 ◽

Vol 208 (3) ◽

pp. 703-711 ◽

Cited By ~ 34

Author(s):

J M Palmer ◽

J P Schwitzguébel ◽

I M Møller

Keyword(s):

Nadh Dehydrogenase ◽

Tricarboxylic Acid Cycle ◽

Plant Mitochondria ◽

Jerusalem Artichoke ◽

Atp Synthesis ◽

Matrix Space ◽

Matrix Surface ◽

The Matrix ◽

Nadh Dehydrogenases ◽

Malate Oxidation

Exogenous NAD+ stimulated the rotenone-resistant oxidation of all the NAD+-linked tricarboxylic acid-cycle substrates in mitochondria from Jerusalem artichoke (Helianthus tuberosus L.) tubers. The stimulation was not removed by the addition of EGTA, which is known to inhibit the oxidation of exogenous NADH. It is therefore concluded that added NAD+ gains access to the matrix space and stimulates oxidation by the rotenone-resistant NADH dehydrogenase located on the matrix surface of the inner membrane. Added NAD+ stimulated the activity of malic enzyme and displaced the equilibrium of malate dehydrogenase; both observations are consistent with entry of NAD+ into the matrix space. Analysis of products of malate oxidation showed that rotenone-resistant oxygen uptake only occurred when the concentration of oxaloacetate was low and that of NADH was high. Thus it is proposed that the concentration of NADH regulates the activity of the two internal NADH dehydrogenases. Evidence is presented to suggest that the rotenone-resistant NADH dehydrogenase is engaged under conditions of high phosphorylation potential, which restricts electron flux through the rotenone-sensitive dehydrogenase (coupled to ATP synthesis).

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Metabolic evidence for distinct pyruvate pools inside plant mitochondria

10.1101/2021.10.30.466557 ◽

2021 ◽

Author(s):

Xuyen Le ◽

Chun Pong Lee ◽

Dario Monachello ◽

A. Harvey Millar

Keyword(s):

Malic Enzyme ◽

Metabolic Regulation ◽

Plant Mitochondria ◽

Tca Cycle ◽

Pool Size ◽

Isolated Mitochondria ◽

Metabolic Products ◽

The Matrix ◽

Exogenous Addition ◽

Different Sources

The majority of the pyruvate inside plant mitochondria is either transported into the matrix from the cytosol via the mitochondria pyruvate carrier (MPC) or synthesised in the matrix by alanine aminotransferase (AlaAT) or NAD-malic enzyme (NAD-ME). Pyruvate from these origins could mix into a single pool in the matrix and contribute indistinguishably to respiration, or they could maintain a degree of independence in metabolic regulation. Here, we demonstrated that feeding isolated mitochondria with U-13C-pyruvate and unlabelled malate enables the assessment of pyruvate contribution from different sources to TCA cycle intermediate production. Imported pyruvate is the preferred source for citrate production even when the synthesis of NAD-ME-derived pyruvate was optimised. Genetic or pharmacological elimination of MPC activity removed this preference and allowed an equivalent amount of citrate to be generated from the pyruvate produced by NAD-ME. Increasing mitochondrial pyruvate pool size by exogenous addition only affected metabolites from pyruvate transported by MPC whereas depleting pyruvate pool size by transamination to alanine only affected metabolic products derived from NAD-ME. Together, these data reveal respiratory substrate supply in plants involves distinct pyruvate pools inside the matrix that can be flexibly mixed based on the rate of pyruvate transport from the cytosol. These pools are independently regulated and contribute differentially to organic acids export from plant mitochondria.

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ηQ Meson Photoproduction in Ultrarelativistic Heavy Ion Collisions

Advances in High Energy Physics ◽

10.1155/2017/2379319 ◽

2017 ◽

Vol 2017 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Gong-Ming Yu ◽

Gao-Gao Zhao ◽

Zhen Bai ◽

Yan-Bing Cai ◽

Hai-Tao Yang ◽

...

