Protein interactions are the foundation of cell biology. For robust signal transduction to occur, proteins interact selectively and modulate their behavior to direct specific biological outcomes. ...Frequently, modular protein interaction domains are central to these processes. Some of these domains bind proteins bearing post‐translational modifications, such as phosphorylation, whereas other domains recognize and bind to specific amino acid motifs. Other modules act as diverse protein interaction scaffolds or can be multifunctional, forming head‐to‐head homodimers and binding specific peptide sequences or membrane phospholipids. Additionally, the so‐called head‐to‐tail oligomerization domains (SAM, DIX, and PB1) can form extended polymers to regulate diverse aspects of biology. Although the mechanism and structures of these domains are diverse, they are united by their modularity. Together, these domains are versatile and facilitate the evolution of complex protein interaction networks. In this review, we will highlight the role of select modular protein interaction domains in various aspects of plant biology.
The ability for proteins to interact is central to their biological functions. Modular protein domains act as a biological toolkit that allow evolution of protein interactions. In this review, we provide a snapshot of how individual domains drive protein versatility and lay the groundwork for complex protein interactions in plants.
•α-Olefins are important bulk and fine chemicals employed for the synthesis of plastics, detergent alcohols and lubricants for instance. The synthesis of α-olefins from ethylene, an abundantly ...available and inexpensive feedstock, is highly attractive, is carried out in megaton scale annually and is a key application of homogenous catalysis. Unfortunately, the synthesis of branched olefins is challenging especially in direct or so call on-purpose synthesis. We recently reported a molecular Ti catalyst (Science 2022) permitting the selective reaction between an α-olefin and two ethylene molecules to overcome this problem. Unfortunately, the synthesis of the Ti pre-catalyst(s) is very challenging preventing easy derivative modifications to fully exploiting the potential of the novel reaction.•We report on an easily accessible zirconium catalyst that permits the co-oligomerization of 1-hexene and ethylene.•We report synthesis and structure of six novel Zr precatalysts.•Some of the Zr catalyst systems introduced here show an extremely high activity in ethylene homo-oligomerization.
Selective co-oligomerizations between α-olefins and ethylene are of high interest since they allow to extend the α-olefin scope employing inexpensive and abundantly available ethylene. Here we report on an easily accessible zirconium catalyst that permits the co-oligomerization of 1-hexene and ethylene with an activity of 2200 kg/mol h bar and a co-oligomer selectivity of 65 mol%. In more detail, we report synthesis and structure of six novel Zr precatalysts, their ethylene homo-oligomerization behavior and the co-oligomerization of the most promising of the six precatalysts. Criteria were activity and selectivity (α-value). Some of the Zr catalyst systems introduced here show an extremely high activity in ethylene homo-oligomerization up to 96,600 kg/mol h bar.
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•A micro-kinetic model was constructed for the ethylene oligomerization.•Hexene is formed via a series of ethylene coordination-insertion steps.•Octene is formed via ...co-oligomerization of ethylene and desorbed butene.
We report the kinetics of ethylene oligomerization over the Ni-H-Beta for temperatures ranging between 50 and 100 °C and pressures ranging between 5 and 28 atm. According to our results, the apparent activation energies involved in the formation of butene, hexene, and octene are 44, 78, and 60 kJ.mol−1, respectively. The measured lower apparent activation energy for butene formation relative to hexene and octene is a likely result of the fact that the measured butene formation is not the true (forward) rate of formation of butene but it the net rate because of the consumption of butene in secondary reactions. Analysis of the reaction order indicates that participation of butene in chain-growth reactions takes place via desorption followed by re-adsorption of butene on the catalyst. The results also indicate that hexene undergoes a similar process. In the present paper, we refer to the pathway involving co-oligomerization of butene and hexene as “cascade co-oligomerization”. Based on these findings, we proposed a reaction network and modeled reaction rate expressions for ethylene consumption and butene, hexene, and octene formation based on the construction of a micro-kinetic model. We calculated the kinetic parameters involved in the reaction network proposed and found evidence that the formation of octene proceeds mainly via the “cascade co-oligomerization” of re-adsorbed butene with ethylene.
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•The 5-lump kinetic model describes oligomerization and catalyst deactivation.•Catalyst activities for the reactions are considered by selective deactivation model.•Gasoline yield at ...275 °C, 1.5 bar and 1-butene partial pressure of 0.88 bar is 39.4 %.•The kinetic model predicts a gasoline yield of 60 % with space time 30 gcathmolC−1.•Model is relevant for the scale-up of low pressure oligomerization to gasoline.
A five lump kinetic model (C4=, C8=, C12=, C1-C4 and C5-C12) has been established for 1-butene (C4=) oligomerization at low pressure (1.5 bar) and 275 °C on an HZSM-5 zeolite catalyst agglomerated in a γ-Al2O3 mesoporous matrix. The kinetic parameters have been calculated based on the results obtained in a packed-bed reactor for different concentrations of 1-butene in the feed (with N2 as diluent) and different values of space time (0.5–9.5 gcatalyst h molC-1). The model quantifies the evolution with time on stream of the concentrations of the lumps, considering the selective deactivation of the catalyst for the oligomerization, cracking and pool of secondary reactions. Furthermore, it allows to calculate the remnant activity of the catalyst in the pseudo-steady state (>5h on stream) for the different reaction groups, as well as the corresponding product distribution. The kinetic model has been used in the simulation of the packed-bed reactor to study the effect of space time and 1-butene partial pressure variables. At the conditions range studied experimentally, 39.4 % gasoline yield (C5-C12 fraction, mainly composed of olefins) and a 1-butene conversion of 45 % are achieved in the pseudo-steady state of the catalyst, at a space time of 9.5 gcatalyst h molC-1 and a partial pressure of 1-butene of 0.8 bar. Additionally, for values exceeding those studied experimentally, the model predicts at the pseudo-steady state a gasoline yield of 60 % at a space time of 30 gcatalyst h molC-1 and a partial pressure of 1-butene of ∼ 0.5 bar.
