BN-PAGE analysis of the respiratory chain complexes in mitochondria of cucumber MSC16 mutant

Rearrangements of mitochondrial DNA in MSC16 mutant of cucumber (Cucumis sativus L.) affect mitochondrial functioning due to the alteration mainly of Complex I resulting in several metabolic changes. One-dimensional Blue-Native polyacrylamide gel electrophoresis (BN-PAGE) and densitometric measurements showed that the level and in-gel capacity of Complex I were lower in MSC16 leaf and root mitochondria as compared to wild-type (WT). The level and capacity of supercomplex I + III₂ were always lower in leaf but not in MSC16 root mitochondria. Two-dimensional BN/SDS-PAGE indicated that the band abundance for most of the subunits of Complex I was lower in MSC16 leaf and root mitochondria. Supercomplex I + III₂ level was only altered in MSC16 leaf mitochondria as measured after 2D BN/SDS-PAGE. No differences in the qualitative composition of the subunits of Complex I and supercomplex I + III₂ between MSC16 and WT mitochondria were observed. In MSC16 mitochondria Complex I impairment could be compensated to some extent by additional respiratory chain NADH dehydrogenases. A higher capacity and level of NDB-1 protein of external NADH dehydrogenase was observed in MSC16 leaf and root mitochondria as compared to WT. The level of COX II, mitochondrial-encoded subunit of Complex IV, was higher in MSC16 leaf and root mitochondria. However, the capacity of Complex IV was slightly higher only in MSC16 leaf mitochondria. The levels of complexes: III₂ and V and Complex V capacity did not differ in mitochondria between genotypes. An abundance of the subunits of respiratory complexes is one of the key factors determining not only their structure and functional stability but also a formation of the supercomplexes. We discuss here mitochondrial genome rearrangements in MSC16 mutant in a relation to assembly and/or stability (the lower level and capacity) of Complex I and supercomplex I + III₂.     

Supramolecular structure of the OXPHOS system in highly thermogenic tissue of Arum maculatum

The protein complexes of the mitochondrial respiratory chain associate in defined ways forming supramolecular structures called respiratory supercomplexes or respirasomes. In plants, additional oxidoreductases participate in respiratory electron transport, e.g. the so-called “alternative NAD(P)H dehydrogenases” or an extra terminal oxidase called “alternative oxidase” (AOX). These additional enzymes were previously reported not to form part of respiratory supercomplexes. However, formation of respiratory supercomplexes might indirectly affect “alternative respiration” because electrons can be channeled within the supercomplexes which reduces access of the alternative enzymes towards their electron donating substrates. Here we report an investigation on the supramolecular organization of the respiratory chain in thermogenic Arum maculatum appendix mitochondria, which are known to have a highly active AOX for heat production. Investigations based on mild membrane solubilization by digitonin and protein separation by blue native PAGE revealed a very special organization of the respiratory chain in A. maculatum, which strikingly differs to the one described for the model plant Arabidopsis thaliana: (i) complex I is not present in monomeric form but exclusively forms part of a I + III₂ supercomplex, (ii) the III₂ + IV and I + III₂ + IV supercomplexes are detectable but of low abundance, (iii) complex II has fewer subunits than in A. thaliana, and (iv) complex IV is mainly present as a monomer in a larger form termed “complex IVa”. Since thermogenic tissue of A. maculatum at the same time has high AOX and I + III₂ supercomplex abundance and activity, negative regulation of the alternative oxidase by supercomplex formation seems not to occur. Functional implications are discussed.     

Cardiolipin-dependent Reconstitution of Respiratory Supercomplexes from Purified Saccharomyces cerevisiae Complexes III and IV

