scholarly journals Inhomogeneities in PNIPAM Aqueous Solutions: The Inside View by Spin Probe EPR Spectroscopy

Polymers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3829
Author(s):  
Ekaterina M. Zubanova ◽  
Sergei V. Kostjuk ◽  
Peter S. Timashev ◽  
Yury A. Rochev ◽  
Alexander I. Kokorin ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Coming Out ◽  
Epr Spectroscopy ◽  
Spin Probe ◽  
Guest Molecule ◽  
Continuous Wave ◽  
Paramagnetic Resonance ◽  
Molten Globules ◽  
The Individual ◽  
Tempo Radical

Coil to globule transition in poly(N-isopropylacrylamide) aqueous solutions was studied using spin probe continuous-wave electronic paramagnetic resonance (CW EPR) spectroscopy with an amphiphilic TEMPO radical as a guest molecule. Using Cu(II) ions as the “quencher” for fast-moving radicals in the liquid phase allowed obtaining the individual spectra of TEMPO radicals in polymer globule and observing inhomogeneities in solutions before globule collapsing. EPR spectra simulations confirm the formation of molten globules at the first step with further collapsing and water molecules coming out of the globule, making it denser.

scholarly journals Characterizing SPASM/twitch Domain-Containing Radical SAM Enzymes by EPR Spectroscopy

2021 ◽  
Author(s):  
Aidin R. Balo ◽  
Lizhi Tao ◽  
R. David Britt
Keyword(s):  
Epr Spectroscopy ◽  
Continuous Wave ◽  
Spectroscopic Studies ◽  
Paramagnetic Species ◽  
Paramagnetic Resonance ◽  
Iron Sulfur Cluster ◽  
Radical Sam Enzymes ◽  
Iron Sulfur ◽  
Pulse Epr ◽  
Multiple Domains

AbstractOwing to their importance, diversity and abundance of generated paramagnetic species, radical S-adenosylmethionine (rSAM) enzymes have become popular targets for electron paramagnetic resonance (EPR) spectroscopic studies. In contrast to prototypic single-domain and thus single-[4Fe–4S]-containing rSAM enzymes, there is a large subfamily of rSAM enzymes with multiple domains and one or two additional iron–sulfur cluster(s) called the SPASM/twitch domain-containing rSAM enzymes. EPR spectroscopy is a powerful tool that allows for the observation of the iron–sulfur clusters as well as potentially trappable paramagnetic reaction intermediates. Here, we review continuous-wave and pulse EPR spectroscopic studies of SPASM/twitch domain-containing rSAM enzymes. Among these enzymes, we will review in greater depth four well-studied enzymes, BtrN, MoaA, PqqE, and SuiB. Towards establishing a functional consensus of the additional architecture in these enzymes, we describe the commonalities between these enzymes as observed by EPR spectroscopy.

A Study of V3+/4+ Levels in Semi-insulating 6H-SiC using Optical Admittance and Electron Paramagnetic Resonance Spectroscopies

2006 ◽  
Vol 911 ◽  
Author(s):  
Wonwoo Lee ◽  
Mary E Zvanut
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Charge State ◽  
Conduction Band ◽  
Epr Spectroscopy ◽  
Admittance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Characteristic Spectrum ◽  
Epr Measurements ◽  
The Individual ◽  
Electron Paramagnetic

AbstractThe purpose of this study is to identify the vanadium acceptor levels in semi-insulating (SI) 6H-SiC using optical admittance spectroscopy (OAS) and electron paramagnetic resonance (EPR) spectroscopy. OAS conductance peaks near at 0.67 ± 0.02 eV and 0.70 ± 0.02 eV are identified as V3+/4+ levels at the quasi-cubic sites. An OAS peak at 0.87 eV is assigned to the same transition at the hexagonal site. EPR measurements before illumination revealed the characteristic spectrum of V3+. The presence of the V3+ signal supports the identification of the OAS peaks as transitions from the V3+/4+ level to the conduction band. Photo-induced EPR measurements reveal a change in the intensity of V3+ and V4+ at 0.8 ± 0.1 eV, where the amplitude of the V3+ charge state decreases and that of V4+ increases by approximately equal amounts. Although the individual sites are not resolved in the photo-induced EPR data, the 0.8 eV feature strongly supports the assignment of the three OAS peaks as acceptor levels.

