Electron Spin Resonance.: Part One: A Diagnostic Method in the Biomedical Sciences

Abstract

A review is presented of some of the ways in which electron spin resonance (ESR) spectroscopy may be useful to investigate systems of relevance to the biomedical sciences. Specifically considered are: spin-trapping in biological media; the determination of antioxidant efficiencies; lipid-peroxidation; the use of nitroxides as probes of metabolic activity in cells and as structural probes of cell-membranes; ESR coupled with materials for radiation-dosimetry; foodand drug-irradiation; studies of enzyme systems and of cyclodextrins; diagnosis of cancer and rheumatoid arthritis; measurement of oxidative stress in synovial tissue in preparation for joint replacement; determination of oxidative species during kidney dialysis; measurement of biological oxygen concentrations (oximetry); trapping in living cells of the endothelium-derived relaxing factor nitric oxide (NO); measurement of hydrogen peroxide; determination of drugs of abuse (opiates); ESR measurements of whole blood and as a means to determine the age of bloodstains for forensic analysis are surveyed, and also a determination of the aqueous volume of human sperm cells is described, among other topics.

Biological effects and medical applications of infrared radiation

“…Electron paramagnetic resonance spectroscopy is based on the resonant absorption of microwave radiation by matching the energy difference of the spins of free unpaired electron in a magnetic field, and spin reversal and absorption of microwave energy can be measured [73]. The rotational effect in tissue water with a significant damping induced by the resonant absorption of microwave radiation should be considered to avoid a consequence of the high impedance at this frequency level (10 9 Hz).…”

Muonium–the Second Radioisotope of Hydrogen: A Remarkable and Unique Radiotracer in the Chemical, Materials, Biological and Environmental Sciences

“…We assign resonance (a) to the 14 N nucleus, for which a coupling of +52.4 MHz is derived. Corresponding to 18.7 G, the coupling is significantly greater than is normally encountered for dialkyl nitroxyl radicals, which for both (3) and (4) is 15.6 G as measured in ethanol solution 30 . Resonance (b) yields either a proton coupling of +64.6 MHz using Eqn (1), or a reduced muon coupling of 65.5 MHz (A μ = 2γ μ .B res /3.1833) assuming it is from the Δm = 1 transition.…”

“…In contrast, both radical isomers were detected in each of the other compounds. It is suggested that 43,44 , although H 2 C • -CH(Mu)SiMe 3 , H 2 C • -CH(Mu)Si(OMe) 3 and H 2 C • -CH(Mu)P(O) (OEt) 2 , are formally "primary" radicals, the stabilising effect of the second-row substituent is sufficient to increase their relative yields to detectable limits. The muon couplings are all reduced from the value in ethyl 38,39 , H 2 C • -CH 2 Mu, indeed indicating a stabilising interaction, and a minimum energy conformation (7) in which the second-row substituent (X) eclipses the unpaired-electron orbital, preferentially over the muonium atom.…”

“…The decay of the muon produces a positron e + [Eqn (2)] plus two neutrinos; it is, of course, the positrons which are counted. μ + → e + + ν e + ̅ ν e (2) π + → μ + + ν μ (3) μ + + e -→ Mu • (4) Although they occur naturally as a consequence of cosmic radiation striking the nuclei of light atoms (e.g. O 2 , N 2 ) in the atmosphere, muons are needed in high fluxes for research purposes.…”

“…As an isotopic hydrogen label, tritium ( 3 H) is often used, since its nucleus has spin (I=1/2) so NMR experiments are feasible, and being also radioactive may be detected by scintillation counting of the β-particles (electrons) produced in its decay [Eqn (1)] 6 . 1 3 H → 2 3 He + e -+ ̅ ν e (1) Indeed, 3 H is usually considered the radioisotope of hydrogen. Since the muon is radioactive also being a β-emitter [Eqn (2)], muonium atoms either free or as bound in molecules, may similarly be detected by scintillation counting; it is, however, a positively charged electron (positron) which is produced, since μ + is "anti-matter"!…”