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Structural Evidence (structural + evidence)
Selected AbstractsStructural Evidence for Zn Intersititials in Ferromagnetic Zn1,xCoxO Films,ADVANCED MATERIALS, Issue 19 2007L. MacManus-Driscoll Post-annealing studies in different atmospheres combined with high resolution x-ray studies on epitaxial ZnO and Zn1,xCoxO films revealed that the c -axis lattice parameter decreases when interstitial zinc is removed from ZnO. The ,c' parameter change reverses sign when samples are re-annealed in a Zn-rich atmosphere. Stronger ferromagnetism occurs in Zn1,xCoxO film for higher ,c' parameters and hence higher Zn interstitial concentrations. [source] Structural evidence for a constant c11 ring stoichiometry in the sodium F-ATP synthaseFEBS JOURNAL, Issue 21 2005Thomas Meier The Na+ -dependent F-ATP synthases of Ilyobacter tartaricus and Propionigenium modestum contain membrane-embedded ring-shaped c subunit assemblies with a stoichiometry of 11. Subunit c from either organism was overexpressed in Escherichia coli using a plasmid containing the corresponding gene, extracted from the membrane using detergent and then purified. Subsequent analyses by SDS/PAGE revealed that only a minor portion of the c subunits had assembled into stable rings, while the majority migrated as monomers. The population of rings consisted mainly of c11, but more slowly migrating assemblies were also found, which might reflect other c ring stoichiometries. We show that they consisted of higher aggregates of homogeneous c11 rings and/or assemblies of c11 rings and single c monomers. Atomic force microscopy topographs of c rings reconstituted into lipid bilayers showed that the c ring assemblies had identical diameters and that stoichiometries throughout all rings resolved at high resolution. This finding did not depend on whether the rings were assembled into crystalline or densely packed assemblies. Most of these rings represented completely assembled undecameric complexes. Occasionally, rings lacking a few subunits or hosting additional subunits in their cavity were observed. The latter rings may represent the aggregates between c11 and c1, as observed by SDS/PAGE. Our results are congruent with a stable c11 ring stoichiometry that seems to not be influenced by the expression level of subunit c in the bacteria. [source] On the roles of deformation and fluid during rejuvenation of a polymetamorphic terrane: inferences on the geodynamic evolution of the Ruker Province, East AntarcticaJOURNAL OF METAMORPHIC GEOLOGY, Issue 8 2007G. PHILLIPS Abstract Evaluating pressure,temperature (P,T) conditions through mineral equilibria modelling within an amphibolite facies polymetamorphic terrane requires knowledge of the fluid content of the rocks. The Archean-Palaeoproterozoic basement rocks of the Ruker Province, East Antarctica, preserve evidence of three metamorphic events (M1,M3). Of particular interest is the M3 event, which is constrained to the early Palaeozoic (c. 550,480 Ma). Evaluation of the tectonic setting during this time is important because the Ruker Province is located within a critical region with respect to models of Gondwana assembly. Structural evidence of the early Palaeozoic event is preserved as large (up to ,500 m wide) high strain zones that cut the orthogneiss-metasedimentary basement (Tingey Complex) of the Ruker Province. Rocks within these zones have been thoroughly recrystallized and preserve a dominant shear fabric and M3 mineral assemblages that formed at P,T conditions of 4.0,5.2 kbar and 565,640 °C. Distal to these zones, rocks preserve more complex petrographic relationships with S1 and S2 foliations, being incompletely overgrown by M3 retrograde assemblages. We show that the mineral assemblages preserved during the M3 event are highly dependent on the availability of fluid H2O, which is strongly influenced by the structural setting (i.e. proximity to the high-strain zones). P,T structural and fluid flow constraints support a model of basin inversion during early Palaeozoic crustal rejuvenation in the Ruker Province. [source] Affinity enhancement of an in vivo matured therapeutic antibody using structure-based computational designPROTEIN SCIENCE, Issue 5 2006Louis A. Clark Abstract Improving the affinity of a high-affinity protein,protein interaction is a challenging problem that has practical applications in the development of therapeutic biomolecules. We used a combination of structure-based computational methods to optimize the binding affinity of an antibody fragment to the I-domain of the integrin VLA1. Despite the already high affinity of the antibody (Kd ,7 nM) and the moderate resolution (2.8 Å) of the starting crystal structure, the affinity was increased by an order of magnitude primarily through a decrease in the dissociation