1
|
4-Dialkylamino-2,5-dihydroimidazol-1-oxyls with Functional Groups at the Position 2 and at the Exocyclic Nitrogen: The pH-Sensitive Spin Labels. Gels 2021; 8:gels8010011. [PMID: 35049546 PMCID: PMC8774874 DOI: 10.3390/gels8010011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 12/17/2021] [Accepted: 12/17/2021] [Indexed: 11/16/2022] Open
Abstract
Local acidity and electrostatic interactions are associated both with catalytic properties and the adsorption activity of various materials, and with the vital functions of biomolecules. The observation of acid–base equilibria in stable free radicals using EPR spectroscopy represents a convenient method for monitoring pH changes and the investigation of surface electrostatics, the advantages of which are especially evident in opaque and turbid samples and in porous materials such as xerogels. Imidazoline nitroxides are the most commonly used pH-sensitive spin probes and labels due to the high sensitivity of the parameters of the EPR spectra to pH changes, their small size, and their well-developed chemistry. In this work, several new derivatives of 4-(N,N-dialkylamino)-2,5-dihydrioimidazol-1-oxyl, with functional groups suitable for specific binding, were synthesized. The dependence of the parameters of their EPR spectra on pH was studied. Several showed a pKa close to 7.4, following the pH changes in a normal physiological range, and some demonstrated a monotonous change of the hyperfine coupling constant by 0.14 mT upon pH variation by four units.
Collapse
|
2
|
Wang X, Peng C, He K, Ji K, Tan X, Han G, Liu Y, Liu Y, Song Y. Intracellular delivery of liposome-encapsulated Finland trityl radicals for EPR oximetry. Analyst 2020; 145:4964-4971. [PMID: 32510063 DOI: 10.1039/d0an00108b] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Tetrathiatriarylmethyl (TAM, trityl) radicals have found wide applications in electron paramagnetic resonance (EPR) oximetry. However, the biomedical applications of TAM radicals were exclusively limited to an extracellular region owing to their negatively charged nature. The intracellular delivery of TAM radicals still remains a challenge. In the present work, we report a liposome-based method to encapsulate the water-soluble Finland trityl radical CT-03 for its intracellular delivery. Using the thin lipid film hydration method, CT-03-loaded liposomes were prepared from DSPC/cholesterol/DOTAP with a mean size of 167.5 ± 2.4 nm and a zeta potential of 27.8 ± 0.8 mV. EPR results showed that CT-03 was entrapped into the liposomes and still exhibited good oxygen (O2) sensitivity. Moreover, CT-03 was successfully delivered into HepG2 cells and HUVECs using the CT-03-loaded liposomes. Importantly, the combination of the liposome-encapsulated radical CT-03 and the other TAM radical CT02-H enabled simultaneous measurements of the intracellular and extracellular O2 concentrations and O2 consumption rates in HepG2 cells. Our present study provides a new approach for intracellular delivery of TAM radicals and could significantly expand their biomedical applications.
Collapse
Affiliation(s)
- Xing Wang
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China.
| | | | | | | | | | | | | | | | | |
Collapse
|
3
|
Khramtsov VV. In Vivo Molecular Electron Paramagnetic Resonance-Based Spectroscopy and Imaging of Tumor Microenvironment and Redox Using Functional Paramagnetic Probes. Antioxid Redox Signal 2018; 28:1365-1377. [PMID: 29132215 PMCID: PMC5910053 DOI: 10.1089/ars.2017.7329] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
SIGNIFICANCE A key role of the tumor microenvironment (TME) in cancer progression, treatment resistance, and as a target for therapeutic intervention is increasingly appreciated. Among important physiological components of the TME are tissue hypoxia, acidosis, high reducing capacity, elevated concentrations of intracellular glutathione (GSH), and interstitial inorganic phosphate (Pi). Noninvasive in vivo pO2, pH, GSH, Pi, and redox assessment provide unique insights into biological processes in the TME, and may serve as a tool for preclinical screening of anticancer drugs and optimizing TME-targeted therapeutic strategies. Recent Advances: A reasonable radiofrequency penetration depth in living tissues and progress in development of functional paramagnetic probes make low-field electron paramagnetic resonance (EPR)-based spectroscopy and imaging the most appropriate approaches for noninvasive assessment of the TME parameters. CRITICAL ISSUES Here we overview the current status of EPR approaches used in combination with functional paramagnetic probes that provide quantitative information on chemical TME and redox (pO2, pH, redox status, Pi, and GSH). In particular, an application of a recently developed dual-function pH and redox nitroxide probe and multifunctional trityl probe provides unsurpassed opportunity for in vivo concurrent measurements of several TME parameters in preclinical studies. The measurements of several parameters using a single probe allow for their correlation analyses independent of probe distribution and time of measurements. FUTURE DIRECTIONS The recent progress in clinical EPR instrumentation and development of biocompatible paramagnetic probes for in vivo multifunctional TME profiling eventually will make possible translation of these EPR techniques into clinical settings to improve prediction power of early diagnostics for the malignant transition and for future rational design of TME-targeted anticancer therapeutics. Antioxid. Redox Signal. 28, 1365-1377.
