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Transcontinental retroarc sediment routing controlled by subduction geometry and climate change (Central and Southern Andes, Argentina)
AbstractCentral Argentina from the Pampean flatâslab segment to northern Patagonia (27°â41°S) represents a classic example of a broken retroarc basin with strong tectonic and climatic control on fluvial sediment transport. Combined with previous research focused on coastal sediments, this actualistic provenance study uses framework petrography and heavyâmineral data to trace multistep dispersal of volcaniclastic detritus first eastwards across central Argentina for up to ca. 1,500 km and next northwards for another 760 km along the Atlantic coast. Although detritus generated in the Andes is largely derived from mesosilicic volcanic rocks of the cordillera, its compositional signatures reflect different tectonoâstratigraphic levels of the orogen uplifted along strike in response to varying subduction geometry as well as different character and crystallization condition of arc magmas through time and space. River sand, thus, changes from feldspathoâlithoâquartzose or lithoâfeldspathoâquartzose in the north, where sedimentary detritus is more common, to mostly quartzoâfeldspathoâlithic in the centre and to feldspathoâlithic in the south, where volcanic detritus is dominant. The transparentâheavyâmineral suite changes markedly from amphibole â« clinopyroxene > orthopyroxene in the north, to amphibole â clinopyroxene â orthopyroxene in the centre and to orthopyroxene â„ clinopyroxene â« amphibole in the south. In the presently dry climate, fluvial discharge is drastically reduced to the point that even the Desaguadero trunk river has become endorheic and orogenic detritus is dumped in the retroarc basin, reworked by winds and temporarily accumulated in dune fields. During the Quaternary, instead, much larger amounts of water were released by melting of the Cordilleran ice sheet or during pluvial events. The sedimentâladen waters of the Desaguadero and Colorado rivers then rushed from the tract of the Andes with greatest topographic and structural elevation, fostering alluvial fans inland and flowing in much larger valleys than today towards the Atlantic Ocean. Sand and gravel supply to the coast was high enough not only to promote rapid progradation of large deltaic lobes but also to feed a cell of littoral sediment transport extending as far north as the RĂo de la Plata estuary
Role of Secondary Motifs in Fast Folding Polymers: A Dynamical Variational Principle
A fascinating and open question challenging biochemistry, physics and even
geometry is the presence of highly regular motifs such as alpha-helices in the
folded state of biopolymers and proteins. Stimulating explanations ranging from
chemical propensity to simple geometrical reasoning have been invoked to
rationalize the existence of such secondary structures. We formulate a
dynamical variational principle for selection in conformation space based on
the requirement that the backbone of the native state of biologically viable
polymers be rapidly accessible from the denatured state. The variational
principle is shown to result in the emergence of helical order in compact
structures.Comment: 4 pages, RevTex, 4 eps figure
Selected reactive oxygen species and antioxidant enzymes in common bean after Pseudomonas syringae pv. phaseolicola and Botrytis cinerea infection
Phaseolus vulgaris cv. Korona plants were
inoculated with the bacteria Pseudomonas syringae pv.
phaseolicola (Psp), necrotrophic fungus Botrytis cinerea
(Bc) or with both pathogens sequentially. The aim of the
experiment was to determine how plants cope with multiple
infection with pathogens having different attack strategy.
Possible suppression of the non-specific infection with
the necrotrophic fungus Bc by earlier Psp inoculation was
examined. Concentration of reactive oxygen species
(ROS), such as superoxide anion (O2
-) and H2O2 and
activities of antioxidant enzymes such as superoxide dismutase
(SOD), catalase (CAT) and peroxidase (POD) were
determined 6, 12, 24 and 48 h after inoculation. The
measurements were done for ROS cytosolic fraction and
enzymatic cytosolic or apoplastic fraction. Infection with
Psp caused significant increase in ROS levels since the
beginning of experiment. Activity of the apoplastic
enzymes also increased remarkably at the beginning of
experiment in contrast to the cytosolic ones. Cytosolic
SOD and guaiacol peroxidase (GPOD) activities achieved
the maximum values 48 h after treatment. Additional forms
of the examined enzymes after specific Psp infection were
identified; however, they were not present after single Bc
inoculation. Subsequent Bc infection resulted only in
changes of H2O2 and SOD that occurred to be especially
important during plantâpathogen interaction. Cultivar Korona
of common bean is considered to be resistant to Psp and mobilises its system upon infection with these bacteria.
We put forward a hypothesis that the extent of defence
reaction was so great that subsequent infection did not
trigger significant additional response
A self-organized model for cell-differentiation based on variations of molecular decay rates
Systemic properties of living cells are the result of molecular dynamics
governed by so-called genetic regulatory networks (GRN). These networks capture
all possible features of cells and are responsible for the immense levels of
adaptation characteristic to living systems. At any point in time only small
subsets of these networks are active. Any active subset of the GRN leads to the
expression of particular sets of molecules (expression modes). The subsets of
active networks change over time, leading to the observed complex dynamics of
expression patterns. Understanding of this dynamics becomes increasingly
important in systems biology and medicine. While the importance of
transcription rates and catalytic interactions has been widely recognized in
modeling genetic regulatory systems, the understanding of the role of
degradation of biochemical agents (mRNA, protein) in regulatory dynamics
remains limited. Recent experimental data suggests that there exists a
functional relation between mRNA and protein decay rates and expression modes.
