Competing pathways in the photochemistry of a 2,5-pentadienone

1969 ◽  
Vol 91 (18) ◽  
pp. 5177-5178 ◽  
Author(s):  
Jerrold Meinwald ◽  
John W. Kobzina
Keyword(s):  
Competing Pathways

Radical Capture at Ni(II) Complexes: C-C, C-N, and C-O Bond Formation

2019 ◽  
Author(s):  
Abolghasem (Gus) Bakhoda ◽  
Stefan Wiese ◽  
Christine Greene ◽  
Bryan C. Figula ◽  
Jeffery A. Bertke ◽  
...  
Keyword(s):  
Functional Groups ◽  
Bond Formation ◽  
Dft Studies ◽  
Bond Forming ◽  
Aryl Amines ◽  
Shed Light ◽  
Competing Pathways

<p>The dinuclear b-diketiminato Ni<sup>II</sup><i>tert</i>-butoxide {[Me<sub>3</sub>NN]Ni}<sub>2</sub>(<i>μ</i>-O<i><sup>t</sup></i>Bu)<sub>2 </sub>(<b>2</b>), synthesized from [Me<sub>3</sub>NN]Ni(2,4-lutidine) (<b>1</b>) and di-<i>tert</i>-butylperoxide, is a versatile precursor for the synthesis of a series of Ni<sup>II</sup>complexes [Me<sub>3</sub>NN]Ni-FG to illustrate C-C, C-N, and C-O bond formation at Ni<sup>II </sup>via radicals. {[Me<sub>3</sub>NN]Ni}<sub>2</sub>(<i>μ</i>-O<i><sup>t</sup></i>Bu)<sub>2 </sub>reacts with nitromethane, alkyl and aryl amines, acetophenone, benzamide, ammonia and phenols to deliver corresponding mono- or dinuclear [Me<sub>3</sub>NN]Ni-FG species (FG = O<sub>2</sub>NCH<sub>2</sub>, R-NH, ArNH, PhC(O)NH, PhC(O)CH<sub>2</sub>, NH<sub>2</sub>and OAr). Many of these Ni<sup>II </sup>complexes are capable of capturing the benzylic radical PhCH(•)CH<sub>3 </sub>to deliver corresponding PhCH(FG)CH<sub>3 </sub>products featuring C-C, C-N or C-O bonds. DFT studies shed light on the mechanism of these transformations and suggest two competing pathways that depend on the nature of the functional groups. These radical capture reactions at [Ni<sup>II</sup>]-FG complexes outline key C-C, C-N, and C-O bond forming steps and suggest new families of nickel radical relay catalysts.</p>

scholarly journals Engineering of Saccharomyces cerevisiae for the accumulation of high amounts of triacylglycerol

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Simon Arhar ◽  
Gabriela Gogg-Fassolter ◽  
Mojca Ogrizović ◽  
Klavdija Pačnik ◽  
Katharina Schwaiger ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fatty Acid ◽  
Lipid Level ◽  
Pharmaceutical Products ◽  
Acetyl Coa Carboxylase ◽  
Oleaginous Yeasts ◽  
Regulatory Subunits ◽  
Gene Coding ◽  
Tag Accumulation ◽  
Competing Pathways

Abstract Background Fatty acid-based substances play an important role in many products, from food supplements to pharmaceutical products and biofuels. The production of fatty acids, mainly in their esterified form as triacylglycerol (TAG), has been intensively studied in oleaginous yeasts, whereas much less effort has been invested into non-oleaginous species. In the present work, we engineered the model yeast Saccharomyces cerevisiae, which is commonly regarded as non-oleaginous, for the storage of high amounts of TAG, comparable to the contents achieved in oleaginous yeasts. Results We investigated the effects of several mutations with regard to increased TAG accumulation and identified six of them as important for this phenotype: a point mutation in the acetyl-CoA carboxylase Acc1p, overexpression of the diacylglycerol acyltransferase Dga1p, deletions of genes coding for enzymes involved in the competing pathways glycogen and steryl ester synthesis and TAG hydrolysis, and a deletion of CKB1, the gene coding for one of the regulatory subunits of casein kinase 2. With the combination of these mutations in a S. cerevisiae strain with a relatively high neutral lipid level already in the non-engineered state, we achieved a TAG content of 65% in the dry biomass. High TAG levels were not only obtained under conditions that favor lipid accumulation, but also in defined standard carbon-limited media. Conclusions Baker's yeast, which is usually regarded as inefficient in the storage of TAG, can be converted into a highly oleaginous strain that could be useful in processes aiming at the synthesis of fatty acid-based products. This work emphasizes the importance of strain selection in combination with metabolic engineering to obtain high product levels.

scholarly journals Reaction of allene esters with Selectfluor/TMSX (X = I, Br, Cl) and Selectfluor/NH4SCN: Competing oxidative/electrophilic dihalogenation and nucleophilic/conjugate addition

2015 ◽  
Vol 11 ◽  
pp. 1641-1648 ◽  
Author(s):  
A Srinivas Reddy ◽  
Kenneth K Laali
Keyword(s):  
Ionic Liquids ◽  
Conjugate Addition ◽  
Nucleophilic Additions ◽  
Product Analysis ◽  
Imidazolium Ionic Liquids ◽  
Presence And Absence ◽  
Competing Pathways