Here, we report for the first time in vitro reconstitution of the respiratory supercomplexes from individual complexes III and IV. Complexes III and IV were purified from Saccharomyces cerevisiae mitochondria. Complex III contained eight molecules of cardiolipin, and complex IV contained two molecules of cardiolipin, as determined by electrospray ionization-mass spectrometry. Complex IV also contained Rcf1p. No supercomplexes were formed upon mixing of the purified complexes, and low amounts of the supercomplex trimer III₂IV₁ were formed after reconstitution into proteoliposomes containing only phosphatidylcholine and phosphatidylethanolamine. Further addition of cardiolipin to the proteoliposome reconstitution mixture resulted in distinct formation of both the III₂IV₁ supercomplex trimer and III₂IV₂ supercomplex tetramer. No other anionic phospholipid was as effective as cardiolipin in supporting tetramer formation. Phospholipase treatment of complex IV prevented trimer formation in the absence of cardiolipin. Both trimer and tetramer formations were restored by cardiolipin. Analysis of the reconstituted tetramer by single particle electron microscopy confirmed native organization of individual complexes within the supercomplex. In conclusion, although some trimer formation occurred dependent only on tightly bound cardiolipin, tetramer formation required additional cardiolipin. This is consistent with the high cardiolipin content in the native tetramer. The dependence on cardiolipin for supercomplex formation suggests that changes in cardiolipin levels resulting from changes in physiological conditions may control the equilibrium between individual respiratory complexes and supercomplexes in vivo.     

Purification of Active Respiratory Supercomplex from Bovine Heart Mitochondria Enables Functional Studies

To understand the roles of mitochondrial respiratory chain supercomplexes, methods for consistently separating and preparing supercomplexes must be established. To this end, we solubilized supercomplexes from bovine heart mitochondria with digitonin and then replaced digitonin with amphipol (A8–35), an amphiphilic polymer. Afterward, supercomplexes were separated from other complexes by sucrose density gradient centrifugation. Twenty-six grams of bovine myocardium yielded 3.2 mg of amphipol-stabilized supercomplex. The purified supercomplexes were analyzed based on their absorption spectra as well as Q₁₀ (ubiquinone with ten isoprene units) and lipid assays. The supercomplex sample did not contain cytochrome c but did contain complexes I, III, and IV at a ratio of 1:2:1, 6 molecules of Q₁₀, and 623 atoms of phosphorus. When cytochrome c was added, the supercomplex exhibited KCN-sensitive NADH oxidation; thus, the purified supercomplex was active. Reduced complex IV absorbs at 444 nm, so we measured the resonance Raman spectrum of the reduced amphipol-solubilized supercomplex and the mixture of amphipol-solubilized complexes I₁, III₂, and IV₁ using an excitation wavelength of 441.6 nm, allowing measurement precision comparable with that obtained for complex IV alone. Use of the purified active sample provides insights into the effects of supercomplex formation.     

Megacomplex organization of the oxidative phosphorylation system by structural analysis of respiratory supercomplexes from potato

The individual protein complexes of the oxidative phosphorylation system (OXPHOS complexes I to V) specifically interact and form defined supramolecular structures, the so-called “respiratory supercomplexes”. Some supercomplexes appear to associate into larger structures, or megacomplexes, such as a string of dimeric ATP synthase (complex V₂). A row-like organization of OXPHOS complexes I, III and IV into respiratory strings has also been proposed. These transient strings cannot be purified after detergent solubilization. Hence the shape and composition of the respiratory string was approached by an extensive structural characterization of all its possible building blocks, which are the supercomplexes. About 400,000 molecular projections of supercomplexes from potato mitochondria were processed by single particle electron microscopy. We obtained two-dimensional projection maps of at least five different supercomplexes, including the supercomplex I + III₂, III₂ + IV₁, V₂, I + III₂ + IV₁ and I₂ + III₂ in different types of position. From these maps the relative position of the individual complexes in the largest unit, the I₂ + III₂ + IV₂ supercomplex, could be determined in a coherent way. The maps also show that the I + III₂ + IV₁ supercomplex, or respirasome, differs from its counterpart in bovine mitochondria. The new structural features allow us to propose a consistent model of the respiratory string, composed of repeating I₂ + III₂ + IV₂ units, which is in agreement with dimensions observed in former freeze-fracture electron microscopy data.     

