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PubMed2002

Dicopper(II) complexes of H-BPMP-type ligands: pH-induced changes of redox, spectroscopic ((19)F NMR studies of fluorinated complexes), structural properties, and catecholase activities.

Substitution of the methyl group from the H-BPMP (HL(CH)3) ligand (2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenol) by electron withdrawing (F or CF(3)) or electron donating (OCH(3)) groups afforded a series of dinucleating ligand (HL(OCH)3, HL(F), HL(CF)3), allowing one to understand the changes in the properties of the corresponding dicopper complexes. Dinuclear Cu(II) complexes have been synthesized and characterized by spectroscopic (UV-vis, EPR, (1)H NMR) as well as electrochemical techniques and, in some cases, by single-crystal X-ray diffraction: [Cu(2)(L(OCH)3)(muOH)][(ClO(4))(2)].C(4)H(8)O, [Cu(2)(L(F))(muOH)][(ClO(4))(2)], [Cu(2)(L(F))(H(2)O)(2)][(ClO(4))(3)].C(3)D(6)O, and [Cu(2)(L(CF)3)(H(2)O)(2)][(ClO(4))(3)].4H(2)O. Significant differences are observed for the Cu-Cu distance in the two mu-hydroxo complexes (2.980 A (R = OCH(3)) and 2.967 A (R = F)) compared to the two bis aqua complexes (4.084 A (R = F) and 4.222 A (R = CF(3))). The mu-hydroxo and bis aqua complexes are reversibly interconverted upon acid/base titration. In basic medium, new species are reversibly formed and identified as the bis hydroxo complexes except for the complex from HL(CF)3 which is irreversibly transformed near pH = 10. pH-driven interconversions have been studied by UV-vis, EPR, and (1)H NMR, and the corresponding pK are determinated. In addition, with the fluorinated complexes, the changes in the coordination sphere around the copper centers and in their redox states are evidenced by the fluorine chemical shift changes ((19)F NMR). For all the complexes described here, investigations of the catechol oxidase activities (oxidation of 3,5-di-tert-butylcatechol to the corresponding quinone) are of interest in modeling the catecholase enzyme active site and in understanding aspects of structure/reactivity. These studies show the pH-dependence for the catalytic abilities of the complexes, related with changes in the coordination sphere of the metal centers: only the mu-hydroxo complexes from HL(CH)3, HL(F), and HL(OCH)3 exhibit a catecholase activity. Modification on R-substituent induces a drastic effect on the catecholase activity: the presence of an electron donating group on the ligand increases this activity; the reverse effect is observed with an electron withdrawing group.

Catalysis↗
PubMed2000

Helical-chain copper(II) complexes and a cyclic tetranuclear copper(II) complex with single syn-anti carboxylate bridges and ferromagnetic exchange interactions.

Tridentate Schiff-base carboxylate-containing ligands, derived from the condensation of 2-imidazolecarboxaldehyde with the amino acids beta-alanine (H2L1) and 2-aminobenzoic acid (H2L5) and the condensation of 2-pyridinecarboxaldehyde with beta-alanine (HL2), D,L-3-aminobutyric acid (HL3), and 4-aminobutyric acid (HL4), react with copper(II) perchlorate to give rise to the helical-chain complexes [[Cu(mu-HL1)(H2O)](ClO4)]n (1), [[Cu(mu-L2)(H2O)](ClO4).2H2O]n (2), and [[Cu(mu-L3)(H2O)](ClO4).2H2O]n (3), the tetranuclear complex [[Cu(mu-L4)(H2O)](ClO4)]4 (4), and the mononuclear complex [Cu(HL5)(H2O)](ClO4).1/2H2O (5). The reaction of copper(II) chloride with H2L1 leads not to a syn-anti carboxylate-bridged compound but to the chloride-bridged dinuclear complex [Cu(HL1)(mu-Cl)]2 (6). The structures of these complexes have been solved by X-ray crystallography. In complexes 1-4, roughly square-pyramidal copper(II) ions are sequentially bridged by syn-anti carboxylate groups. Copper(II) ions exhibit CuN2O3 coordination environments with the three donor atoms of the ligand and one oxygen atom belonging to the carboxylate group of an adjacent molecule occupying the basal positions and an oxygen atom (from a water molecule in the case of compounds 1-3 and from a perchlorate anion in 4) coordinated in the apical position. Therefore, carboxylate groups are mutually cis oriented and each syn-anti carboxylate group bridges two copper(II) ions in basal-basal positions with Cu...Cu distances ranging from 4.541 A for 4 to 5.186 A for 2. In complex 5, the water molecule occupies an equatorial position in the distorted octahedral environment of the copper(II) ion and the Cu-O carboxylate distances in axial positions are very large (>2.78 A). Therefore, this complex can be considered as mononuclear. Complex 6 exhibits a dinuclear parallel planar structure with Ci symmetry. Copper(II) ions display a square-pyramidal coordination geometry (tau = 0.06) for the N2OCl2 donor set, where the basal coordination sites are occupied by one of the bridging chlorine atoms and the three donor atoms of the tridentate ligand and the apical site is occupied by the remaining bridging chlorine atom. Magnetic susceptibility measurements indicate that complexes 1-4 exhibit weak ferromagnetic interactions whereas a weak antiferromagnetic coupling has been established for 6. The magnetic behavior can be satisfactorily explained on the basis of the structural data for these and related complexes.

