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The ventricular system, subarachnoid spaces, and meninges are structures that lend structure, support, and protection to the brain and spinal cord. This article provides a detailed look at the anatomy of the intracranial portions of these structures with a particular focus on neuroimaging methods.

BACKGROUND Neurocysticercosis is a parasitic infection that commonly affects the ventricles, subarachnoid spaces, and spinal cord of the central nervous system. The authors report an unusual manifestation of purely posterior fossa neurocysticercosis treated with endoscope-assisted open craniotomy for resection. OBSERVATIONS A 67-year-old male presented with 2 months of progressive dizziness, gait ataxia, headaches, decreased hearing, and memory impairment. Imaging revealed an extra-axial cystic lesion occupying the foramen magnum and left cerebellopontine angle with significant mass effect and evidence of early hydrocephalus. Gross-total resection was accomplished via a left far lateral craniotomy with open endoscopic assistance, and pathological findings were consistent with neurocysticercosis. Postoperatively, he was noted to have a sixth nerve palsy, and adjuvant therapy included albendazole. By 9 months postoperatively, he exhibited complete resolution of an immediate postoperative sixth nerve palsy in addition to all preoperative symptoms. His hydrocephalus resolved and did not require permanent cerebrospinal fluid (CSF) diversion. LESSONS When combined with traditional skull base approaches, open endoscopic techniques allow for enhanced visualization and resection of complex lesions otherwise inaccessible under the microscope alone. Recognition and obliteration of central nervous system neurocysticercosis can facilitate excellent neurological recovery without the need for CSF diversion.

Head and neck sarcomas are a complex, heterogeneous group of tumors that present a diagnostic challenge to radiologists because they have many overlapping imaging features. The purpose of this article is to review the imaging and clinical features and highlight distinguishing features of head and neck sarcomas.An understanding of characteristic imaging and clinical features of head and neck sarcomas is important for the radiologist to narrow the differential diagnosis and help guide management.

Glioblastoma is the most common primary malignant neoplasm of the brain in patients over the age of 50 years. At initial diagnosis, the most typical MR imaging findings of glioblastoma include an intraaxial mass with irregular peripheral enhancement, peripheral diffusion restriction, central necrosis, and outer nonenhancing zone of T2 FLAIR hyperintensity. Following maximal safe surgical resection, MR imaging is routinely performed within 24-48 hours to assess the adequacy of resection. Radiotherapy plus concomitant temozolomide is usually started 4–5 weeks following surgery. MR imaging surveillance begins approximately 1 month following completion of concurrent chemo-radiation and continues every 3 months thereafter. Early detection of tumor recurrence is the most important trigger for consideration of a change in therapeutic strategy. MRI is the primary imaging modality for initial diagnosis, immediate postoperative imaging, and posttreatment surveillance of glioblastoma. Molecular imaging techniques have also shown promise in differentiating recurrent tumor from treatment-related effects. The appearance of recurrent glioblastoma and posttreatment effects overlap significantly on conventional MR imaging. Advanced MR imaging and molecular imaging techniques have shown much better results in the differentiation of recurrent tumor from posttreatment effects. To date, much of the investigation in this area has focused on single imaging modalities. More recent investigations have shown improved diagnostic performance with the combination of multiple imaging modalities.

The cerebral ventricles have been studied since the fourth century BC and were originally thought to harbor the soul and higher executive functions. During the infancy of neuroradiology, alterations to the ventricular shape and position on pneumoencephalography and ventriculography were signs of mass effect or volume loss. However, in the current era of high-resolution cross-sectional imaging, variation in ventricular anatomy is more easily detectable and its clinical significance is still being investigated. Interpreting radiologists must be aware of anatomic variations of the ventricular system to prevent mistaking normal variants for pathology. We will review of the anatomy and development of the lateral ventricles and discuss several ventricular variations.