Taz1, an outer mitochondrial membrane protein, affects stability and assembly of inner membrane protein complexes: implications for Barth Syndrome

The Saccharomyces cerevisiae Taz1 protein is the orthologue of human Tafazzin, a protein that when inactive causes Barth Syndrome (BTHS), a severe inherited X-linked disease. Taz1 is a mitochondrial acyltransferase involved in the remodeling of cardiolipin. We show that Taz1 is an outer mitochondrial membrane protein exposed to the intermembrane space (IMS). Transport of Taz1 into mitochondria depends on the receptor Tom5 of the translocase of the outer membrane (TOM complex) and the small Tim proteins of the IMS, but is independent of the sorting and assembly complex (SAM). TAZ1 deletion in yeast leads to growth defects on nonfermentable carbon sources, indicative of a defect in respiration. Because cardiolipin has been proposed to stabilize supercomplexes of the respiratory chain complexes III and IV, we assess supercomplexes in taz1delta mitochondria and show that these are destabilized in taz1Delta mitochondria. This leads to a selective release of a complex IV monomer from the III2IV2 supercomplex. In addition, assembly analyses of newly imported subunits into complex IV show that incorporation of the complex IV monomer into supercomplexes is affected in taz1Delta mitochondria. We conclude that inactivation of Taz1 affects both assembly and stability of respiratory chain complexes in the inner membrane of mitochondria.     

Mitochondrial respiratory chain supercomplexes are destabilized in Barth Syndrome patients

Mutations in the human TAZ gene are associated with Barth Syndrome, an often fatal X-linked disorder that presents with cardiomyopathy and neutropenia. The TAZ gene encodes Tafazzin, a putative phospholipid acyltranferase that is involved in the remodeling of cardiolipin, a phospholipid unique to the inner mitochondrial membrane. It has been shown that the disruption of the Tafazzin gene in yeast (Taz1) affects the assembly and stability of respiratory chain Complex IV and its supercomplex forms. However, the implications of these results for Barth Syndrome are restricted due to the additional presence of Complex I in humans that forms a supercomplex with Complexes III and IV. Here, we investigated the effects of Tafazzin, and hence cardiolipin deficiency in lymphoblasts from patients with Barth Syndrome, using blue-native polyacrylamide gel electrophoresis. Digitonin extraction revealed a more labile Complex I/III(2)/IV supercomplex in mitochondria from Barth Syndrome cells, with Complex IV dissociating more readily from the supercomplex. The interaction between Complexes I and III was also less stable, with decreased levels of the Complex I/III(2) supercomplex. Reduction of Complex I holoenzyme levels was observed also in the Barth Syndrome patients, with a corresponding decrease in steady-state subunit levels. We propose that the loss of mature cardiolipin species in Barth Syndrome results in unstable respiratory chain supercomplexes, thereby affecting Complex I biogenesis, respiratory activities and subsequent pathology.     

Calcium and mitochondrial metabolism in ceramide-induced cardiomyocyte death

Ceramides are important intermediates in the biosynthesis and degradation of sphingolipids that regulate numerous cellular processes, including cell cycle progression, cell growth, differentiation and death. In cardiomyocytes, ceramides induce apoptosis by decreasing mitochondrial membrane potential and promoting cytochrome-c release. Ca^2 + overload is a common feature of all types of cell death. The aim of this study was to determine the effect of ceramides on cytoplasmic Ca^2 + levels, mitochondrial function and cardiomyocyte death. Our data show that C₂-ceramide induces apoptosis and necrosis in cultured cardiomyocytes by a mechanism involving increased Ca^2 + influx, mitochondrial network fragmentation and loss of the mitochondrial Ca^2 + buffer capacity. These biochemical events increase cytosolic Ca^2 + levels and trigger cardiomyocyte death via the activation of calpains.     

An in situ study of bioenergetic properties of human colorectal cancer: The regulation of mitochondrial respiration and distribution of flux control among the components of ATP synthasome

