Cyclophilins, which bind to immunosuppressant cyclosporin A (CsA), are ubiquitous proteins and constitute a multigene family in higher organisms. Several members of this family are reported to ...catalyze cis-trans isomerisation of the peptidyl-prolyl bond, which is a rate limiting step in protein folding. The physiological role of these proteins in plants, with few exceptions, is still a matter of speculation. Although Arabidopsis genome is predicted to contain 35 cyclophilin genes, biochemical characterization, imperative for understanding their cellular function(s), has been carried only for few of the members. The present study reports the biochemical characterization of an Arabidopsis cyclophilin, AtCyp19-3, which demonstrated that this protein is enzymatically active and possesses peptidyl-prolyl cis-trans isomerase (PPIase) activity that is specifically inhibited by CsA with an inhibition constant (Ki) of 18.75 nM. The PPIase activity of AtCyp19-3 was also sensitive to Cu(2+), which covalently reacts with the sulfhydryl groups, implying redox regulation. Further, using calmodulin (CaM) gel overlay assays it was demonstrated that in vitro interaction of AtCyp19-3 with CaM is Ca(2+)-dependent, and CaM-binding domain is localized to 35-70 amino acid residues in the N-terminus. Bimolecular fluorescence complementation assays showed that AtCyp19-3 interacts with CaM in vivo also, thus, validating the in vitro observations. However, the PPIase activity of the Arabidopsis cyclophilin was not affected by CaM. The implications of these findings are discussed in the context of Ca(2+) signaling and cyclophilin activity in Arabidopsis.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The sub-luminal phase velocity of electromagnetic waves in free space is generally unobtainable, being closely linked to forbidden faster than light group velocities. The requirement of sub-luminal ...phase-velocity in laser-driven particle acceleration schemes imposes a limit on the total acceleration achievable in free space, and necessitates the use of dispersive structures or waveguides for extending the field-particle interaction. We demonstrate a travelling source approach that overcomes the sub-luminal propagation limits. The approach exploits ultrafast optical sources with slow group velocity propagation, and a group-to-phase front conversion through nonlinear optical interaction. The concept is demonstrated with two terahertz generation processes, nonlinear optical rectification and current-surge rectification. We report measurements of longitudinally polarised single-cycle electric fields with phase and group velocity between 0.77c and 1.75c. The ability to scale to multi-megawatt-per-metre field strengths is demonstrated. Our approach paves the way towards the realisation of cheap and compact particle accelerators with femtosecond scale control of particles.Controlled generation of terahertz radiation with subluminal phase velocities is a key issue in laser-driven particle acceleration. Here, the authors demonstrate a travelling-source approach utilizing the group-to-phase front conversion to overcome the sub-luminal propagation limit.
Agricultural productivity is severely affected by soil salinity. One possible mechanism by which plants could survive salt stress is to compartmentalize sodium ions away from the cytosol. ...Overexpression of a vacuolar Na$^+$/H$^+$ antiport from Arabidopsis thaliana in Arabidopsis plants promotes sustained growth and development in soil watered with up to 200 millimolar sodium chloride. This salinity tolerance was correlated with higher-than-normal levels of AtNHX1 transcripts, protein, and vacuolar Na$^+$/H$^+$ (sodium/proton) antiport activity. These results demonstrate the feasibility of engineering salt tolerance in plants.
We demonstrate that full temporal characterisation of few-cycle electromagnetic pulses, including retrieval of the carrier envelope phase (CEP), can be directly obtained from Frequency Resolved ...Optical Gating (FROG) techniques in which the interference between non-linear frequency mixing processes is resolved. We derive a framework for this scheme, defined Real Domain FROG (ReD-FROG), for the cases of interference between sum and difference frequency components and between fundamental and sum / difference frequency components. A successful numerical demonstration of ReD-FROG as applied to the case of a self-referenced measurement is provided. A proof-of-principle experiment is performed in which the CEP of a single-cycle THz pulse is accurately obtained and demonstrates the possibility for THz detection beyond optical probe duration limitations inherent to electro-optic sampling.
The original version of this Article contained an error in the abstract, referring to "multi-megawatt-per-metre" instead of "multi-megavolt-per-metre". This has now been corrected in both the PDF and ...HTML versions of the Article.