Background Neurologic complications including hemorrhage, ischemia, and infarction are often identified in neonates undergoing extracorporeal membrane oxygenation (ECMO) and may contribute to the high morbidity observed in ECMO survivors. Screening for intracranial complications is reliant on bedside transcranial ultrasound (CUS) prior to and during ECMO therapy, and advanced imaging [i.e. computed tomography (CT)/magnetic resonance imaging (MRI)] is recommended after completion of ECMO support. The goal of this study is to describe the correlation of intracranial complications identified on CUS during ECMO and MRI after completion of ECMO. Methods Fifty-five neonates underwent ECMO support at the Children’s Hospital of Georgia at Augusta University from January 1, 2012 to December 31, 2017. Forty-four (80%) had a brain MRI performed prior to transfer or discharge. Ultrasound studies were reviewed by a single blinded pediatric radiologist and MRIs were reviewed by a single blinded neuro-radiologist. Results Of the 44 neonates with post-ECMO MRI, CUS during ECMO identified intracranial lesions in nine neonates, which were all confirmed on post-ECMO MRI. Sixteen subjects (46%) with unremarkable CUS during ECMO had identifiable lesions on post-ECMO MRI, yielding a sensitivity of 36% and a specificity of 100% for CUS in the detection of intracranial lesions. Despite the lack of correlation between CUS and MR, 84.6% of survivors exhibited normal development at 24 months of age. Conclusion While necessary for the identification of intracranial lesions during neonatal ECMO, CUS demonstrated low correlation with post-ECMO MRI in the identification of intracranial lesions, which supports Extracorporeal Life Support Organization (ELSO) recommendations.

Children with hemoglobin SC (HbSC) disease suffer a significant incidence of silent cerebral infarcts but stroke is rare. A 2-year-old African American boy with HbSC disease presented with focal neurologic deficits associated with magnetic resonance imaging evidence of cerebral infarction with vascular abnormalities. After the acute episode he was treated with monthly transfusions and subsequently transitioned to hydroxyurea therapy. The benefits of hydroxyurea as a fetal hemoglobin inducer in HbSC disease, to ameliorate clinical symptoms are supported by retrospective studies. This case highlights the rare occurrence of stroke in a child with HbSC disease and the use of hydroxyurea therapy.

Cross-linking of ethylene propylene diene monomer (EPDM) rubbers containing different amounts of dicyclopentadiene (DCPD), 5-ethylidene-2-norbornene (ENB) and 5-vinyl-2-norbornene (VNB) dienes was examined by EPR spectroscopy. The cross-linking was initiated by thermal decomposition of dicumyl peroxide at 440 K. The concentration of free radicals increased towards the end of the cross-linking process before reaching a maximum and decaying to zero. This is explained by the spatial confinement of the radicals in the cross-linked rubber, which leads to increased life time and, hence, higher radical concentration at a time when most peroxide has decomposed. The EPR spectra showed the presence of two components: a well-resolved spectrum overlapping a broad line. Both components are assigned to allyl radicals possessing different mobility. The more mobile component is assigned to allyl radicals along the EPDM chains, whereas the immobilised allyl radicals are formed in the cross-links. The stability of the allyl radicals decreases in the order DCPD > ENB > VNB. EPDMs containing two dienes show more persistent radicals than their single-diene counterparts. The most persistent radicals are observed for highly cross-linked (e.g., 28% ENB) or mixed diene EPDMs (e.g., 2.2% DCPD–4.4% ENB); the EPR spectra of free radicals in these systems can be observed for several hours.

The oxidation of phenols, cinnamic acids and methyl aryl sulfides by hydrogen peroxide, using three catalyst systems, [L2Mn2IV(μ-O)3](PF6)2, L = 1,4,7-trimethyl-1,4,7-triazacyclononane; [LMnIV(OMe)3(PF6); and MnII/L/H2O2, have been studied. The results from a combination of spectroscopic and kinetic studies, coupled with Hammett correlations and 18O labelling experiments, suggest that with each system the active oxidant is an electrophilic, mononuclear oxo-manganese (V) species. The influence of additives that can act as co-ligands for the manganese species has been investigated, with a view to controlling the activity/selectivity of the active oxidant. The two-step, sulfide–sulfoxide–sulfone, oxidation shows an unusual switch in the philicity of the active oxidant from electrophilic in the first step to nucleophilic in the second. Mechanisms for the oxidations are proposed.

