Rearrangement Of Complex Research Articles

Synthesis, structure, and rearrangements of new tricarbonylchromium complexes of substituted heptalenes

Reactions of 1,2,5,6,8,10-hexamethylheptalene (1) and its bond isomer, 1,4,5,6,8,10-hexamethylheptalene (2), with tricarbonylchromium complexes L{in3}Cr(CO){in3} (L=NH{in3} and Py) have been investigated. Thermodynamically less stable complex 1 exhibits higher reactivity with respect to Py{in3}Cr(CO){in3}/BF{in3} · Et{in2}O under the conditions of Ofele's reaction than complex2. At 10–30 °C, the Cr(CO){in3} group is coordinated to the asymmetrically substituted ring, which is accomplished by the shift of double bonds in the ligand, to afford tricarbonyl-[1,4,5,6,8,10-hexamethyl-η{su6}-(10a, 1–5)heptalene]-chromium (6) as the only mononuclear complex. Under more drastic conditions (Raush's reaction, 80 °C),1 ↔ 2 interconversion proceeds faster than the reaction of individual bond isomers with coordinatively unsaturated “hot” particles (solv){inn}Cr(CO){in3}. In this case, all of the four possible isomeric mononuclear complexes (6–9) and two binuclear complexes (10 and 11) are formed. The structures of complexes 6–11 have been studied by NMR and mass spectrometry, the structure of6 has been established by X-ray diffraction analysis. Heating a solution of6 in octane at 115 °C results in the isomerization of6 into complex7 through the intracycle 1,2-shift of the Cr(CO){in3} group and also in its conversion into complex8, which is the first example of interring η{su6}→η{su6}-haptotropic rearrangement in nonplanar seven-membered π-systems.

Photoinduced electron transfer from the triplet state of zinc cytochrome c to ferricytochrome b5 is gated by configurational fluctuations of the diprotein complex.

The intracomplex electron-transfer reaction 3Zncyt/b5(III)-->Zncyt+/b5(II) within electrostatic and covalent complexes of zinc(II) cytochrome c and ferricytochrome b5 is studied by laser flash photolysis. Kinetic effects of protein cross-linking and of solution viscosity are interpreted in terms of dynamic mobility of the associated proteins with respect to each other. The rate constant for the monoexponential reaction in the electrostatic complex is 3.5 x 10(5) s-1 in aqueous solution; this value is independent of protein concentration and ionic strength, but it decreases markedly as viscosity is raised by addition of glycerol or sucrose. The multiexponential reaction in the covalent complex was analyzed also in terms of the stretched exponential, exp[-(kt)n]. The best fit requires k = 6.8 x 10(4) s-1 and n = 0.56 in aqueous solution; this rate constant is independent of protein concentration and ionic strength, but it decreases slightly as viscosity is raised. Fitting of the viscosity dependence to a simple two-state kinetic model yields a rate constant of 3.0 x 10(5) s-1 for rearrangement of the electrostatic complex 3Zncyt/b5(III) from the initial docking configuration to a different, more reactive, configuration. The corresponding rate constant for rearrangement of the electrostatic complex 3Zncyt/pc(II) containing plastocyanin, determined previously, is 2.5 x 10(5) s-1. Evidently, the intracomplex reaction in both electrostatic complexes is gated by a rearrangement process.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural and functional properties of human and mouse apolipoprotein A-I

Mouse and human plasma apolipoprotein A-I (apo A-I m and apo A-I h, respectively) were investigated to compare their molecular properties in solution, their incorporation into palmitoyloleoylphosphatidylcholine-apo A-I (POPC-apo A-I) discoidal complexes, their structural stability in discoidal complexes and high-density lipoproteins (HDL), and their effect on structural rearrangement of discoidal complexes upon interaction with low-density lipoproteins (LDL). Unlike apo A-I h, only minimal concentration-dependent self-association was observed for apo A-I m. While both apo A-I m and apo A-I h formed discoidal complexes of distinct composition and size that reflected reassembly molar ratios of POPC/apo A-I, apo A-I m demonstrated specific deficiencies in formation of larger-sized complexes. Denaturation of both apo A-I m- or apo A-I h-containing complexes and HDL with guanidine hydrochloride (GuHCl) indicated significantly reduced stabilization of apo A-I m by lipid in these particles. Interaction of apo A-I m- or apo A-I h-containing discoidal complexes with human plasma LDL revealed a more extensive conversion of apo A-I m-complexes to smaller species. Mean hydrophobicities and mean hydrophobic moments of amphipathic helical segments in apo A-I m and apo A-I h were compared; differences potentially contributing to differential lipid-binding properties between apo A-I m and apo A-I h were identified. Our results demonstrate differences between apo A-I m and apo A-I h that may contribute to the major changes in plasma HDL distribution and function observed in apo A-I h transgenic mice.