Collapse
Affiliation(s)
- Valery V Khramtsov
- 1 In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University , Morgantown, West Virginia.,2 Department of Biochemistry, West Virginia University School of Medicine , Morgantown, West Virginia
| |
Collapse
|
4
|
Khramtsov VV, Bobko AA, Tseytlin M, Driesschaert B. Exchange Phenomena in the Electron Paramagnetic Resonance Spectra of the Nitroxyl and Trityl Radicals: Multifunctional Spectroscopy and Imaging of Local Chemical Microenvironment. Anal Chem 2017; 89:4758-4771. [PMID: 28363027 PMCID: PMC5513151 DOI: 10.1021/acs.analchem.6b03796] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This Feature overviews the basic principles of using stable organic radicals involved in reversible exchange processes as functional paramagnetic probes. We demonstrate that these probes in combination with electron paramagnetic resonance (EPR)-based spectroscopy and imaging techniques provide analytical tools for quantitative mapping of critical parameters of local chemical microenvironment. The Feature is written to be understandable to people who are laymen to the EPR field in anticipation of future progress and broad application of these tools in biological systems, especially in vivo, over the next years.
Collapse
Affiliation(s)
- Valery V. Khramtsov
- In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506, United States
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia 26506, United States
| | - Andrey A. Bobko
- In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506, United States
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia 26506, United States
| | - Mark Tseytlin
- In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506, United States
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia 26506, United States
| | - Benoit Driesschaert
- In Vivo Multifunctional Magnetic Resonance center, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia 26506, United States
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia 26506, United States
| |
Collapse
|
5
|
Margita K, Voinov MA, Smirnov AI. Effect of Solution Ionic Strength on the pK a of the Nitroxide pH EPR Probe 2,2,3,4,5,5-Hexamethylimidazolidin-1-oxyl. Cell Biochem Biophys 2017; 75:185-193. [PMID: 28210984 DOI: 10.1007/s12013-017-0780-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 01/03/2017] [Indexed: 10/20/2022]
Abstract
Spin probe and spin labeling Electron Paramagnetic Resonance methods are indispensable research tools for solving a wide range of bioanalytical problems-from measuring microviscosity and polarity of phase-separated liquids to oxygen concentrations in tissues. One of the emerging uses of spin probes are the studies of proton transfer-related and surface electrostatic phenomena. The latter Electron Paramagnetic Resonance methods rely on molecular probes containing an additional functionality capable of reversible ionization (protonation, in particular) in the immediate proximity to an Electron Paramagnetic Resonance-active reporter group, such as (N-O•) for nitroxides. The consequent formation of protonated and nonprotonated nitroxide species with different magnetic parameters (A iso, g iso) could be readily distinguished by Electron Paramagnetic Resonance. Bioanalytical Electron Paramagnetic Resonance studies employing pH-sensitive paramagnetic probes typically involve determination of the equilibrium constant (pK a) between the protonated and nonprotonated forms of the nitroxide. However, any chemical equilibrium involving charged species, such as ionization of acids and bases, and so the reversible protonation of the nitroxide, is known to be affected by an ionic strength of the solution. Currently, only scarce data for the effect of the solution ionic strength on the experimental pK a's of the ionizable nitroxides can be found in the literature. Here we have carried out a series of Electron Paramagnetic Resonance titration experiments for aqueous solutions of 2,2,3,4,5,5-hexamethylimidazolidin-1-oxyl (HMI) nitroxide known for one of the largest differences in the isotropic nitrogen hyperfine coupling constant A iso between the protonated and nonprotonated forms. Electrolyte concentration was varied over an exceptionally large range (i.e., from 0.05 to 5.0 M) to elucidate the effect of ionic strength on the ionization constant of this pH-sensitive Electron Paramagnetic Resonance probe and the data were compared to the Debye-Hückel limiting law. Effects of the ionic strength on the magnetic parameters of the ionizable nitroxides are also discussed.