Abstract
The human non-canonical inflammasome controls caspase-4 activation and gasdermin-D-dependent pyroptosis in response to cytosolic bacterial lipopolysaccharide (LPS). Since LPS binds and ...oligomerizes caspase-4, the pathway is thought to proceed without dedicated LPS sensors or an activation platform. Here we report that interferon-induced guanylate-binding proteins (GBPs) are required for non-canonical inflammasome activation by cytosolic
Salmonella
or upon cytosolic delivery of LPS. GBP1 associates with the surface of cytosolic
Salmonella
seconds after bacterial escape from their vacuole, initiating the recruitment of GBP2-4 to assemble a GBP coat. The GBP coat then promotes the recruitment of caspase-4 to the bacterial surface and caspase activation, in absence of bacteriolysis. Mechanistically, GBP1 binds LPS with high affinity through electrostatic interactions. Our findings indicate that in human epithelial cells GBP1 acts as a cytosolic LPS sensor and assembles a platform for caspase-4 recruitment and activation at LPS-containing membranes as the first step of non-canonical inflammasome signaling.
The semiempirical tight-binding based quantum chemistry method GFN2-xTB is used in the framework of meta-dynamics (MTD) to globally explore chemical compound, conformer, and reaction space. The ...biasing potential given as a sum of Gaussian functions is expressed with the root-mean-square-deviation (RMSD) in Cartesian space as a metric for the collective variables. This choice makes the approach robust and generally applicable to three common problems (i.e., conformer search, chemical reaction space exploration in a virtual nanoreactor, and for guessing reaction paths). Because of the inherent locality of the atomic RMSD, functional group or fragment selective treatments are possible facilitating the investigation of catalytic processes where, for example, only the substrate is thermally activated. Due to the approximate character of the GFN2-xTB method, the resulting structure ensembles require further refinement with more sophisticated, for example, density functional or wave function theory methods. However, the approach is extremely efficient running routinely on common laptop computers in minutes to hours of computation time even for realistically sized molecules with a few hundred atoms. Furthermore, the underlying potential energy surface for molecules containing almost all elements (Z = 1–86) is globally consistent including the covalent dissociation process and electronically complicated situations in, for example, transition metal systems. As examples, thermal decomposition, ethyne oligomerization, the oxidation of hydrocarbons (by oxygen and a P450 enzyme model), a Miller-Urey model system, a thermally forbidden dimerization, and a multistep intramolecular cyclization reaction are shown. For typical conformational search problems of organic drug molecules, the new MTD(RMSD) algorithm yields lower energy structures and more complete conformer ensembles at reduced computational effort compared with its already well performing predecessor.
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•Oligomerization of aniline takes place near neutral pH.•Only 800 ppm H2O2 and 2 ppm Fe-TAML are needed to treat 1000 ppm aniline.•The treatment requires much less H2O2 than other ...advanced oxidation processes.•Aniline oligomers can be removed as precipitation from wastewaters.•No secondary waste is produced from the treatment of aniline.
Aniline is a nitrogen-containing compound that contributes to both total organic carbon (TOC) and total nitrogen (TN) in wastewaters. Herein, we focus on converting aniline into oligomers, which aggregate into solid particles and can be separated from the wastewaters. By using this strategy, we can remove not only aniline but also TOC and TN in the wastewater without producing any secondary wastes. In this reaction, aniline is first reacted with H2O2 in the presence of Iron-tetraamidomacrocyclic ligand (Fe-TAML) near a neutral pH. Only 800 ppm of H2O2 and 2 ppm of Fe-TAML are needed to react with 1000 ppm of aniline at pH 8. After 2 days of reaction, solid particles are produced, and they can be filtered out with a membrane. The treatment efficiency can be further improved by lowering the pH to 6. Under this condition, the solid particles are big enough to settle under gravity in one day. After that, the top-layer solution can be separated from the solid particles. Following the oxidation- settling strategy, aniline, TOC, and TN of the decanted solution are reduced to 27.0, 99.0, and 29.0 ppm, respectively. This new strategy is effective in aniline removal with minimal H2O2 and catalyst usages.
The objective of this review is the analysis and comment of recent publication results (from July 2010 until February 2017) obtained for selective ethylene oligomerization toward 1-hexene and ...1-octene catalyzed by chromium-based catalytic systems. Both the scientific and patent literature was taken into the consideration. The catalytic systems for ethylene oligomerization are classified on the basis of the ligand type employed. The activities and selectivities of the catalysts are provided throughout the text. Despite a big success in the field, there is still rather limited choice of catalysts affording simultaneously high activity, selectivity and low polymer proportion. This is especially true for ethylene to 1-octene tetramerization reaction. The results of the studies concerning oligomerization mechanisms obtained over the recent years are also included in this review.
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