The electron paramagnetic resonance signal of the cupric ion (its perpendicular component) at −196°C was found to be different in shape in human blood plasma and serum. On the addition of acid, substrate of ceruloplasmin, reducing agent, or denaturing agent, serum exhibited a complex electron paramagnetic resonance spectrum similar to that of a copper-diethyldithiocarbamate complex in an organic solvent, with a simultaneous disappearance of the cupric ion signal. Such an electron paramagnetic resonance spectrum occurred only from human serum but not from animal (guinea pig, mouse, rat, cattle, or monkey) serum.. PDF Article ...
TY - JOUR. T1 - Electron paramagnetic resonance spectrum of radical pairs in ultraviolet irradiated (Nh4)2s208 single crystals. AU - Liu, Kuo Tung. AU - Yu, Jiang Tsu. N1 - Funding Information: The authors gratefully thank the National Science Council of the Republic of China for the support given during the period of this investigation.. PY - 1994/9. Y1 - 1994/9. N2 - Irradiation of (NH4)2S208 single crystals with ultraviolet (UV) light produces two kinds of radical pair, I and II. Radical pair I is stable at room temperature, and can be produced via UV irradiation at room temperature. The electron paramagnetic resonance (EPR) spectrum exhibited by radical pair I is similar to that of SOJ pairs in UV irradiated K2S208 crystals observed previously, and can be identified similarly. Radical pair II can be produced by UV irradiation and detected by EPR only at low temperatures. Radical pair II, which could be identified as SOJ pairs, exhibits a limited lifetime at room temperature. A rigorous ...
This chapter presents the background, nomenclature, and theory of ESR spectroscopy. domains in ESR parameter space. PDF. ESR-1 Experiment #2B: Electron Spin Resonance Spectroscopy I. John E. Wertz, James R. Bolton. Electron Spin Resonance Spectroscopy Electron Spin Resonance (ESR) spectroscopy, also referred to as Electron Paramagnetic Resonance (EPR) spectroscopy, is a versatile, nondestructive analytical technique based on the absorption of microwave radiation in presence of an applied field by paramagnetic species. Request PDF , Principles and Applications of ESR Spectroscopy , The ESR (electron spin resonance) method is employed for studies of paramagnetic substances … Pages 1-20. Electron spin resonance spectroscopy (ESR) or electron paramagnetic resonance (EPR) is a technique for studying chemical species that have one or more unpaired electrons, such as organic and inorganic free radicals or inorganic complexes possessing a transition metal ion. Introduction Electron spin resonance ...
Read An Electron Paramagnetic Resonance Method for Measuring the Affinity of a Spin-Labeled Analog of Cholesterol for Phospholipids, The Journal of Membrane Biology on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.
TY - JOUR. T1 - Kinetic and stoichiometric assessment of the antioxidant activity of flavonoids by electron spin resonance spectroscopy. AU - McPhail, D B AU - Hartley, R C AU - Gardner, P T AU - Duthie, G G. PY - 2003/3/12. Y1 - 2003/3/12. N2 - dThere is current interest in the use of naturally occurring flavonoids as antioxidants for the preservation of foods and the prevention of diseases such as atherosclerosis and cancers. To establish the molecular characteristics required for maximum antioxidant activity, electron spin resonance (ESR) spectroscopy has been used to determine the stoichiometry and kinetics of the hydrogen-donating ability of 15 flavonoids and D-alpha-tocopherol to galvinoxyl, a resonance-stabilized, sterically protected aryloxyl radical. The second-order reaction rates, which will be governed by O-H bond dissociation energies, were myricetin , morin , quercetin , fisetin similar to catechin , kaempferol similar to luteolin , rutin , D-alpha-tocopherol , taxifolin , ...
Electron Spin Resonance David J. Lurie, PhD Bio-Medical Physics, School of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK 1. 13/02/2020 14/04/2020 Chemistry ABC 0 Comments electron spin resonance, esr, resonance, spectroscopy After Very Hardworking by contacting Toppers of Gate we have got E S R Spectroscopy Handwritten Notes Pdf. • Net spin S = 0 • Some chemical species have UNPAIRED electrons • Atoms H, Na, transition metals • Recall Stern-Gerlach experiment (s = ±±±± ½) • Molecules: O 2, NO Proportionality Factor Atherton, N. M. Principles of Electron Spin Resonance; Ellis Horwood: Chichester, 1993. how is, Nuclear Magnetic Resonance - . nuclear magnetic resonance (nmr), ATOMIC SPECROSCOPY (AS) - . PPT - Electron Spin Resonance Spectroscopy PowerPoint presentation , free to download - id: 3c9577-Y2VkZ, The Adobe Flash plugin is needed to view this content. The PowerPoint PPT presentation: Electron Paramagnetic Resonance (EPR) is the property of ...