The aim of this study is to characterize the function of mitochondria and main energy fluxes in human colorectal cancer (HCC) cells. We have performed quantitative analysis of cellular respiration in post-operative tissue samples collected from 42 cancer patients. Permeabilized tumor tissue in combination with high resolution respirometry was used.Our results indicate that HCC is not a pure glycolytic tumor and the oxidative phosphorylation (OXPHOS) system may be the main provider of ATP in these tumor cells. The apparent Michaelis–Menten constant (K_m) for ADP and maximal respiratory rate (V_m) values were calculated for the characterization of the affinity of mitochondria for exogenous ADP: normal colon tissue displayed low affinity (K_m = 260 ± 55 μM) whereas the affinity of tumor mitochondria was significantly higher (K_m = 126 ± 17 μM). But concurrently the V_m value of the tumor samples was 60–80% higher than that in control tissue. The reason for this change is related to the increased number of mitochondria. Our data suggest that in both HCC and normal intestinal cells tubulin β-II isoform probably does not play a role in the regulation of permeability of the MOM for adenine nucleotides.The mitochondrial creatine kinase energy transfer system is not functional in HCC and our experiments showed that adenylate kinase reactions could play an important role in the maintenance of energy homeostasis in colorectal carcinomas instead of creatine kinase.Immunofluorescent studies showed that hexokinase 2 (HK-2) was associated with mitochondria in HCC cells, but during carcinogenesis the total activity of HK did not change. Furthermore, only minor alterations in the expression of HK-1 and HK-2 isoforms have been observed.Metabolic Control analysis showed that the distribution of the control over electron transport chain and ATP synthasome complexes seemed to be similar in both tumor and control tissues. High flux control coefficients point to the possibility that the mitochondrial respiratory chain is reorganized in some way or assembled into large supercomplexes in both tissues.     

Acute effects of cocaine,morphine and their combination on bioenergetic function and susceptibility to oxidative stress of rat liver mitochondria

AimsCocaine and heroin are frequently co-abused in a combination known as speedball. Despite the relevance of the liver in the metabolism and detoxification of these drugs, little is known about the impact of speedball on liver function.Main methodsIn this work, we evaluated the effects of cocaine, morphine and morphine + cocaine (Mor + Coc) combination (1:1) in isolated rat liver mitochondria, upon glutamate/malate or succinate energization, on bioenergetics and oxidative stress-related parameters by using Clark O₂, Ca^2 +, TPP⁺ and pH electrodes and by measuring thiobarbituric acid reactive substances (TBARS) and H₂O₂ production.Key findingsCocaine and Mor + Coc at the higher concentrations (1 mM) similarly increased O₂ consumption at state 2, state 4 and state oligomycin. In these conditions, maximum respiration was decreased only upon glutamate/malate energization, suggesting an involvement of complex I. Morphine (1 mM) only increased state 2 respiration. Cocaine and Mor + Coc induced a similar decrease in maximum mitochondrial membrane potential and in ADP-induced depolarization, whereas morphine had no effect. The drugs and their combination similarly decreased mitochondrial ATPase activity and had no effect on Ca^2 +-induced permeability transition. Morphine and Mor + Coc prevented lipid peroxidation, since in these conditions there was a decrease in O₂ consumption and in TBARS upon ADP/Fe^2 + stimulus, and a decrease in H₂O₂ formation, suggesting an antioxidant effect. Interestingly, heroin did not share morphine antioxidant properties.SignificanceOur results show that the sequential direct exposure of liver mitochondria to morphine and cocaine does not alter the effects observed in the presence of each drug alone.     

C11orf83, a Mitochondrial Cardiolipin-Binding Protein Involved in bc1 Complex Assembly and Supercomplex Stabilization

Mammalian mitochondria may contain up to 1,500 different proteins, and many of them have neither been confidently identified nor characterized. In this study, we demonstrated that C11orf83, which was lacking experimental characterization, is a mitochondrial inner membrane protein facing the intermembrane space. This protein is specifically associated with the bc₁ complex of the electron transport chain and involved in the early stages of its assembly by stabilizing the bc₁ core complex. C11orf83 displays some overlapping functions with Cbp4p, a yeast bc₁ complex assembly factor. Therefore, we suggest that C11orf83, now called UQCC3, is the functional human equivalent of Cbp4p. In addition, C11orf83 depletion in HeLa cells caused abnormal crista morphology, higher sensitivity to apoptosis, a decreased ATP level due to impaired respiration and subtle, but significant, changes in cardiolipin composition. We showed that C11orf83 binds to cardiolipin by its α-helices 2 and 3 and is involved in the stabilization of bc₁ complex-containing supercomplexes, especially the III₂/IV supercomplex. We also demonstrated that the OMA1 metalloprotease cleaves C11orf83 in response to mitochondrial depolarization, suggesting a role in the selection of cells with damaged mitochondria for their subsequent elimination by apoptosis, as previously described for OPA1.     