The structure and bonding of the azo dye Orange II (Acid Orange 7) in parent and reduced forms have been studied using NMR, infrared, Raman, UV-visible, and electron paramagnetic resonance (EPR) spectroscopy, allied with density functional theory (DFT) calculations on three hydrazone models (no sulfonate, anionic sulfonate, and protonated sulfonate) and one azo model (protonated sulfonate). The calculated structures of the three hydrazone models are similar to each other and that of the model without a sulfonate group (Solvent Yellow 14) closely matches its reported crystal structure. The 1H and 13C NMR resonances of Orange II, assigned directly from 1D and 2D experimental data, indicate that it is present asor = 95% hydrazone in aqueous solution, and as a ca. 70:30 hydrazone:azo mixture in dimethyl sulfoxide at 300 K. Overall, the experimental data from Orange II are matched well by calculations on the hydrazone model with a protonated sulfonate group; the IR, Raman, and UV-visible spectra of Orange II are assigned to specific vibrational modes and electronic transitions calculated for this model. The EPR spectrum obtained on one-electron reduction of Orange II by the 2-hydroxy-2-propyl radical (*CMe2OH) at pH 4 is attributed to the hydrazyl radical produced on protonation of the radical anion. Calculations on reduced forms of the model dyes support this assignment, with electron spin density on the two nitrogen atoms and the naphthyl ring; in addition, they provide estimates of the structures, vibrational spectra, and electronic transitions of the radicals.

A series of Au nanoparticles modified with a nitroxide-functionalized ligand was prepared with a range of spin-label coverage. The X-band EPR spectra of frozen solutions of these nanoparticles showed coverage-dependent line-broadening due to dipole-dipole interactions between spin labels. We developed a methodology to analyze such spectra in terms of geometrical features of the nanoparticles (e.g., Au core size and the length of the spin-labeled ligand). Our method is based on the assumption that the spectral line shape is determined by the average distance between nearest-neighboring spin labels adsorbed on the Au particle. Geometrical and statistical analysis then relates this distance to the line shape parameter d1/d, which was calibrated using a model system. Application of this methodology to the experimental spectra provided information about the conformation of ligands on the Au surface. We found that, if the spin-labeled ligand is substantially longer than the surrounding protecting layer, it does not adopt a fully stretched conformation but wraps around the particle immediately above the layer of surrounding ligand. Our results also show that the ligands do not adsorb cooperatively on the Au surface.

The mechanism of a place-exchange reaction of ligand-protected Au nanoparticles was investigated using diradical disulfide spin labels. Analysis of reaction mixtures using a combination of GPC and EPR allowed us to determine concentration profile and propose a kinetic model for the reaction. In this model, only one branch of the disulfide ligand is adsorbed on the Au surface during exchange; the other branch forms mixed disulfide with the outgoing ligand. The two branches of the disulfide ligand therefore do not adsorb in adjacent positions on the surface of Au nanoparticles; this was ultimately proven by the powder EPR spectra of frozen exchange reaction mixtures. Our data also suggest the presence of different binding sites with different reactivity in the exchange reaction. The most-active sites are likely to be nanoparticle surface defects.

l,4,7-Trimethyl-l,4,7-triazacyclononane (TMTACN), MnSO4 and H2O2, in basic aqueous acetonitrile, is an effective system for the epoxidation of cinnamic acid. The influence of a selection of organic additives, potential co-ligands for the manganese species, on the reactions has been studied by UV–vis spectroscopy and ESI-MS. The mechanism of the most efficient system, with added oxalic acid, has been investigated in more detail using cinnamic acid and seven of its 3- or 4-substituted derivatives. A Hammett correlation of rate data shows that the active oxidant is electrophilic (ρ value −0.63). Oxygen ( 18 O ) labelling experiments reveal that H2O2 and not H2O is the source of the oxygen in the epoxide. Possible mechanisms for the reactions are discussed.

The oxidation of phenolic substrates with H2O2 catalysed by [MnIV2(μ-O)3(TMTACN)2](PF6)21, (TMTACN, 1,4,7-trimethyl-1,4,7-triazacyclononane) has been investigated by use of ESI mass spectrometry. The role of the phenols as one-electron reductants and as co-ligands in the stabilisation and reaction of an intermediate OMnV species has been analysed and the presence of a variety of manganese species in solution has been explained. Our results lead to a proposed mechanism for the catalytic oxidation of phenols in this system.