scholarly journals An EPR Investigation of Defect Structure and Electron Transfer Mechanism in Mixed-Conductive LiBO2-V2O5 Glasses

2021 ◽  
Author(s):  
Jacob N. Spencer ◽  
Andrea Folli ◽  
Hong Ren ◽  
Damien M. Murphy
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Transfer ◽  
Epr Spectroscopy ◽  
Defect Structure ◽  
Continuous Wave ◽  
Transfer Mechanism ◽  
Paramagnetic Resonance ◽  
Electron Transfer Mechanism ◽  
Electron Paramagnetic

Continuous Wave (CW) Electron Paramagnetic Resonance (EPR) spectroscopy was used to study the defect structure and electron transfer mechanism in a series of LiBO2-V2O5 mixed conductive glasses of varying V2O5...

scholarly journals Molecular-Level Interactions of Nanodisc-Forming Copolymers Dissected by EPR Spectroscopy

2021 ◽  
Author(s):  
Jana Eisermann ◽  
Matthias Hoffmann ◽  
Florian A. Schöffmann ◽  
manabendra das ◽  
Carolyn Vargas ◽  
...  
Keyword(s):  
Light Scattering ◽  
Guest Molecule ◽  
Continuous Wave ◽  
Interaction Patterns ◽  
Temperature Dependent ◽  
Paramagnetic Resonance ◽  
Covalent Interaction ◽  
Nitroxide Spin Probes ◽  
Tracer Molecules ◽  
Electron Paramagnetic

In this study, we focus on analyzing the non-covalent interaction patterns between three lipid-nanodisc-forming polymers and nitroxide radicals which are used as small organic tracer molecules. Besides the negatively charged polymers DIBMA and SMA(2:1), we characterize the solvation behavior of a new zwitterionic styrene/maleic amide sulfobetaine copolymer named SMA-SB. The used nitroxide spin probes vary in their respective chemical structure, allowing the report of different local micropolarities and nanoscopic regions by recording temperature-dependent continuous-wave electron paramagnetic resonance (CW EPR) spectra. In combination with dynamic light scattering (DLS) and electrophoretic light scattering (ELS) experiments, we are able to provide a nanoscopic interpretation of the dominant interaction patterns between the polymer and the chosen guest molecule.

scholarly journals Molecular-Level Release of Coumarin-3-Carboxylic Acid and Warfarin-Derivatives from BSA-Based Hydrogels

Pharmaceutics ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1661
Author(s):  
Niuosha Sanaeifar ◽  
Karsten Mäder ◽  
Dariush Hinderberger
Keyword(s):  
Carboxylic Acid ◽  
Epr Spectroscopy ◽  
Continuous Wave ◽  
Molecular Level ◽  
Controlled Drug Delivery ◽  
Gel Formation ◽  
Release Behavior ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic ◽  
Bsa Interaction

This investigation aimed at developing BSA hydrogels as a controlled release system to study the release behavior of spin-labeled coumarin-3-carboxylic acid (SL-CCS) and warfarin (SL-WFR). The release profiles of these spin-labeled (SL-) pharmaceuticals from BSA hydrogels prepared with different procedures are compared in detail. The mechanical properties of the gels during formation and release were studied via rheology, while a nanoscopic view on the release behavior was achieved by analyzing SL-drugs–BSA interaction using continuous wave electron paramagnetic resonance (CW EPR) spectroscopy. The influence of type of drug, drug concentration, duration of gel formation, and gelation methods on release behavior were characterized by CW EPR spectroscopy, EPR imaging (EPRI), and dynamic light scattering (DLS), which provide information on the interaction of BSA with SL-drugs, the percentage of drug inside the hydrogel and the nature and size of the released structures, respectively. We found that the release rate of SL-CCS and SL-WFR from BSA hydrogels is tunable through drug ratios, hydrogel incubation time and gelation procedures. All of the results indicate that BSA hydrogels can be potentially exploited in controlled drug delivery applications.

scholarly journals Peek Inside the Water Mixtures of Ionic Liquids at Molecular Level: Microscopic Properties Probed by EPR Spectroscopy

