María Luján

Role of décollement material with different rheological properties in the structure of the Aljibe thrust imbricate (Flysch Trough, Gibraltar Arc): an analogue modelling approach

Abstract The Miocene Aljibe thrust imbricate (Flysch Trough), in the external zone of the Gibraltar Arc, shows large changes in structural style towards the foreland. Rheological variation of the decollement rocks—Triassic evaporitic rocks and Mesozoic limestones—appears to be the main factor controlling the contrasts in structural style that characterise adjacent wedge domains. In order to test this hypothesis, we carried out analogue experiments involving three-dimensional variations of decollement material. A plate of viscous material was placed in the central part of the models, at the base of the sand multilayers. Different geometries of the viscous plate were used. Experimental results show a strong link between the rheological properties of the decollement material and the structure of the overlying thrust wedge. These results compare well with the internal geometry and vergence distribution in the Aljibe thrust imbricate. Indeed, the tectonic style of the wedge can be explained as a consequence of variations of rock type along the basal decollement.

Contractional and extensional tectonics in Flysch and Penibetic units (Gibraltar Arc, SW Spain) : new constraints on emplacement mechanisms

Abstract The Aljibe Unit (Flysch Trough Complex), which can be described as a thin-skinned contractional belt, represents a major element of the Gibraltar Arc accretionary prism. It is shown that this unit underwent WNW–ESE shortening during the Miocene, as did the underlying Penibetic units. The organization of the Aljibe unit suggests a push-from-behind emplacement mechanism during this first contractional event. By contrast, the current boundary between the Penibetic and Aljibe units is found to be a normal, low-to-moderate angle fault that was later folded. This extensional faulting occurred between two compressional pulses (Lower-to-Middle and Upper Miocene in age) with similar shortening directions.

A simple and efficient method to prepare pure dimers and monomers of the cytochrome b6f complex from spinach

Using a single size-exclusion chromatography we were able to isolate highly pure dimers and monomers of the Cyt b6f complex from spinach from a bulk preparation of that protein complex obtained with a standard procedure. At higher protein/detergent ratio during the chromatography most of the Cyt b6f complex remained as dimers. In contrast, at lower protein/detergent ratio (around 15 times lower), most dimers became monomerized. As a bonus, this chromatography also allowed the elimination of potential Chl a contaminant to the Cyt b6f preparations. SDS-PAGE protein analysis with 18% (w/v) acrylamide revealed the loss of the ISP subunit in our monomeric preparation. However, it fully retained the content of Chl a, a prerequisite to perform any spectroscopic study involving this unique pigment.

Probing Energy Landscapes of Cytochrome b6f with Spectral Hole Burning: Effects of Deuterated Solvent and Detergent

In non-photochemical spectral hole burning (NPHB) and spectral hole recovery experiments, cytochrome b6f protein exhibits behavior that is almost independent of the deuteration of the buffer/glycerol glassy matrix containing the protein, apart from some differences in heat dissipation. On the other hand, strong dependence of the hole burning properties on sample preparation procedures was observed and attributed to a large increase of the electron-phonon coupling and shortening of the excited-state lifetime occurring when n-dodecyl β-d-maltoside (DM) is used as a detergent instead of n-octyl β-d-glucopyranoside (OGP). The data was analyzed assuming that the tunneling parameter distribution or barrier distribution probed by NPHB and encoded into the spectral holes contains contributions from two nonidentical components with accidentally degenerate excited state λ-distributions. Both components likely reflect protein dynamics, although with some small probability one of them (with larger md2) may still represent the dynamics involving specifically the -OH groups of the water/glycerol solvent. Single proton tunneling in the water/glycerol solvent environment or in the protein can be safely excluded as the origin of observed NPHB and hole recovery dynamics. The intensity dependence of the hole growth kinetics in deuterated samples likely reflects differences in heat dissipation between protonated and deuterated samples. These differences are most probably due to the higher interface thermal resistivity between (still protonated) protein and deuterated water/glycerol outside environment.

In vivo reconstitution of a homodimeric cytochrome b559 like structure: The role of the N-terminus α-subunit from Synechocystis sp. PCC 6803.

The cytochrome b559 is a heme-bridged heterodimeric protein with two subunits, α and β. Both subunits from Synechocystis sp. PCC 6803 have previously been cloned and overexpressed in Escherichia coli and in vivo reconstitution experiments have been carried out. The formation of homodimers in the bacterial membrane with endogenous heme was only observed in the case of the β-subunit (β/β) but not with the full length α-subunit. In the present work, reconstitution of a homodimer (α/α) cytochrome b559 like structure was possible using a chimeric N-terminus α-subunit truncated before the amino acid isoleucine 17, eliminating completely a short amphipathic α-helix that lays on the surface of the membrane. Overexpression and in vivo reconstitution in the bacteria was clearly demonstrated by the brownish color of the culture pellet and the use of a commercial monoclonal antibody against the fusion protein carrier, the maltoside binding protein, and polyclonal antibodies against a synthetic peptide of the α-subunit from Thermosynechococcus elongatus. Moreover, a simple partial purification after membrane solubilization with Triton X-100 confirmed that the overexpressed protein complex corresponded with the maltoside binding protein-chimeric α-subunit cytochrome b559 like structure. The features of the new structure were determined by UV-Vis, electron paramagnetic resonance and redox potentiometric techniques. Ribbon representations of all possible structures are also shown to better understand the mechanism of the cytochrome b559 maturation in the bacterial cytoplasmic membrane.