Organometallic Complexes of Tantalum That Contain the Triamidoamine Ligand, [(Me3SiNCH2CH2)3N]3-, Including an Ethylidene Complex Formed via a Phosphine-Catalyzed Rearrangement of an Ethylene Complex

Organometallic Complexes of Tantalum That Contain the Triamidoamine Ligand, [(Me3SiNCH2CH2)3N]3-, Including an Ethylidene Complex Formed via a Phosphine-Catalyzed Rearrangement of an Ethylene Complex

Donor-Acceptor N → P Interaction and its Effect on the Phosphorylation of α-Aminoketones

Abstract Aminovinylphosphites of Z-configuration R2″PO-CR═CH-NR2' are formed in the reaction of α-aminoketones RCOCH2NR2' and chlorophosphites with the use of triethylamine as a base. The high stereoselectivity of this process is due to the preliminary coordination of phosphorus chloride to the amino group of the substrate and the following intramolecular rearrangement in the complex with the simultaneous evolution of the salt of hydrogen chloride with triethylamine. A thermodynamic study of the complex formation between reactants in the first stage of the above mentioned process supports this idea.

Formation of Nitric Acid by Structural Rearrangements of Gas-phase Ionic Complexes of Ammonium Nitrate

Formation of Nitric Acid by Structural Rearrangements of Gas-phase Ionic Complexes of Ammonium Nitrate

Formation and rearrangement of (siloxymethyl)zirconocene chloride complexes

Formation and rearrangement of (siloxymethyl)zirconocene chloride complexes

Skeletal rearrangements of arylborane complexes mediated by redox reactions: thermal and photochemical oxidation by metal ions

A variety of metal salts have been found to undergo reduction by thermal and photochemical interaction with tetraarylborate salts and with neutral alkyl- and aryl-borane complexes. In the cases of Cu 2+, Cu +, Ni 2+, Co 2+, Pd 2+, Pt 2+, Ag +, Zn 2+, Hg 2+, Sn 2+, Pb 2+ and Rh 3+ salts, such photochemical reductions with NaBPh 4 led to the deposition of the free metal, while a number of binary mixtures of metal salts led to the deposition of both metals, sometimes as true alloys, under such photoreductions. In the course of these reductions the arylborate reductants underwent oxidative coupling of the aryl groups to form biaryls in a strictly intra-ionic (for BAr 4 −) or intramolecular (Ar 3B) manner respectively. Individual studies of the photochemistry of the tetraarylborate anion itself, of cuprous tetraphenylborate and of the triphenylborane—pyridine complex have adduced evidence for a gamut of reactive intermediates capable of serving as the photoreductant for metal ions, such as triarylborane radical anions, diarylborate(I) anions or arylborenes, 7-borabicycloheptadiene anions or neutral complexes and finally arylborohydride anions or arylboronhydrides. The role of these intermediates both in the photoinduced skeletal rearrangements of arylboranes and in the concomitant reduction of metal ions is discussed in critical detail.

Carbonylation of the alkyl compounds [U(η-C5H4R)3R′] and rearrangement of the acyl derivatives [U(η-C5H4R)3-(η2-COR′)] into C6H4RR′. Influence of R and R′(Me, Prior But) and role of the solvent (benzene or totrahydrofuran)

Carbonylation of the alkyl compounds [U(η-C5H4R)3R′]1 into the acyl derivatives [U(η-C5H4R)3(η2-COR′)]2 exhibited pseudo first-order kinetics (pCO = 1 atm). The rate constants were dependent on R, following the order But < Pri < Me < H and varied with R′ in the unusual order Pri < Me < But < Bun; for [U(η-C5H5)3R′], k(Bun)= 2k(But)= 4k(Pri). The rates were similar in benzene and in tetrahydrofuran. These results suggest that the migratory insertion of CO into the metal–carbon bond is not the rate-determining step. The rearrangement of the acyl complexes 2 afforded the alkylbenzene molecules C6H4RR′, resulting from ring enlargement of a C5H4R ligand by incorporation of the CR′ fragment. This reaction exhibited first-order kinetics. Whatever the solvent, the rate constants were found to depend markedly on R′, increasing in the order But < Pri < Bun < Me. In benzene, the rates varied with R in the sequence H < Me < Pri < But whereas the opposite trend was observed in tetrahydrofuran. For a given solvent, the relative proportions of meta- and para-isomers of C6H4RR′ were practically constant, whatever R and R′. These facts are best explained by a mechanism which involves a cyclopropyl intermediate resulting from addition of the oxycarbene group to the cyclopentadienyl ligand.