Collapse
Affiliation(s)
- Kaleigh Margita
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, 27606, NC, USA
| | - Maxim A Voinov
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, 27606, NC, USA
| | - Alex I Smirnov
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, 27606, NC, USA.
| |
Collapse
|
6
|
Kovaleva EG, Molochnikov LS, Stepanova DP, Pestov AV, Trofimov DG, Kirilyuk IA, Smirnov AI. Interfacial Electrostatic Properties of Hydrated Mesoporous and Nanostructured Alumina Powders by Spin Labeling EPR. Cell Biochem Biophys 2016; 75:159-170. [PMID: 27815780 DOI: 10.1007/s12013-016-0767-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Accepted: 10/14/2016] [Indexed: 11/24/2022]
Abstract
Acid-base equilibria and interfacial electrostatic properties of hydrated mesoporous and nanostructured alumina powders are determining factors for the use of these materials in heterogeneous catalysis and as a sorption media for filtration and chromatographic applications including life sciences. Here spin probe electron paramagnetic resonance spectroscopy of pH-sensitive nitroxides was employed to evaluate the surface charge and interfacial acid-base equilibria at the pore surface of mesoporous powders of α-Al2O3, γ-Al2O3, Al2O3 × nH2O, and basic γ-Al2O3 and nanostructured Al2O3 in the form of pristine materials and modified with aluminum-tri-sec-butoxide, hydroxyaluminum glycerate, and several phospholipids. A new pH-sensitive nitroxide probe, 4-dimethylamino-5,5-dimethyl-2-(4-(chloromethyl)phenyl)-2-ethyl-2,5-dihydro-1H-imidazol-1-oxyl hydrochloride semihydrate (nitroxide R1), has been synthesized and characterized. It was found that conditions of preparation of alumina powders exert strikingly large effects on the apparent pK a of nitroxides measured from electron paramagnetic resonance titration curves. Specifically, while the electron paramagnetic resonance titrations curves for the nitroxide R1 in mesoporous powders prepared from basic γ-Al2O3 and Al2O3 × nH2O were shifted by ΔpK a≈ +0.6 and up to ≈ +1.2 pH units respectively, the shift for γ-Al2O3 was found to be much higher: ΔpK a = +3.5. Assuming approximately the same ∆pH = 0.5-1.0 arising from a difference in the hydrogen ion activity between the bulk solution phase and that in a confined pore volume, the samples were ranked in the following order of descending magnitude of the effective surface electrostatic potential Ψ: mesoporous γ-Al2O3 > Al2O3 × nH2O > basic γ-Al2O3 > α-Al2O3. Conditions of the Al2O3 synthesis as well as the surface modification procedures were found to have profound effects on the interfacial electrostatic properties of hydrated samples that are likely related to the nature and concentration of the active sites on the alumina surfaces.
Collapse
Affiliation(s)
- Elena G Kovaleva
- Institute of Chemical Engineering, Ural Federal University, 19 Mira St., Yekaterinburg, 620002, Russian Federation.
| | - Leonid S Molochnikov
- Department of Chemistry, Ural State Forest Engineering University, 37 Siberian Highway, Yekaterinburg, 620100, Russian Federation.
| | - Darya P Stepanova
- Institute of Chemical Engineering, Ural Federal University, 19 Mira St., Yekaterinburg, 620002, Russian Federation
| | - Alexander V Pestov
- Laboratory of Organic Materials, I.Ya. Postovsky Institute of Organic Synthesis, Ural Branch of the Russian Academy of Sciences, Akademicheskaya / S. Kovalevskoi, 22/20, Ekaterinburg, 620990, Russian Federation
| | - Dmitrii G Trofimov
- Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrent'ev Av. 9, Novosibirsk, 630090, Russian Federation
| | - Igor A Kirilyuk
- Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrent'ev Av. 9, Novosibirsk, 630090, Russian Federation
- Novosibirsk State University, Pirogova Str. 2, Novosibirsk, 630090, Russian Federation
| | - Alex I Smirnov
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, NC, 27695-8204, USA.