Using three readily-prepared free-radicals of DPPH type, with different oxidation potential, it is possible to generate, via one electron transfer or hydrogen-atom abstraction, short-lived radicals, characterised by the EPR spin- trapping technique. PBN, DMPO and DEPMPO were employed as spin-traps. The results show that DPPH and its congeners can be successfully employed for generation of short-lived oxygen-, sulfur-, carbon-, nitrogen-, and phosphorus-centered radicals.

Dimanganese decacarbonyl (Mn2(CO)10) initiates the radical polymerization of methyl methacrylate (MMA) in the presence of a variety of organic halides including C6H5CH2Br, Me2C(Br)CO2Et, BrCH2C(Br)CH2, and ClCH2C(Cl)CH2 in toluene at 60−90 °C. When using allylic halides (e.g., BrCH2C(Br)CH2 or BrCH2C(CO2Me)CH2), the number-average molecular weights and molecular weight distributions of the PMMA were both low and relatively narrow. The production of relatively low molecular weight polymers when using allylic halides could be explained by an addition-fragmentation chain-transfer mechanism and this is supported by end-group analysis.

The structure of dodecylamine (DDA) aggregates acting as templates in the synthesis of mesoporous silica (in the DDA/water/ethanol/tetraethoxysilane (TEOS) system) has been studied via the EPR spectra of a variety of spin probes and of a spin-labeled silica precursor. Two recipes have been examined: one, starting from a water-rich DDA solution, A0, reported to produce a silica with framework mesopores and textural pores comparable in volume, and another, starting from an ethanol-rich solution, B0 which yields a solid having practically only framework pores. For both compositions the relative positions of the spin probes in the aggregates have been determined, the local polarities expressed in terms of the Kosower scale and their motions examined. The aggregates formed have been characterized as emulsion droplets for A0 and micelles with radii

A kinetic and mechanistic study is reported of the oxidation of a number of azonaphthol dyes with hydrogen peroxide in aqueous solution, catalysed by some mono and dinuclear manganese(IV) complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3TACN). The results of UV-Vis investigations, augmented by EPR and ESI-MS studies, are described for a series of experiments in which concentrations, pH and ionic strength have been varied. The reactions are characterised by an induction period followed by a relatively rapid oxidation. For the dinuclear manganese complex 2, these are consistent with an initial perhydrolysis of the manganese complex involving both the dye anion and HO2-, to give mononuclear manganese species and the operation of a catalytic cycle incorporating MnIIIL(OH)3, O = MnVL(OH)2 and MnIVL(OH)3 (L = Me3TACN) (cf. the reactions of peroxidase enzymes). ESI-MS results provide evidence for the formation and reaction (with the dye) of MnIVL(OH)3. With the mononuclear manganese complex MnIVL(OMe)3, there is a short lag-phase attributed to perhydrolysis by HO2- followed by the same catalytic cycle.

EPR spectroscopy has been employed to study directly the selectivity of hydrogen-atom abstraction by some alkoxyl radicals from a variety of linear and branched alkanes, as well as linear alkenes, chosen as models for low molecular-weight polyolefin cross-linking systems. In situ thermal and photolytic approaches, as well as spin-trapping, have been employed to provide information relating to an accessible temperature range of 233–453 K, in part to mimic conditions relevant to melt processing of polyolefins. Rate constants (in the range 3 × 103 − 3.7 × 105 dm3 mol−1 s−1 per hydrogen) have been determined for C–H abstraction at room temperature. Radical selectivity is largely governed by enthalpic effects (modelled via bond dissociation energy calculations and kinetic analysis). Direct evidence has been obtained for lack of reactivity, as a result of unfavourable steric interactions, for the secondary and tertiary C–H bonds in 2,4-dimethylpentane and 2,4,6-trimethylheptane, models for polypropylene. This has been rationalized via free-energy calculations using DFT.

Electron paramagnetic resonance (EPR) spin-trapping experiments, employing the novel spin-trap DEPMPO, provide evidence for the formation of protein-peroxyl radicals from the reaction of bovine serum albumin (BSA) or lysozyme with HO · in the presence of O 2 . Spin-trapping leads to the detection of anisotropic spectra of partially immobilized protein-peroxyl spin-adducts; positive identification is based on a novel spectrum simulation approach (through which broadened anisotropic spectra are simulated and compared with experiment) and by comparison of results with those obtained when MeO 2 · is trapped and the adduct frozen in a solid matrix.

