Formation of a carbinolamine intermediate in the tertiary amine catalyzed enolization of oxaloacetic acid. An alternative mechanism for enolization

1983 ◽  
Vol 105 (15) ◽  
pp. 4982-4996 ◽  
Author(s):  
Paula Yurkanis Bruice
Keyword(s):  
Tertiary Amine ◽  
Alternative Mechanism ◽  
Oxaloacetic Acid

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

Can Mouse-tracking Reveal Attribute Processing Speeds in Dietary Self-control? Commentary on Sullivan et al. (2015) and Lim et al. (2018) with A Simulation Study

2018 ◽  
Author(s):  
Chao Zhang ◽  
Martijn Willemsen ◽  
Daniel Lakens
Keyword(s):  
Simulation Study ◽  
Processing Speed ◽  
Empirical Data ◽  
Self Control ◽  
Alternative Mechanism ◽  
Mouse Tracking ◽  
Tracking Method ◽  
Cognitive Mechanism ◽  
Speed Difference ◽  
Original Hypothesis

In this commentary, we re-examine the use of a mouse-tracking method for revealing attribute processing speed difference in dietary self-control (Sullivan et al. 2015; Lim et al., 2018). Through re-analyses of Sullivan et al. (2015)’s data and a simulation study, it can be shown that the attribute-angle correlations in the empirical data, which were used to estimate processing speeds, are attributed primarily to their common correlations with choice. The simulation study further suggests that when we account for the choice-mediated attribute-angle correlations, the data patterns used for supporting the original hypothesis can be produced by implementing a plausible alternative mechanism unrelated to processing speeds. The mouse-tracking method therefore fails to provide clear evidence for processing speed difference as a cognitive mechanism of self-control. Researchers should be cautious when using the mouse-tracking method to estimate attribute processing speeds.

Non-canonical Functions of Telomerase Reverse Transcriptase: Emerging Roles and Biological Relevance

2020 ◽  
Vol 20 (6) ◽  
pp. 498-507 ◽  
Author(s):  
Connor A.H. Thompson ◽  
Judy M.Y. Wong
Keyword(s):  
Oxidative Stress ◽  
Dna Damage ◽  
Reverse Transcriptase ◽  
Cancer Cells ◽  
Telomere Length ◽  
Telomere Maintenance ◽  
Telomerase Reverse Transcriptase ◽  
Alternative Mechanism ◽  
Dependent Manner ◽  
Mitochondrial Integrity

Increasing evidence from research on telomerase suggests that in addition to its catalytic telomere repeat synthesis activity, telomerase may have other biologically important functions. The canonical roles of telomerase are at the telomere ends where they elongate telomeres and maintain genomic stability and cellular lifespan. The catalytic protein component Telomerase Reverse Transcriptase (TERT) is preferentially expressed at high levels in cancer cells despite the existence of an alternative mechanism for telomere maintenance (alternative lengthening of telomeres or ALT). TERT is also expressed at higher levels than necessary for maintaining functional telomere length, suggesting other possible adaptive functions. Emerging non-canonical roles of TERT include regulation of non-telomeric DNA damage responses, promotion of cell growth and proliferation, acceleration of cell cycle kinetics, and control of mitochondrial integrity following oxidative stress. Non-canonical activities of TERT primarily show cellular protective effects, and nuclear TERT has been shown to protect against cell death following double-stranded DNA damage, independent of its role in telomere length maintenance. TERT has been suggested to act as a chromatin modulator and participate in the transcriptional regulation of gene expression. TERT has also been reported to regulate transcript levels through an RNA-dependent RNA Polymerase (RdRP) activity and produce siRNAs in a Dicer-dependent manner. At the mitochondria, TERT is suggested to protect against oxidative stress-induced mtDNA damage and promote mitochondrial integrity. These extra-telomeric functions of TERT may be advantageous in the context of increased proliferation and metabolic stress often found in rapidly-dividing cancer cells. Understanding the spectrum of non-canonical functions of telomerase may have important implications for the rational design of anti-cancer chemotherapeutic drugs.

scholarly journals Overview on the Different Patterns of Tumor Vascularization

Cells ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 639
Author(s):  
Domenico Ribatti ◽  
Francesco Pezzella
Keyword(s):  
Vasculogenic Mimicry ◽  
Endothelial Cell Proliferation ◽  
Published Data ◽  
Alternative Mechanism ◽  
Tumor Vascularization ◽  
Angiogenic Therapy ◽  
Physiological Processes ◽  
Inhibition Of Angiogenesis ◽  
Therapeutic Development

Angiogenesis is a crucial event in the physiological processes of embryogenesis and wound healing. During malignant transformation, dysregulation of angiogenesis leads to the formation of a vascular network of tumor-associated capillaries promoting survival and proliferation of the tumor cells. Starting with the hypothesis formulated by Judah Folkman that tumor growth is angiogenesis-dependent, this area of research has a solid scientific foundation and inhibition of angiogenesis is a major area of therapeutic development for the treatment of cancer. Over this period numerous authors published data of vascularization of tumors, which attributed the cause of neo-vascularization to various factors including inflammation, release of angiogenic cytokines, vasodilatation, and increased tumor metabolism. More recently, it has been demonstrated that tumor vasculature is not necessarily derived by endothelial cell proliferation and sprouting of new capillaries, but alternative vascularization mechanisms have been described, namely vascular co-option and vasculogenic mimicry. In this article, we have analyzed the mechanisms involved in tumor vascularization in association with classical angiogenesis, including post-natal vasculogenesis, intussusceptive microvascular growth, vascular co-option, and vasculogenic mimicry. We have also discussed the role of these alternative mechanism in resistance to anti-angiogenic therapy and potential therapeutic approaches to overcome resistance.

scholarly journals Design of ferrocenylseleno-dopamine derivatives to optimize the Fenton-like reaction efficiency and antitumor efficacy

RSC Advances ◽  
2021 ◽  
Vol 11 (41) ◽  
pp. 25477-25483
Author(s):  
Qianya Cheng ◽  
Tong Zhou ◽  
Qing Xia ◽  
Xiulian Lu ◽  
Heng Xu ◽  
...  
Keyword(s):  
Tertiary Amine ◽  
Antitumor Efficacy ◽  
Reaction Efficiency

The tertiary amine in F4b facilitates the Fenton-like reaction to generate toxic ˙OH which induces apoptosis through CDK-2 inactivation.

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