Specialist Periodical Reports provide systematic and detailed review coverage of progress in the major areas of chemical research. Written by experts in their specialist fields the series creates a unique service for the active research chemist, supplying regular critical in-depth accounts of progress in particular areas of chemistry. For over 80 years the Royal Society of Chemistry and its predecessor, the Chemical Society, have been publishing reports charting developments in chemistry, which originally took the form of Annual Reports. However, by 1967 the whole spectrum of chemistry could no longer be contained within one volume and the series Specialist Periodical Reports was born. The Annual Reports themselves still existed but were divided into two, and subsequently three, volumes covering Inorganic, Organic and Physical Chemistry. For more general coverage of the highlights in chemistry they remain a 'must'. Since that time the SPR series has altered according to the fluctuating degree of activity in various fields of chemistry. Some titles have remained unchanged, while others have altered their emphasis along with their titles; some have been combined under a new name whereas others have had to be discontinued. The current list of Specialist Periodical Reports can be seen on the inside flap of this volume.
Electron Spin Resonance Volume 11B
A Review of Recent Literature to mid-1988
By M. C. R. SymonsThe Royal Society of Chemistry
Copyright © 1989 The Royal Society of Chemistry
All rights reserved.
ISBN: 978-0-85186-871-4Contents
CHAPTER 1 In Vivo Detection of Free Radical Metabolites by Spin Trapping By R.P. Mason, K.R. Maples, and K.T. Knecht,
1 Introduction, 1,
2 Spin Trapping In Vivo, 2,
3 Folch Extraction, 3,
4 Biological Fluids, 5,
5 Conclusion, 8,
CHAPTER 2 Theoretical Aspects of E.S.R. By A. Hudson,
1 Introduction, 11,
2 Applications of Quantum Chemistry, 12,
3 Spin Relaxation and Line Broadening Effects, 13,
4 CIDEP and Related Phenomena, 17,
5 Numerical Methods and Spectral Analysis, 17,
CHAPTER 3 Transition Metal Ions By J.F. Gibson,
1 Introduction, 24,
2 Selected Topics, 25,
3 S = 1/2, 52,
4 s = 1, 71,
5 s = 2, 72,
6 s = 3/2, 73,
7 s = 5/2, 75,
CHAPTER 4 Recent Developments of ENDOR Spectroscopy in the Study of Defects in Solids By J.-M. Spaeth,
1 Introduction, 89,
2 Structure Determination of Defects by Magnetic Resonance, 90,
3 Hyperfine and Superhyperfine Structure of ESR Spectra, 92,
4 Electron Nuclear Double Resonance (ENDOR), 97,
5 Advanced ENDOR Methods, 120,
6 Optically detected ENDOR, 130,
7 Conclusions, 133,
CHAPTER 5 Inorganic and Organometallic Radicals and Clusters prepared in a Rotating Cryostat by Metal Vapour Techniques By J.A. Howard and B. Mile,
1 Introduction, 136,
2 Atoms, 141,
3 Clusters, 143,
4 Monoligand Intermediates, 147,
5 Diligand Intermediates, 165,
6 Triligand Complexes, 167,
7 Tetraligand Intermediates, 169,
CHAPTER 6 Inorganic and Organometallic Radicals By Martyn C.R. Symons,
1 Introduction, 175,
2 Trapped and Solvated Electrons, 177,
3 Atoms, Monatomic Ions and Related Centres, 180,
4 Diatomic Radicals and Radical-Ions (AB), 183,
5 Triatomic Radicals (ABz) and Related Species, 188,
6 Tetra-atomic Radicals (AB 3) and Related Species, 189,
7 Penta-atomic Radicals (AB4) and Related Species, 190,
8 Other Radicals, 192,
9 Radicals in Inorganic Materials, 195,
10 The Use of Spin-Traps, 198,
11 Metal Carbonyls and Related Species, 199,
12 Gas Phase Radicals and Ions, 200,
CHAPTER 7 Metalloproteins By G.R. Hanson and G.L. Wilson,
1 Introduction, 209,
2 Copper Proteins, 209,
3 Iron Proteins, 213,
4 Iron Sulfur Proteins, 223,
5 Hydrogenase and Other Nickel Containing Enzymes, 226,
6 Molybdenum Enzymes, 229,
7 Vanadium Enzymes, 232,
8 Cobalt Enzymes, 233,
9 Manganese Enzymes, 234,
10 Paramagnetic Metal Substituted Enzymes, 234,
11 Mitochondrial Enzymes, 238,
12 Photosynthetic Enzymes, 241,
CHAPTER 8 Complexes of Paramagnetic Metals with Paramagnetic Ligands By Sandra S. Eaton and Gareth R. Eaton,
1 Introduction, 258,
2 Complexes with Spin-labeled Ligands, 259,
3 Complexes with Nitroxyl Radicals Coordinated vi the Nitroxyl Oxygen, 264,
4 Semiquinone Complexes, 269,
CHAPTER 1
In Vivo Detection of Free Radical Metabolites by Spin Trapping