| |
Collapse
|
7
|
Leong WF, Berton-Carabin CC, Elias RJ, Lecomte J, Villeneuve P, Zhao Y, Coupland JN. Effect of lipophilization on the distribution and reactivity of ingredients in emulsions. J Colloid Interface Sci 2015; 459:36-43. [DOI: 10.1016/j.jcis.2015.07.070] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2014] [Revised: 07/28/2015] [Accepted: 07/30/2015] [Indexed: 11/29/2022]
|
8
|
Voinov MA, Smirnov AI. Ionizable Nitroxides for Studying Local Electrostatic Properties of Lipid Bilayers and Protein Systems by EPR. Methods Enzymol 2015; 564:191-217. [PMID: 26477252 PMCID: PMC5008871 DOI: 10.1016/bs.mie.2015.08.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Electrostatic interactions are known to play a major role in the myriad of biochemical and biophysical processes. Here, we describe biophysical methods to probe local electrostatic potentials of proteins and lipid bilayer systems that are based on an observation of reversible protonation of nitroxides by electron paramagnetic resonance (EPR). Two types of probes are described: (1) methanethiosulfonate derivatives of protonatable nitroxides for highly specific covalent modification of the cysteine's sulfhydryl groups and (2) spin-labeled phospholipids with a protonatable nitroxide tethered to the polar head group. The probes of both types report on their ionization state through changes in magnetic parameters and degree of rotational averaging, thus, allowing the electrostatic contribution to the interfacial pKa of the nitroxide, and, therefore, the local electrostatic potential to be determined. Due to their small molecular volume, these probes cause a minimal perturbation to the protein or lipid system. Covalent attachment secures the position of the reporter nitroxides. Experimental procedures to characterize and calibrate these probes by EPR, and also the methods to analyze the EPR spectra by simulations are outlined. The ionizable nitroxide labels and the nitroxide-labeled phospholipids described so far cover an exceptionally wide range of ca. 2.5-7.0 pH units, making them suitable to study a broad range of biophysical phenomena, especially at the negatively charged lipid bilayer surfaces. The rationale for selecting proper electrostatically neutral interface for probe calibration, and examples of lipid bilayer surface potential studies, are also described.
Collapse
Affiliation(s)
- Maxim A Voinov
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina, USA
| | - Alex I Smirnov
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina, USA.
| |
Collapse
|
9
|
Casano G, Poulhès F, Tran TK, Ayhan MM, Karoui H, Siri D, Gaudel-Siri A, Rockenbauer A, Jeschke G, Bardelang D, Tordo P, Ouari O. High binding yet accelerated guest rotation within a cucurbit[7]uril complex. Toward paramagnetic gyroscopes and rolling nanomachines. NANOSCALE 2015; 7:12143-12150. [PMID: 26123621 DOI: 10.1039/c5nr03288a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The (15-oxo-3,7,11-triazadispiro[5.1.5.3]hexadec-7-yl)oxidanyl, a bis-spiropiperidinium nitroxide derived from TEMPONE, can be included in cucurbit[7]uril to form a strong (K(a)∼ 2 × 10(5) M(-1)) CB[7]@bPTO complex. EPR and MS spectra, DFT calculations, and unparalleled increased resistance (a factor of ∼10(3)) toward ascorbic acid reduction show evidence of deep inclusion of bPTO inside CB[7]. The unusual shape of the CB[7]@bPTO EPR spectrum can be explained by an anisotropic Brownian rotational diffusion, the global tumbling of the complex being slower than rotation of bPTO around its "long molecular axis" inside CB[7]. The CB[7] (stator) with the encapsulated bPTO (rotator) behaves as a supramolecular paramagnetic rotor with increased rotational speed of the rotator that has great potential for advanced nanoscale machines requiring wheels such as cucurbiturils with virtually no friction between the wheel and the axle for optimum wheel rotation (i.e. nanopulleys and nanocars).
Collapse
Affiliation(s)
- G Casano
- Aix-Marseille Université, CNRS, Institut de Chimie Radicalaire, UMR 7273, 13013 Marseille, France.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Bagryanskaya EG, Krumkacheva OA, Fedin MV, Marque SR. Development and Application of Spin Traps, Spin Probes, and Spin Labels. Methods Enzymol 2015; 563:365-96. [DOI: 10.1016/bs.mie.2015.06.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
11
|
Veremeeva PN, Grishina IV, Lapteva VL, Yaroslavov AA, Sybachin AV, Palyulin VA, Zefirov NS. pH-Sensitive liposomes with embedded 3,7-diazabicyclo[3.3.1]nonane derivative. MENDELEEV COMMUNICATIONS 2014. [DOI: 10.1016/j.mencom.2014.04.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
12
|
Samouilov A, Efimova OV, Bobko AA, Sun Z, Petryakov S, Eubank TD, Trofimov DG, Kirilyuk IA, Grigor'ev IA, Takahashi W, Zweier JL, Khramtsov VV. In vivo proton-electron double-resonance imaging of extracellular tumor pH using an advanced nitroxide probe. Anal Chem 2014; 86:1045-52. [PMID: 24372284 DOI: 10.1021/ac402230h] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A variable radio frequency proton-electron double-resonance imaging (VRF PEDRI) approach for pH mapping of aqueous samples has been recently developed (Efimova et al. J. Magn. Reson. 2011, 209, 227-232). A pH map is extracted from two PEDRI acquisitions performed at electron paramagnetic resonance (EPR) frequencies of protonated and unprotonated forms of a pH-sensitive probe. To translate VRF PEDRI to an in vivo setting, an advanced pH probe was synthesized. Probe deuteration resulted in a narrow spectral line of 1.2 G compared to a nondeuterated analogue line width of 2.1 G allowing for an increase of Overhauser enhancements and reduction in rf power deposition. Binding of the probe to the cell-impermeable tripeptide, glutathione (GSH), allows for targeting to extracellular tissue space for monitoring extracellular tumor acidosis, a prognostic factor in tumor pathophysiology. The probe demonstrated pH sensitivity in the 5.8-7.8 range, optimum for measurement of acidic extracellular tumor pH (pH(e)). In vivo VRF PEDRI was performed on Met-1 tumor-bearing mice. Compared to normal mammary glands with a neutral mean pH(e) (7.1 ± 0.1), we observed broader pH distribution with acidic mean pH(e) (6.8 ± 0.1) in tumor tissue. In summary, VRF PEDRI in combination with a newly developed pH probe provides an analytical approach for spatially resolved noninvasive pHe monitoring, in vivo.