Genetic variability of respiratory complex abundance,organization and activity in mouse brain

Mitochondrial dysfunction is implicated in the etiology and pathogenesis of numerous human disorders involving tissues with high energy demand. Murine models are widely used to elucidate genetic determinants of phenotypes relevant to human disease, with recent studies of C57BL/6J (B6), DBA/2J (D2) and B6xD2 populations implicating naturally occurring genetic variation in mitochondrial function/dysfunction. Using blue native polyacrylamide gel electrophoresis, immunoblots and in‐gel activity analyses of complexes I, II, III, IV and V, our studies are the first to assess abundance, organization and catalytic activity of mitochondrial respiratory complexes and supercomplexes in mouse brain. Remarkable strain differences in supercomplex assembly and associated activity are evident, without differences in individual complexes I, II, III or IV. Supercomplexes I₁III₂IV_2–3 exhibit robust complex III immunoreactivity and activities of complexes I and IV in D2, but with little detected in B6 for I₁III₂IV₂, and I₁III₂IV₃ is not detected in B6. I₁III₂IV₁ and I₁III₂ are abundant and catalytically active in both strains, but significantly more so in B6. Furthermore, while supercomplex III₂IV₁ is abundant in D2, none is detected in B6. In aggregate, these results indicate a shift toward more highly assembled supercomplexes in D2. Respiratory supercomplexes are thought to increase electron flow efficiency and individual complex stability, and to reduce electron leak and generation of reactive oxygen species. Our results provide a framework to begin assessing the role of respiratory complex suprastructure in genetic vulnerability and treatment for a wide variety of mitochondrial‐related disorders .     

Enhanced charge-independent mitochondrial free Ca2 + and attenuated ADP-induced NADH oxidation by isoflurane: Implications for cardioprotection

Modulation of mitochondrial free Ca^2 + ([Ca^2 +]_m) is implicated as one of the possible upstream factors that initiates anesthetic-mediated cardioprotection against ischemia–reperfusion (IR) injury. To unravel possible mechanisms by which volatile anesthetics modulate [Ca^2 +]_m and mitochondrial bioenergetics, with implications for cardioprotection, experiments were conducted to spectrofluorometrically measure concentration-dependent effects of isoflurane (0.5, 1, 1.5, 2 mM) on the magnitudes and time-courses of [Ca^2 +]_m and mitochondrial redox state (NADH), membrane potential (ΔΨ_m), respiration, and matrix volume. Isolated mitochondria from rat hearts were energized with 10 mM Na⁺- or K⁺-pyruvate/malate (NaPM or KPM) or Na⁺-succinate (NaSuc) followed by additions of isoflurane, 0.5 mM CaCl₂ (≈ 200 nM free Ca^2 + with 1 mM EGTA buffer), and 250 μM ADP. Isoflurane stepwise: (a) increased [Ca^2 +]_m in state 2 with NaPM, but not with KPM substrate, despite an isoflurane-induced slight fall in ΔΨ_m and a mild matrix expansion, and (b) decreased NADH oxidation, respiration, ΔΨ_m, and matrix volume in state 3, while prolonging the duration of state 3 NADH oxidation, respiration, ΔΨ_m, and matrix contraction with PM substrates. These findings suggest that isoflurane's effects are mediated in part at the mitochondrial level: (1) to enhance the net rate of state 2 Ca^2 + uptake by inhibiting the Na⁺/Ca^2 + exchanger (NCE), independent of changes in ΔΨ_m and matrix volume, and (2) to decrease the rates of state 3 electron transfer and ADP phosphorylation by inhibiting complex I. These direct effects of isoflurane to increase [Ca^2 +]_m, while depressing NCE activity and oxidative phosphorylation, could underlie the mechanisms by which isoflurane provides cardioprotection against IR injury at the mitochondrial level.     