Journal Article↗
PubMed1994

Isolation of lipoprotein-proteoglycan complexes from balloon catheter deendothelialized aortas and the uptake of these complexes by blood monocyte-derived macrophages.

Lipoprotein-Proteoglycan (LP-PG) complexes from the neointima, developed in response to injury, were studied to examine their ability to stimulate lipid accumulation in blood monocyte-derived macrophages (BMDM). LP-PG complexes were extracted from intimal-medial tissues from normal and balloon catheter deendothelialized aortas of normocholesterolemic rabbits, in 0.16 M NaCl for 24 h at 4 degrees C. The extract was purified through an anti-apo-B affinity column. Adsorbed material dissociated with 4 M Gu-HCI buffer was analyzed for lipoproteins (LP) and glycosaminoglycans (GAG). Results demonstrated that LP-PG complexes consisted of apo-B associated with chondroitin sulfate and hyaluronic acid. BMDM were incubated with 125I-LP, 125I-LP-NPG (from normal aortas) or 125I-LP-IPG (from injured aortas) for 20 h at 37 degrees C. LP binding, internalization and degradation was markedly increased for LP-NPG and LP-IPG over native LP. Phagocytosis appeared to be the primary route of uptake of LP-PG complexes. Competition experiments indicated that about 40% of the uptake of LP-PG complexes is mediated by the apo-B/E receptor pathway. The scavenger receptor played a minor part in the uptake of LP-PG complexes. Data from this study indicate that LP-PG complexes are present in normal and injured aortas of normocholesterolemic rabbits and these complexes accelerate LP uptake by BMDM more than native LP. Therefore, LP-PG complexes may contribute to lipid accumulation by BMDM, thus generating foam cells. Furthermore, LP-PG complexes prepared from PG of injured aortas are more effective in lipid accumulation than LP-PG complexes from PG of normal aortas.

Animals↗
PubMed1992

Biochemical evidence for the rapid assembly and disassembly of processed antigen-major histocompatibility complex class II complexes in acidic vesicles of B cells.

Helper T cell recognition of antigen requires that it be processed within antigen-presenting cells (APC) to peptide fragments that subsequently bind to major histocompatibility complex (MHC) class II molecules and are displayed on the APC surface. Heretofore, processed antigen-MHC class II complexes have been detected by functional assays, measuring the activation of specific T cells. We now report direct, biochemical evidence for the assembly of processed antigen-MHC class II complexes within splenic B cells as APC. The I-Ek MHC class II molecules were immunoprecipitated from B cells that had processed the model protein antigen cytochrome c radiolabeled across its entire length by reductive methylation of lysine residues and covalently coupled to Ig-specific antibodies, allowing internalization after binding to surface Ig. Our previous studies showed that I-Ek immunoaffinity purified from B cells that had processed cytochrome c contains functional processed antigen--MHC class II complexes and that approximately 0.2% of the I-Ek molecules are specifically associated with one of two predominant processed antigenic fragments. Here we show that these complexes are rapidly assembled, within 30-60 min after antigen binding to surface Ig on splenic B cells. Maximal numbers of complexes are assembled by 2 h in a process that is sensitive to acidic vesicle inhibitors but not to inhibitors of protein synthesis. The processed antigen-I-Ek complexes have a relatively short half-life of 2-4 h and are disassembled or degraded within 8 h after antigen is first internalized. The disassembly or degradation of the processed antigen-I-Ek complexes requires acidic vesicle function, and in the presence of an acidic vesicle inhibitor the complexes are long lived. Thus, using a biochemical assay to monitor processed antigen-I-Ek complexes, we find that, in B cells, processed antigen is relatively rapidly associated in acidic vesicles with preexisting MHC class II molecules, and the complexes are disassembled 4-6 h later in processes that also require acid vesicle function.