rate. We determined the crystal structure of a high-affinity quadruple mutant complex at 2.2 Å. The structure shows that the design makes the predicted contacts. Structural evidence and mutagenesis experiments that probe a hydrogen bond network illustrate the importance of satisfying hydrogen bonding requirements while seeking higher-affinity mutations. The large and diverse set of interface mutations allowed refinement of the mutant binding affinity prediction protocol and improvement of the single-mutant success rate. Our results indicate that structure-based computational design can be successfully applied to further improve the binding of high-affinity antibodies. [source] Structural myocardial changes after coronary artery surgeryEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 11 2000F. Eberhardt Background Postoperative contractile dysfunction or ,myocardial stunning' has been described after coronary artery bypass grafting (CABG). In the present study we sought to determine if and to what extent clinical, structural and histochemical evidence of myocardial changes associated with stunning could be found in patients after CABG and cold crystalloid cardioplegia. Materials and methods Left ventricular (LV) biopsies were obtained from CABG patients (n = 10) prior to and at the end of cardiopulmonary bypass (CPB). These biopsies were immunostained for the inducible heat-shock protein 70 (HSP-70i), intercellular adhesion molecule-1 (ICAM-1) and actin. ATP was measured by bioluminescence. Results Biopsies pre-CPB showed no evidence of myocardial damage as HSP-70i was absent and a regular actin cross-striation pattern and only constitutive ICAM-1-expression were present. After CPB we found significantly increased HSP-70i and ICAM-1 levels as well as a deranged actin cross-striation pattern with a widening of actin bands. ATP levels declined from 10 mmol L,1 pre-CPB to 4.9 mmol L,1 after CPB. Correspondingly, coronary sinus effluent showed a significant lactate production. Although, cardiac function determined by transoesophageal echocardiography did not deteriorate, significant inotropic support was necessary to maintain cardiac output. Conclusions Our results present clinical and structural evidence of ,myocardial stunning' after CABG and cold crystalloid cardioplegia. Increased HSP-70i and ICAM-1 expression, as well as a deranged actin cross-striation pattern, might be structural markers to determine ,myocardial stunning' in clinical settings. [source] Structure of Sumatra and its implications for the tectonic assembly of Southeast Asia and the destruction of PaleotethysISLAND ARC, Issue 1 2009Anthony J. Barber Abstract It is now generally accepted that Southeast Asia is composed of continental blocks which separated from Gondwana with the formation of oceanic crust during the Paleozoic, and were accreted to Asia in the Late Paleozoic or Early Mesozoic, with the subduction of the intervening oceanic crust. From east to west the Malay peninsula and Sumatra are composed of three continental blocks: East Malaya with a Cathaysian Permian flora and fauna; Sibumasu, including the western part of the Malay peninsula and East Sumatra, with Late Carboniferous,Early Permian ,pebbly mudstones' interpreted as glaciogenic diamictites; and West Sumatra, again with Cathaysian fauna and flora. A further unit, the Woyla nappe, is interpreted as an intraoceanic arc thrust over the West Sumatra block in the mid Cretaceous. There are varied opinions concerning the age of collision of Sibumasu with East Malaya and the destruction of Paleotethys. In Thailand, radiolarites have been used as evidence that Paleotethys survived until after the Middle Triassic. In the Malay peninsula, structural evidence and the ages of granitic intrusions are used to support a Middle Permian to Early Triassic age for the destruction of Paleotethys. It is suggested that the West Sumatra block was derived from Cathaysia and emplaced against the western margin of Sibumasu by dextral transcurrent faulting along a zone of high deformation, the Medial Sumatra Tectonic Zone. These structural units can be traced northwards in Southeast Asia. The East Malaya block is considered to be part of the Indochina block, Sibumasu can be traced through Thailand into southern China, the Medial Sumatra Tectonic Zone is correlated with the Mogok Belt of Myanmar, the West Burma block is the extension of the West Sumatra block, from which it was separated by the formation of the Andaman Sea in the Miocene, and the Woyla nappe is correlated with the Mawgyi nappe of Myanmar. [source] The evolution of black plumage from blue in Australian fairy-wrens (Maluridae): genetic and structural evidenceJOURNAL OF AVIAN BIOLOGY, Issue 5 2010Amy C. Driskell Genetic variation in the melanocortin-1 receptor (MC1R) locus is responsible for color