BY R. P. MASON, K. R. MAPLES AND K. T. KNECHT
1 Introduction
1.1 The Problem.-In vivo detection of free radical metabolites is a very challenging task that has only recently been undertaken. One reason for the late development of this area is that most biochemicals, as opposed to drugs and industrial chemicals, are not easily metabolized through free radical intermediates. In addition, detection of something as ephemeral as a free radical inside a whole animal is inherently not easy. Production rates of free radicals in animals are slow in comparison to chemical systems; therefore, the highest possible sensitivity is of paramount importance. water, with its high dielectric constant, is the worst solvent for ESR spectroscopy in that only very small samples can be studied. This decreases the molar sensitivity of biological samples just when sensitivity is needed most. However, unless free radical metabolites can be demonstrated with a whole animal, there will always be some question as to their actual existence in biology.
1.2 Approaches.-Over the last thirty years, several approaches have been tried to circumvent the problem of working with aqueous samples. Freezing water lowers its dielectric constant so that larger samples can be studied. The freeze quench technique is useful for enzymes where solutions can be frozen in milliseconds. Frozen tissues, however, must be ground to fit into ESR sample tubes, and this leads to mechanically induced radicals or artifacts. In addition, the resulting powder spectra are poorly resolved, and their interpretation in complex biological systems is very difficult, if not impossible. Lyophilized, or freeze-dried tissue is plagued by the same problems of artifacts and poor resolution. Low-frequency ESR enables the study of larger samples, and perhaps even small animals could be studied directly, that is, with in vivo spectroscopy. Unfortunately, sensitivity is strongly dependent on frequency, and low-frequency instruments are unlikely to achieve the molar sensitivity of the standard X-band instruments. Spin trapping, in that it ideally integrates free radicals formed over time, appears to be the most attractive approach to the detection of free radicals in vivo. Since the concentration of naturally occurring radicals in body tissues is generally near the sensitivity limit of ESR spectroscopy, the spintrapping technique is not limited by background signals.
2 Spin Trapping In Vivo
2.1 Spin Trapping.-The technique of spin trapping involves the addition of a reactive, primary free radical across the double bond of a diamagnetic compound, the spin trap, to form a more persistent, secondary free radical, the radical adduct. This technique allows the indirect detection of primary free radicals that cannot be directly observed by conventional ESR due to low steady-state concentrations or to very short radical relaxation times, which lead to very broad lines.
To date, all in vivo spin trapping investigations have used the nitrone spin traps, phenyl-tert-butylnitrone (PBN), α-2,4,6-trimethoxy-PBN ((MeO)3PBN) and 5,5-dimethyl-l-pyrroline N-oxide (DMPO). In most cases, radical adducts of nitrone spin traps produce six-line ESR spectra. The hyperfine splittings arise from the nitrogen and β-hydrogen of the spin trap rather than from atoms of the primary radical. Identification of the trapped radical species, therefore, depends on a careful comparison of hyperfine splitting values with those of reference nitroxides analyzed under exactly the same experimental conditions. If the radical is trapped at a nucleus with nonzero spin such as 14N, then additional hyperfine splittings occur which greatly facilitate the identification of the radical adduct. A very useful approach for the radical adducts of C-and a-centered free radicals is isotopic substitution at this center in the radical precursor with 13C or 17O, respectively.
2.2 Difficulties.-Production of a radical adduct stable enough to be detected in biological samples is a major difficulty, but other factors must also be considered. When using the spin-trapping technique in whole animals, spin traps may interfere with the experimental system by inhibiting or stimulating enzymes, or by producing toxicity. The latter possibility has not seemed...