Reaction of benzyl and ethyl allenoates with TMSX (X = I, Br, Cl) and with NH4SCN were investigated in MeCN, DMF, and in imidazolium ionic liquids [BMIM][NTf2] and [BMIM][PF6] as solvent, in the presence and absence of Selectfluor. Comparative product analysis studies demonstrate that the ability of Selectflour to promote oxidative/electrophilic dihalogenation/dithiocyanation with TMSX/NH4SCN (as observed previously for 1-arylallenes) is diminished in allenoates, most significantly in reactions with TMSCl, and essentially disappearing in reactions with NH4SCN, in favor of nucleophilic/conjugate addition. The study underscores the contrasting reactivity patterns in 1-arylallenes and allenoates toward electrophilic and nucleophilic additions in halofunctionalization with TMSX/Selectfluor and thiocyanation reactions with NH4SCN/Selectfluor. These competing pathways are influenced by the nature of the anion, allene structure, and the choice of solvent.

scholarly journals A Systematic Review on Psychological and Biological Mediators Between Adversity and Psychosis: Potential Targets for Treatment

2019 ◽  
Author(s):  
Luis Alameda ◽  
Victoria Rodriguez ◽  
Ewan Carr ◽  
Monica Aas ◽  
Giulia Trotta ◽  
...  
Keyword(s):  
Systematic Review ◽  
Clinical Samples ◽  
Traditional Treatment ◽  
Affective Dysregulation ◽  
Cognitive Behavioural ◽  
Study Results ◽  
Registration Number ◽  
Meta Analyses ◽  
Competing Pathways

AbstractVarious psychological and biological pathways have been proposed as mediators between childhood adverse events (CA) and psychosis. A systematic review of the evidence in this domain is needed. The aim of this work is to systematically review the evidence on psychological and biological mediators between CA and psychosis across the psychosis spectrum. This systematic review followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (registration number: CRD42018100846). Articles published between 1979 and July 2019 were identified through a literature search in OVID (PsychINFO; Medline and Embase). The evidence by each analysis and each study results are presented by group of mediator categories found in the review. The percentage of total effect mediated was calculated. 47 studies were included, with a total of 79,668 from general population (GP) and 3,189 from clinical samples. The quality of studies was judged as “fair”. Our results showed (i) solid evidence of mediation between CA and psychosis by negative cognitive schemas about the self, the world, and others (NS); by dissociation and other PTSD symptoms; (ii) evidence of al mediation through an affective pathway (affective dysregulation, anxiety, and depression) in GP; (iii) lack of studies exploring biological mediators. To conclude, we found evidence suggesting that various overlapping and not competing pathways contribute partially to the link between adversity and psychosis. Experiences of adversity, along with relevant mediators such as PTSD and mood related symptoms and NS, should be routinely assessed in patients with psychosis. Targeting such mediators through cognitive behavioural aproaches using trauma-focused therapy and/or pharmacological means could be a useful addition to the traditional treatment of positive symptoms.

scholarly journals Thermal versus Mechanical Unfolding in a Model Protein

2019 ◽  
Author(s):  
Rafael Tapia-Rojo ◽  
Juan J. Mazo ◽  
Fernando Falo
Keyword(s):  
Free Energy ◽  
Force Spectroscopy ◽  
Reaction Coordinate ◽  
Force Extension ◽  
Thermal Dynamics ◽  
Zero Force ◽  
Protein Model ◽  
Model Protein ◽  
State Models ◽  
Competing Pathways

Force spectroscopy techniques are often used to learn about the free energy landscape of single biomolecules, typically by recovering free energy quantities that, extrapolated to zero force, are compared to those measured in bulk experiments. However, it is not always clear how the information obtained from a mechanically perturbed system can be related to that obtained using other denaturants, since tensioned molecules unfold and refold along a reaction coordinate imposed by the force, which is unlikely meaningful in its absence. Here, we explore this dichotomy by investigating the unfolding landscape of a model protein, which is first unfolded mechanically through typical force spectroscopy-like protocols, and next thermally. When unfolded by non-equilibrium force extension and constant force protocols, we recover a simple two-barrier landscape, as the protein reaches the extended conformation through a metastable intermediate. Interestingly, folding-unfolding equilibrium simulations at low forces suggested a totally different scenario, where this metastable state plays little role in the unfolding mechanism, and the protein unfolds through two competing pathways27. Finally, we use Markov state models to describe the configurational space of the unperturbed protein close to the critical temperature. The thermal dynamics is well understood by a one-dimensional landscape along an appropriate reaction coordinate, however very different from the mechanical picture. In this sense, in our protein model the mechanical and thermal descriptions provide incompatible views of the folding/unfolding landscape of the system, and the estimated quantities to zero force result hard to interpret.

scholarly journals Competing pathways control host resistance to virus via tRNA modification and programmed ribosomal frameshifting

2012 ◽  
Vol 8 (1) ◽  
pp. 567 ◽  
Author(s):  
Nathaniel D Maynard ◽  
Derek N Macklin ◽  
Karla Kirkegaard ◽  
Markus W Covert
Keyword(s):  
Host Resistance ◽  
Trna Modification ◽  
Ribosomal Frameshifting ◽  
Competing Pathways
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