Collapse
Affiliation(s)
- Alexandre Samouilov
- The Dorothy M. Davis Heart and Lung Research Institute: ‡Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, and §Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University , Columbus, Ohio 43210, United States
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Frecus B, Rinkevicius Z, Ågren H. π-Stacking effects on the EPR parameters of a prototypical DNA spin label. Phys Chem Chem Phys 2013; 15:10466-71. [PMID: 23685812 DOI: 10.1039/c3cp51129d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The character and value of spin labels for probing environments like double-stranded DNA depend on the degree of change in the spin Hamiltonian parameters of the spin label induced by the environment. Herein we provide a systematic theoretical investigation of this issue, based on a density functional theory method applied to a spin labeled DNA model system, focusing on the dependence of the EPR properties of the spin label on the π stacking and hydrogen bonding that occur upon incorporating the spin label into the selected base pair inside DNA. It is found that the EPR spin Hamiltonian parameters of the spin label are only negligibly affected by its incorporation into DNA, when compared to its free form. This result gives a theoretical ground for the common empirical assumption regarding the behaviour of spin Hamiltonian parameters made in EPR based measurements of the distance between spin labels incorporated into DNA.
Collapse
Affiliation(s)
- Bogdan Frecus
- KTH Royal Institute of Technology, School of Biotechnology, Division of Theoretical Chemistry & Biology, SE-106 91 Stockholm, Sweden.
| | | | | |
Collapse
|
14
|
Frecus B, Rinkevicius Z, Murugan NA, Vahtras O, Kongsted J, Ågren H. EPR spin Hamiltonian parameters of encapsulated spin-labels: impact of the hydrogen bonding topology. Phys Chem Chem Phys 2013; 15:2427-34. [DOI: 10.1039/c2cp43951d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|
15
|
Bobko AA, Ivanov A, Khramtsov VV. Discriminative EPR detection of NO and HNO by encapsulated nitronyl nitroxides. Free Radic Res 2012; 47:74-81. [PMID: 23136998 DOI: 10.3109/10715762.2012.746460] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Nitric oxide, •NO, is one of the most important molecules in the biochemistry of living organisms. By contrast, nitroxyl, NO-, one-electron reduced analog of •NO which exists at physiological conditions in its protonated form, HNO, has been relatively overlooked. Recent data show that HNO might be produced endogenously and display unique biological effects. However, there is a lack of specific and quantitative methods of detection of endogenous HNO production. Here we present a new method for discriminative •NO and HNO detection by nitronyl nitroxides (NNs) using electron paramagnetic resonance (EPR). It was found that NNs react with •NO and HNO with similar rate constants of about 10(4) M(-1) s(-1) but yield different products: imino nitroxides and the hydroxylamine of imino nitroxides, correspondingly. An EPR approach for discriminative •NO and HNO detection using liposome-encapsulated NNs was developed. The membrane barrier of liposomes protects NNs against reduction in biological systems while is permeable to both analytes, •NO and HNO. The sensitivity of this approach for the detection of the rates of •NO/HNO generation is about 1 nM/s. The application of encapsulated NNs for real-time discriminative •NO/HNO detection might become a valuable tool in nitric oxide-related studies.
