Choosing an approach to statistical processing of the ship’s pitching record

The developed instrumentation and software provides discrete values for the angles of a vessel’s list on an operational voyage in sea conditions at specified time intervals.The half-periods of pitching are considered; the half-period and the corresponding pitching amplitude can be obtained in three different ways: as the amplitude from one board to the other one with the reference of the initial peak-to-peak amplitude or with the reference of the final peak-to-peak amplitude; as the time interval of the ship listing on one side between zero roll angles. It was found that each method corresponds to its own, different from the others, amplitude-period statistics. This makes it difficult to compare different registrations and identify the essential reactions of the vessel to the seaway, unless a method is specified for determining the half-periods and linking the roll amplitudes to them. The proposal is justified to unify the processing by defining the half-period as the time of the ship listing on one board with the corresponding amplitude angle of the roll, that is, as the difference of the moments of time between two next values of the zero angle of the roll.

Structural insights into bifunctional thaumarchaeal crotonyl-CoA hydratase and 3-hydroxypropionyl-CoA dehydratase from Nitrosopumilus maritimus

The ammonia-oxidizing thaumarchaeal 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB) cycle is one of the most energy-efficient CO2 fixation cycles discovered thus far. The protein encoded by Nmar_1308 (from Nitrosopumilus maritimus SCM1) is a promiscuous enzyme that catalyzes two essential reactions within the thaumarchaeal 3HP/4HB cycle, functioning as both a crotonyl-CoA hydratase (CCAH) and 3-hydroxypropionyl-CoA dehydratase (3HPD). In performing both hydratase and dehydratase activities, Nmar_1308 reduces the total number of enzymes necessary for CO2 fixation in Thaumarchaeota, reducing the overall cost for biosynthesis. Here, we present the first high-resolution crystal structure of this bifunctional enzyme with key catalytic residues in the thaumarchaeal 3HP/4HB pathway.

Structural Insights into Bifunctional Thaumarchaeal Crotonyl-CoA Hydratase and 3-Hydroxypropionyl-CoA Dehydratase from Nitrosopumilus maritimus

The ammonia-oxidizing thaumarchaeal 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB) cycle is one of the most energy-efficient CO2 fixation cycles discovered thus far. The protein encoded by Nmar_1308 (from Nitrosopumilus maritimus SCM1) is a promiscuous enzyme that catalyzes two essential reactions within the thaumarchaeal 3HP/4HB cycle, functioning as both a crotonyl-CoA hydratase (CCAH) and 3-hydroxypropionyl-CoA dehydratase (3HPD). In performing both hydratase and dehydratase activities, Nmar_1308 reduces the total number of enzymes necessary for CO2 fixation in Thaumarchaeota, reducing the overall cost for biosynthesis. Here, we present the first high-resolution crystal structure of this bifunctional enzyme with key catalytic residues in the thaumarchaeal 3HP/4HB pathway.

Wittig Reactions of Maleimide Derived Stabilized Ylides with Alkyl Pyruvates: Concise Approach to Methyl Ester of (±)-Chaetogline A

A facile synthesis of methyl ester of chaetogline A is reported starting from the corresponding methyl 1-methyltryptophanate derived maleimide. A stereoselective Wittig olefination with a carbonyl function in methyl pyruvate followed by phosphorous pentoxide induced regioselective dehydrative cyclization are the essential reactions. An acid induced thermodynamically driven stereoselective β- to α-position migration of the exocyclic carbon−carbon double unit in ethyl tetrahydroindolizinoindolylidenepropanoate is described.

Activation modes in biocatalytic radical cyclization reactions

Radical cyclizations are essential reactions in the biosynthesis of secondary metabolites and the chemical synthesis of societally valuable molecules. In this review, we highlight the general mechanisms utilized in biocatalytic radical cyclizations. We specifically highlight cytochrome P450 monooxygenases (P450s) involved in the biosynthesis of mycocyclosin and vancomycin, non-heme iron- and α-ketoglutarate-dependent dioxygenases (Fe/αKGDs) used in the biosynthesis of kainic acid, scopolamine, and isopenicillin N, and radical S-adenosylmethionine (SAM) enzymes that facilitate the biosynthesis of oxetanocin A, menaquinone, and F420. Beyond natural mechanisms, we also examine repurposed flavin-dependent ‘ene’-reductases (ERED) for non-natural radical cyclization. Overall, these general mechanisms underscore the opportunity for enzymes to augment and enhance the synthesis of complex molecules using radical mechanisms.

Selective oxidation of alcohols by graphene-like carbon with electrophilic oxygen and integrated pyridinic nitrogen active sites

The selective oxidations of alcohols into the corresponding aldehydes or ketones are essential reactions for organic synthesis. The development of facile, green and cost-effective protocols to accomplish the selective oxidation...