Keyword(s):

Heavy Ion Collisions ◽

Hadron Collider ◽

Heavy Ion ◽

Relativistic Heavy Ion Collisions ◽

Heavy Quarkonium ◽

Color Singlet ◽

Initial State ◽

Color Octet ◽

Ion Collisions ◽

The Matrix

The transverse momentum distributions for inclusive ηc,b meson described by gluon-gluon interactions from photoproduction processes in relativistic heavy ion collisions are calculated. We considered the color-singlet (CS) and color-octet (CO) components within the framework of Nonrelativistic Quantum Chromodynamics (NRQCD) in the production of heavy quarkonium. The phenomenological values of the matrix elements for the color-singlet and color-octet components give the main contribution to the production of heavy quarkonium from the gluon-gluon interaction caused by the emission of additional gluon in the initial state. The numerical results indicate that the contribution of photoproduction processes cannot be negligible for midrapidity in p-p and Pb-Pb collisions at the Large Hadron Collider (LHC) energies.

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In Vitro Import of a Nuclearly Encoded tRNA into Mitochondria of Solanum tuberosum

Molecular and Cellular Biology ◽

10.1128/mcb.23.11.4000-4012.2003 ◽

2003 ◽

Vol 23 (11) ◽

pp. 4000-4012 ◽

Cited By ~ 42

Author(s):

Ludovic Delage ◽

André Dietrich ◽

Anne Cosset ◽

Laurence Maréchal-Drouard

Keyword(s):

Solanum Tuberosum ◽

Higher Plants ◽

Plant Mitochondria ◽

Protein Translation ◽

Trna Genes ◽

Vitro Assay ◽

Trna Import

ABSTRACT Some of the mitochondrial tRNAs of higher plants are nuclearly encoded and imported into mitochondria. The import of tRNAs encoded in the nucleus has been shown to be essential for proper protein translation within mitochondria of a variety of organisms. Here, we report the development of an in vitro assay for import of nuclearly encoded tRNAs into plant mitochondria. This in vitro system utilizes isolated mitochondria from Solanum tuberosum and synthetic tRNAs transcribed from cloned nuclear tRNA genes. Although incubation of radioactively labeled in vitro-transcribed tRNAAla, tRNAPhe, and tRNAMet-e with isolated potato mitochondria resulted in importation, as measured by nuclease protection, the amount of tRNA transcripts protected at saturation was at least five times higher for tRNAAla than for the two other tRNAs. This difference in in vitro saturation levels of import is consistent with the in vivo localization of these tRNAs, since cytosolic tRNAAla is naturally imported into potato mitochondria whereas tRNAPhe and tRNAMet-e are not. Characterization of in vitro tRNA import requirements indicates that mitochondrial tRNA import proceeds in the absence of any added cytosolic protein fraction, involves at least one protein component on the surface of mitochondria, and requires ATP-dependent step(s) and a membrane potential.

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Processing and Testing of Reinforced PA66 Based Composites

Materials ◽

10.3390/ma14237299 ◽

2021 ◽

Vol 14 (23) ◽

pp. 7299

Author(s):

Alejandro Pereira ◽

Alberto Tielas ◽

Teresa Prado ◽

Maria Fenollera ◽

José Antonio Pérez

Keyword(s):