2021 ◽  
Vol 22 (21) ◽  
pp. 11900
Author(s):  
Mikhail Yu. Ivanov ◽  
Yuliya F. Polienko ◽  
Igor A. Kirilyuk ◽  
Sergey A. Prikhod’ko ◽  
Nicolay Yu. Adonin ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Epr Spectroscopy ◽  
Continuous Wave ◽  
Molecular Level ◽  
Glassy State ◽  
Residual Water ◽  
Pulse Electron Paramagnetic Resonance ◽  
Spin Probes ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

Many ionic liquids (ILs) can be mixed with water, forming either true solutions or emulsions. This favors their applications in many respects, but at the same time might strongly alter their physicochemical properties. A number of methods exist for studying the macroscopic properties of such mixtures, whereas understanding their characteristics at micro/nanoscale is rather challenging. In this work we investigate microscopic properties, such as viscosity and local structuring, in binary water mixtures of IL [Bmim]BF4 in liquid and glassy states. For this sake, we use continuous wave and pulse electron paramagnetic resonance (EPR) spectroscopy with dedicated spin probes, located preferably in IL-rich domains or distributed in IL- and water-rich domains. We demonstrate that the glassy-state nanostructuring of IL-rich domains is very similar to that in neat ILs. At the same time, in liquid state the residual water makes local viscosity in IL-rich domains noticeably different compared to neat ILs, even though the overwhelming amount of water is contained in water-rich domains. These results have to be taken into account in various applications of IL-water mixtures, especially in those cases demanding the combinations of optimum micro- and macroscopic characteristics.

Long-range distance determinations in biomacromolecules by EPR spectroscopy

2007 ◽  
Vol 40 (1) ◽  
pp. 1-53 ◽  
Author(s):  
Olav Schiemann ◽  
Thomas F. Prisner
Keyword(s):  
Long Range ◽  
Epr Spectroscopy ◽  
Structural Changes ◽  
Continuous Wave ◽  
Double Resonance ◽  
Theoretical Background ◽  
Spin Labels ◽  
Paramagnetic Resonance ◽  
Pulsed Epr ◽  
Amino Acid Radicals

AbstractElectron paramagnetic resonance (EPR) spectroscopy provides a variety of tools to study structures and structural changes of large biomolecules or complexes thereof. In order to unravel secondary structure elements, domain arrangements or complex formation, continuous wave and pulsed EPR methods capable of measuring the magnetic dipole coupling between two unpaired electrons can be used to obtain long-range distance constraints on the nanometer scale. Such methods yield reliably and precisely distances of up to 80 Å, can be applied to biomolecules in aqueous buffer solutions or membranes, and are not size limited. They can be applied either at cryogenic or physiological temperatures and down to amounts of a few nanomoles. Spin centers may be metal ions, metal clusters, cofactor radicals, amino acid radicals, or spin labels. In this review, we discuss the advantages and limitations of the different EPR spectroscopic methods, briefly describe their theoretical background, and summarize important biological applications. The main focus of this article will be on pulsed EPR methods like pulsed electron–electron double resonance (PELDOR) and their applications to spin-labeled biosystems.

scholarly journals Posttranscriptional Site-Directed Spin Labeling of Large RNAs with an Unnatural Base Pair System Under Non-Denaturing Conditions

2020 ◽  
Author(s):  
Yan Wang ◽  
Venkatesan Kathiresan ◽  
Yaoyi Chen ◽  
Yanping Hu ◽  
Wei Jiang ◽  
...  
Keyword(s):  
Epr Spectroscopy ◽  
Base Pair ◽  
Continuous Wave ◽  
Double Resonance ◽  
Rnase P ◽  
Spin Labeling ◽  
Paramagnetic Resonance ◽  
Site Directed Spin Labeling ◽  
And Function