Formate dependent heterodisulfide reduction in a Methanomicrobiales archaeon

Hydrogenotrophic methanogens produce CH4 using H2 as an electron donor to reduce CO2. In the absence of H2, many are able to use formate or alcohols as alternate electron donors. Methanogens from the order Methanomicrobiales are capable of growth with H2, but many lack genes encoding hydrogenases that are typically found in other hydrogenotrophic methanogens. In an effort to better understand electron flow in methanogens from the Methanomicrobiales, we undertook a genetic and biochemical study of heterodisulfide reductase (Hdr) in Methanoculleus thermophilus. Hdr catalyzes an essential reaction by coupling the first and last steps of methanogenesis through flavin-based electron bifurcation. Hdr from M. thermophilus co-purified with formate dehydrogenase (Fdh) and only displayed activity when formate was supplied as an electron donor. We found no evidence of an Hdr associated hydrogenase, and H2 could not function as an electron donor, even with Hdr purified from cells grown on H2. We found that cells catalyze a formate hydrogenlyase activity that is likely essential for generating the formate needed for the Hdr reaction. Together, these results highlight the importance of formate as an electron donor for methanogenesis and suggest the ability to use formate is closely integrated into the methanogenic pathway in organisms from the order Methanomicrobiales. Importance Methanogens from the order Methanomicrobiales are thought to prefer H2 as an electron donor for growth. They are ubiquitous in anaerobic environments such as in wastewater treatment facilities, anaerobic digesters, and the rumen where they catalyze the terminal steps in the breakdown of organic matter. However, despite their importance, the metabolism of these organisms remains understudied. Using a genetic and biochemical approach, we show that formate metabolism is closely integrated into methanogenesis in Methanoculleus thermophilus. This is due to a requirement for formate as the electron donor to heterodisulfide reductase (Hdr), an enzyme responsible for catalyzing essential reactions in methanogenesis by linking the initial CO2 fixing step to the exergonic, terminal reaction of the pathway. These results suggest that hydrogen is not necessarily the preferred electron donor for all hydrogenotrophic methanogens and provide insight into the metabolism of methanogens from the order Methanomicrobiales.

Mechanisms of ebselen as a therapeutic and its pharmacology applications

Ebselen is a synthetic organoselenium radical scavenger compound that possesses glutathione peroxidase-like activity and its own unique bioactivity by reacting with thiols, hydroperoxides and peroxynitrites. Owing to its high affinity toward several essential reactions, ebselen protects cellular components from oxidative and free radical damage, and it has been employed as a useful tool for studying redox-related mechanisms. Based on numerous in vitro and in vivo research, mechanisms are proposed to understand the biomedical and molecular actions of ebselen in health and disease, and it is currently under clinical trials for the prevention and treatment of various human disorders. Based on these outstanding discoveries, this review summarizes the current understanding of the biochemical and molecular characteristics, pharmacological applications and future directions of ebselen.

Tunable Aryl Imidazolium Recyclable Ionic Liquid with Dual Brønsted–Lewis Acid as Green Catalyst for Friedel–Crafts Acylation and Thioesterification

Unique tunable aryl imidazolium ionic liquids successfully catalyzed Friedel–Crafts acylation and thioesterification in sealed tubes. These reactions can form a C−C bond and a C−S bond with high atom economy. Ionic liquids exhibited high activity and catalyzed essential reactions with good to excellent yields while retaining their catalytic activities for recycling.

Computational Identification of Metabolic Pathways ofPlasmodium falciparumusing thek-Shortest Path Algorithm

Plasmodium falciparum, a malaria pathogen, has shown substantial resistance to treatment coupled with poor response to some vaccines thereby requiring urgent, holistic, and broad approach to prevent this endemic disease. Understanding the biology of the malaria parasite has been identified as a vital approach to overcome the threat of malaria. This study is aimed at identifying essential proteins unique to malaria parasites using a reconstructediPfagenome-scale metabolic model (GEM) of the 3D7 strain ofPlasmodium falciparumby filling gaps in the model with nineteen (19) metabolites and twenty-three (23) reactions obtained from the MetaCyc database. Twenty (20) currency metabolites were removed from the network because they have been identified to produce shortcuts that are biologically infeasible. The resulting modifiediPfaGEM was a model using thek-shortest path algorithm to identify possible alternative metabolic pathways in glycolysis and pentose phosphate pathways ofPlasmodium falciparum. Heuristic function was introduced for the optimal performance of the algorithm. To validate the prediction, the essentiality of the reactions in the reconstructed network was evaluated using betweenness centrality measure, which was applied to every reaction within the pathways considered in this study. Thirty-two (32) essential reactions were predicted among which our method validated fourteen (14) enzymes already predicted in the literature. The enzymatic proteins that catalyze these essential reactions were checked for homology with the host genome, and two (2) showed insignificant similarity, making them possible drug targets. In conclusion, the application of the intelligent search technique to the metabolic network ofP. falciparumpredicts potential biologically relevant alternative pathways using graph theory-based approach.