Composite Materials ◽

Glass Fibre ◽

High Rate ◽

Injection Process ◽

Production Processes ◽

Short Glass Fibre ◽

The Matrix ◽

Plastic Injection ◽

Short Glass ◽

Resistance Tests

The new requirements in different sectors, such as aerospace, automotive and construction, for lightweight materials have led to an increase in demand for composite materials suitable for use in high rate production processes, such as plastic injection. This makes it necessary to look for matrices and reinforcements that, in addition to being compatible with each other, are also compatible with the injection process. It is in this area of research where the work presented here arises. To meet the two requirements mentioned above, this study contemplates a battery of composite materials obtained by combining PA66 and fiberglass, in different proportions and configuration, both for the preparation of the matrix and for reinforcement. For the elaboration of the matrix, two options have been evaluated, PA66 and PA66 reinforced at 35% with short glass fibre. To obtain reinforcement, six different options have been evaluated; two conventional fiberglass fabrics (each with different density) and four hybrid fabrics obtained from the previous ones by adding PA66 in different configurations (two over-stitched fabrics and two other fabrics). The different composite materials obtained were validated by means of the corresponding adhesion, peeling and resistance tests.

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CHONDROGENESIS, STUDIED WITH THE ELECTRON MICROSCOPE

The Journal of Cell Biology ◽

10.1083/jcb.8.3.719 ◽

1960 ◽

Vol 8 (3) ◽

pp. 719-760 ◽

Cited By ~ 202

Author(s):

Gabriel C. Godman ◽

Keith R. Porter

Keyword(s):

Golgi Apparatus ◽

Ground Substance ◽

Cell Cortex ◽

Matrix Space ◽

Cytoplasmic Inclusions ◽

Structural Modifications ◽

Fetal Rat ◽

The Matrix ◽

Connective Tissue Matrix ◽

Tissue Matrix

The role of the cells in the fabrication of a connective tissue matrix, and the structural modifications which accompany cytodifferentiation have been investigated in developing epiphyseal cartilage of fetal rat by means of electron microscopy. Differentiation of the prechondral mesenchymal cells to chondroblasts is marked by the acquisition of an extensive endoplasmic reticulum, enlargement and concentration of the Golgi apparatus, the appearance of membrane-bounded cytoplasmic inclusions, and the formation of specialized foci of increased density in the cell cortex. These modifications are related to the secretion of the cartilage matrix. The matrix of young hyaline cartilage consists of groups of relatively short, straight, banded collagen fibrils of 10 to 20 mµ and a dense granular component embedded in an amorphous ground substance of moderate electron density. It is postulated that the first phase of fibrillogenesis takes place at the cell cortex in dense bands or striae within the ectoplasm subjacent to the cell membrane. These can be resolved into sheaves of "primary" fibrils of about 7 to 10 mµ. They are supposedly shed (by excortication) into the matrix space between the separating chondroblasts, where they may serve as "cores" of the definitive matrix fibrils. The diameter of the fibrils may subsequently increase up to threefold, presumably by incorporation of "soluble" or tropocollagen units from the ground substance. The chondroblast also discharges into the matrix the electrondense amorphous or granular contents of vesicles derived from the Golgi apparatus, and the mixed contents of large vacuoles or blebs bounded by distinctive double membranes. Small vesicles with amorphous homogeneous contents of moderate density are expelled in toto from the chondroblasts. In their subsequent evolution to chondrocytes, both nucleus and cytoplasm of the chondroblasts undergo striking condensation. Those moving toward the osteogenic plate accumulate increasingly large stores of glycogen. In the chondrocyte, the enlarged fused Golgi vesicles with dense contents, massed in the juxtanuclear zone, are the most prominent feature of the cytoplasm. Many of these make their way to the surface to discharge their contents. The hypertrophied chondrocytes of the epiphyseal plate ultimately yield up their entire contents to the matrix.