<div> <p>Site-directed spin labeling (SDSL) of large RNAs for electron paramagnetic resonance (EPR) spectroscopy remains challenging up-to-date. We here demonstrate an efficient and generally applicable posttranscriptional SDSL method for large RNAs under non-denaturing conditions using an expanded genetic alphabet containing the NaM-TPT3 unnatural base pair (UBP). An alkyne-modified TPT3 ribonucleotide triphosphate (rTPT3<sup>CO</sup>TP) is synthesized and site-specifically incorporated into large RNAs by <i>in vitro</i> transcription, which allows attachment of the azide-containing nitroxide through click chemistry. We validate this strategy using a 419-nucleotide Ribonuclease P (RNase P) RNA from Bacillus <i>stearothermophilus. </i>The effects of site-directed UBP incorporation and subsequent spin labeling to global structure and function of RNase P are marginal as evaluated by Circular Dichroism spectroscopy, Small Angle X-ray Scattering, and enzymatic assay. Continuous-wave EPR analyses reveal that the labeling reaction is efficient and specific, and Pulsed Electron-Electron Double Resonance measurements yield an inter-spin distance distribution that agrees well with the crystal structure. Thus, the labeling strategy as presented overcomes the size constraint of RNA labeling, opening new possibilities for application of EPR spectroscopy in investigating structure and dynamics of large RNA.</p> </div> <br>

scholarly journals Posttranscriptional Site-Directed Spin Labeling of Large RNAs with an Unnatural Base Pair System Under Non-Denaturing Conditions

2020 ◽  
Author(s):  
Yan Wang ◽  
Venkatesan Kathiresan ◽  
Yaoyi Chen ◽  
Yanping Hu ◽  
Wei Jiang ◽  
...  
Keyword(s):  
Epr Spectroscopy ◽  
Base Pair ◽  
Continuous Wave ◽  
Double Resonance ◽  
Rnase P ◽  
Spin Labeling ◽  
Paramagnetic Resonance ◽  
Site Directed Spin Labeling ◽  
And Function

<div> <p>Site-directed spin labeling (SDSL) of large RNAs for electron paramagnetic resonance (EPR) spectroscopy remains challenging up-to-date. We here demonstrate an efficient and generally applicable posttranscriptional SDSL method for large RNAs under non-denaturing conditions using an expanded genetic alphabet containing the NaM-TPT3 unnatural base pair (UBP). An alkyne-modified TPT3 ribonucleotide triphosphate (rTPT3<sup>CO</sup>TP) is synthesized and site-specifically incorporated into large RNAs by <i>in vitro</i> transcription, which allows attachment of the azide-containing nitroxide through click chemistry. We validate this strategy using a 419-nucleotide Ribonuclease P (RNase P) RNA from Bacillus <i>stearothermophilus. </i>The effects of site-directed UBP incorporation and subsequent spin labeling to global structure and function of RNase P are marginal as evaluated by Circular Dichroism spectroscopy, Small Angle X-ray Scattering, and enzymatic assay. Continuous-wave EPR analyses reveal that the labeling reaction is efficient and specific, and Pulsed Electron-Electron Double Resonance measurements yield an inter-spin distance distribution that agrees well with the crystal structure. Thus, the labeling strategy as presented overcomes the size constraint of RNA labeling, opening new possibilities for application of EPR spectroscopy in investigating structure and dynamics of large RNA.</p> </div> <br>

scholarly journals Molecular-Level Interactions of Nanodisc-Forming Copolymers Dissected by EPR Spectroscopy

2021 ◽  
Author(s):  
Jana Eisermann ◽  
Matthias Hoffmann ◽  
Florian A. Schöffmann ◽  
manabendra das ◽  
Carolyn Vargas ◽  
...  
Keyword(s):  
Light Scattering ◽  
Guest Molecule ◽  
Continuous Wave ◽  
Interaction Patterns ◽  
Temperature Dependent ◽  
Paramagnetic Resonance ◽  
Covalent Interaction ◽  
Nitroxide Spin Probes ◽  
Tracer Molecules ◽  
Electron Paramagnetic

In this study, we focus on analyzing the non-covalent interaction patterns between three lipid-nanodisc-forming polymers and nitroxide radicals which are used as small organic tracer molecules. Besides the negatively charged polymers DIBMA and SMA(2:1), we characterize the solvation behavior of a new zwitterionic styrene/maleic amide sulfobetaine copolymer named SMA-SB. The used nitroxide spin probes vary in their respective chemical structure, allowing the report of different local micropolarities and nanoscopic regions by recording temperature-dependent continuous-wave electron paramagnetic resonance (CW EPR) spectra. In combination with dynamic light scattering (DLS) and electrophoretic light scattering (ELS) experiments, we are able to provide a nanoscopic interpretation of the dominant interaction patterns between the polymer and the chosen guest molecule.

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