Acids↗
PubMed1975

Relaxation complexes of poasmid DNA and protein. III. Association of protein with the 5' terminus of the broken DNA strand in the relaxed complex of plasmid ColE1.

The location of the protein in the open circular DNA form of the ColE1 DNA-protein relaxation complex, induced by treatment with sodium dodecyl sulfate, has been studied using several enzymes of DNA metabolism. Escherichia coli exonucleases I and III are able to degrade extensively the nicked strand of the relaxed complex from the 3' end. DNA polymerase I can initiate synthesis using the relaxed complex as template-primer and specifically extends the 3' end of the nicked strand. The 5' end of the sodium dodecyl sulfate-relaxed complex, however, is blocked to the 5'-3' hydrolitic action T7 exonuclease. This block remains after trypsin treatment of the sodium dodecyl sulfate-relaxed complex but is removed by Pronase treatment. T4 DNA ligase is unable to seal either the sodium dodecyl sulfate-relaxed complex or the Pronase-treated relaxed complex even after pretreatment of the relaxed complex with T4 DNA polymerase and polynucleotide kinase. However, pretreatment with DNA polymerase I and the four deoxyribonucleoside triphosphates facilitates ligase closure of the Pronase-treated relaxed complex but not the sodium dodecyl sulfate-relaxed complex. These studies indicate that the protein in the relaxed ColE1 complex is located at or near the 5' end of the nicked strand.

Bacterial Proteins↗
PubMed1991

The CD19 complex of B lymphocytes. Activation of phospholipase C by a protein tyrosine kinase-dependent pathway that can be enhanced by the membrane IgM complex.

We have investigated the mechanism by which the membrane protein complex of the B lymphocyte that contains CD19 and CR2 activates phospholipase C (PLC) to induce a rise in [CA2+]i. The CD19 complex resembled the membrane IgM complex in that three protein tyrosine kinase inhibitors suppressed increases in [Ca2+]i and inositol bisphosphate and inositol triphosphate generation. However, the activation of PLC by the CD19 complex could be distinguished from that by the membrane IgM complex by slower kinetics of generation of inositol phosphates, resistance to inhibition by activators of protein kinase C, and different pattern of tyrosine-phosphorylated cellular substrates. Western blot analysis of lysates from cells stimulated by the CD19 complex demonstrated a single new phosphotyrosine-containing protein of 85 kDa, whereas multiple other phosphotyrosine-containing proteins were present in cells activated by the mIgM complex. In particular, PLC-gamma 1, which is a substrate for the protein tyrosine kinase activated by the mIgM complex, was not tyrosine-phosphorylated in cells stimulated by the CD19 complex. Cross-linking the two complexes together caused a synergistic increase in [CA2+]i which was neither suppressed by activation of protein kinase C nor associated with increased tyrosine-phosphorylation of PLC, characteristic of the CD19 pathway. Therefore, the B cell has two signal transduction complexes, associated with membrane IgM and CD19, that activate PLC by different mechanisms and that can synergistically interact to enhance this function by the CD19 pathway.

Antigens, CD↗
PubMed1985

Fe(III).ATP complexes. Models for ferritin and other polynuclear iron complexes with phosphate.