variation, particularly melanism, in many groups of vertebrates. Fairy-wrens, Maluridae, are a family of Australian and New Guinean passerines with several instances of dramatic shifts in plumage coloration, both intra- and inter-specifically. A number of these color changes are from bright blue to black plumage. In this study, we examined sequence variation at the MC1R locus in most genera and species of fairy-wrens. Our primary focus was subspecies of the white-winged fairy-wren Malurus leucopterus in which two subspecies, each endemic to islands off the western Australian coast, are black while the mainland subspecies is blue. We found fourteen variable amino acid residues within M. leucopterus, but at only one position were alleles perfectly correlated with plumage color. Comparison with other fairy-wren species showed that the blue mainland subspecies, not the black island subspecies, had a unique genotype. Examination of MC1R protein sequence variation across our sample of fairy-wrens revealed no correlation between plumage color and sequence in this group. We thus conclude that amino acid changes in the MC1R locus are not directly responsible for the black plumage of the island subspecies of M. leucopterus. Our examination of the nanostructure of feathers from both black and blue subspecies of M. leucopterus and other black and blue fairy-wren species clarifies the evolution of black plumage in this family. Our data indicate that the black white-winged fairy-wrens evolved from blue ancestors because vestiges of the nanostructure required for the production of blue coloration exist within their black feathers. Based on our phylogeographic analysis of M. leucopterus, in which the two black subspecies do not appear to be each other's closest relatives, we infer that there have been two independent evolutionary transitions from blue to black plumage. A third potential transition from blue to black appears to have occurred in a sister clade. [source] Hydathodal leaf teeth of Chloranthus japonicus (Chloranthaceae) prevent guttation-induced flooding of the mesophyllPLANT CELL & ENVIRONMENT, Issue 9 2005TAYLOR S. FEILD ABSTRACT Why the leaves of cold temperate deciduous and moisture-loving angiosperms are so often toothed has long puzzled biologists because the functional consequences of teeth remain poorly understood. Here we provide functional and structural evidence that marginal leaf teeth of Chloranthus japonicus, an understory herb, enable the release of guttation sap during root pressure. When guttation from teeth hydathodes was experimentally blocked, we found that the leaf intercellular airspaces became flooded. Measurements of chlorophyll a fluorescence revealed that internal flooding resulted in an inhibition of photosynthesis, most likely through the formation of a film of water within the leaf that reduced CO2 diffusion. Comparing a developmental series of leaves with and without teeth experimentally covered with wax, we found that teeth did not affect overall leaf stomatal conductance and CO2 uptake. However, maximal and effective light-saturation PSII quantum yields of teeth were found to be lower or equal to the surrounding lamina throughout leaf ontogeny. Collectively, our results suggest hydathodes and their development on teeth apices enable the avoidance of mesophyll flooding by root pressure. We discuss how these new findings bear on the potential physiological interpretations of models that apply leaf marginal traits to infer ancient climates. [source] Identification of a novel set of scaffolding residues that are instrumental for the inhibitory property of Kunitz (STI) inhibitorsPROTEIN SCIENCE, Issue 3 2010Susmita Khamrui Abstract For canonical serine protease inhibitors (SPIs), scaffolding spacer residue Asn or Arg religates cleaved scissile peptide bond to offer efficient inhibition. However, several designed "mini-proteins," containing the inhibitory loop and the spacer(s) with trimmed scaffold behave like substrates, indicating that scaffolding region beyond the spacer is also important in the inhibitory process. To understand the loop-scaffold compatibility, we prepared three chimeric proteins ECIL -WCIS, ETIL -WCIS, and STIL -WCIS, where the inhibitory loop of ECI, ETI, and STI is placed on the scaffold of their homolog WCI. Results show that although ECIL -WCIS and STIL -WCIS behave like good inhibitors, ETIL -WCIS behaves like a substrate. That means a set of loop residues (SRLRSAFI), offering strong trypsin inhibition in ETI, act as a substrate when they seat on the scaffold of WCI. Crystal structure of ETIL -WCIS shows that the inhibitory loop is of noncanonical conformation. We identified three novel scaffolding residues Trp88, Arg74, and Tyr113 in ETI that act as barrier to confine the inhibitory loop to canonical conformation. Absence of this