Resulting energy levels of an electron in a magnetic field Ebsworth, E. A. V.; Rankin, David W. H.; Cradock, Stephen Structural Methods in Inorganic Chemistry; CRC Press: Boca Raton, 1987. infrared. Winner of the Standing Ovation Award for Best PowerPoint Templates from Presentations Magazine. To Provide A Classical Analog PPT. - ... spinning protons act like bar magnets. A surprisingly large number of materials have unpaired electrons. The electron spin resonance spectrum of a free radical or coordination complex with one unpaired electron is the simplest of all forms of spectroscopy. - Electron Spin Resonance (ESR) Spectroscopy applied to species having one or more unpaired electrons : free radicals, biradicals, other triplet states, transition ... Nuclear Magnetic Resonance (NMR) Spectroscopy. ESR is an acronym for Electron Spin Resonance. EPR (Electron Paramagnetic Resonance) is a spectroscopic technique that detects species that have unpaired electrons. optical microscopy -, ...
Реферат: Electron spin−echo envelope modulation (ESEEM) spectroscopy of phospholipids spin-labeled systematically down the sn-2 chain was used to detect the penetration of water (D2O) into bilayer membranes of dipalmitoyl phosphatidylcholine with and without 50 mol % cholesterol. Three-pulse stimulated echoes allow the resolution of two superimposed 2H-ESEEM spectral components of different widths, for spin labels located in the upper part of the lipid chains. Quantum chemical calculations (DFT) and ESEEM simulations assign the broad spectral component to one or two D2O molecules that are directly hydrogen bonded to the N−O group of the spin label. Classical ESEEM simulations establish that the narrow spectral component arises from nonbonded water (D2O) molecules that are free in the hydrocarbon chain region of the bilayer membrane. The amplitudes of the broad 2H-ESEEM spectral component correlate directly with those of the narrow component for spin labels at different positions down ...
Rainer Grün. This will be achieved by looking for the spin … Electron spin resonance (ESR) is a spectroscopic technique that detects the transitions induced by electromagnetic radiation between the energy levels of electron spins in the presence of a static magnetic field. Uhlenbeck, in 1925, recommended that an electron has an inherent angular momentum that is a magnetic moment that is recognized as spin.In atomic physics, the inherent angular momentum of a particular particle is parametrized by spin quantum number. ESR only works with unpaired electrons, though, not the usual paired electrons of molecules. Energy-level Diagram For Two Spin States as a Function of Applied Field B. For electron spin resonance (ESR) studies, we obtained solvent-extractable free radicals from 1,3-butadiene soot from brief liquid-solid extractions with ultra-pure toluene, DMSO:water (4:1, v/v), n-hexane, and 3% aqueous sodium dodecyl sulfate. electron spin resonance synonyms, electron spin resonance ...
ELECTRON SPIN RESONANCE OBJECTIVES * To learn some properties of a simple microwave reflection spectrometer. Here, we report a cavity-less technique which makes use of only an impedance analyzer and a copper strip coil to detect L-band EPR ( f = 1-3 GHz) in the standard EPR marker 2,2-diphenyl … The radical scavenging effects of chitooligosaccharides (COSs) on hydroxyl radical, superoxide radical, alkyl radical, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical were investigated using a spin-trapping electron spin resonance (ESR) method and compared with the ESR signal intensity. ×zÆE^{¯êb¸]Á&] ðBÁ÷¢VQ^ ¥¢¦; WF0 ác³ Electron spin resonance (ESR) is a useful tool for investigating the energy absorption spectra of many materials with unpaired electrons (paramagnetic materials). 2. A ball with a central rod magnet, which rotates with low fric- tion on an air cushion, acts as model electron. Determination of antioxidant capacity of diverse fruits by electron spin resonance (ESR) and ...