Hydrocarbon exploration in the last decade has yielded sufficient data to evaluate the Gulf of Mexico basin response to the Chicxulub asteroid impact. Given its passive marine setting and proximity ...to the impact structure on the Yucatán Peninsula, the gulf is the premier locale in which to study the near‐field geologic effect of a bolide impact. We mapped a thick (decimeter‐ to hectometer‐scale) deposit of carbonate debris at the Cretaceous‐Paleogene boundary that is ubiquitous in the gulf and readily identifiable on borehole and seismic data. We interpret deposits seen in seismic and borehole data in the deepwater gulf to be predominately muddy debrites with minor turbidites based on cores in the southeastern gulf. Mapping of the deposit in the northern Gulf of Mexico reveals that the impact redistributed roughly 1.05 × 105 km3 of sediment therein and over 1.98 × 105 km3 gulfwide. Deposit distribution suggests that the majority of sediment derived from coastal and shallow‐water environments throughout the gulf via seismic and megatsunamic processes initiated by the impact. The Texas shelf and northern margin of the Florida Platform were significant sources of sediment, while the central and southern Florida Platform underwent more localized platform collapse. The crustal structure of the ancestral gulf influenced postimpact deposition both directly and indirectly through its control on salt distribution in the Louann Salt Basin. Nevertheless, impact‐generated deposition overwhelmed virtually all topography and depositional systems at the start of the Cenozoic, blanketing the gulf with carbonate debris within days.
Key Points
The Chicxulub impact redistributed more than 1.98 × 105 km3 of sediment in the Gulf of Mexico
Sediment gravity flow was the primary mechanism for impact‐generated transport
Crustal structure and salt influenced impact‐generated deposition regionally and locally
Particle accelerators driven by laser-generated terahertz (THz) pulses promise unprecedented control over the energy–time phase space of particle bunches compared with conventional radiofrequency ...technology. Here we demonstrate acceleration of a relativistic electron beam in a THz-driven linear accelerator. Narrowband THz pulses were tuned to the phase-velocity-matched operating frequency of a rectangular dielectric-lined waveguide for extended collinear interaction with 35 MeV, 60 pC electron bunches, imparting multicycle energy modulation to chirped (6 ps) bunches and injection phase-dependent energy gain (up to 10 keV) to subcycle (2 ps) bunches. These proof-of-principle results establish a route to whole-bunch linear acceleration of subpicosecond particle beams, directly applicable to scaled-up and multistaged concepts capable of preserving beam quality, thus marking a key milestone for future THz-driven acceleration of relativistic beams.Relativistic 35 MeV electron bunches with charges of 60 pC are accelerated in a terahertz-wave-driven dielectric waveguide. When the terahertz pulse energy is 0.8 μJ, an accelerating gradient of 2 MeV m−1 and energy gain of 10 keV are achieved.
We present the first sequential structural restoration with flexural backstripping of the Gulf of Mexico US‐Mexico conjugate margin salt basin. We construct four large‐scale (100s of km) balanced, ...sequential structural restorations to investigate spatio‐temporal patterns of subsidence, geometry of the original salt basin, feedbacks between post‐salt structural and stratigraphic evolution, paleo‐bathymetry, and crustal configurations. The restorations are based on interpretations of 2D and 3D seismic data, and include sequential sedimentary decompaction, flexural isostatic backstripping, and thermal isostatic corrections. The spatially variable crustal thinning factor is directly measured from seismic data, and lithologic parameters are determined by well penetrations. We present a model for the original salt basin and discuss evidence for and implications of a deep water salt basin setting for the GoM. Our analysis suggests a salt basin that contained ∼1–2 km thick salt in a basin 175–390 km across with ∼1 km of bathymetry after salt deposition. The base of salt is mostly smooth with <1 km of local relief in the form of normal faults that disrupt a pre‐salt sedimentary section. We find that supra‐salt extension and shortening are not balanced, with measurable extension exceeding shortening by 18–30 km on each cross‐section. Our subsidence analysis reveals anomalous subsidence totaling 1–2 km during Late Jurassic and Early Cretaceous times that may reflect dynamic topography or depth‐dependent thinning. We offer an interpretation of crustal breakup invoking pre‐salt clastic sedimentation, salt deposition in a deep water syn‐thinning basin, and post‐salt lower‐crustal exhumation.
