TfCut2 from Thermobifida fusca KW3 and the metagenome‐derived LC‐cutinase are bacterial polyester hydrolases capable of efficiently degrading polyethylene terephthalate (PET) films. Since the ...enzymatic PET hydrolysis is inhibited by the degradation intermediate mono‐(2‐hydroxyethyl) terephthalate (MHET), a dual enzyme system consisting of a polyester hydrolase and the immobilized carboxylesterase TfCa from Thermobifida fusca KW3 was employed for the hydrolysis of PET films at 60°C. HPLC analysis of the reaction products obtained after 24 h of hydrolysis showed an increased amount of soluble products with a lower proportion of MHET in the presence of the immobilized TfCa. The results indicated a continuous hydrolysis of the inhibitory MHET by the immobilized TfCa and demonstrated its advantage as a second biocatalyst in combination with a polyester hydrolase for an efficient degradation oft PET films. The dual enzyme system with LC‐cutinase produced a 2.4‐fold higher amount of degradation products compared to TfCut2 after a reaction time of 24 h confirming the superior activity of his polyester hydrolase against PET films.
Biocatalytic degradation of polyethylene terephthalate (PET) by a dual enzyme reaction system. PET was hydrolyzed to mono‐(2‐hydroxyethyl) terephthalate (MHET) with the polyester hydrolases TfCut2 and LC‐cutinase. MHET, an inhibitor of the polyesterases, was simultaneously hydrolyzed by the immobilized carboxylesterase TfCa resulting in a significant enhancement of the enzymatic PET hydrolysis process.
The North Atlantic bloom corresponds to a strong seasonal increase in phytoplankton that produces organic carbon through photosynthesis. It is still debated what physical and biological conditions ...trigger the bloom, because comprehensive time series of the vertical distribution of phytoplankton biomass are lacking. Vertical profiles from nine floats that sampled the waters of the North Atlantic every few days for a couple of years reveal that phytoplankton populations start growing in early winter at very weak rates. A proper bloom with rapidly accelerating population growth rates instead starts only in spring when atmospheric cooling subsides and the mixed layer rapidly shoals. While the weak accumulation of phytoplankton in winter is crucial to maintaining a viable population, the spring bloom dominates the overall seasonal production of organic carbon.
Organelles juxtaposition has been detected for decades, although only recently gained importance due to a pivotal role in the regulation of cellular processes dependent on membrane contact sites. ...Endoplasmic reticulum (ER) and mitochondria interaction is a prime example of organelles contact sites. Mitochondria-associated membranes (MAM) are proposed to harbor ER-mitochondria tether complexes, mainly when these organelles are less than 30 nm apart. Dysfunctions of proteins located at the MAM are associated with neurodegenerative diseases such as Parkinson’s, Alzheimer’s and amyotrophic lateral sclerosis, as well as neurodevelopmental disorders; hence any malfunction in MAM can potentially trigger cell death. This review will focus on the role of ER-mitochondria contact sites, regarding calcium homeostasis, lipid metabolism, autophagy, morphology and dynamics of mitochondria, mainly in the context of neurodegenerative diseases. Approaches that have been employed so far to study organelles contact sites, as well as methods that were not used in neurosciences yet, but are promising and accurate ways to unveil the functions of MAM during neurodegeneration, is also discussed in the present review.
Abstract
Turbulent mixing produced by breaking of internal waves plays an important role in setting the patterns of downwelling and upwelling of deep dense waters and thereby helps sustain the global ...deep ocean overturning circulation. A key parameter used to characterize turbulent mixing is its efficiency, defined here as the fraction of the energy available to turbulence that is invested in mixing. Efficiency is conventionally approximated by a constant value near one sixth. Here we show that efficiency varies significantly in the abyssal ocean and can be as large as approximately one third in density stratified regions near topographic features. Our results indicate that variations in efficiency exert a first‐order control over the rate of overturning of the lower branch of the meridional overturning circulation.
Key Points
Efficiency of turbulent mixing in the abyssal ocean is highly variable, as opposed to being considered a constant traditionally
Variations in mixing efficiency has a leading order impact on the rate of overturning of the abyssal branch of circulation
Abyssal ocean turbulence plays a leading role in regulating the ocean's role in the carbon cycle and likely other tracer budgets
Density fronts are ubiquitous features of the upper ocean. Here, numerical simulations show that restratification at fronts inhibits vertical mixing, triggering phytoplankton blooms in low‐light ...conditions. The stability of the water column at fronts is set by a competition between frontal instabilities, which restratify the upper ocean, and turbulent mixing, which acts to destroy this stratification. Recent studies have found that frontal instabilities can restratify the upper ocean, even in the presence of strong surface cooling and destabilizing winds. During winter at high latitudes, primary production by phytoplankton is generally limited by low ambient light levels and deep turbulent mixing. When the turbulent mixing, inhibited by frontal restratification, becomes smaller than a ‘critical turbulence’ threshold, a phytoplankton bloom can develop. The finding that fronts can trigger phytoplankton blooms by reducing mixing, provides an explanation for satellite observations of high chlorophyll concentrations at high latitude fronts.