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Experimental investigation, modeling and optimization study on the mechanical properties of B4Cp/MWCNT/epoxy multi-scale hybrid composite

Polymers and Polymer Composites ◽

10.1177/0967391120971189 ◽

2020 ◽

pp. 096739112097118

Author(s):

Mustafa Taşyürek

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Process Parameters ◽

Hybrid Composite ◽

Optimization Method ◽

High Rate ◽

Dominant Factor ◽

Mechanical And Thermal Properties ◽

Multi Scale ◽

The Matrix

In this study, process parameters and mechanical properties of the multi-scale composite were investigated experimentally and predictably. Multi-scale material includes boron carbide particles and multi walled carbon nanotubes (MWCNTs) in the epoxy-based matrix. Both reinforcements were reinforced into the matrix with various rates simultaneously. Average three tensile strength and hardness values were determined. The tensile strength and hardness were enhanced thanks to high rate of B4C usage up to 54.09% and 2.54%, respectively. The microstructure of the hybrid composite was investigated by Scanning Electron Microscopy. Also, Fourier Transform Infrared Spectroscopy was used to interpret spectral bands. The experimental data were analyzed using optimization method. Optimal process parameters for tensile strength and interfacial properties were determined. The Analysis of Variance (ANOVA) was used to obtain most significant factor and optimum levels of parameters. Finally, it was observed that B4C ratio is the most dominant factor affecting the mechanical and thermal properties.

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Rat liver mitochondrial ADP-ribose pyrophosphatase in the matrix space with low Km for free ADP-ribose

Biochemical Journal ◽

10.1042/bj2990679 ◽

1994 ◽

Vol 299 (3) ◽

pp. 679-682 ◽

Cited By ~ 19

Author(s):

D Bernet ◽

R M Pinto ◽

M J Costas ◽

J Canales ◽

J C Cameselle

Keyword(s):

Rat Liver ◽

Gradient Centrifugation ◽

Liver Mitochondria ◽

Rat Liver Mitochondria ◽

Matrix Space ◽

The Matrix ◽

Submitochondrial Fractions

A study involving markers of subcellular and submitochondrial fractions, gradient centrifugation, latency measurements and extraction with digitonin, demonstrates the association of a specific ADP-ribose pyrophosphatase with rat liver mitochondria and its localization in the matrix space. The enzyme hydrolyses ADP-ribose to AMP, with a Km of 2-3 microM. The results support the occurrence of a specific turnover pathway for free ADP-ribose and its relevance in mitochondria.

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Effects of tetrahydrofolate polyglutamates on the kinetic parameters of serine hydroxymethyltransferase and glycine decarboxylase from pea leaf mitochondria

Biochemical Journal ◽

10.1042/bj2920425 ◽

1993 ◽

Vol 292 (2) ◽

pp. 425-430 ◽

Cited By ~ 43

Author(s):

V Besson ◽

F Rebeille ◽

M Neuburger ◽

R Douce ◽

E A Cossins

Keyword(s):

Kinetic Parameters ◽

Serine Hydroxymethyltransferase ◽

Affinity Constant ◽

Plant Tissues ◽

Glycine Decarboxylase ◽

Glycine Cleavage System ◽

Matrix Space ◽

The Matrix ◽

Order Of Magnitude ◽

Glycine Cleavage

Plant tissues contain highly conjugated forms of folate. Despite this, the ability of plant folate-dependent enzymes to utilize tetrahydrofolate polyglutamates has not been examined in detail. In leaf mitochondria, the glycine-cleavage system and serine hydroxymethyltransferase, present in large amounts in the matrix space and involved in the photorespiratory cycle, necessitate the presence of tetrahydrofolate as a cofactor. The aim of the present work was to determine whether glutamate chain length (one to six glutamate residues) influenced the affinity constant for tetrahydrofolate and the maximal velocities displayed by these two enzymes. The results show that the affinity constant decreased by at least one order of magnitude when the tetrahydrofolate substrate contained three or more glutamate residues. In contrast, maximal velocities were not altered in the presence of these substrates. These results are consistent with analyses of mitochondrial folates which revealed a pool of polyglutamates dominated by tetra and pentaglutamates. The equilibrium constant of the serine hydroxymethyltransferase suggests that, during photorespiration, the reaction must be permanently pushed toward the formation of serine (the unfavourable direction) to allow the recycling of tetrahydrofolate necessary for the operation of the glycine decarboxylase T-protein.

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