Collapse
Affiliation(s)
- Andrey A Bobko
- Division of Pulmonary, Allergy, Critical Care & Sleep Medicine, The Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA.
| | | | | |
Collapse
|
16
|
Muir BW, Acharya DP, Kennedy DF, Mulet X, Evans RA, Pereira SM, Wark KL, Boyd BJ, Nguyen TH, Hinton TM, Waddington LJ, Kirby N, Wright DK, Wang HX, Egan GF, Moffat BA. Metal-free and MRI visible theranostic lyotropic liquid crystal nitroxide-based nanoparticles. Biomaterials 2011; 33:2723-33. [PMID: 22209558 DOI: 10.1016/j.biomaterials.2011.12.018] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Accepted: 12/06/2011] [Indexed: 02/05/2023]
Abstract
The development of improved, low toxicity, clinically viable nanomaterials that provide MRI contrast have tremendous potential to form the basis of translatable theranostic agents. Herein we describe a class of MRI visible materials based on lyotropic liquid crystal nanoparticles loaded with a paramagnetic nitroxide lipid. These readily synthesized nanoparticles achieved enhanced proton-relaxivities on the order of clinically used gadolinium complexes such as Omniscan™ without the use of heavy metal coordination complexes. Their low toxicity, high water solubility and colloidal stability in buffer resulted in them being well tolerated in vitro and in vivo. The nanoparticles were initially screened in vitro for cytotoxicity and subsequently a defined concentration range was tested in rats to determine the maximum tolerated dose. Pharmacokinetic profiles of the candidate nanoparticles were established in vivo on IV administration to rats. The lyotropic liquid crystal nanoparticles were proven to be effective liver MRI contrast agents. We have demonstrated the effective in vivo performance of a T1 enhancing, biocompatible, colloidally stable, amphiphilic MRI contrast agent that does not contain a metal.
Collapse
Affiliation(s)
- Benjamin W Muir
- CSIRO Materials Science and Engineering, Bayview Avenue, Clayton 3168, Australia.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Komarov DA, Dhimitruka I, Kirilyuk IA, Trofimiov DG, Grigor'ev IA, Zweier JL, Khramtsov VV. Electron paramagnetic resonance monitoring of ischemia-induced myocardial oxygen depletion and acidosis in isolated rat hearts using soluble paramagnetic probes. Magn Reson Med 2011; 68:649-55. [PMID: 22162021 DOI: 10.1002/mrm.23251] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Revised: 09/15/2011] [Accepted: 09/19/2011] [Indexed: 01/08/2023]
Abstract
A new low-field electron paramagnetic resonance approach for noninvasive measurements of myocardial oxygen tension and tissue acidity was developed. The approach was applied to monitor myocardial pO(2) and pH in a model of global no-flow ischemia (30 min) and reperfusion in isolated perfused rat hearts. The myocardial oxygen measurements were performed using deuterated Finland trityl radical probe. A rapid decrease in myocardial pO(2) from 160 mmHg to about 2 ± 1 mmHg was observed within the first minute of ischemia followed by incomplete restoration of pO(2) to 50 mmHg during 30 min of reperfusion. The lower oxygen concentration after ischemia was attributed to the 50% reduction in coronary flow after ischemia as a consequence of myocardial ischemia and reperfusion damage. Myocardial pH measurements using a specially designed imidazoline pH-sensitive nitroxide showed severe myocardial acidification to pH 6.25 during 30 min of ischemia. Preconditioning of the hearts with two 5-min periods of ischemia significantly reduced the acidification of myocardial tissue during sustained ischemia. Noninvasive electron paramagnetic resonance monitoring of myocardial oxygenation and pH may provide important insights into the mechanisms of ischemia and reperfusion injury and a background for development of new therapeutic approaches.
Collapse
Affiliation(s)
- Denis A Komarov
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | | | | | | | | | | | | |
Collapse
|
18
|
Bobko AA, Eubank TD, Voorhees JL, Efimova OV, Kirilyuk IA, Petryakov S, Trofimiov DG, Marsh CB, Zweier JL, Grigor'ev IA, Samouilov A, Khramtsov VV. In vivo monitoring of pH, redox status, and glutathione using L-band EPR for assessment of therapeutic effectiveness in solid tumors. Magn Reson Med 2011; 67:1827-36. [PMID: 22113626 DOI: 10.1002/mrm.23196] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Revised: 06/22/2011] [Accepted: 08/03/2011] [Indexed: 01/27/2023]
Abstract
Approach for in vivo real-time assessment of tumor tissue extracellular pH (pH(e)), redox, and intracellular glutathione based on L-band EPR spectroscopy using dual function pH and redox nitroxide probe and disulfide nitroxide biradical, is described. These parameters were monitored in PyMT mice bearing breast cancer tumors during treatment with granulocyte macrophage colony-stimulating factor. It was observed that tumor pH(e) is about 0.4 pH units lower than that in normal mammary gland tissue. Treatment with granulocyte macrophage colony-stimulating factor decreased the value of pH(e) by 0.3 units compared with PBS control treatment. Tumor tissue reducing capacity and intracellular glutathione were elevated compared with normal mammary gland tissue. Granulocyte macrophage colony-stimulating factor treatment resulted in a decrease of the tumor tissue reducing capacity and intracellular glutathione content. In addition to spectroscopic studies, pH(e) mapping was performed using recently proposed variable frequency proton-electron double-resonance imaging. The pH mapping superimposed with MRI image supports probe localization in mammary gland/tumor tissue, shows high heterogeneity of tumor tissue pH(e) and a difference of about 0.4 pH units between average pH(e) values in tumor and normal mammary gland. In summary, the developed multifunctional approach allows for in vivo, noninvasive pH(e), extracellular redox, and intracellular glutathione content monitoring during investigation of various therapeutic strategies for solid tumors.