In atomic physics, hyperfine structure refers to small shifts and splittings in the energy levels of atoms, molecules, and ions, due to interaction between the state of the nucleus and the state of the electron clouds. In atoms, hyperfine structure arises from the energy of the nuclear magnetic dipole moment interacting with the magnetic field generated by the electrons and the energy of the nuclear electric quadrupole moment in the electric field gradient due to the distribution of charge within the atom. Molecular hyperfine structure is generally dominated by these two effects, but also includes the energy associated with the interaction between the magnetic moments associated with different magnetic nuclei in a molecule, as well as between the nuclear magnetic moments and the magnetic field generated by the rotation of the molecule. Hyperfine structure contrasts with fine structure, which results from the interaction between the magnetic moments associated with electron spin and the ...
Since electron spin resonance is an excellent analytical method for paramagnetic species and free radicals, it can be used to obtain a variety of kinetic and thermodynamic data. To provide a classical analog to spin resonance mental model, a spinning ball with a central magnet is required. Structure Determination: Nuclear Magnetic Resonance Spectroscopy. 1. concepts. brief discussion of principle, instrumentation and applications optical microscopy -, Ultraviolet-Visible Spectroscopy - . The two states are labeled by the projection of the electron spin, m s, on the direction of the magnetic field. A surprisingly large number of materials have unpaired electrons. EPR = ESR E Electron -study of unpaired electron spins, and their interaction with their environment. nonzero. what is the source and how is it working? To view this presentation, youll need to allow Flash. And theyre ready for you to use in your PowerPoint presentations the moment you need them. Electron Spin Resonance, ESR, is a ...
The ultimate ambition of this project is to perform an EMR study of radiation-induced radicals on DNA samples, comparably successful as for sucrose. This would provide the most direct way to determine the precise role of sugar radicals in radiation damage to DNA. Mainly because of the lack of DNA single crystals (DNA fibers are only partially oriented), literature studies have so far been restricted to EPR studies of polycrystalline or frozen solution DNA, with high risk of erroneous conclusions based only on isotropic parameters, as the UGent group demonstrated recently for trehalose . This could be avoided if information on the anisotropy of g and hyperfine tensors is collected for confrontation with DFT calculations. Therefore we are exploring the possibilities of powder ENDOR (and/or pulsed EPR), first on DNA-related materials and later in the project on DNA. It is known, but still remarkable that anisotropic information can be retrieved from powder materials exploiting the orientation ...
As the silicon technology approaches to its physical limit, the future electronic devices will depend on behaviors of a few electrons. This study is to exp
These new states, along with their respective energies and transitions, are shown schematically in Figure (1). 14NO and 15NO adducts of ferrous heme-heme oxygenase exhibit EPR hyperfine splittings of … The parallel mode EPR technique has been applied to several of these systems to verify their integer spin state. The electron paramagnetic resonance (EPR) parameters (g factors g parallel, g perpendicular and hyperfine structure constants A parallel, A perpendicular) for Co2+ ions in LiNbO3 and LiTaO3 crystals are calculated from the second-order perturbation formulas based on the cluster approach for 3d7 ions in trigonal octahedral clusters. Application of a magnetic field gives the following spin Hamiltonian for the system. To describe the theory of parallel mode EPR we must first define the system that we wish to characterize. An example of a parallel mode EPR spectrum of a high spin (S=2) Fe(IV)-oxo compound, measured by Hendrich and coworkers at Pennsylvania State University, is shown in ...
The Interest Groups are member driven groups which exist to benefit RSC members, and the wider chemical science community, in line with the RSCs strategy and charter. The Interest Groups are member driven groups which exist to benefit RSC members, and the wider chemical science community, in line with the RSCs strategy and charter. SEUNG‐JAE … The ESR spectroscopy has been used to estimate polynuclear hydrocarbons, which are first, converted in to radical cations and then absorbed in the surface of an activated silica-alumina catalyst. An intense external magnetic field produces a difference between the energy levels of the electron spins m s = + ½ and m s = - ½, leading to resonance absorption of an applied microwave beam in the spectrometer. Electron Spin resonance spectroscopy is based on the absorption of microwave radiation by an unpaired electron when it is exposed to a strong magnetic field. ESR Spectroscopy • Electron Spin Resonance Spectroscopy • Also called EPR Spectroscopy ...
Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. principles and applications of esr spectroscopy Oct 29, 2020 Posted By Yasuo Uchida Media Publishing TEXT ID e476e21e Online PDF Ebook Epub Library molecular physics physical chemistry biochemistry or spectroscopy the This method and the related NMR or nuclear magnetic resonance Principles and Applications of ESR Spectroscopy fills the gap between the detailed monographs in ESR spectroscopy and the general textbooks in molecular physics, physical chemistry, biochemistry or spectroscopy. Electron spin resonance spectroscopy (ESR) or electron paramagnetic resonance (EPR) is a technique for studying chemical species that have one or more unpaired electrons, such as organic and inorganic free radicals or inorganic complexes possessing a transition metal ion. The ESR (electron spin resonance) method is employed for studies of paramagnetic substances most commonly in liquids and solids. ...
Applications of NMR spectroscopy. Structure of organic and inorganic free radicals can be identified. Applications Electron spin resonance (ESR) spectroscopy is also known as Electron paramagnetic resonance (EPR) It is absorption spectroscopy similar to NMR, possible only with molecules having unpaired electrons Instead of Radiowaves in NMR, Microwaves is used in ESR 2. Structural elucidation: Most organic compounds have hydrogen in them. A broad-spectrum review of the applications of electron spin resonance to advanced materials is presented. Thus it helps to understand the structure of a compound. 2 Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy is a method for studying materials with unpaired electrons.The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but it is electron spins that are excited instead of the spins of atomic nuclei.EPR spectroscopy is particularly useful for studying metal complexes or organic radicals. ...
Janis has standard designs available for electron spin resonance (ESR) spectroscopy, plus the capability of custom building any system to your specifications. Electron spin resonance (ESR) spectroscopy has been used for over 50 years to study a variety of paramagnetic species. Finally, the potential use of ESR technique in investigating microstructure change, phase transition and viscosity related properties during food formulation, processing, and storage was briefly mentioned, along with its potential in determination of radio‐stability of food components. Applications of ESR spectra: • It decides the site of unpaired electrons. Fax: +1(301)‐314‐3313. (Also known as EPR, Electron Paramagnetic Resonance) ESR is a method for observing the behavior (dynamics) of the electrons within a suitable molecule, and for analyzing various phenomena by identifying the electron environment. Wide Field of Applications. Systems Biology of Free Radicals and Antioxidants. Principles and Applications of ...
Synthetically useful hydrocarbon oxidations are catalysed by bio-inspired non-heme iron complexes using hydrogen peroxide as oxidant, and carboxylic acid addition enhances their selectivity and catalytic efficiency. Talsi has identified a low-intensity g = 2.7 electron paramagnetic resonance signal in such catalytic systems and attributed it to an oxoiron(V)-carboxylate oxidant. Herein we report the use of Fe-II(TPA(star)) (TPA(star) = tris (3,5-dimethyl-4-methoxypyridyl-2-methyl)amine) to generate this intermediate in 50% yield, and have characterized it by ultraviolet-visible, resonance Raman, Mossbauer and electrospray ionization mass spectrometric methods as a low-spin acylperoxoiron(III) species. Kinetic studies show that this intermediate is not itself the oxidant but decays via a unimolecular rate-determining step to unmask a powerful oxidant. The latter is shown by density functional theory calculations to be an oxoiron(V) species that oxidises substrate without a barrier. This study ...
The magnetic and electronic properties of heavily doped n-type 6H SiC samples with a nitrogen concentration of 10{sup 19} and 4 × 10{sup 19 }cm{sup −3} were studied with electron spin resonance (ESR) at 5-150 K. The observed ESR line with a Dysonian lineshape was attributed to the conduction electrons (CE). The CE ESR (CESR) line was fitted by Lorentzian (insulating phase) (T , 40 K) and by Dysonian lineshape (metallic phase) above 40 K, demonstrating that Mott insulator-metal (IM) transition takes place at ∼40 K, accompanied by significant change in the microwave conductivity. The temperature dependence of CESR linewidth follows the linear Korringa law below 40 K, caused by the coupling of the localized electrons (LE) and CE, and is described by the exponential law above 40 K related to the direct relaxation of the LE magnetic moments via excited levels driven by the exchange interaction of LE with CE. The g-factor of the CESR line (g{sub ‖} = 2.0047(3), g{sub ⊥} = 2.0034(3)) is ...
