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You searched for subject:(flash AND trap method). Showing records 1 – 2 of 2 total matches.

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1. Saracini, Claudio. CARBON MONOXIDE AND DIOXYGEN PHOTO-RELEASE, BINDING KINETICS, AND THERMODYNAMICS IN 1:1 MONONUCLEAR AND 2:1 DINUCLEAR COPPER/DIOXYGEN COMPLEXES.

Degree: 2014, Johns Hopkins University

Enzymes where the active site contains one or more copper ions catalyze a wide range of organic substrate transformations in Nature. The structures and function of such active sites have been finely tuned by evolution to reach the point where dioxygen binding, activation, and utilization for oxidative chemistry has become finely modulated. As is overviewed in Chapter 1, it is useful to categorize the enzymes supported by two copper centers in their active sites as 'uncoupled' (i.e. in peptidylglycine -hydroxylating monooxygenase (PHM) and in dopamine -monooxygenase (DM)) or 'coupled' (i.e. in tyrosinase (Tyr) and in catechol oxidase (Co)) on the basis of the spatial proximity of the two metals in the three-dimensional matrix of the protein. This proximity has profound effects on the chemistry displayed by these two classes of enzymes. Importantly, dioxygen binding to the copper centers is the first step of the catalytic cycle in all of these systems. However, both mononuclear 1:1 and dinuclear 2:1 copper/O2 adducts forming in the enzymes have been shown to be unstable and their detection and their study has been difficult. As it is also discussed in Chapter 1, low temperature spectroscopic techniques together with synthetic model chemistry have come into play and greatly improved our understanding of the mechanistic details involved in such kinds of reactivity. In this work, laser flash-photolysis techniques in combination with copper-synthetic model chemistry have been employed to help the elucidation of fundamental physical and chemical properties of copper/O2 coordination and dynamics. One of the methods that has been successfully employed to study labile copper/dioxygen adducts is laser flash-photolysis of synthetic (L)copper(I)-CO compounds (L =ligand) in the presence of O2 in organic solvents. In Chapter 2, a flash-photolysis study of tridentate N-donor ligand-copper(I)-CO complexes is presented using such techniques. The implications of tricoordination vs. tetracoordination of copper ion on the dynamics of CO and O2 binding to the metal are discussed for these metal complexes. Tricoordinate environments are more similar in their coordination sphere with those present in the enzymes, as compared to their tetracoordinated synthetic counterparts. In Chapter 3, a new method to study copper/dioxygen binding for mononuclear copper complexes is presented. The previously employed carbon monoxide utilization to start from stable (L)copper(I)-CO complexes is bypassed, in this work, by affording direct O2 photo-release from relatively stable mononuclear copper(II)-superoxide complexes. Interestingly, a different quantum yield for O2 release was found depending on the excitation wavelength used and in collaborative efforts, this effect has been investigated by means of Time-Dependent Density Functional Theory (TD-DFT) studies. This work was further extended and presented in Chapter 4, where the same technique was employed for dinuclear 2:1 Cu/O2 synthetic adducts with a peroxo fragment bound in a side-on mode to the… Advisors/Committee Members: Karlin, Kenneth D (advisor).

Subjects/Keywords: Oxygen activation; coupled copper enzymes; uncoupled copper enzymes; mononuclear and dinuclear copper?O2 adducts; copper synthetic model chemistry; laser flash-photolysis; physical properties; transient absorption spectroscopy; carbon monoxide; dioxygen; tricoordinate; tetracoordinate; flash-and-trap method; copper(II)-superoxide; dicopper(II) peroxo; quantum yield; excitation wavelength; TD-DFT; end-on; side-on; irradiation; visible light; one-photon two-electron; oxidation; hydrogen atom abstraction; reversible; thermodynamics; kinetics; kinetic relaxation model; pseudo-first-order; second-order; rate constant; binding dynamics; tyrosinase; hemocyanin; catechol oxidase; PHM; DBM; irradiation; laser.

…Possible O2 reactive species. 79 xv Scheme 4. Flash-and-trap kinetic model. 81 Chart 1… …101 3.1 Flash-Photolysis Experiments… …solvent. 108 Scheme 1. Flash-photolysis studies of 1 and 2. 92 Chart 1. Structure of ligands… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Saracini, C. (2014). CARBON MONOXIDE AND DIOXYGEN PHOTO-RELEASE, BINDING KINETICS, AND THERMODYNAMICS IN 1:1 MONONUCLEAR AND 2:1 DINUCLEAR COPPER/DIOXYGEN COMPLEXES. (Thesis). Johns Hopkins University. Retrieved from http://jhir.library.jhu.edu/handle/1774.2/37054

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Saracini, Claudio. “CARBON MONOXIDE AND DIOXYGEN PHOTO-RELEASE, BINDING KINETICS, AND THERMODYNAMICS IN 1:1 MONONUCLEAR AND 2:1 DINUCLEAR COPPER/DIOXYGEN COMPLEXES.” 2014. Thesis, Johns Hopkins University. Accessed April 19, 2021. http://jhir.library.jhu.edu/handle/1774.2/37054.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Saracini, Claudio. “CARBON MONOXIDE AND DIOXYGEN PHOTO-RELEASE, BINDING KINETICS, AND THERMODYNAMICS IN 1:1 MONONUCLEAR AND 2:1 DINUCLEAR COPPER/DIOXYGEN COMPLEXES.” 2014. Web. 19 Apr 2021.

