Mechanistic Studies of Single-Step Styrene Production Catalyzed by Rh Complexes with Diimine Ligands: An Evaluation of the Role of Ligands and Induction Period

ACS Catalysis ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 7457-7475 ◽  
Author(s):  
Weihao Zhu ◽  
Zhongwen Luo ◽  
Junqi Chen ◽  
Chang Liu ◽  
Lu Yang ◽  
...  
Keyword(s):  
Induction Period ◽  
Single Step ◽  
Mechanistic Studies ◽  
Diimine Ligands ◽  
Styrene Production

scholarly journals Mechanistic Studies of Single-Step Styrene Production Using a Rhodium(I) Catalyst

2017 ◽  
Vol 139 (4) ◽  
pp. 1485-1498 ◽  
Author(s):  
Benjamin A. Vaughan ◽  
Sarah K. Khani ◽  
J. Brannon Gary ◽  
James D. Kammert ◽  
Michael S. Webster-Gardiner ◽  
...  
Keyword(s):  
Single Step ◽  
Mechanistic Studies ◽  
Styrene Production

scholarly journals Chemoselective α-Sulfidation of Amides Using Sulfoxide Reagents

2020 ◽  
Author(s):  
Mario Leypold ◽  
Kyan A. D’Angelo ◽  
Mohammad Movassaghi
Keyword(s):  
Critical Role ◽  
Single Step ◽  
Mechanistic Studies ◽  
Selective Functionalization ◽  
Sulfonium Ions ◽  
Activation Conditions ◽  
Tertiary Amides ◽  
Amide Activation

The direct α-sulfidation of tertiary amides using sulfoxide reagents under electrophilic amide activation conditions is described. Employing readily available reagents, selective functionalization takes place to generate isolable sulfonium ions en route to α-sulfide amides. Mechanistic studies support the critical role of activated sulfoxides that promote the desired transformation. For benzylic amide substrates, a single-step protocol featuring a spontaneous dealkylation step of a sulfonium ion intermediate was developed.

scholarly journals Chemoselective α-Sulfidation of Amides Using Sulfoxide Reagents

2020 ◽  
Author(s):  
Mario Leypold ◽  
Kyan A. D’Angelo ◽  
Mohammad Movassaghi
Keyword(s):  
Critical Role ◽  
Single Step ◽  
Mechanistic Studies ◽  
Selective Functionalization ◽  
Sulfonium Ions ◽  
Activation Conditions ◽  
Tertiary Amides ◽  
Amide Activation

The direct α-sulfidation of tertiary amides using sulfoxide reagents under electrophilic amide activation conditions is described. Employing readily available reagents, selective functionalization takes place to generate isolable sulfonium ions en route to α-sulfide amides. Mechanistic studies support the critical role of activated sulfoxides that promote the desired transformation. For benzylic amide substrates, a single-step protocol featuring a spontaneous dealkylation step of a sulfonium ion intermediate was developed.

Fibrin Formation: The Role of the Fibrinogen-Fibrin Monomer Complex

1976 ◽  
Vol 36 (01) ◽  
pp. 037-048 ◽  
Author(s):  
Eric P. Brass ◽  
Walter B. Forman ◽  
Robert V. Edwards ◽  
Olgierd Lindan
Keyword(s):  
Particle Size ◽  
Induction Period ◽  
Fibrin Clot ◽  
Clot Formation ◽  
Appreciable Amount ◽  
Buffer System ◽  
Homeostatic Mechanism ◽  
Fibrin Formation ◽  
Fibrin Monomer

SummaryThe process of fibrin formation using highly purified fibrinogen and thrombin was studied using laser fluctuation spectroscopy, a method that rapidly determines particle size in a solution. Two periods in fibrin clot formation were noted: an induction period during which no fibrin polymerization occurred and a period of rapid increase in particle size. Direct measurement of fibrin monomer polymerization and fibrinopeptide release showed no evidence of an induction period. These observations were best explained by a kinetic model for fibrin clot formation incorporating a reversible fibrinogen-fibrin monomer complex. In this model, the complex serves as a buffer system during the earliest phase of fibrin formation. This prevents the accumulation of free polymerizable fibrin monomer until an appreciable amount of fibrinogen has reacted with thrombin, at which point the fibrin monomer level rises rapidly and polymerization proceeds. Clinically, the complex may be a homeostatic mechanism preventing pathological clotting during periods of elevated fibrinogen.