barrier in the scaffold of WCI makes the inhibitory loop flexible in ETIL -WCIS leading to a loss of canonical conformation, explaining its substrate-like behavior. Incorporation of this barrier back in ETIL -WCIS through mutations increases its inhibitory power, supporting our proposition. Our study provides structural evidence for the contribution of remote scaffolding residues in the inhibitory process of canonical SPIs. Additionally, we rationalize why the loop-scaffold swapping is not permitted even among the members of highly homologous inhibitors, which might be important in the light of inhibitor design. [source] Elucidation of the mechanism of the regulatory function of the Ig1 module of the fibroblast growth factor receptor 1PROTEIN SCIENCE, Issue 10 2006Vladislav V. Kiselyov Abstract The extracellular part of the fibroblast growth factor (FGF) receptor (FGFR) consists of up to three Ig modules (Ig1,Ig3), in which the Ig2 and Ig3 modules determine affinity and specificity for FGF and heparin. The FGFR isoforms lacking the Ig1 module have higher affinity for FGF and heparin than the triple Ig-module isoforms, suggesting that the Ig1 module is involved in the regulation of the FGFR,ligand interaction. We show here by surface plasmon resonance and NMR analyses that the Ig1 module binds to the Ig2 module, and identify by NMR the binding sites involved in the Ig1,Ig2 interaction. The identified binding site in the Ig2 module was found to be in the area of the FGF,Ig2 and Ig2,heparin contact sites, thus providing direct structural evidence that the Ig1 module functions as a competitive autoinhibitor of the FGFR,ligand interaction. Furthermore, the Ig1 binding site of the Ig2 module overlaps the Ig2,Ig2 contact site. This suggests that the function of the Ig1 module is not only regulation of the FGFR,ligand binding affinity but also prevention of spontaneous FGFR dimerization (through a direct Ig2,Ig2 interaction) in the absence of FGF. [source] The disulfide bond pattern of catrocollastatin C, a disintegrin-like/cysteine-rich protein isolated from Crotalus atrox venomPROTEIN SCIENCE, Issue 7 2000Juan J. Calvete Abstract The disulfide bond pattern of catrocollastatin-C was determined by N-terminal sequencing and mass spectrometry. The N-terminal disintegrin-like domain is a compact structure including eight disulfide bonds, seven of them in the same pattern as the disintegrin bitistatin. The protein has two extra cysteine residues (XIII and XVI) that form an additional disulfide bond that is characteristically found in the disintegrin-like domains of cellular metalloproteinases (ADAMs) and PIII snake venom Zn-metalloproteinases (SVMPs). The C-terminal cysteine-rich domain of catrocollastatin-C contains five disulfide bonds between nearest-neighbor cysteines and a long range disulfide bridge between CysV and CysX. These results provide structural evidence for a redefinition of the disintegrin-like and cysteine-rich domain boundaries. An evolutionary pathway for ADAMs, PIII, and PII SVMPs based on disulfide bond engineering is also proposed. [source] Cleaved antitrypsin polymers at atomic resolutionPROTEIN SCIENCE, Issue 2 2000Michelle A. Dunstone Abstract ,1 -Antitrypsin deficiency, which can lead to both emphysema and liver disease, is a result of the accumulation of ,1 antitrypsin polymers within the hepatocyte. A wealth of biochemical and biophysical data suggests that ,1 -antitrypsin polymers form via insertion of residues from the reactive center loop of one molecule into the ,-sheet of another. However, this long-standing hypothesis has not been confirmed by direct structural evidence. Here, we describe the first crystallographic evidence of a ,-strand linked polymer form of ,1 -antitrypsin: the crystal structure of a cleaved ,1 -antitrypsin polymer. [source] Monitoring structural transformations in crystals.ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2010The geometrical parameters governing the potential for the photocyclization reaction occurring in crystals of 2,3,4,5,6-pentamethylbenzophenone, C18H20O, (I), 1,3-diphenylbutan-1-one, C16H16O, (II), and 2,4,6-triisopropyl-4,-methoxybenzophenone, C23H30O2, (IV), have been evaluated. Compound (IV) undergoes photocyclization but (I) and (II) do not, despite the fact that their geometrical parameters appear equally favourable for reaction. The structure of the partially reacted crystal of the photoactive compound, i.e. 2,4,6-triisopropyl-4,-methoxybenzophenone,3,5-diisopropyl-7-(4-methoxyphenyl)-8,8-dimethylbicyclo[4.2.0]octa-1,3,5-trien-7-ol (9/1), 0.90C23H30O2·0.10C23H30O2, (III), was also determined, providing structural evidence for the reactivity of the compound. It has been found that the carbonyl group of the photoactive compound reacts with one of the two o -isopropyl groups. The study has shown that the