Polynuclear iron complexes of Fe(III) and phosphate occur in seawater and soils and in cells where the iron core of ferritin, the iron storage protein, contains up to 4500 Fe atoms in a complex with an average composition of (FeO.OH)8FeO.OPO3H2. Although phosphate influences the size of the ferritin core and thus the availability of stored iron, little is known about the nature of the Fe(III)-phosphate interaction. In the present study, Fe-phosphate interactions were analyzed in stable complexes of Fe(III).ATP which, in the polynuclear iron form, had phosphate at interior sites. Such Fe(III).ATP complexes are important not only as models but also because they may play a role in intracellular iron transport and in iron toxicity; the complexes were studied by extended x-ray absorption fine structure, EPR, NMR spectroscopy, and measurement of proton release. Mononuclear iron complexes exhibiting a g' = 4.3 EPR signal were formed at Fe:ATP ratios less than or equal to 1:3, and polynuclear iron complexes (Fe greater than or equal to 250, EPR silent at g' = 4.3) were formed at an Fe:ATP ratio of 4:1. No NMR signals due to ATP were observed when Fe was in excess (Fe:ATP = 4:1). Extended x-ray absorption fine structure analysis of the polynuclear Fe(III).ATP complex was able to distinguish an Fe-P distance at 3.27 A in addition to the octahedral O at 1.95 A and 4-5 Fe atoms at 3.36 A. The Fe-O and Fe-Fe distances are the same as in ferritin, and the Fe-P distance is analogous to that in another metal-ATP complex. An observable Fe-P environment in such a large polynuclear iron cluster as the Fe(III).ATP (4:1) complex indicates that the phosphate is distributed throughout rather than merely on the surface, in contrast to earlier models of chelate-stabilized iron clusters. Complexes of Fe(III) and ATP similar to those described here may form in vivo either as normal components of intracellular iron metabolism or during iron excess where the consequent alteration of free nucleotide triphosphate pools could contribute to the observed toxicity of iron.

Adenosine Triphosphate↗
PubMed1983

Alpha-1-antitrypsin-human leukocyte elastase complexes in blood: quantification by an enzyme-linked differential antibody immunosorbent assay and comparison with alpha-2-plasmin inhibitor-plasmin complexes.

An enzyme-linked immunosorbent assay (ELISA) has been developed for the quantification of alpha 1-antitrypsin-human leukocyte elastase (alpha 1AT-E) complexes. In the ELISA, the alpha 1AT-E complex is bound to a surface by rabbit antileukocyte elastase antibody, and the inhibitor-proteinase complex is quantified by a second antibody, rabbit anti-alpha 1-antitrypsin F(ab')2, labeled with alkaline phosphatase. alpha 1AT-E complexes were detected when a final concentration of 2.2 nmol/liter of leukocyte elastase was added to plasma. The concentration of these complexes increased with additional elastase. In clotting blood, alpha 1AT-E complexes were generated in parallel with the conversion of 125I-fibrinogen to fibrin, whereas alpha 2-plasmin inhibitor-plasmin (alpha 2PI-P) complexes were not formed. The concentration of alpha 1AT-E complexes in 19 of 21 controls was less than 2.2 nmol/liter. Patients with laboratory evidence for disseminated intravascular coagulation (DIC) demonstrated elevated alpha 2PI-P complexes with either increased or normal concentrations of alpha 1AT-E complexes. Patients without evidence for DIC, but who demonstrated prolonged reptilase clotting times, were studied. This group had increased alpha 1AT-E but normal alpha 2PI-P complex levels, raising the possibility that elastase release in vivo may be accompanied by limited degradation of fibrinogen. These assays thus serve as useful probes for the study of leukocyte activation and of the interactions between cellular and plasma proteolytic enzyme systems.

Adult↗
PubMed1998

The Arabidopsis homologue of an eIF3 complex subunit associates with the COP9 complex.

The Arabidopsis COP9 complex is a multi-subunit repressor of photomorphogenesis which is conserved among multicellular organisms. Approximately 12 proteins copurify with the COP9 complex. Seven of these proteins are orthologues of subunits of the recently published mammalian COP9 complex. Four of the proteins show amino acid similarity to various subunits of the COP9 complex, eIF3 complex and 19S cap of the proteasome. We have studied one of these proteins in order to determine if it is a component of the COP9 complex. Arabidopsis p105 is highly similar to the p110 subunit of the human elF3. The p105 gene is induced during photomorphogenesis, and RNA and protein analysis reveal different tissue accumulation patterns. p105 is found in a large protein complex. p105 interacts in yeast with both COP9 and FUS6, two known components of the COP9 complex. Our results indicate that p105 is not a component of the COP9 core complex, though it may interact with components of the complex.

Amino Acid Sequence↗
PubMed1996

Deletion of a B800-850 light-harvesting complex in Rhodospirillum molischianum DSM119 leads to "revertants" expressing a B800-820 complex: insights into pigment binding.