Synthetic and Mechanistic Studies of a Versatile Heteroaryl Thioether Directing Group for Pd(II) Catalysis

2019 ◽  
Author(s):  
Andrew Romine ◽  
Kin Yang ◽  
Malkanthi Karunananda ◽  
Jason Chen ◽  
Keary Engle
Keyword(s):  
Mechanistic Studies ◽  
Salvianolic Acid ◽  
Wide Range ◽  
Computational Data ◽  
Synthetic Utility ◽  
Directing Group ◽  
High Yields ◽  
Julia Olefination ◽  
Reaction Progress Kinetic Analysis

A weakly coordinating monodentate heteroaryl thioether directing group has been developed for use in Pd(II) catalysis to orchestrate key elementary steps in the catalytic cycle that require conformational flexibility in a manner that is difficult to accomplish with traditional strongly coordinating directing groups. This benzothiazole thioether, (BT)S, directing group can be used to promote oxidative Heck reactivity of internal alkenes providing a wide range of products in moderate to high yields. To demonstrate the broad applicability of this directing group, arene C–H olefination was also successfully developed. Reaction progress kinetic analysis provides insights into the role of the directing group in each reaction, which is supplemented with computational data for the oxidative Heck reaction. Furthermore, this (BT)S directing group can be transformed into a number of synthetically useful functional groups, including a sulfone for Julia olefination, allowing it to serve as a “masked olefin” directing group in synthetic planning. In order to demonstrate this synthetic utility, natural products (+)-salvianolic acid A and salvianolic acid F are formally synthesized using the (BT)S directed C–H olefination as the key step.

scholarly journals Global phosphoproteomics reveals DYRK1A regulates CDK1 activity in glioblastoma cells

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Ariadna Recasens ◽  
Sean J. Humphrey ◽  
Michael Ellis ◽  
Monira Hoque ◽  
Ramzi H. Abbassi ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Cyclin B ◽  
Anaphase Promoting Complex ◽  
Mechanistic Studies ◽  
Glioblastoma Cells ◽  
Cycle Arrest ◽  
Dual Specificity ◽  
Rb Pathway ◽  
High Doses

AbstractBoth tumour suppressive and oncogenic functions have been reported for dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A). Herein, we performed a detailed investigation to delineate the role of DYRK1A in glioblastoma. Our phosphoproteomic and mechanistic studies show that DYRK1A induces degradation of cyclin B by phosphorylating CDC23, which is necessary for the function of the anaphase-promoting complex, a ubiquitin ligase that degrades mitotic proteins. DYRK1A inhibition leads to the accumulation of cyclin B and activation of CDK1. Importantly, we established that the phenotypic response of glioblastoma cells to DYRK1A inhibition depends on both retinoblastoma (RB) expression and the degree of residual DYRK1A activity. Moderate DYRK1A inhibition leads to moderate cyclin B accumulation, CDK1 activation and increased proliferation in RB-deficient cells. In RB-proficient cells, cyclin B/CDK1 activation in response to DYRK1A inhibition is neutralized by the RB pathway, resulting in an unchanged proliferation rate. In contrast, complete DYRK1A inhibition with high doses of inhibitors results in massive cyclin B accumulation, saturation of CDK1 activity and cell cycle arrest, regardless of RB status. These findings provide new insights into the complexity of context-dependent DYRK1A signalling in cancer cells.