Cytotoxic effects of daunomycin were investigated upon differentiation of Friend erythroleukemia cells induced with hexamethylene bisacetamide, a process during which a 20-fold increase in the hemoglobin content occurred. Daunomycin proved to be more toxic to differentiated Friend cells than to their undifferentiated counterparts. No changes in the daunomycin uptake rates of the two cell types were detectable. Externally added catalase and desferrioxamine mesylate protected against the additional cytotoxicity of daunomycin in differentiated cells, pointing to hydrogen peroxide and iron ions as mediators of the toxic effect. Daunomycin-dependent, cyanide-insensitive oxygen consumption of control and induced cells did not differ significantly, and the rate of formation of the daunomycin semiquinone radical electron paramagnetic resonance signal was similar in both cell types, indicating that the difference in toxicity was not due to increased drug activation by plasma membrane enzymes. ...
a longitudinal rather than a transverse magnetic field in a laser cavity From: Handbook of Adhesives and Surface Preparation, 2011 All rights reserved. Powered by, Boron-Tri-Fluoride (10BF3) Gas Filled Proportional Counters for Thermal Neutron Detection, Difference between Ionizing radiation & Non-ionizing radiation. a days, ESR is used in the analysis of enzymatic activity of nitric oxide synthetase (NOS), the main enzymes delivering, evolutionary biology. method for determination of Vanadium in petroleum products. These include free radicals, many transition metal ions, and defects in materials. It is critical that the substance have unpaired electrons. Much of the ESR work on photosynthesis has. Specific features of ESR in modern biotechnology are: indirectly by other free radicals. Electron spin resonance spectroscopy, in Instrumental methods of chemical analysis. In vivo ESR, experiments revealed that multimellar liposomes enhance the topical delivery of hydrophilic compound, drugs used to ...
Nitric oxide (NO) production in the regenerating liver was estimated from the intensity of the electron paramagnetic resonance signal of the mononitrosyl complexes of iron and diethylthiocarbamate (DETC). Preformed complexes of intracellular non-heme Fe2+ and added DETC served as a trap for endogeneously produced NO. The data revealed dynamic changes of NO production temporally connected with the time periodicity of the liver regeneration. The first increase of NO production occurred ca. 1 h after partial hepatectomy (PHE) coinciding with the rapid response of the liver to injury. The second more pronounced production of NO was observed about 6 h after PHE, when the hepa-tocytes entered the first cell cycle, and originated mainly from them. The following minimum of NO synthesis coincided with the maximal rate of DNA synthesis. The third gradual rise of NO production was seen at the end of the investigated period, covering G2+M phases and the transit from the first to the second cell cycle of the ...
ESR Spectroscopy (Electron Spin Resonance Spectroscopy or Electron Paramagnetic Resonance Spectroscopy) is a technique used for studying chemical species that
en] The C-phenyl-N-tert-butylnitrone/azobisisobutyronitrile pair is able to impart control to the radical polymerization of n-butyl acrylate as long as a two-step process is implemented, that is, the prereaction of the nitrone and the initiator in toluene at 85 degrees C for 4 h followed by the addition and polymerization of n-butyl acrylate at 110 degrees C. The structure of the in situ formed nitroxide has been established from kinetic and electron spin resonance data. The key parameters (the dissociation rate constant, combination rate constant, and equilibrium constant) that govern the process have been evaluated. The equilibrium constant between the dormant and active species is close to 1.6 x 10(-12) mol L-1 at 110 degrees C. The dissociation rate constant and the activation energy for the C-ON bond homolysis are 1.9 x 10(-3) s(-1) and 122 +/- 15 kJ mol(-1), respectively. The rate constant of recombination between the propagating adical and the nitroxide is as high as 1.2 x 10(9) L mol(-1) ...