A B800-850 light-harvesting complex (also called LH2) deficient strain of Rhodospirillum molischianum was constructed by replacing a portion of the LH2 gene cluster by a kanamycin resistance gene cartridge. The LH2 deficient strain was characterized spectroscopically and by Southern blot analysis. Surprisingly, pseudorevertants were obtained which express a B800-820 complex which could not be observed in the wild type. This B800-820 complex was isolated and characterized. It consists of an alpha- and a beta subunit with 56 and 45 amino acid residues, respectively. The amino acid sequences of both subunits are extremely similar to those of the corresponding B800-850 complex. Resonance Raman spectroscopy shows that in the B800-820 complex the two 2-acetylcarbonyl groups of the bacteriochlo-rophyll a (BChl a) molecules absorbing at 820 nm are free from hydrogen bond interactions, whereas one of the two 2-acetylcarbonyl groups of the pair of BChl a molecules absorbing at 850 nm of the B800- 850 complex is involved in hydrogen bonds. These different protein- pigment interactions are due to the replacement of alpha Trp43 in the B800-850 complex by a Phe in the B800- 820 complex. Comparison of the amino acid sequences of the B800-850 and B800-820 complexes of Rs. molischianum and Rhodopseudomonas acidophila reveals a conserved motif comprised of three amino acid residues. Molecular modeling using the known LH2 structure of Rps. acidophila Ac 10050 indicates that this motif might be important for the precise structural arrangement of the native complex and fine tuning of its spectroscopic properties.

Amino Acid Sequence↗
PubMed1981

Studies on circulating soluble immune complexes of the liver disease. 7. Immune complexes in the clinical course and their ultracentrifugal analysis.

Immune complexes were investigated in the clinical course of 35 patients with the liver disease diagnosed by clinical and laboratory criteria, including the liver biopsy. Immune complexes were assayed by use of radio-labelled polyclonal rheumatoid and C1q as reactants with immune complexes. Although the highest amounts of immune complexes were determined in a few number of sera from patients with primary biliary cirrhosis, significantly higher amounts of immune complexes were observed in sera from patients with fulminant hepatitis, liver cirrhosis, chronic aggressive hepatitis (2B), lupoid hepatitis and hepatocellular carcinoma. However, no significant increase in immune complexes was seen in the clinical course of patients with chronic aggressive hepatitis (2A), chronic persistent hepatitis and acute hepatitis. Clinical follow-up studies of patients with higher amounts of immune complexes showed significant changes in the amounts of immune complexes in parallel with clinical, biochemical and immunological variables. The ultracentrifugal analysis demonstrated that immune complexes involved in the liver disease seemed to be larger than 19s in the size, since their concentration fluctuated according to the clinical course, although smaller complexes sedimenting at 7s and those between 8s and 19s were recognized without any significant changes in the clinical course.

Antibodies, Antinuclear↗
PubMed2002

CIA30 complex I assembly factor: a candidate for human complex I deficiency?

The human mitochondrial NADH:ubiquinone oxidoreductase (complex I), the first complex of the oxidative phosphorylation system, is composed of at least 42 subunits. Little is known about the assembly process of these subunits into the mature complex. Recently, two proteins in Neurospora crassa have been found to be involved in the assembly of complex I. These proteins are not constituent parts of the mature complex but are associated with smaller intermediate complexes of the assembly process and have a chaperone-like function. We have characterized the human homologue of one of these two complex I intermediate associated proteins, named CIA30, and show that expression of the human CIA30 protein is ubiquitous with a slightly higher expression in various heart tissues, kidney, lung and liver. As deletion of the Neurospora crassa CIA genes results in severe disruption of the assembly process, human CIA30 can be considered as a candidate gene related to complex I deficiency. Thirteen patients with an isolated complex I deficiency, but who were ruled out for mutations in the 35 nuclear genes of the complex and mtDNA, were subjected to mutational analysis of the gene coding for the human CIA30 protein. Four new single nucleotide polymorphisms (SNPs) were detected but no functional mutation was found.

Amino Acid Sequence↗
PubMed1997

Memory and imprinting effects in multienzyme complexes--I. Isolation, dissociation, and reassociation of a phosphoribulokinase-glyceraldehyde-3-phosphate dehydrogenase complex from Chlamydomonas reinhardtii chloroplasts.