Plain Language Summary
The Gulf of Mexico is a large basin that formed over 200 million years ago due to tectonically driven extension of a supercontinent. Early in its formation it accumulated thick salt deposits. Due to that salt and the later deposition of several kilometers of sedimentary rock that conceal the deep geology, it is difficult to know exactly how extension started and progressed. This study uses new 2D and 3D seismic data that images the deep geology corresponding to that early extension. We sequentially remove each rock layer to reconstruct what the margin looked like in the Mesozoic. By systematically moving back in time we are able to reconstruct the changing geometry, deformation, and bathymetry of the Gulf of Mexico. Our results reveal periods of time when the bathymetry was influenced by unknown factors, which we posit reflects mantle forces.
Key Points
We present sequential structural restorations with flexural backstripping of the post‐rift eastern GoM conjugate US‐MX margin from Mesozoic to present
We interpret the geometry and bathymetry of the restored Mesozoic salt basin
Our analysis indicates significant and widespread Mesozoic anomalous subsidence
Newly available two‐dimensional (2D) and limited three‐dimensional (3D) reflection seismic data coupled with publicly available well and core data were used to generate the first comprehensive ...regional basin evolution model for the deep‐water Neogene to recent southern Gulf of Mexico (GoM). This evolution is presented in the context of contemporaneous onshore tectonic drivers and predecessor basin tectonic history. Dynamic uplift to the west in North America, transpression to the south and tectonically influenced salt tectonics to the east served to collapse the margins of the southern Gulf of Mexico Basin throughout the late Neogene and into the modern. This collapse and salt inflation served to shut off efficient sediment transport into the axial deep basin. Newly developed nearshore extensional accommodation along both the western margin of the basin and salt‐rooted orogenic structures to the south and east appear to have baffled coarser‐caliber sediment input from southern (Mexican) sediment sources into the deep Gulf of Mexico Basin beginning in the late Miocene. This sequence is recorded in the southern GoM basin by a transition from large early–mid Miocene submarine channel belts to late Miocene–recent sediment wave fields and mass transport deposits. Improved resolution of new 2D and 3D subsurface seismic reflection data shows that sediment waves of the southern Gulf of Mexico are supercritical bedforms, long wavelength antidunes and cyclic steps, not contourites. These supercritical bedforms are among the most spatially expansive and morphologically largest documented globally. The location and evolution of these bedforms appears closely tied to the tectonically driven history of margin collapse, salt inflation and the starving of the deep basin of coarse‐grained sediment. Cumulatively, the tectonic drivers that intuitively should have increased sediment flux into the deep southern Gulf of Mexico acted to ‘pinch off’ the basin, starving it of sediment supplied from southern sediment sources.
The evolution of southern Gulf of Mexico deep‐marine depositional systems was strongly controlled by onshore dynamic and transpressional tectonics through the Neogene and into the modern. Nearshore extensional accommodation generated by margin collapse and salt inflation served to progressively starve the deep southern Gulf of sediment. This is recorded in the deep‐water basin center as a transition from large Miocene submarine channel systems to late Miocene to modern mass transport deposits and supercritical sediment waves.
One of the key issues concerning the development of efficient polymer solar cell technology is the lack of viable materials which absorb in the near‐infrared (NIR) region. This could be resolved by ...up‐converting energy from the NIR into visible using triplet fusion (TF) with an additional layer that is fabricated separately from the solar cell and deposited on top. Theoretically a maximum upconversion (UC) via TF efficiency of 50% could be obtained. Here, it is demonstrated that in a film of commercially available poly(para‐phenylene vinylene) copolymer “super yellow” (SY) doped with 4% palladium(meso‐tetraphenyl‐tetrabenzoporphyrin) (PdTPBP) sensitizer, an UC efficiency of 6% can be achieved. By using femtosecond and nanosecond spectroscopies it is shown that the main UC efficiency loss mechanism is due to triplet quenching in PdTPBP aggregates. The PdTPBP intersystem crossing rate constant is determined to be 1.8 × 1011 s−1 and the triplet energy transfer rate constant from PdTPBP to SY to be 109 s−1. Quenching in PdTPBP aggregates can account for a triplet concentration loss in the range of 76‐99%. As such, preventing sensitizer aggregation in NIR‐to‐visible upconverting films is crucial and may lead to substantial increase of UC efficiencies in films.
Energy upconversion via triplet fusion is achieved in “super yellow” polymer films doped with sensitizer. The main upconversion efficiency loss mechanism is due to triplet quenching in sensitizer aggregates and this could account for a loss in the range of 76–99%. Preventing sensitizer aggregation in near‐infraredto‐to‐visible upconverting films is crucial and could lead to substantial increase of upconversion efficiencies.
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