intramolecular geometrical parameters are not the only factors influencing the reactivity of compounds in crystals. [source] 1-Deoxy-1-(4-fluorophenyl)-,- d -ribofuranose, its hemihydrate, and 1-deoxy-1-(2,4-difluorophenyl)-,- d -ribofuranose: structural evidence for intermolecular C,H,F,C interactionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2000Jan W. Bats The structures of 1-deoxy-1-(4-fluorophenyl)-,- d -ribofuranose in two crystal forms, (Ia) and (Ib) (C11H13FO4), 1-deoxy-1-(4-fluorophenyl)-,- d -ribofuranose hemihydrate, (Ic) (C11H13FO4·0.5H2O) and 1-deoxy-1-(2,4-difluorophenyl)-,- d -ribofuranose, (II) (C11H12F2O4), show two-dimensional networks of intermolecular hydrogen bonds between the hydroxyl groups. Weak intermolecular C,H,F,C and C,H,,arene interactions complete the packing in the third dimension. The ribofuranose ring has a conformation intermediate between a C1,- exo,C2,- endo twist and a C2,- endo envelope for (Ia) and (Ic), a conformation intermediate between a C2,- endo,C3,- exo twist and a C2,- endo envelope for (Ib) and an unsymmetrical C2,- exo,C3,- endo twist conformation for (II). [source] Structural asymmetry and intersubunit communication in muscle creatine kinaseACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2007Jeffrey F. Ohren The structure of a transition-state analog complex of a highly soluble mutant (R134K) of rabbit muscle creatine kinase (rmCK) has been determined to 1.65,Å resolution in order to elucidate the structural changes that are required to support and regulate catalysis. Significant structural asymmetry is seen within the functional homodimer of rmCK, with one monomer found in a closed conformation with the active site occupied by the transition-state analog components creatine, MgADP and nitrate. The other monomer has the two loops that control access to the active site in an open conformation and only MgADP is bound. The N-terminal region of each monomer makes a substantial contribution to the dimer interface; however, the conformation of this region is dramatically different in each subunit. Based on this structural evidence, two mutational modifications of rmCK were conducted in order to better understand the role of the amino-terminus in controlling creatine kinase activity. The deletion of the first 15 residues of rmCK and a single point mutant (P20G) both disrupt subunit cohesion, causing the dissociation of the functional homodimer into monomers with reduced catalytic activity. This study provides support for a structural role for the amino-terminus in subunit association and a mechanistic role in active-site communication and catalytic regulation. [source] High-resolution structure of a plasmid-encoded dihydrofolate reductase: pentagonal network of water molecules in the D2 -symmetric active siteACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2006Narendra Narayana R67 plasmid-encoded dihydrofolate reductase (R67 DHFR) is an NADPH-dependent homotetrameric enzyme that catalyzes the reduction of dihydrofolate to tetrahydrofolate. The amino-acid sequence and molecular architecture of R67 DHFR and its inhibitory properties toward folate analogues are different from those of chromosomal DHFR. Here, the crystal structure of R67 DHFR refined using 1.1,Å resolution data is presented. Blocked full-matrix least-squares refinement without restraints resulted in a final R factor of 11.4%. The anisotropic atomic displacement parameters analyzed by Rosenfield matrices and translation,libration,screw validation suggested four quasi-rigid domains. A total of ten C,,HO hydrogen bonds were identified between the ,-strands. There is reasonable structural evidence that His62 is not protonated in the tetramer, which is in accord with previous pH-profile studies. The side chain of Gln67 that protrudes into the active site exhibits dual conformation, a feature noticed for the first time owing to the availability of atomic resolution data. The R67 DHFR active site is unique: it has D2 symmetry and is a large active site with a pentagonal network of water molecules and exposure of backbone atoms to solvent; the central pore is favorable for planar ring-stacking interactions. The geometrical shape, overall symmetry, local asymmetry and waters appear to dominate the binding of ligands, catalysis and inhibition. [source] Structure of the nucleotide-binding domain of Plasmodium falciparum Rab6 in the GDP-bound formACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2000Debasish Chattopadhyay Rab proteins are small Ras-like GTPases which play important roles in regulating intracellular vesicle trafficking. The nucleotide-binding domain of Rab6 from the malaria parasite Plasmodium falciparum was crystallized with GDP bound to the active site. The MAD phasing technique was used to determine the crystal structure to 2.3,Å