With more than 940,000 new colorectal cancer cases worldwide each year, there is no better way for colorectal cancer routine screening. The aim of this study was to investigate whether the fatty acid binding to albumin is detectably and significantly altered in colorectal cancer patients when compared with healthy people, in order to find a better way for colorectal cancer diagnosis. One hundred and forty-one patients operatively treated for colorectal cancer were included in the examination, and 180 healthy people were also enrolled as controls. Commercial 16-doxyl stearic acid was used as spin probe. Serum albumin was analyzed by electron paramagnetic resonance (EPR) with spin probe. Discriminant analysis was carried out using the measured EPR spectra by SPSS 20.0. Of the original grouped cases, 89.4% were correctly classified. Of the
However, electron spins have yet to be used in realistic electronic devices except as part of magnetic devices for information storage. The reason is that spin polarization in a semiconductor is easily randomized, and consequently, it is difficult to transport spin polarization over a long distance.. An electron spin itself is a quantum spin angular momentum. Electrical transport and the manipulation of spin polarization are essential technologies if electron spins are to be employed in a device.. However, in actual materials, electron spins are randomized by the multiple scattering of electrons, resulting in spin depolarization in finite time. This phenomenon is called spin relaxation, and it results in spin polarization having a short transport length in a device. To realize spin functional devices, it is important to suppress spin relaxation and achieve more stable manipulation of electron spins.. The research team has demonstrated long-distance spin transport by electrical means in a ...
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Preliminary Study on Electron Paramagnetic Resonance(EPR) Signal Properties of Mobile Phone Components for Dose Estimation in Radiation Accident - Radiation accident;Electron spin resonance;Electron paramagnetic resonance;Dosimetry;
The heterogeneous oxidation of some substituted phenols has been studied by means of electron spin resonance. Strong signals, observed during the oxidation of the phenols with a free para-position, are due to secondary radicals derived from C4-O linked dimeric and polymeric phenols (A) are not to substituted 4, 4-di-pheno-semiquinones (B). Special attention has been given to the oxidation of 2, 6-dimethylphenol which yields a radical with non-equivalent methyl groups. The e. s. r. spectra of the secondary radicals from some 4-substituted 2, 6-dimethylphenol are identical to each other and to that from 2, 6-dimethylphenol itself. This indicates that in these radicals the para-substituent had been displaced by an aryloxy group. The ease of this displacement can be determined by use of the flow technique. ...
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Get this from a library! Electron Paramagnetic Resonance of d Transition Metal Compounds.. [F E Mabbs; D Collison] -- Electron paramagnetic resonance (epr) spectroscopy is a sensitive and versatile method of studying paramagnets, which is finding increasing use in chemistry, biochemistry, earth and materials ...
Magnetic Resonance Imaging of Tumor Physiology. Characterizing tumors and related pathological conditions on a physiologic basis by noninvasive radiological techniques is a potentially useful capability for diagnosis as well as for devising appropriate cancer treatment approaches. Magnetic resonance imaging (MRI) is a commonly used clinical imaging procedure that provides images of soft tissue anatomy with excellent detail. Recent advances have made it possible to provide functional information such as brain function using functional MRI (fMRI) techniques. To obtain physiological information such as oxygen or tissue redox stats in pathological situations such as solid tumors or ischemic/hypoxic tissue, quantitatively and noninvasively, we are developing imaging techniques based on electron paramagnetic resonance (EPR). EPR is similar to nuclear magnetic resonance (NMR) in many ways. NMR probes nuclei such as 1H, 13C, and 31P, while EPR detects paramagnetic species. Paramagnetic species by ...
TY - JOUR. T1 - ENDOR study on the dynamic properties of the first stable paramagnetic center in γ-irradiated L-alanine crystrals. AU - Rakvin, Boris. AU - Maltar-Strmecki, N.. AU - Kattnig, Daniel. AU - Grampp, Günter. PY - 2010. Y1 - 2010. U2 - 10.1021/jp103883x. DO - 10.1021/jp103883x. M3 - Article. VL - 114. SP - 7500. EP - 7505. JO - The journal of physical chemistry (Washington, DC) / A. JF - The journal of physical chemistry (Washington, DC) / A. SN - 1089-5639. ER - ...
Four heteroleptic copper(I) complexes containing phenanthroline and monoanionic nido-carborane-diphosphine ligands have been prepared and structurally characterized by various spectroscopic techniques and X-ray diffraction. These complexes exhibit intense absorptions in the visible range and excited-state lifetimes on the microsecond scale. Their application in visible-light-induced cross-dehydrogenative coupling reactions was investigated. Preliminary studies showed that one of the four copper(I) complexes is an efficient catalyst for photoinduced oxidative C[BOND]H functionalization using oxygen as oxidant. Furthermore, α-functionalized tertiary amines were obtained in good-to-excellent yields by light irradiation (λ>420 nm) of a mixture of our CuI complex, tertiary amines, and a variety of nucleophiles (nitroalkane, acetone, or indoles) under aerobic conditions. Electron paramagnetic resonance measurements provided evidence for the formation of superoxide radical anions (O2−⋅) rather ...