In this paper we propose a model for the dynamics of successions of sequences
of active subnetworks of the GRN. The model is able to reproduce key
characteristics of molecular dynamics, including homeostasis, multi-stability,
periodic dynamics, alternating activity, differentiability, and self-organized
critical dynamics. Moreover the model allows to naturally understand the
mechanism behind the relation between decay rates and expression modes. The
model explains recent experimental observations that decay-rates (or turnovers)
vary between differentiated tissue-classes at a general systemic level and
highlights the role of intracellular decay rate control mechanisms in cell
differentiation.Comment: 16 pages, 5 figure
Conformational dynamics is more important than helical propensity for the folding of the all alpha-helical protein Im7
Im7 folds via an on-pathway intermediate that contains three of the four native α-helices. The missing helix, helix III, is the shortest and its failure to be formed until late in the pathway is related to frustration in the structure. Im7H3M3, a 94-residue variant of the 87-residue Im7 in which helix III is the longest of the four native helices, also folds via an intermediate. To investigate the structural basis for this we calculated the frustration in the structure of Im7H3M3 and used NMR to investigate its dynamics. We found that the native state of Im7H3M3 is highly frustrated and in equilibrium with an intermediate state that lacks helix III, similar to Im7. Model-free analysis identified residues with chemical exchange contributions to their relaxation that aligned with the residues predicted to have highly frustrated interactions, also like Im7. Finally, we determined properties of urea-denatured Im7H3M3 and identified four clusters of interacting residues that corresponded to the α-helices of the native protein. In Im7 the cluster sizes were related to the lengths of the α-helices with cluster III being the smallest but in Im7H3M3 cluster III was also the smallest, despite this region forming the longest helix in the native state. These results suggest that the conformational properties of the urea-denatured states promote formation of a three-helix intermediate in which the residues that form helix III remain non-helical. Thus it appears that features of the native structure are formed early in folding linked to collapse of the unfolded state
Substrate protein folds while it is bound to the ATP-independent chaperone Spy
Chaperones assist the folding of many proteins in the cell. While the most well studied chaperones use cycles of ATP binding and hydrolysis to assist protein folding, a number of chaperones have been identified that promote protein folding in the absence of highenergy cofactors. Precisely how ATP-independent chaperones accomplish this feat is
unclear. Here we have characterized the kinetic mechanism of substrate folding by the small, ATP-independent chaperone, Spy. Spy rapidly associates with its substrate, Immunity protein 7 (Im7), eliminating its potential for aggregation. Remarkably, Spy then allows Im7 to fully fold into its native state while remaining bound to the surface of the chaperone. These results establish a potentially widespread mechanism whereby ATP-independent chaperones can assist in protein refolding. They also provide compelling evidence that substrate proteins can fold while continuously bound to a chaperone
The Initial Phase of the Argumentative Discussions Between Parents and Children
This chapter examines the initial phase of parent\u2013child argumentative discussions during mealtime. The conceptual tool adopted for the analysis is based on the pragma-dialectical ideal model of a critical discussion (van Eemeren & Grootendorst\u201a 2004). The types of issues leading parents and children to engage in argumentative discussions during mealtime as well as the contribution that parents and children provide to the inception of argumentation are described and discussed. The analysis of the initial phase of parent\u2013child argumentative discussions also considers the role played by the specificity of the parent\u2013child relationship and the distinctive features of the activity of family mealtime for the beginning of an argumentative discussion. Exemplary argumentative
sequences that bring to light the results obtained through the qualitative analysis of a larger corpus of argumentative discussions between parents and children are presented and discussed
Symptoms of Anxiety, Depression, and Aggression in Non-clinical Children: Relationships with Self-report and Performance-based Measures of Attention and Effortful Control
This study investigated the relation between the regulative trait of effortful control, and in particular attention control, and psychopathological symptoms in a sample of 207 non-clinical children aged 8â12 years. For this purpose, children completed self-report scales for measuring regulative traits and various types of psychopathological symptoms (i.e., anxiety, depression, and aggression) and were tested with a neuropsychological battery for measuring attention/effortful control capacity. Results indicated that self-report and performance-based measures of attention/effortful control were at best moderately correlated. Further, it was found that self-report indexes of attention/effortful control were clearly negatively related to psychopathological symptoms, which provides support for the notion that low regulation is associated with higher levels of psychopathology. Finally, the performance-based measure of attention/effortful control was not convincingly related to psychopathological symptoms
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