A review of the NE Atlantic conjugate margins based on seismic refraction data

The NE Atlantic region evolved through several rift episodes, leading to break-up in the Eocene that was associated with voluminous magmatism along the conjugate margins of East Greenland and NW Europe. Existing seismic refraction data provide good constraints on the overall tectonic development of the margins, despite data gaps at the NE Greenland shear margin and the southern Jan Mayen microcontinent. The maximum thickness of the initial oceanic crust is 40 km at the Greenland–Iceland–Faroe Ridge, but decreases with increasing distance to the Iceland plume. High-velocity lower crust interpreted as magmatic underplating or sill intrusions is observed along most margins but disappears north of the East Greenland Ridge and the Lofoten margin, with the exception of the Vestbakken Volcanic Province at the SW Barents Sea margin. South of the narrow Lofoten margin, the European side is characterized by wide margins. The opposite trend is seen in Greenland, with a wide margin in the NE and narrow margins elsewhere. The thin crust beneath the basins is generally underlain by rocks with velocities of >7 km s−1 interpreted as serpentinized mantle in the Porcupine and southern Rockall basins; while off Norway, alternative interpretations such as eclogite bodies and underplating are also discussed

Moho and basement depth in the NE Atlantic Ocean based on seismic refraction data and receiver functions

Seismic refraction data and results from receiver functions were used to compile the depth to the basement and Moho in the NE Atlantic Ocean. For interpolation between the unevenly spaced data points, the kriging technique was used. Free-air gravity data were used as constraints in the kriging process for the basement. That way, structures with little or no seismic coverage are still presented on the basement map, in particular the basins off East Greenland. The rift basins off NW Europe are mapped as a continuous zone with basement depths of between 5 and 15 km. Maximum basement depths off NE Greenland are 8 km, but these are probably underestimated. Plate reconstructions for Chron C24 (c. 54 Ma) suggest that the poorly known Ammassalik Basin off SE Greenland may correlate with the northern termination of the Hatton Basin at the conjugate margin. The most prominent feature on the Moho map is the Greenland–Iceland–Faroe Ridge, with Moho depths >28 km. Crustal thickness is compiled from the Moho and basement depths. The oceanic crust displays an increased thickness close to the volcanic margins affected by the Iceland plume

Crustal structure beneath western and eastern Iceland from surface waves and receiver functions

We determine the crustal structures beneath 14 broad-band seismic stations, deployed in western, eastern, central and southern Iceland, using surface wave dispersion curves and receiver functions. We implement a method to invert receiver functions using constraints obtained from genetic algorithm inversion of surface waves. Our final models satisfy both data sets. The thickness of the upper crust, as defined by the velocity horizon Vs= 3.7 km s−1, is fairly uniform at ∼6.5–9 km beneath the Tertiary intraplate areas of western and eastern Iceland, and unusually thick at 11 km beneath station HOT22 in the far south of Iceland. The depth to the base of the lower crust, as defined by the velocity horizon Vs= 4.1 km s−1 is ∼20–26 km in western Iceland and ∼27–33 km in eastern Iceland. These results agree with those of explosion profiles that detect a thinner crust beneath western Iceland than beneath eastern Iceland. An earlier report of a substantial low-velocity zone beneath the Middle Volcanic Zone in the lower crust is confirmed by a similar observation beneath an additional station there. As was found in previous receiver function studies, the most reliable feature of the results is the clear division into an upper sequence that is a few kilometres thick where velocity gradients are high, and a lower, thicker sequence where velocity gradients are low. The transition to typical mantle velocities is variable, and may range from being very gradational to being relatively sharp and clear. A clear Moho, by any definition, is rarely seen, and there is thus uncertainty in estimates of the thickness of the crust in many areas. Although a great deal of seismic data are now available constraining the structures of the crust and upper mantle beneath Iceland, their geological nature is not well understood

Frizzled 7 and PIP₂ binding by syntenin PDZ₂ domain supports Frizzled 7 trafficking and signalling

PDZ domain-containing proteins work as intracellular scaffolds to control spatio-temporal aspects of cell signalling. This function is supported by the ability of their PDZ domains to bind other proteins such as receptors, but also phosphoinositide lipids important for membrane trafficking. Here we report a crystal structure of the syntenin PDZ tandem in complex with the carboxy-terminal fragment of Frizzled 7 and phosphatidylinositol 4,5-bisphosphate (PIP₂). The crystal structure reveals a tripartite interaction formed via the second PDZ domain of syntenin. Biophysical and biochemical experiments establish co-operative binding of the tripartite complex and identify residues crucial for membrane PIP₂-specific recognition. Experiments with cells support the importance of the syntenin–PIP₂ interaction for plasma membrane targeting of Frizzled 7 and c-jun phosphorylation. This study contributes to our understanding of the biology of PDZ proteins as key players in membrane compartmentalization and dynamics

Recombinant human complement component C2 produced in a human cell line restores the classical complement pathway activity in-vitro: an alternative treatment for C2 deficiency diseases

Background: Complement C2 deficiency is the most common genetically determined complete complement deficiency and is associated with a number of diseases. Most prominent are the associations with recurrent serious infections in young children and the development of systemic lupus erythematosus (SLE) in adults. The links with these diseases reflect the important role complement C2 plays in both innate immunity and immune tolerance. Infusions with normal fresh frozen plasma for the treatment of associated disease have demonstrated therapeutic effects but so far protein replacement therapy has not been evaluated. Results: Human complement C2 was cloned and expressed in a mammalian cell line. The purity of recombinant human C2 (rhC2) was greater than 95% and it was characterized for stability and activity. It was sensitive to C1s cleavage and restored classical complement pathway activity in C2-deficient serum both in a complement activation ELISA and a hemolytic assay. Furthermore, rhC2 could increase C3 fragment deposition on the human pathogen Streptococcus pneumoniae in C2-deficient serum to levels equal to those with normal serum. Conclusions: Taken together these data suggest that recombinant human C2 can restore classical complement pathway activity and may serve as a potential therapeutic for recurring bacterial infections or SLE in C2-deficient patients

An Atlas of the Thioredoxin Fold Class Reveals the Complexity of Function-Enabling Adaptations

The group of proteins that contain a thioredoxin (Trx) fold is huge and diverse. Assessment of the variation in catalytic machinery of Trx fold proteins is essential in providing a foundation for understanding their functional diversity and predicting the function of the many uncharacterized members of the class. The proteins of the Trx fold class retain common features—including variations on a dithiol CxxC active site motif—that lead to delivery of function. We use protein similarity networks to guide an analysis of how structural and sequence motifs track with catalytic function and taxonomic categories for 4,082 representative sequences spanning the known superfamilies of the Trx fold. Domain structure in the fold class is varied and modular, with 2.8% of sequences containing more than one Trx fold domain. Most member proteins are bacterial. The fold class exhibits many modifications to the CxxC active site motif—only 56.8% of proteins have both cysteines, and no functional groupings have absolute conservation of the expected catalytic motif. Only a small fraction of Trx fold sequences have been functionally characterized. This work provides a global view of the complex distribution of domains and catalytic machinery throughout the fold class, showing that each superfamily contains remnants of the CxxC active site. The unifying context provided by this work can guide the comparison of members of different Trx fold superfamilies to gain insight about their structure-function relationships, illustrated here with the thioredoxins and peroxiredoxins