In the last few years, fast arbitrary waveform generates (AWGs) have become commercially available in the field of electron paramagnetic resonance (EPR). Pairing AWGs with local oscillator devices gives access to frequency and amplitude modulated microwave pulses and sufficiently broadband digitizers exist for appropriate detection. But replacing monochromatic rectangular pulses with frequency and amplitude modulated pulses is not an innocent procedure. Compared to the one during monochromatic rectangular pulse, spin dynamics during frequency-swept pulses is fundamentally different and as a consequence routine experiments can lead to surprising new results. Although passage pulses are well known and studied in nuclear magnetic resonance (NMR) spectroscopy, their effects are far from being fully understood in EPR spectroscopy. In response to the need of a way to simulate pulse EPR experiments with frequency swept-pulses, the open-source spin dynamics analysis (SPIDYAN) toolbox, which runs in ...
In-beam measurement of the hydrogen hyperfine splitting and prospects for antihydrogen spectroscopy Nature Communications, Published online: 12 June 2017; doi:10.1038/ncomms15749 Comparing the ground-state hyperfine structure of antihydrogen to that of hydrogen will provide insights into CPT symmetry in nature. Here the authors report the most precise in-beam measurement of this quantity for hydrogen to demonstrate…
We combine inorganic synthesis, chemical biology and spectroscopy to relate the structures of metal centres to reactivity. Many of the systems we study are paramagnetic, and we use electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) to study paramagnetic metal centres and radical chemistry. We also use NMR extensively to characterise diamagnetic species produced by redox processes, and to study reaction products and kinetics in catalytic systems. These methods are supplemented by DFT calculations of molecular properties and spectroscopic parameters. ...
This report summarizes recent investigations that relate physical changes in macromolecular protein structures to biological functions. It is based on a review by scientists studying protein structure changes induced by van der Waals forces model cell membrane systems that measure the functions of the enzyme permeases the biological applications of nuclear magnetic resonance and electron spin resonance spectra and spin-labeling techniques fluorescence spectra, polarization and decay times, and absorption spectroscopy as indicators of biological events and the significance of molecular geometric changes in a series of biologically active compounds as related to their chemical structure. The topics include the nature of changes produced by chemicals at cell surfaces, enzyme-substrate interactions, novel concepts of charge transport through biological substrates, and their relationship to fine-structure changes in living systems. Author
my name is Artemis. These days I study at University of Science and Technology in Cracow. Due to the fact that semester is almost over one of my tutors asked me to do a quick presentation about Ways of measuring hyperfine interactions. I would appreciate it a lot if anyone of you could help me with this subject by just by mentioning me the ways how to do it, as I need to write about 6 methods and I cant find even one. Please help me ...
Turkish pink shrimp (Parapenaeus longirostris) samples were studied by electron spin resonance (ESR) spectroscopy for identification and dose assessment purposes. In this work, the calcified shells of shrimps were used as a sample material. Before irradiation, all shrimp shell samples exhibit one weak ESR singlet with a g-factor of 2.0047. After irradiation, all samples exhibit two asymmetric ESR signal components centered at g-values of 2.0013 and 1.9959. The dose-response curves of the samples exposed to gamma radiations were found to be described well by a single saturation exponential function. Variation of ESR signal intensity of irradiated samples at room and-20 degrees C temperatures with time in a long-term showed that free radicals responsible from the ESR spectrum of shrimp shells were not stable but still detectable after 87 days. Also, the kinetic behavior of signal at g=2.0013 was studied and the additive dose method was used to evaluate the dose in the product. ...
We calculated hyperfine structure constants of the 5d6s^{2}, 5d^{2}6s, 5d^{3}, 5d^{2}7s, 5d6s7s, 5d6p^{2}, 4f^{2}5d, 4f6s6p, 5d6s6p, 5d^{2}6p, 4f5d6s and 4f5d^{2} levels for ^{139}La I (Z=57). The calculations are based upon the multiconfiguration Hartree-Fock method within the framework of the Breit-Pauli relativistic corrections. Moreover, the results obtained were compared with other available calculations and experiments ...