Interaction of Mn(III)Tetraphenylporphyrin with Superoxide; The Reaction Mechanism and Evidence for a Peroxo Complex

Cathodic one-electron reduction of Mn(III)TPP and O2 in an aprotic solvent yields Mn(II)TPP and the superoxide anion radical O2-. The Mn(II)TPP and O2- react in solution to the side-on peroxo complex Mn(III)TPP-O22-, which is oxidized at the electrode at a peak potential of Epa = 0.40 V vs NHE (k ≈ 104 dm3 mol-1 s-1). The rate-determining step of the overall two-electron oxidation is the transfer of the first electron coupled with a structure rearrangement of the peroxo complex to a superoxo complex.

Genomic rearrangement of the α-globin gene complex during mammalian evolution

Genomic rearrangement of the α-globin gene complex during mammalian evolution

Genomic rearrangement of the α-globin gene complex during mammalian evolution

In man, the gene for hydroxyacyl glutathione hydrolase (HAGH; glyoxalase II) is closely linked to the alpha-globin locus (HB alpha) on Chromosome 16. HAGH polymorphism in the mouse has now enabled the mapping of the murine homologue. Deletion mapping, congenic strain studies, and characterization of 41 recombinant inbred strains establish that the mouse Hagh locus lies very close to the alpha-globin pseudogene (Hba-ps4) in the vicinity of the major histocompatibility locus (H-2) on chromosome 17. Several other loci have been identified previously that are also closely linked to the human alpha-globin locus but near the alpha-globin pseudogene Hba-ps4 in the mouse. These linkage relationships suggest that during the evolution of mice a translocation occurred that subdivided the alpha-globin locus, leaving one inactive alpha-globin gene still associated with the Hagh locus and linked sequences, while moving and inserting the active alpha-globin locus and all distal sequences into an internal location on another autosome, the predecessor to mouse chromosome 11.

Insulin-Like Growth Factor-1 Potentiates Expansion of Interleukin-7–Dependent Pro-B Cells

Commitment to B-lymphocyte differentiation is characterized by expression of the B220 form of the common leukocyte antigen (Ly-5) and D-JH rearrangement of the Ig heavy chain gene complex. B-lineage progenitor cells, or pro-B cells, that have initiated Ig gene rearrangement, but do not express detectable Ig heavy or light chain protein, have recently been shown to retain substantial capacity for expansion in vitro in the presence of bone marrow (BM) stromal cells and interleukin-7 (IL-7). Although the potentiating effect of stromal cells on pro-B-cell proliferation can be partially attributed to the ligand for the proto-oncogene receptor c-kit (c-kit ligand [KL] or stem cell factor), several lines of evidence suggest that c-kit-mediated cell signalling is not required for pro-B-cell expansion. Previous studies from this laboratory demonstrated that insulin-like growth factor-1 (IGF-1) potentiated the proliferative effect of IL-7 on nonadherent cells from lymphoid long-term BM cultures in a manner similar to that shown for KL. To further delineate specific cell stages that respond to lymphopoietic cytokines, we derived continuously proliferating pro-B-cell lines from day-14 murine fetal liver in the presence of IL-7 and BM stromal cell clone S10. Initial expansion and continued proliferation of these pro-B-cell lines was absolutely dependent on the presence of both IL-7 and stromal cells. In the absence of KL, IL-7-stimulated proliferation of these cells in short-term cultures and addition of either recombinant IGF-1 or KL significantly potentiated this proliferative response. Although IGF-2 and insulin also potentiated the effect of IL-7, our data suggest that neither IGF-2 nor insulin represent normal regulators of intramyeloid lymphocyte development. IGF-1 and KL activate unique cascades of intracellular signalling events and inclusion of both cytokines in cultures of IL-7-stimulated pro-B cells resulted in additive potentiation of the proliferative response. Taken together, these results suggest that expansion of pro-B cells in vivo is maintained by at least three stromal cell-derived cytokines. IL-7 appears to be unique in delivering the primary proliferative signal for pro-B-cell expansion; however, both KL and IGF-1 potentiate the proliferative effect of IL-7 on these cells. The functional redundancy and additive effects of IGF-1 and KL as amplification signals for developing B-lineage cells underscore the essential nature of clonal expansion and diversification in development of immunocompetent lymphoid cells.

