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Identification of a key water molecule involved in the macrophage migration inhibitory factor‐catalyzed tautomerization of para ‐hydroxyphenylpyruvate using neutron crystallography
Abstract Neutron crystallography was used to determine a 2.5‐Å resolution all‐atom structure of macrophage migration inhibitory factor (MIF) interacting with 3‐(4‐hydroxyphenyl)‐pyruvate (HPP). MIF is a pro‐inflammatory, pro‐tumorigenic protein that may be an attractive therapeutic target. MIF catalyzes the interconversion of the keto and enol forms of HPP by a tautomerase reaction. Although HPP is evidently not a physiological substrate of MIF, many compounds that inhibit this activity in enzymatic assays have been found also to inhibit physiological activities of MIF. Therefore, the MIF‐catalyzed HPP tautomerization reaction is used in initial screening of compounds in the search for inhibitors of MIF physiological activity. The neutron diffraction‐derived crystal structure reveals the position of a water molecule involved in the tautomerization reaction, and also confirms the charged state of lysine‐32 in the active site. The structure confirms the previously proposed catalytic mechanism of MIF, with the N‐terminal Pro‐1 abstracting a proton to generate an HPP enolate intermediate which is subsequently protonated. The structure reported herein reveals that this proton is supplied by a neighboring water molecule. Along with the neutron structure, a room‐temperature synchrotron x‐ray crystal structure reveals a covalent adduct between HPP and MIF. While this adduct is a result of radiation‐induced chemistry, its formation confirms the catalytic role of the active site residue because a covalent complex could only form if the reactive carbon of the substrate is correctly positioned by the enzyme.
Trocylation of 3-quinuclidinol, a key marker for the chemical warfare agent 3-quinuclidinyl benzilate, for its enhanced detection at low levels in complex soil matrices by electron ionization gas chromatography–mass spectrometry
Detection of 3-quinuclidinol (3Q), a marker for the chemical warfare agent 3-quinuclidinyl benzilate, is very difficult by gas chromatography–mass spectrometry (GC/MS), providing low, broad signals even when analyzed in isolated form. Therefore, a method that can convert 3Q into a substrate with enhanced detectability by GC/MS would be an important tool for its analysis. 2,2,2-Trichloroethoxycarbonyl chloride (TrocCl) was used in the derivatization of 3Q in three different soils of varying composition and total organic content (Virginia type A soil, Nebraska EPA standard soil and Ottawa sand) when present at a 10 μg g -1 concentration in each. A direct derivatization protocol and one involving the pre-extraction of the analyte were evaluated for their individual efficiencies and subsequent analysis using electron ionization GC/MS. The practical derivatization of 3Q, when present at low levels (10 μg g -1 ) in three different soil matrices, was found to be rapid (1 h) and to take place smoothly at ambient temperature (and as low as 4°C). The method detection limit was determined to be 30 ng mL -1 for the Virginia type A soil, 49 ng mL -1 for the Nebraska EPA standard soil and 72 ng mL -1 for the Ottawa sand sample. An expedient and practical derivatization method for 3Q, a chemical warfare degradation product difficult to detect by GC/MS, has been realized using trichloroethyl chloroformate. The reaction provides 3Q-Troc, a derivative with better detectability than 3Q by electron ionization GC/MS such as peak sharpness and a unique mass spectrum for its unambiguous identification.
Atomic Layer Co 3 O 4 Nanosheets: The Key to Knittable Zn-Air Batteries
Flexible, wearable, and portable energy storage devices with high-energy density are crucial for next-generation electronics. However, the current battery technologies such as lithium ion batteries have limited theoretical energy density. Additionally, battery materials with small scale and high flexibility which could endure the large surface stress are highly required. In this study, a yarn-based 1D Zn-air battery is designed, which employs atomic layer thin Co 3 O 4 nanosheets as the oxygen reduction reaction/oxygen evolution reaction catalyst. The ultrathin nanosheets are synthesized by a high-yield and facile chemical method and show a thickness of only 1.6 nm, corresponding to few atomic layers. The 1D Zn-air battery shows high cycling stability and high rate capability. The battery is successfully knitted into clothes and it shows high stability during the large deformation and knotting conditions.
Bioenergy and biodiversity: Key lessons from the Pan American region
Understanding how large-scale bioenergy production can affect biodiversity and ecosystems is important if society is to meet current and future sustainable development goals. A variety of bioenergy production systems have been established within different contexts throughout the Pan American region, with wide-ranging results in terms of documented and projected effects on biodiversity and ecosystems. The Pan American region is home to the majority of commercial bioenergy production and therefore the region offers a broad set of experiences and insights on both conflicts and opportunities for biodiversity and bioenergy. This paper synthesizes lessons learned focusing on experiences in Canada, the United States, and Brazil, regarding the conflicts that can arise between bioenergy production and ecological conservation, and benefits that can be derived when bioenergy policies promote planning and more sustainable land management systems. Lastly, we propose a research agenda to address priority information gaps that are relevant to biodiversity concerns and related policy challenges in the Pan American region.