Importance of the core structure of flavones in promoting inhibition of the mitochondrial respiratory chain

Flavonoids are a large group of polyphenolic compounds that have received considerable attention because of their biological and physiological importance. The flavone (2-phenyl-4H-1-benzopyran-4one) used in this work is found in some cereal grains and generates several biological activities, including: apoptosis induction, cell cycle arrest, caspase activation and inhibition of tumor cell proliferation. However, its effects on the hepatic mitochondrial metabolism are still unknown. We evaluated the effect of flavone on the metabolism of mitochondria isolated from rat liver. Polarographic experiments using 200 μmol L^?1 flavone and rat liver mitochondria oxidizing glutamate or succinate indicated that both substrates underwent: (i) reduction of state 3 respiration; (ii) stimulation of state 4 respiration; (iii) reduction of the respiratory control coefficient; and (iv) reduction of the ADP/O ratio. An analysis of the activity of enzymatic complexes in the respiratory chain showed that flavone acts between complexes I and III. Flavone reduced the membrane electric potential at doses of 100, 150 and 200 μmol L^?1. Flavone at certain doses (75–200 μmol L^?1) reduced mitochondrial swelling in the presence of valinomycin and KNO₃, suggesting that flavone could induce changes in mitochondrial membrane properties. These results demonstrate that the inhibition of mitochondrial enzymes in the respiratory chain coupled with the effects on membrane properties are promoted by the core structure of flavones, and these effects may be in part responsible for the cytotoxic effects of flavones.     

Induction of mitochondrial biogenesis protects against caspase-dependent and caspase-independent apoptosis in L6 myoblasts

Apoptotic signaling plays an important role in skeletal muscle degradation, atrophy, and dysfunction. Mitochondria are central executers of apoptosis by directly participating in caspase-dependent and caspase-independent cell death signaling. Given the important apoptotic role of mitochondria, altering mitochondrial content could influence apoptosis. Therefore, we examined the direct effect of modest, but physiological increases in mitochondrial biogenesis and content on skeletal muscle apoptosis using a cell culture approach. Treatment of L6 myoblasts with SNAP or AICAR (5 h/day for 5 days) significantly increased PGC-1, AIF, cytochrome c, and MnSOD protein content as well as MitoTracker staining. Following induction of mitochondrial biogenesis, L6 myoblasts displayed decreased sensitivity to apoptotic cell death as well as reduced caspase-3 and caspase-9 activation following exposure to staurosporine (STS) and C2-ceramide. L6 myoblasts with higher mitochondrial content also exhibited reduced apoptosis and AIF release following exposure to hydrogen peroxide (H₂O₂). Analysis of several key apoptosis regulatory proteins (ARC, Bax, Bcl-2, XIAP), antioxidant proteins (catalase, MnSOD, CuZnSOD), and reactive oxygen species (ROS) measures (DCF and MitoSOX fluorescence) revealed that these mechanisms were not responsible for the observed cellular protection. However, myoblasts with higher mitochondrial content were less sensitive to Ca^2 +-induced mitochondrial permeability transition pore formation (mPTP) and mitochondrial membrane depolarization. Collectively, these data demonstrate that increased mitochondrial content at physiological levels provides protection against apoptotic cell death by decreasing caspase-dependent and caspase-independent signaling through influencing mitochondrial Ca^2 +-mediated apoptotic events. Therefore, increasing mitochondrial biogenesis/content may represent a potential therapeutic approach in skeletal muscle disorders displaying increased apoptosis.     

Aim24 stabilizes respiratory chain supercomplexes and is required for efficient respiration

The mitochondrial respiratory chain is essential for the conversion of energy derived from the oxidation of metabolites into the membrane potential, which drives the synthesis of ATP. The electron transporting complexes bc₁ complex and the cytochrome c oxidase assemble into large supercomplexes, allowing efficient energy transduction. Currently, we have only limited information about what determines the structure of the supercomplex. Here, we characterize Aim24 in baker’s yeast as a protein, which is integrated in the mitochondrial inner membrane and is required for the structural integrity of the supercomplex. Deletion of AIM24 strongly affects activity of the respiratory chain and induces a growth defect on non-fermentable medium. Our data indicate that Aim24 has a function in stabilizing the respiratory chain supercomplexes.     