A bienzyme complex made up of phosphoribulokinase and glyceraldehyde-3-phosphate dehydrogenase has been isolated and purified from chloroplasts of Chlamydomonas reinhardtii. The complex contains four phosphoribulokinase and eight glyceraldehyde-3-phosphate dehydrogenase polypeptide chains. As phosphoribulokinase is dimeric and glyceraldehyde-3-phosphate dehydrogenase tetrameric, it is concluded that the complex comprises two phosphoribulokinase and two glyceraldehyde-3-phosphate dehydrogenase molecules. Its overall molecular mass is 460 kDa, which is in excellent agreement with its stoichiometry. Moreover, owing to the nature of the two enzymes, this complex must catalyse two nonconsecutive reactions. The bienzyme complex tended to spontaneously dissociate into the free enzymes upon dilution. This dissociation process was considerably promoted by reducing agents such as dithiothreitol or reduced thioredoxin. The kinetics of the dissociation process induced by dithiothreitol or reduced thioredoxin were paralleled by an increase of activity of phosphoribulokinase. The dissociation of the complex was reversible. If oxidized phosphoribulokinase and glyceraldehyde-3-phosphate dehydrogenase were mixed, a certain amount of the complex was formed. The reconstituted complex displayed properties that were indistinguishable from those of the native complex extracted from chloroplasts of Chlamydomonas reinhardtii. These results suggest that the concentration of the complex in vivo must vary depending on the light intensity.

Animals↗
PubMed1979

Soluble oligovalent antigen--antibody complexes. II. The effect of various selective forces upon relative stability of isolated complexes.

Soluble oligovalent antigen--antibody complexes were isolated and analysed by ultracentrifugation to assess the effect of several forces upon the composition and stability of soluble complexes. Complexes were prepared with fluorescein (F) conjugates of rabbit serum albumin (RSA) or thyroglobulin (RTg) and high affinity rabbit anti-F antibodies. Isolated complexes containing two antigen molecules (Ag2 complexes) tended to dissociate and form an equilibrium with complexes containing one antigen molecule (Ag1 complexes). This equilibrium was thermolabile, concentration dependent and affected by the original combining ratio and the area in the gradient from which complexes were harvested. Small amounts of free antibody dissociated from soluble complexes also to form a dynamic equilibrium; this equilibrium was much less affected by the above parameters. The data support the concept that complexes grow in size by a process analogous to polymerization of simple subunits and that the driving forces for polymerization are of a lower order of magnitude and more affected by physical variables than the primary reaction between antibody and its antigen.

Antibody Affinity↗
PubMed1994

The role of major histocompatibility complex and non-major histocompatibility complex encoded antigens in generation of bile duct lesions during hepatic graft-vs.-host responses mediated by helper or cytotoxic T cells.

In these studies, we examined the role of discrete classes of alloantigen differences in generating nonsuppurative cholangitis during graft-vs.-host disease. Transfer of C57BL/6J (B6) splenocytes to class I major histocompatibility complex-disparate bm1 x B6 F1, class II major histocompatibility complex-disparate B6 x bm12 F1, or multiple non-major histocompatibility complex antigen-disparate Balb,B x B6 F1 mice led to the development of periportal inflammatory infiltrates and lymphocyte invasion of bile duct walls. However, frank destruction of bile duct walls was observed only in strain combinations with class I major histocompatibility complex or multiple non-major histocompatibility complex-encoded disparities. The concomitant presence of class II major histocompatibility complex differences and class I major histocompatibility complex or multiple non-major histocompatibility complex differences did not increase and in some cases was associated with less severe bile duct disease than was observed in strain combinations with discrete histocompatibility antigen differences. Depletion of L-leucyl-L-leucine methyl ester-sensitive cytotoxic T lymphocytes from donor inocula reduced the incidence of destructive bile duct lesions observed early in the course of graft-vs.-host disease in B6-->Balb.B x B6 F1 or B6-->bm1 x B6 F1 mice. However, transfer of CD8-negative, L-leucyl-L-leucine methyl ester-resistant T helper cells alone was sufficient to generate destructive cholangitis in class I+II major histocompatibility complex-disparate or multiple non-major histocompatibility complex antigen-disparate strain combinations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Chemical probes for water-oxidation: synthetic manganese complexes in photoactivation of water splitting complex and as exogenous electron donors to photosystem II.