The Key for Preventing Recanalization May be High Packing Density: Reply to Rajagopal et al
No abstract prepared.
Key predictors of soil organic matter vulnerability to mineralization differ with depth at a continental scale
Abstract Soil organic matter (SOM) is the largest terrestrial pool of organic carbon, and potential carbon-climate feedbacks involving SOM decomposition could exacerbate anthropogenic climate change. However, our understanding of the controls on SOM mineralization is still incomplete, and as such, our ability to predict carbon-climate feedbacks is limited. To improve our understanding of controls on SOM decomposition, A and upper B horizon soil samples from 26 National Ecological Observatory Network (NEON) sites spanning the conterminous U.S. were incubated for 52 weeks under conditions representing site-specific mean summer temperature and sample-specific field capacity (−33 kPa) water potential. Cumulative carbon dioxide respired was periodically measured and normalized by soil organic C content to calculate cumulative specific respiration (CSR), a metric of SOM vulnerability to mineralization. The Boruta algorithm, a feature selection algorithm, was used to select important predictors of CSR from 159 variables. A diverse suite of predictors was selected (12 for A horizons, 7 for B horizons) with predictors falling into three categories corresponding to SOM chemistry, reactive Fe and Al phases, and site moisture availability. The relationship between SOM chemistry predictors and CSR was complex, while sites that had greater concentrations of reactive Fe and Al phases or were wetter had lower CSR. Only three predictors were selected for both horizon types, suggesting dominant controls on SOM decomposition differ by horizon. Our findings contribute to the emerging consensus that a broad array of controls regulates SOM decomposition at large scales and highlight the need to consider changing controls with depth.
Development of Tailor-Made Superabsorbent Polymers: Review of Key Aspects from Raw Material to Kinetic Model
The ability of superabsorbent polymers (SAP) to absorb and retain a large amount of water and/or aqueous solution enables their applications in areas such as agriculture, medicine and water treatment. This versatility has attracted the attention of researchers interested in developing new materials, especially bio-based polymers. As a result, there are numerous studies reporting different types of monomers and crosslinks to produce SAP. Conversely, in the literature there is a lack of discussion of the modeling approaches to describe SAP production. This paper makes a comprehensive and systematic review of the main issues for the synthesis of new SAP materials: monomer and crosslink types, as well as the kinetic model. A database on the raw materials to produce SAP for the main applications should be useful for those interested in producing new SAP materials. The mathematical model correlates structural properties with the synthesis conditions, thus supporting the development of tailor-made products.
Transcriptional dynamics during cell wall removal and regeneration reveals key genes involved in cell wall development in rice
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Bicarbonate is a key regulator but not a substrate for O2 evolution in Photosystem II
Abstract Photosystem II (PSII) uses light energy to oxidize water and to reduce plastoquinone in the photosynthetic electron transport chain. O 2 is produced as a byproduct. While most members of the PSII research community agree that O 2 originates from water molecules, alternative hypotheses involving bicarbonate persist in the literature. In this perspective, we provide an overview of the important roles of bicarbonate in regulating PSII activity and assembly. Further, we emphasize that biochemistry, spectroscopy, and structural biology experiments have all failed to detect bicarbonate near the active site of O 2 evolution. While thermodynamic arguments for oxygen-centered bicarbonate oxidation are valid, the claim that bicarbonate is a substrate for photosynthetic O 2 evolution is challenged.
Critical Systematic Evaluation and Thermodynamic Optimization of the Mn-RE System (RE = Tb, Dy, Ho, Er, Tm and Lu) with Key Experiments for the Mn-Dy System
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Screening pre-renal transplant: Risk factors appear key but important questions remain
No abstract prepared.
Search for key manifestations to predict inflammation on cardiac PET in suspected cardiac sarcoidosis population
No abstract prepared.
Cardiopulmonary exercise testing and SPECT myocardial perfusion imaging: Pre-test probability is the key
No abstract prepared.
Chemokine receptors: Key for molecular imaging of inflammation in atherosclerosis
No abstract prepared.
Genomics for Key Players in the N Cycle
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Strong interfaces: the key to high strength in nano metallic laminates
Excellent mechanical properties of nanomaterials are usually attributed to their nanoscale feature size and high-density interfaces. This work explores the effects of intrinsic interface properties on mechanical properties of nano metallic laminates (NMLs). We show that the interface strength significantly affects the mechanical properties of NMLs. Via in situ mechanical testing and characterization, we investigate the deformation behavior and concurrent microstructure evolution in NMLs with four types of dissimilar interfaces. Our results show that the strength and deformation behaviors of NMLs are largely determined by interface strength. Strong interfaces can simultaneously increase the strength, work hardening capability, and deformability of NMLs. In conclusion, this work brings new insight into the design of advanced metallic materials through tuning of interface properties.