Structures,magnetic properties,and XPS of cyanide-bridged NdIII/SmIII/GdIII–CrIII complexes

Synthesis, structural characterization, and spectroscopic and magnetic properties of three new cyano-bridged 3d–4f bimetallic complexes, Ln^III(DMF)₄(H₂O)₃Cr^III (CN)₆ · nH₂O (Ln = Nd, Sm, Gd), have been described. The Nd–Cr complex crystallizes in the monoclinic P2₁/n space group with the following unit cell parameters: a = 20.063(7) Å, b = 8.967(4) Å, c = 18.023(6) Å, b = 96.12(3)°, V = 3224(2) Å³, and Z = 4. The neodymium (III) ion, which adopts anti-prism eight-coordination environment, is linked to the [Cr^III(CN)₆]³⁻ moiety through a bridging cyanide ligand with Nd–N = 2.550(4) Å and Nd–N–C = 164.4(4)°. The variable-temperature (0.5 T at 2–300 K) and variable-field (0–5 T at 2 and 5 K) magnetic measurements reveal that the weak interaction of Gd–Cr complexes differs from that of Nd–Cr and Sm–Cr ones mainly because of the lack of orbital angular momentum. The XPS and diffuse reflectance electronic spectra were also measured to discuss charge transfer transitions concerning π-backdonation from the viewpoint of magneto-optical functions.     

Synthesis,crystal structures and properties of three new lanthanide 2,6-pyridinedicarboxylate complexes with zero-dimensional structure

Three new lanthanide dipicolinate complexes with zero-dimensional structure have been synthesized by mild hydrothermal method. In these complexes the lanthanide is surrounded by three dipicolinate groups in the usual tridentate mode. For two of them, (CN₃H₆)₃[La(C₇H₃NO₄)₃] · 3H₂O I and (C₄N₂H₁₂)_1.5[Ce(C₇H₃NO₄)₃] · 7H₂O II, the dipicolinate groups are wholly unprotonated. The resulting molecular entity is three-times negatively charged and the balance charge is insured by the presence of guanidinium or piperazinium ions for the first and second, respectively. For the third complex, [Eu(C₇H₄NO₄)₃]₂ · 2.5H₂O III, one hydrogen atom remains globally on each dipicolinate and so the molecular entities are neutral. For the latter complex, the resulting molecular entities are connected into chains through strong hydrogen bonding. Thermogravimetric analyses and luminescent behaviour of complex III have been carried out.     

Mitochondrial bioenergetics deregulation caused by long-chain 3-hydroxy fatty acids accumulating in LCHAD and MTP deficiencies in rat brain: A possible role of mPTP opening as a pathomechanism in these disorders?

Long-chain 3-hydroxylated fatty acids (LCHFA) accumulate in long-chain 3-hydroxy-acyl-CoA dehydrogenase (LCHAD) and mitochondrial trifunctional protein (MTP) deficiencies. Affected patients usually present severe neonatal symptoms involving cardiac and hepatic functions, although long-term neurological abnormalities are also commonly observed. Since the underlying mechanisms of brain damage are practically unknown and have not been properly investigated, we studied the effects of LCHFA on important parameters of mitochondrial homeostasis in isolated mitochondria from cerebral cortex of developing rats. 3-Hydroxytetradecanoic acid (3 HTA) reduced mitochondrial membrane potential, NAD(P)H levels, Ca^2 + retention capacity and ATP content, besides inducing swelling, cytochrome c release and H₂O₂ production in Ca^2 +-loaded mitochondrial preparations_. We also found that cyclosporine A plus ADP, as well as ruthenium red, a Ca^2 + uptake blocker, prevented these effects, suggesting the involvement of the mitochondrial permeability transition pore (mPTP) and an important role for Ca^2 +, respectively. 3-Hydroxydodecanoic and 3-hydroxypalmitic acids, that also accumulate in LCHAD and MTP deficiencies, similarly induced mitochondrial swelling and decreased ATP content, but to a variable degree pending on the size of their carbon chain. It is proposed that mPTP opening induced by LCHFA disrupts brain bioenergetics and may contribute at least partly to explain the neurologic dysfunction observed in patients affected by LCHAD and MTP deficiencies.