Collapse
Affiliation(s)
- Andrey A Bobko
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, The Ohio State University, Columbus, Ohio 43210, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Efimova OV, Sun Z, Petryakov S, Kesselring E, Caia GL, Johnson D, Zweier JL, Khramtsov VV, Samouilov A. Variable radio frequency proton-electron double-resonance imaging: application to pH mapping of aqueous samples. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 209:227-232. [PMID: 21320790 PMCID: PMC3065501 DOI: 10.1016/j.jmr.2011.01.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Revised: 12/08/2010] [Accepted: 01/10/2011] [Indexed: 05/30/2023]
Abstract
Proton-electron double-resonance imaging (PEDRI) offers rapid image data collection and high resolution for spatial distribution of paramagnetic probes. Recently we developed the concept of variable field (VF) PEDRI which enables extracting a functional map from a limited number of images acquired at pre-selected EPR excitation fields using specific paramagnetic probes (Khramtsov et al., J. Magn. Reson. 202 (2010) 267-273). In this work, we propose and evaluate a new modality of PEDRI-based functional imaging with enhanced temporal resolution which we term variable radio frequency (VRF) PEDRI. The approach allows for functional mapping (e.g., pH mapping) using specifically designed paramagnetic probes with high quality spatial resolution and short acquisition times. This approach uses a stationary magnetic field but different EPR RFs. The ratio of Overhauser enhancements measured at each pixel at two different excitation frequencies corresponding to the resonances of protonated and deprotonated forms of a pH-sensitive nitroxide is converted to a pH map using a corresponding calibration curve. Elimination of field cycling decreased the acquisition time by exclusion periods of ramping and stabilization of the magnetic field. Improved magnetic field homogeneity and stability allowed for the fast MRI acquisition modalities such as fast spin echo. In total, about 30-fold decrease in EPR irradiation time was achieved for VRF PEDRI (2.4s) compared with VF PEDRI (70s). This is particularly important for in vivo applications enabling one to overcome the limiting stability of paramagnetic probes and sample overheating by reducing RF power deposition.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | - Valery V. Khramtsov
- Corresponding authors: (Alexandre Samouilov); (Valery V. Khramtsov), Primary address for the correspondence during review process: Alexandre Samouilov, PhD, Davis Heart and Lung Research Institute, The Ohio State University, 420 West 12 Ave, Room 611B, Columbus, OH 43210
| | - Alexandre Samouilov
- Corresponding authors: (Alexandre Samouilov); (Valery V. Khramtsov), Primary address for the correspondence during review process: Alexandre Samouilov, PhD, Davis Heart and Lung Research Institute, The Ohio State University, 420 West 12 Ave, Room 611B, Columbus, OH 43210
| |
Collapse
|
20
|
Khramtsov VV, Caia GL, Shet K, Kesselring E, Petryakov S, Zweier JL, Samouilov A. Variable Field Proton-Electron Double-Resonance Imaging: Application to pH mapping of aqueous samples. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 202:267-273. [PMID: 20007019 PMCID: PMC2818733 DOI: 10.1016/j.jmr.2009.11.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Revised: 08/27/2009] [Accepted: 11/20/2009] [Indexed: 05/28/2023]
Abstract
A new concept of Variable Field Proton-Electron Double-Resonance Imaging (VF PEDRI) is proposed. This allows for functional mapping using specifically designed paramagnetic probes (e.g. oxygen or pH mapping) with MRI high quality spatial resolution and short acquisition time. Studies performed at 200 G field MRI with phantoms show that a pH map of the sample can be extracted using only two PEDRI images acquired in 140 s at pre-selected EPR excitation fields providing pH resolution of 0.1 pH units and a spatial resolution of 1.25mm. Note that while concept of functional VF PEDRI was demonstrated using the pH probe, it can be applied for studies of other biologically relevant parameters of the medium such as redox state, concentrations of oxygen or glutathione using specifically designed EPR probes.