Continuous-wave and pulsed electron paramagnetic resonance have been applied to the study of the CuII site of the copper-resistance protein PcoC from Esche
The Robinson group specializes in using a variety of Electron Paramagnetic Resonance (EPR) techniques, including continuous wave and pulsed Saturation Recovery (pSR) and pulsed Electron-Electron Double Resonance (pELDOR) EPR at 2 and 10 GHz. The research areas of interest include: dynamics of B-form duplex DNA and protein-DNA binding (as part of the process of DNA recognition); protein-RNA interactions; the interaction of interfacial signaling proteins and membranes; and the organization of organic chromophores in polymer matrices. The group collaborates with Larry Dalton, J. Michael Schurr, and Michael Gelb (all UW Chemistry) as well as Snorri Sigurdsson (University of Iceland), and Albert Beth and Eric Hustedt (Vanderbilt University).. The Robinson laboratory contains a CW/pulsed 10 GHz and a CW/pulsed 2 GHz EPR spectrometers. In addition, the Robinson group is responsible for the shared EPR instrumentation (from NIH-IEHS), which is used by more than a dozen groups around the UW campus. The ...
The delocalization of the photoexcited triplet state in a linear butadiyne-linked porphyrin dimer is investigated by time-resolved and pulse electron paramagnetic resonance (EPR) with laser excitation. The transient EPR spectra of the photoexcited triplet states of the porphyrin monomer and dimer
Nitric oxide (NO) has been used as a substrate analog to explore the structural and electronic determinants of enzymatic superoxide reduction at the mononuclear iron active site of Pyrococcus furiosus superoxide reductase (SOR) through the use of EPR, resonance Raman, Fourier transform IR, UV-visible absorption, and variable-temperature variable-field magnetic CD spectroscopies. The NO adduct of reduced SOR is shown to have a near-axial S = 3/2 ground state with E/D = 0.06 and D = 12 ± 2 cm-1 (where D and E are the axial and rhombic zero-field splitting parameters, respectively) and the UV-visible absorption and magnetic CD spectra are dominated by an out-of-plane NO-(π*)-to-Fe3+(dπ) charge-transfer transition, polarized along the zero-field splitting axis. Resonance Raman studies indicate that the NO adduct is six-coordinate with NO ligated in a bent conformation trans to the cysteinyl S, as evidenced by the identification of v(N-O) at 1,721 cm-1, v(Fe-NO) at 475 cm-1, and v(Fe-S(Cys), at
As noted in the Introduction, the role of NO in epileptogenesis is unclear. NO has been suggested to be both an anticonvulsant and a proconvulsant in animals (9, 10, 12-16). These inconsistencies may be due to the fact that although these studies measured the effects of NOS inhibitors, they did not actually measure NO production. The advantage of the current L-band EPR study is that we can make direct NO measurements by detecting it as the (DETC)2-Fe-NO complex in the brain of living mice. We were able to confirm that NO levels are elevated in tonic and clonic convulsions.. Both the in vivo and ex vivo EPR measurements confirmed that more NO was produced in the tonic than in the clonic convulsions, perhaps indicating that NO levels were proportional to the intensity of the convulsion. These results suggest that NO works as a proconvulsant. However, in the presence of NOS inhibitors, both L-NNA and 3Br-7NI suppressed the transition from clonic to tonic convulsion at high PTZ doses, while the ...
Dynamic nuclear polarization (DNP)[1][2][3] results from transferring spin polarization from electrons to nuclei, thereby aligning the nuclear spins to the extent that electron spins are aligned. Note that the alignment of electron spins at a given magnetic field and temperature is described by the Boltzmann distribution under the thermal equilibrium. It is also possible that those electrons are aligned to a higher degree of order by other preparations of electron spin order such as: chemical reactions (leading to Chemical-Induced DNP, CIDNP), optical pumping and spin injection. DNP is considered one of several techniques for hyperpolarization. DNP can also be induced using unpaired electrons produced by radiation damage in solids.[4][5] When electron spin polarization deviates from its thermal equilibrium value, polarization transfers between electrons and nuclei can occur spontaneously through electron-nuclear cross relaxation and/or spin-state mixing among electrons and nuclei. For example, ...
Electron paramagnetic resonance (EPR) spectroscopy is an unambiguous method to measure free radicals. The use of selective spin probes...