resolution. Comparisons of the structure of GDP-bound PfRab6 with the recently determined structures of Rab3A in complex with either a GTP analog or with GTP and Rabphillin present structural evidence supporting the traditional model for the molecular GTP/GDP switch in Rab proteins. PfRab6 residues homologous to those distinguishing human Rab6 isoforms, which differ in binding to Rabkinesin-6 in human cells, are located next to the recognized complementarity-determining region (CDR) and constitute a conceptual broadening of that domain. Despite significant observable differences in Golgi ultrastructure, the Rab6 core structure and switch mechanism appear highly conserved when compared with murine Rab3a structures. A significant difference between the PfRab6 and higher eukaryotic Rabs may be the lack of CDR features that allow binding interactions with Rabkinesin-type effectors. [source] Starch phosphorylation,Maltosidic restrains upon 3,- and 6,-phosphorylation investigated by chemical synthesis, molecular dynamics and NMR spectroscopyBIOPOLYMERS, Issue 3 2009Peter I. Hansen Abstract Phosphorylation is the only known in vivo substitution of starch, yet no structural evidence has been provided to explain its implications of the amylosidic backbone and its stimulating effects on starch degradation in plants. In this study, we provide evidence for a major influence on the glucosidic bond in starch specifically induced by the 3-O-phosphate. Two phosphorylated maltose model compounds were synthesized and subjected to combined molecular dynamics (MD) studies and 950 MHz NMR studies. The two phosphorylated disaccharides represent the two possible phosphorylation sites observed in natural starches, namely maltose phosphorylated at the 3,- and 6,-position (maltose-3,-O-phosphate and maltose-6,-O-phosphate). When compared with maltose, both of the maltose-phosphates exhibit a restricted conformational space of the ,(1,4) glycosidic linkage. When maltose is phosphorylated in the 3,-position, MD and NMR show that the glucosidic space is seriously restricted to one narrow potential energy well which is strongly offset from the global potential energy well of maltose and almost 50°degrees from the , angle of the ,-maltose crystal structure. The driving force is primarily steric, but the configuration of the structural waters is also significantly altered. Both the favored conformation of the maltose-3,-phosphate and the maltose-6,-phosphate align well into the 6-fold double helical structure of amylopectin when the effects on the glucosidic bond are not taken into account. However, the restrained geometry of the glucosidic linkage of maltose-3,-phosphate cannot be accommodated in the helical structure, suggesting a major local disturbing effect, if present in the starch granule semi-crystalline lattice. © 2008 Wiley Periodicals, Inc. Biopolymers 91: 179,193, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Deformation history of the eclogite- and jadeitite-bearing mélange from North Motagua Fault Zone, Guatemala: insights in the processes of a fossil subduction channelGEOLOGICAL JOURNAL, Issue 2 2009Michele Marroni Abstract In Guatemala, along the northern side of the Motagua Valley, a mélange consisting of blocks of eclogite and jadeitite set in a metaserpentinitic and metasedimentary matrix crops out. The metasedimentary rocks display a complex deformation history that includes four tectonic phases, from D1 to D4. The D1 phase occurs only as a relic and is characterized by a mineral assemblage developed under pressure temperature (P,T) conditions of 1.00,1.25,GPa and 206,263°C. The D2 phase, characterized by isoclinal folds, schistosity and mineral/stretching lineation, developed at P,T conditions of 0.70,1.20,GPa and 279,409°C. The following D3 and D4 phases show deformations developed at shallower structural levels. Whereas the D1 phase can be interpreted as the result of underplating of slices of oceanic lithosphere during an intraoceanic subduction, the following phases have been acquired by the mélange during its progressive exhumation through different mechanisms. The deformations related to the D2 and D3 phases can be regarded as acquired by extrusion of the mélange within a subduction channel during a stage of oblique subduction. In addition, the structural evidences indicate that the coupling and mixing of different blocks occurred during the D2 phase, as a result of flow reverse and upward trajectory in the subduction channel. By contrast, the D4 phase can be interpreted as related to extension at shallow structural levels. In this framework, the exhumation-related structures in the mélange indicate that this process, probably long-lived, developed through different mechanisms, active in the subduction channel through time. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||