Collapse
Affiliation(s)
| | | | | | | | | | | | - Alexandre Samouilov
- Address for correspondence: Alexandre Samouilov, Davis Heart and Lung Research Institute, The Ohio State University, 420 West 12 Ave, Room 611B, Columbus, OH 43210.
| |
Collapse
|
21
|
Kirilyuk I, Polovyanenko D, Semenov S, Grigor’ev I, Gerasko O, Fedin V, Bagryanskaya E. Inclusion Complexes of Nitroxides of Pyrrolidine and Imidazoline Series with Cucurbit[7]uril. J Phys Chem B 2010; 114:1719-28. [DOI: 10.1021/jp9103678] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- I. Kirilyuk
- Novosibirsk Institute of Organic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 9, Russia, International Tomography Center SB RAS, Novosibirsk, 630090, Institutskaya 3A, Russia, and Nikolaev Institute of Inorganic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 3, Russia
| | - D. Polovyanenko
- Novosibirsk Institute of Organic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 9, Russia, International Tomography Center SB RAS, Novosibirsk, 630090, Institutskaya 3A, Russia, and Nikolaev Institute of Inorganic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 3, Russia
| | - S. Semenov
- Novosibirsk Institute of Organic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 9, Russia, International Tomography Center SB RAS, Novosibirsk, 630090, Institutskaya 3A, Russia, and Nikolaev Institute of Inorganic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 3, Russia
| | - I. Grigor’ev
- Novosibirsk Institute of Organic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 9, Russia, International Tomography Center SB RAS, Novosibirsk, 630090, Institutskaya 3A, Russia, and Nikolaev Institute of Inorganic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 3, Russia
| | - O. Gerasko
- Novosibirsk Institute of Organic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 9, Russia, International Tomography Center SB RAS, Novosibirsk, 630090, Institutskaya 3A, Russia, and Nikolaev Institute of Inorganic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 3, Russia
| | - V. Fedin
- Novosibirsk Institute of Organic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 9, Russia, International Tomography Center SB RAS, Novosibirsk, 630090, Institutskaya 3A, Russia, and Nikolaev Institute of Inorganic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 3, Russia
| | - E. Bagryanskaya
- Novosibirsk Institute of Organic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 9, Russia, International Tomography Center SB RAS, Novosibirsk, 630090, Institutskaya 3A, Russia, and Nikolaev Institute of Inorganic Chemistry SB RAS, 630090 Novosibirsk, pr. Lavrentjeva 3, Russia
| |
Collapse
|
22
|
Woldman YY, Sun J, Zweier JL, Khramtsov VV. Direct chemiluminescence detection of nitric oxide in aqueous solutions using the natural nitric oxide target soluble guanylyl cyclase. Free Radic Biol Med 2009; 47:1339-45. [PMID: 19751819 PMCID: PMC2784612 DOI: 10.1016/j.freeradbiomed.2009.09.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 08/30/2009] [Accepted: 09/06/2009] [Indexed: 01/14/2023]
Abstract
Nitric oxide (NO) is a free radical involved in many physiological processes including regulation of blood pressure, immune response, and neurotransmission. However, the measurement of extremely low, in some cases subnanomolar, physiological concentrations of nitric oxide presents an analytical challenge. The purpose of this methods article is to introduce a new highly sensitive chemiluminescence approach to direct NO detection in aqueous solutions using a natural nitric oxide target, soluble guanylyl cyclase (sGC), which catalyzes the conversion of guanosine triphosphate to guanosine 3',5'-cyclic monophosphate and inorganic pyrophosphate. The suggested enzymatic assay uses the fact that the rate of the reaction increases by about 200 times when NO binds with sGC and, in so doing, provides a sensor for nitric oxide. Luminescence detection of the above reaction is accomplished by converting inorganic pyrophosphate into ATP with the help of ATP sulfurylase followed by light emission from the ATP-dependent luciferin-luciferase reaction. Detailed protocols for NO quantification in aqueous samples are provided. The examples of applications include measurement of NO generated by a nitric oxide donor (PAPA-NONOate), nitric oxide synthase, and NO gas dissolved in buffer. The method allows for the measurement of NO concentrations in the nanomolar range and NO generation rates as low as 100 pM/min.
Collapse
Affiliation(s)
- Yakov Y. Woldman
- Valdosta State University, Valdosta, GA 31698
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, 43210
| | - Jian Sun
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, 43210
| | - Jay L. Zweier
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, 43210
| | - Valery V. Khramtsov
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, 43210
- Corresponding author: Valery V. Khramtsov, Dorothy M. Davis Heart & Lung Research Institute, 201 HLRI, 473 W 12th Ave, The Ohio State University, Columbus, OH 43210; tel. (614)-688-3664; fax (614)-293-4799;
| |
Collapse
|