Key Points
Oceanic fronts reduce turbulent mixing in the upper ocean
Reduced turbulent mixing at fronts triggers high‐latitude phytoplankton blooms
Fronts act as hotspots for primary productivity
Submesoscale eddies generated by baroclinic instability of upper ocean fronts lead to rapid restratification of the mixed layer on a time scale of days. This restratification can be opposed by a ...down‐front wind stress (acting in the direction of the geostrophic velocity) that drives a surface Ekman flow from the dense side to the light side of the front to arrest the slumping of isopycnals. A scaling diagnostic is suggested to determine whether the effect of eddies or wind dominates under different conditions. Using a numerical model, we investigate the juxtaposition of submesoscale eddies and down‐front winds acting on the mixed layer. By estimating the eddy‐induced overturning stream function in the mixed layer, we separate the along‐ and cross‐isopycnal fluxes of buoyancy associated with submesoscale mixed layer eddies and demonstrate the need for parameterization of the advective, along‐isopycnal flux. Though the cross‐front transport of buoyancy induced by the down‐front component of the wind opposes restratification by mixed layer eddies, it becomes diminished as the eddies and growth of the frontal instability disrupt alignment between the wind and frontal axis.
Several bacterial polyester hydrolases are able to hydrolyze the synthetic polyester polyethylene terephthalate (PET). For an efficient enzymatic degradation of PET, reaction temperatures close to ...the glass transition temperature of the polymer need to be applied. The esterases TfH, BTA2, Tfu_0882, TfCut1, and TfCut2 produced by the thermophilic actinomycete Thermobifida fusca exhibit PET‐hydrolyzing activity. However, these enzymes are not sufficiently stable in this temperature range for an efficient degradation of post‐consumer PET materials. The addition of Ca2+ or Mg2+ cations to the enzymes resulted in an increase of their melting points between 10.8 and 14.1°C determined by circular dichroism spectroscopy. The thermostability of the polyester hydrolases was sufficient to degrade semi‐crystalline PET films at 65°C in the presence of 10 mM Ca2+ and 10 mM Mg2+ resulting in weight losses of up to 12.9% after a reaction time of 48 h. The residues Asp174, Asp204, and Glu253 were identified by molecular dynamics simulations as potential binding residues for the two cations in TfCut2. This was confirmed by their substitution with arginine, resulting in a higher thermal stability of the corresponding enzyme variants. The generated variants of TfCut2 represent stabilized catalysts suitable for PET hydrolysis reactions performed in the absence of Ca2+ or Mg2+.
Efficient post‐consumer recycling of polyethylene terephthalate (PET) requires enzymes that are stable at the appropriate reaction temperature. Calcium was found to stabilize the structure of the polyester hydrolase TfCut2 from Thermobifida fusca and to provide sufficient thermal stability for the degradation of PET films at a reaction temperature of 65°C. These findings could contribute to the development of environmentally compatible post‐consumer PET recycling processes.
It is an open question whether turbulent mixing across density surfaces is sufficiently large to play a dominant role in closing the deep branch of the ocean meridional overturning circulation. The ...diapycnal and isopycnal mixing experiment in the Southern Ocean found the turbulent diffusivity inferred from the vertical spreading of a tracer to be an order of magnitude larger than that inferred from the microstructure profiles at the mean tracer depth of 1,500 m in the Drake Passage. Using a high-resolution ocean model, it is shown that the fast vertical spreading of tracer occurs when it comes in contact with mixing hotspots over rough topography. The sparsity of such hotspots is made up for by enhanced tracer residence time in their vicinity due to diffusion toward weak bottom flows. The increased tracer residence time may explain the large vertical fluxes of heat and salt required to close the abyssal circulation.
•Artificial intelligence is used for assessing response to therapy in rectal cancer.•Textural features extraction from high resolution 3 T MR images.•Artificial intelligence model helps personalize ...therapeutic strategy.•Decisions curves analysis confirm clinical utility.
To develop and validate an Artificial Intelligence (AI) model based on texture analysis of high-resolution T2 weighted MR images able 1) to predict pathologic Complete Response (CR) and 2) to identify non-responders (NR) among patients with locally-advanced rectal cancer (LARC) after receiving neoadjuvant chemoradiotherapy (CRT).
Fifty-five consecutive patients with LARC were retrospectively enrolled in this study. Patients underwent 3 T Magnetic Resonance Imaging (MRI) acquiring T2-weighted images before, during and after CRT. All patients underwent complete surgical resection and histopathology was the gold standard. Textural features were automatically extracted using an open-source software. A sub-set of statistically significant textural features was selected and two AI models were built by training a Random Forest (RF) classifier on 28 patients (training cohort). Model performances were estimated on 27 patients (validation cohort) using a ROC curve and a decision curve analysis.
Sixteen of 55 patients achieved CR. The AI model for CR classification showed good discrimination power with mean area under the receiver operating curve (AUC) of 0.86 (95% CI: 0.70, 0.94) in the validation cohort. The discriminatory power for the NR classification showed a mean AUC of 0.83 (95% CI: 0.71,0.92). Decision curve analysis confirmed higher net patient benefit when using AI models compared to standard-of-care.
AI models based on textural features of MR images of patients with LARC may help to identify patients who will show CR at the end of treatment and those who will not respond to therapy (NR) at an early stage of the treatment.
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