Vancouver:

Saracini C. CARBON MONOXIDE AND DIOXYGEN PHOTO-RELEASE, BINDING KINETICS, AND THERMODYNAMICS IN 1:1 MONONUCLEAR AND 2:1 DINUCLEAR COPPER/DIOXYGEN COMPLEXES. [Internet] [Thesis]. Johns Hopkins University; 2014. [cited 2021 Apr 19]. Available from: http://jhir.library.jhu.edu/handle/1774.2/37054.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Saracini C. CARBON MONOXIDE AND DIOXYGEN PHOTO-RELEASE, BINDING KINETICS, AND THERMODYNAMICS IN 1:1 MONONUCLEAR AND 2:1 DINUCLEAR COPPER/DIOXYGEN COMPLEXES. [Thesis]. Johns Hopkins University; 2014. Available from: http://jhir.library.jhu.edu/handle/1774.2/37054

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Virginia Tech

2. Hancock, Amber N. A Radical Approach to Syntheses and Mechanisms.

Degree: PhD, Chemistry, 2011, Virginia Tech

The critically important nature of radical and radical ion mechanisms in biology and chemistry continues to be recognized as our understanding of these unique transient species grows. The work presented herein demonstrates the versatility of kinetic studies for understanding the elementary chemical reactions of radicals and radical ions. Chapter 2 discusses the use of direct ultrafast kinetics techniques for investigation of crucially important enzymatic systems; while Chapter 3 demonstrates the value of indirect competition kinetics techniques for development of synthetic methodologies for commercially valuable classes of compounds. The mechanism of decay for aminyl radical cations has received considerable attention because of their suspected role as intermediates in the oxidation of tertiary amines by monoamine oxygenases and the cytochrome P450 family of enzymes. Radical cations are believed to undergo deprotonation as a key step in catalysis. KIE studies performed by previous researchers indicate N,N-dimethylaniline radical cations deprotonate in the presence of the bases acetate and pyridine. By studying the electrochemical kinetics of the reaction of para substituted N,N-dimethylaniline radical cations with acetate anion, we have produced compelling evidence to the contrary. Rather than deprotonation, acetate reacts with N,N-dimethylaniline radical cation by electron transfer, generating the neutral amine and acetoxyl radical. Transport properties of reactants and solvent polarity changes were investigated and confirmed not to influence the electrochemical behavior forming the basis for our mechanistic hypothesis. To reconcile our conclusion with earlier results, KIEs were reinvestigated electrochemically and by nanosecond laser flash photolysis. Rather than a primary isotope effect (associated with C-H bond cleavage), we believe the observed KIEs are secondary, and can be rationalized on the basis of a quantum effect due to hyperconjugative stabilization in aromatic radical cations during an electron transfer reaction. Product studies performed by constant potential coulometry indicate N,N-dimethylaniline radical cations are catalytic in carboxylate oxidations. Collectively, our results suggest that aminyl radical cation deprotonations may not be as facile as was previously thought, and that in some cases, may not occur at all. Interest in design and synthesis of selenium containing heterocycles stems from their ability to function as antioxidants, anti-virals, anti-inflammatories, and immunomodulators. To establish synthetic feasibility of intramolecular homolytic substitution at selenium for preparation of selenocycles, we set out to determine what factors influence cyclization kinetics. A series of photochemically labile Barton and Kim esters have been syntheisized and employed as radical precursors. The effect of leaving radical stability on kinetics has been investigated through determination of rate constants and activation parameters for intramolecular homolytic substitution of the corresponding… Advisors/Committee Members: Tanko, James M. (committeechair), Marand, Hervé L. (committee member), Marand, Hervé L. (committee member), Long, Timothy E. (committee member), Madsen, Louis A. (committee member), Troya, Diego (committee member).

Subjects/Keywords: Carboxylate; Deprotonation; Electron Transfer; Radical Cyclization; Homolytic Substitution; Selenium; Radical Trap; Rate Constant; Deuterium Isotope Effect; Arrhenius Parameter; N; Mechanism; Kinetics; Cyclic Voltammetry; Constant Potential Coulometry; Competition Kinetics.; Amine Radical Cation; N-dimethylaniline; Digital Simulations; Laser Flash Photolysis

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Hancock, A. N. (2011). A Radical Approach to Syntheses and Mechanisms. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77139

Chicago Manual of Style (16th Edition):

Hancock, Amber N. “A Radical Approach to Syntheses and Mechanisms.” 2011. Doctoral Dissertation, Virginia Tech. Accessed April 19, 2021. http://hdl.handle.net/10919/77139.

MLA Handbook (7th Edition):

Hancock, Amber N. “A Radical Approach to Syntheses and Mechanisms.” 2011. Web. 19 Apr 2021.

Vancouver:

Hancock AN. A Radical Approach to Syntheses and Mechanisms. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2021 Apr 19]. Available from: http://hdl.handle.net/10919/77139.

Council of Science Editors:

Hancock AN. A Radical Approach to Syntheses and Mechanisms. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/77139

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