Insulin-like growth factor-1 potentiates expansion of interleukin-7- dependent pro-B cells

Commitment to B-lymphocyte differentiation is characterized by expression of the B220 form of the common leukocyte antigen (Ly-5) and D-JH rearrangement of the Ig heavy chain gene complex. B-lineage progenitor cells, or pro-B cells, that have initiated Ig gene rearrangement, but do not express detectable Ig heavy or light chain protein, have recently been shown to retain substantial capacity for expansion in vitro in the presence of bone marrow (BM) stromal cells and interleukin-7 (IL-7). Although the potentiating effect of stromal cells on pro-B-cell proliferation can be partially attributed to the ligand for the proto-oncogene receptor c-kit (c-kit ligand [KL] or stem cell factor), several lines of evidence suggest that c-kit-mediated cell signalling is not required for pro-B-cell expansion. Previous studies from this laboratory demonstrated that insulin-like growth factor-1 (IGF-1) potentiated the proliferative effect of IL-7 on nonadherent cells from lymphoid long-term BM cultures in a manner similar to that shown for KL. To further delineate specific cell stages that respond to lymphopoietic cytokines, we derived continuously proliferating pro-B-cell lines from day-14 murine fetal liver in the presence of IL-7 and BM stromal cell clone S10. Initial expansion and continued proliferation of these pro-B-cell lines was absolutely dependent on the presence of both IL-7 and stromal cells. In the absence of KL, IL-7-stimulated proliferation of these cells in short- term cultures and addition of either recombinant IGF-1 or KL significantly potentiated this proliferative response. Although IGF-2 and insulin also potentiated the effect of IL-7, our data suggest that neither IGF-2 nor insulin represent normal regulators of intramyeloid lymphocyte development. IGF-1 and KL activate unique cascades of intracellular signalling events and inclusion of both cytokines in cultures of IL-7-stimulated pro-B cells resulted in additive potentiation of the proliferative response. Taken together, these results suggest that expansion of pro-B cells in vivo is maintained by at least three stromal cell-derived cytokines. IL-7 appears to be unique in delivering the primary proliferative signal for pro-B-cell expansion; however, both KL and IGF-1 potentiate the proliferative effect of IL-7 on these cells. The functional redundancy and additive effects of IGF-1 and KL as amplification signals for developing B- lineage cells underscore the essential nature of clonal expansion and diversification in development of immunocompetent lymphoid cells.

Gating of photoinduced electron transfer from zinc cytochrome c and tin cytochrome c to plastocyanin. Effects of solution viscosity on rearrangement of the metalloprotein complex

Oxidative quenching by pc(II) of the triplet excited states 3 Zn(cyt) and 3 Sn(cyt) is studied by laser flash photolysis. The quenching is biphasic at low ionic strength. The faster component corresponds to the unimolecular electron-transfer reactions within the electrostatic complexes 3 M(cyt) /pc(II), in which M is Zn(II) or Sn(IV); these reactions are the main subject of this study. The slower component corresponds to the bimolecular reactions between the unassociated 3 M(cyt) and pc(II). The relative amplitudes of the two components depend on ionic strength and pc(II) concentration in a predictable way. The unimolecular reaction is studied in solutions whose viscosity is adjusted with glycerol, ethylene glycol, and D-glucose

Subunit rearrangement of the cyclin-dependent kinases is associated with cellular transformation.

In normal human diploid fibroblasts, cyclins of the A, B, and D classes each associate with cyclin-dependent kinases (CDKs), proliferating cell nuclear antigen (PCNA), and p21, thereby forming multiple independent quaternary complexes. Upon transformation of diploid fibroblasts with the DNA tumor virus SV40, or its transforming tumor antigen (T), the cyclin D/p21/CDK/PCNA complexes are disrupted. In transformed cells, CDK4 totally dissociates from cyclin D, PCNA, and p21 and, instead, associates exclusively with a polypeptide of 16 kD (p16). Quaternary complexes containing cyclins A or B1 and p21/CDK/PCNA also undergo subunit rearrangement in transformed cells. Both PCNA and p21 are no longer associated with CDC2-cyclin B1 binary complexes. Cyclin A complexes no longer contain p21, and a new 19-kD polypeptide (p19) is found in association with cyclin A. The pattern of subunit rearrangement of cyclin-CDK complexes in SV40-transformed cells is also shared in those containing adeno- or papilloma viral oncoproteins. Rearrangement also occurs in p53-deficient cells derived from Li-Fraumeni patients that carry no known DNA tumor virus. These findings suggest a mechanism by which oncogenic proteins alter the cell cycle of transformed cells.