The Fe(III)-catalyzed functionalization of saturated hydrocarbons by tert-butyl hydroperoxide: Mechanistic studies on the role of dioxygen

1992 ◽  
Vol 33 (38) ◽  
pp. 5473-5476 ◽  
Author(s):  
Derek H.R. Barton ◽  
Stéphane D. Bévière ◽  
Warinthorn Chavasiri ◽  
Darío Doller ◽  
Bin Hu
Keyword(s):  
Mechanistic Studies ◽  
Saturated Hydrocarbons ◽  
Butyl Hydroperoxide ◽  
Tert Butyl ◽  
Tert Butyl Hydroperoxide

scholarly journals Structural studies on M. tuberculosis O6-methylguanine methyltransferase

2014 ◽  
Vol 70 (a1) ◽  
pp. C832-C832
Author(s):  
Menico Rizzi ◽  
Riccardo Miggiano ◽  
Samarpita Lahiri ◽  
Giuseppe Perugino ◽  
Maria Ciaramella ◽  
...  
Keyword(s):  
Excision Repair ◽  
Single Step ◽  
Double Stranded Dna ◽  
Nucleotide Excision ◽  
Enzymatic Systems ◽  
Methylguanine Methyltransferase ◽  
Mutagenic Effects ◽  
Wild Type Form

Mycobacterium tuberculosis (MTB) is an extremely well adapted human pathogen capable to survive for decades inside the hostile environment represented by the host's infected macrophages despite exposure to multiple potential DNA-damaging stresses. In order to maintain a remarkable low level of genetic diversity, MTB deploys different strategies of DNA repair, including multi-enzymatic systems, such as Nucleotide Excision Repair, and single-step repair. In particular, to counteract the mutagenic effects of DNA alkylation, MTB performs the direct alkylated-base reversal by sacrificing one molecule of a DNA-protein alkyltransferase, such as O6-methylguanine methyltransferase (OGT; orf: Rv1316c). We present here the biochemical and structural characterization of recombinant mycobacterial OGT (MtOGT) in its wild-type form along with its mutated variants mimicking the ones occurring in relevant clinical strains (i.e. MtOGT-T15S and MtOGT-R37L). Our studies reveal that MtOGT-R37L is severely impaired in its activity as consequence of its ten-fold lower affinity for modified double-stranded DNA (dsDNA) (1). Further investigations on a new structure-based panel of OGT versions, designed to explore different molecular environment at position 37, allowed us a better understanding of the functional role of the MtOGT Arg37-bearing loop during catalysis. Moreover, we solved the crystal structure of MtOGT in covalent complex with modified dsDNA that reveals an unprecedented MtOGT::DNA architecture, suggesting that the MtOGT monomer performing the catalysis needs assisting unreacted subunits during cooperative DNA binding. This work is supported by European Community FP7 program SYSTEMTB (Health-F4-2010-241587)

Badania przesiewowe w profilaktyce raka jelita grubego

2018 ◽  
Vol 21 (3) ◽  
Author(s):  
Marta Musińska ◽  
Marta Minkiewicz ◽  
Justyna Wasielica-Berger ◽  
Krystian Kidrycki ◽  
Krzysztof Kurek
Keyword(s):  
Colorectal Cancer ◽  
Screening Program ◽  
Single Step ◽  
Preventive Action ◽  
Asymptomatic Patients ◽  
Oncological Diseases ◽  
History Of ◽  
Genetic And Environmental Factors ◽  
Therapeutic Tools

Colorectal cancer is the second most frequently diagnosed cancer in Poland as well as in the world. In addition, this cancer is the second cause of death among oncological diseases. Genetic and environmental factors with a documented impact on the development and progression of colorectal cancer have been thoroughly investigated. Every case of colorectal cancer begins with the stage of a nonmalignant polyp, whose progression to invasive malignant tumor lasts about 10 years. This period is long enough to implement appropriate preventive action that allow early detection and treatment of pre-cancerous lesions. Colorectal cancer screening is the process of detecting polypoid lesions in asymptomatic patients with no history of cancers. Colonoscopy has the benefit of diagnostic and therapeutic tools, which allows to detect and remove of premalignant polyps in a single step approach. The aim of this work is to present the role of a screening program in the prevention of colorectal cancer.

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