Photoactivation of the water splitting enzyme was performed with 13 different synthetic manganese complexes and characterized by oxygen evolution yield, thermoluminescence and chlorophyll fluorescence induction kinetics. The efficiency of different compounds in photoactivation correlated with the rate of linear electron transport in the presence of these compounds. The organic ligands, associated with the manganese ions, do not prevent the photoactivation of the water splitting complex (WOC). Photoactivation with different manganese complexes depended on the number of the Mn-ions in the complex, their valence state and the nature of their donor atoms. The most efficient restorations were achieved by using tetrameric complexes having a dimer+dimer structure, complexes containing Mn(II) ions, and having 4-6 oxygen and 0-2 nitrogen atoms as donor atoms. Further, the effectiveness of photoactivation depended largely on the structure of the complexes. Our data support the notion that WOC in intact thylakoids requires the cooperation and well determined arrangement of all four manganese ions, and argue against the hypothesis that two manganese ions are sufficient for water splitting. Photoactivation by some complexes led to anomalous flash-oxygen patterns, which are explained by a modified/perturbed water splitting complex.

Chlorides↗
PubMed1999

Impaired energy metabolism in hearts of septic baboons: diminished activities of Complex I and Complex II of the mitochondrial respiratory chain.

Recent findings support the view that the bioenergetic part of septic organ failure is not caused by insufficient supply of oxygen but by disturbances of the mitochondrial function. Therefore, the aim of the present study was to investigate key enzymes of energy metabolism in septic hearts to answer the question whether or not impairment of mitochondrial or glycolytic enzymes occur under these conditions. For this purpose the well established model of septic baboons was used. Baboons under general anesthesia were made septic by infusion of Escherichia coli. Single challenge with infusion of high amounts of bacteria was compared with a multiple challenge protocol (less bacteria infused). Some animals obtained no E. coli (sham). The hearts of the baboons were removed after 72 h (survival: yes) or after death (survival: no) of the animals, frozen in liquid nitrogen, and stored at -80 degrees C until spectrophotometrical measurement of nine mitochondrial and glycolytic enzymes. A reduction of the activity of NADH:cytochrome-c-reductase (Complex I + III) to 67% and succinate:cytochrome-c-reductase (Complex II + III) to 45% was found in the hearts of surviving animals after infusion of high amounts of bacteria. After multiple challenge with lesser amounts of bacteria, no significant changes in enzyme activity were detectable. After lethal septic shock, activities of Complex I + III (12%) and Complex II + III (13%) as well as of phosphofructokinase (16%) were found to be strongly diminished. Decylubiquinol:cytochrome-c-reductase (Complex III, 59%), cytochrome-c-oxidase (51%), succinate dehydrogenase (60%), glucosephosphate isomerase (61%), lactate dehydrogenase (61%), and citrate synthase (120%) were less or unaffected. Similar but less pronounced effects were found after infusion of lesser amounts of bacteria. By means of inhibitor titrations of succinate: cytochrome-c-reductase, it was shown that the loss of activity is not caused by Complex III but by disturbances in Complex II. It is concluded that E. coli-induced sepsis causes decreased activities of Complex I and Complex II in baboon heart mitochondria in a dose-dependent manner.

Animals↗
PubMed1985

The iron-sulfur protein of cytochrome bc1 complex. Its occurrence in the mitochondrial inner membrane in excess of the amount constituting the complex.

Radioimmunoassay and quantitative immunoblot analysis have been developed for quantitation of the iron-sulfur protein of cytochrome bc1 complex in order to compare its content in isolated cytochrome bc1 complex with that in electron transport particles. The result by radioimmunoassay indicated that the content of the iron-sulfur protein/mol of cytochrome b is higher by approximately 30%, on the average, in electron transport particles than in cytochrome bc1 complex. This observation was supported by the data of immunoblot analysis. Since approximately 1/3 of cytochrome b in electron transport particles is not attributed to cytochrome bc1 complex, but to succinate-ubiquinone oxidoreductase complex (Davis, K.A., Hatefi, Y., Poff, K. L., and Butler, W. L. (1973) Biochim. Biophys. Acta 325, 341-356), the ratio of the iron-sulfur protein detectable by radioimmunoassay in electron transport particles to that in cytochrome bc1 complex is calculated to be approximately 2 on the basis of the content of 2 mol of b-type heme/mol of the complex. Therefore, it appears that the mitochondrial inner membrane contains approximately two times as much of the immunoreactive iron-sulfur protein as what is expected from the stoichiometry of one iron-sulfur center and two b-type hemes for cytochrome bc1 complex. This finding affords an interesting aspect in the study of biogenesis of cytochrome bc1 complex.

Animals↗