Low-valent rhenium-oxo compounds. 12. Rearrangement of a rhenium hydroxide complex to an oxo-hydride compound

Low-valent rhenium-oxo compounds. 12. Rearrangement of a rhenium hydroxide complex to an oxo-hydride compound

Mechanism of rearrangement of an allylvinylrhenium complex to an (allyl vinyl ketone)rhenium complex: role of concerted organometallic reactions in avoiding high-energy coordinatively unsaturated intermediates

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanism of rearrangement of an allylvinylrhenium complex to an (allyl vinyl ketone)rhenium complex: role of concerted organometallic reactions in avoiding high-energy coordinatively unsaturated intermediatesCharles P. Casey, Paul C. Vosejpka, Todd L. Underiner, Greg A. Slough, and James A. Gavney Jr.Cite this: J. Am. Chem. Soc. 1993, 115, 15, 6680–6688Publication Date (Print):July 1, 1993Publication History Published online1 May 2002Published inissue 1 July 1993https://doi.org/10.1021/ja00068a027RIGHTS & PERMISSIONSArticle Views131Altmetric-Citations15LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-AlertsSupporting Info (2)»Supporting Information Supporting Information Get e-Alerts

Phagocytosis induced by thyrotropin in cultured thyroid cells is associated with myosin light chain dephosphorylation and stress fiber disruption

The actin/myosin II cytoskeleton and its role in phagocytosis were examined in primary cultures of dog thyroid cells. Two (19 and 21 kD) phosphorylated light chains of myosin (P-MLC) were identified by two-dimensional gel electrophoresis of antimyosin immunoprecipitates, and were associated with the Triton X-100 insoluble, F-actin cytoskeletal fraction. Analyses of Triton-insoluble and soluble 32PO4-prelabeled protein fractions indicated that TSH (via cAMP) or TPA treatment of intact cells decreases the MLC phosphorylation state. Phosphoamino acid and tryptic peptide analyses of 32P-MLCs from basal cells showed phosphorylation primarily at threonine and serine residues; most of the [32P] appeared associated with a peptide containing sites typically phosphorylated by MLC kinase. Even in the presence of the agents which induced dephosphorylation, the phosphatase inhibitor, calyculin A, caused a severalfold increase in MLC phosphorylation at several distinct serine and threonine sites which was also associated with actomyosin and cell contraction. Phosphorylation of cell homogenate proteins or the cytoskeletal fraction with [gamma-32P]ATP indicated that Ca2+, EGTA, or trifluoperazine (TFP) has little effect on the phosphorylation of MLC. Both fluorescent phalloidin and antimyosin staining of cells showed distinct dorsal and ventral stress fiber complexes which were disrupted within 30 min by TSH and cAMP; TPA appeared to cause disruption of dorsal, and rearrangement of ventral complexes. Concomitant with MLC dephosphorylation and stress fiber disruption, TSH/cAMP, but not TPA, induced dorsal phagocytosis of latex beads. While stimulation of either A or C-kinase disrupts dorsal stress fibers and rearranges actomyosin, another event(s) mediated by A-kinase appears necessary for phagocytic activity.

The Escherichia coli chaperones involved in DNA replication.

Mutations in the Escherichia coli heat shock genes, dnaK, dnaJ or grpE, alter host DNA and RNA synthesis, degradation of other proteins, cell division and expression of other heat shock genes. They also block the initiation of DNA replication of bacteriophages lambda and P1, and the mini-F plasmid. An in vitro lambda DNA replication system, composed entirely of purified components, enabled us to describe the molecular mechanism of the dnaK, dnaJ and grpE gene products. DnaK, the bacterial hsp 70 homologue, releases lambda P protein from the preprimosomal complex in an ATP- and DnaJ-dependent reaction (GrpE-independent initiation of lambda DNA replication). In this paper, I show that, when GrpE is present, lambda P protein is not released from the preprimosomal complex, rather it is translocated within the complex in such a way that it does not inhibit DnaB helicase activity. Translocation of lambda P triggers the initiation event allowing DnaB helicase to unwind DNA near the ori lambda sequence, leading to efficient lambda DNA replication. Chaperone activity of the DnaK-DnaJ-GrpE system is first manifested in the selective binding of these heat shock proteins to the preprimosomal complex, followed by its ATP-dependent rearrangement. I show that DnaJ not only tags the preprimosomal complex for recognition by DnaK, but also stabilizes the multi-protein structure. GrpE also participates in the binding of DnaK to the preprimosomal complex by increasing DnaK's affinity to those lambda P proteins which are already with DnaJ.(ABSTRACT TRUNCATED AT 250 WORDS)