Background: Remote limb ischemic conditioning (RLIC) is a promising treatment for ischemic stroke. We have previously shown that RLIC increases cerebral blood flow, reduces infarct size, and improves outcome in a murine thromboembolic stroke model (Hoda N et al. Stroke. 2012; 43:2794). We hypothesized that RLIC will increase CBF in hypoperfused areas in acute stroke patients as detected by MRI Arterial Spin Labeling (ASL) Methods: Patients with an acute ischemic stroke within 14 days and with a persistent mismatch defined by a perfusion defect measured by ASL that was at least 20% larger than the area of infarction as measured by diffusion weighted imaging (DWI) were eligible. Patients underwent 4 cycles of blood pressure cuff inflation (x200 mm Hg) for 5 minutes and deflation for 5 minutes on the leg or arm, 1- 2 times per day. MRI ASL, DWI, and 3D T1-weighted Fast Spoiled Gradient-Echo (FSPGR) images were taken before and 60 minutes after the last cycle of RLIC to measure CBF. Two neuroradiologists analyzed the images. Results: After 3 of 4 RLIC sessions, the CBF improved and the mismatch decreased by at least 15%. In the one patient without a reduction in mismatch, the RLIC was performed on the arm and not the leg. Conclusions: 1.) RLIC increased CBF as measured by ASL in stroke patients with a persistent diffusion-perfusion mismatch. 2.) Since it can be repeated multiple times on the same patient, ASL may be a useful biomarker of the conditioning response in humans. 3.) Further work in a larger sample of patients is needed to define the optimal regimen of RLIC and to determine the utility of ASL as a biomarker.

Free radical cyclisation of a variety of 1,6-dienes using CCl 4 in the presence of diethyl phosphite or diphenylphosphine oxide has been investigated. These reactions involve addition of the trichloromethyl radical to the diene followed by a 5- exo - trig cyclisation reaction. The resultant cyclic primary radical can abstract a chlorine atom from CCl 4 or alternatively, abstract a hydrogen atom from the solvent or the organophosphorus compound.

We report the use of the novel spin trap DEPMPO in conjunction with EPR spectroscopy to provide evidence for free-radical mediated oxidation of some proteins in aqueous solution, with systems including metal ions, peroxides or both. In addition we have used a novel approach involving detailed spectral simulation (to reproduce anisotropic features of phosphorus, hydrogen and nitrogen splittings) to confirm structural assignments. Oxidation of bovine serum albumin (BSA) with either Ce4+ or IrCl62− leads to the predominant formation of spin-trapped oxygen-centred free-radicals, attributed to tyrosyl-based adducts, a reaction also observed for sulfur-free analogues (lysozyme and tyrosine-containing models). Similar spectra were obtained from reactions involving oxidation with HRP/H2O2 and methaemoglobin/H2O2 couples, through intermolecular oxidation of the proteins via oxo–iron intermediates. Oxidation of BSA with peroxynitrite leads to an anisotropic spectrum which is assigned to the trapping of a sulfur-centred radical. This assignment has been confirmed via denaturation of the spin-adduct (and simulation of the resulting less immobilized spectrum). Reaction of the hydroxyl radical with BSA and lysozyme, in Fenton-type reactions, leads to the detection of anisotropic spectra derived from the spin-trapping of carbon-centred radicals, whose assignment is discussed.

We report the synthesis and characterisation of some novel hydrazine-derived monoradicals incorporating nitroxide 14, nitronyl-nitroxide15 and imino-nitroxide 16 functions, as well as the corresponding diradicals assigned the hydrazyl-nitroxide 17, hydrazyl-nitronyl-nitroxide 18 and hydrazyl-imino-nitroxide 19 structures. EPR, UV-Vis and electrochemical (CV) characteristics are reported, along with MS and NMR data where appropriate; pKa and BDE values are calculated as well as the average interelectronic separation in the triplet diradicals 18 and 19 obtained via solid-state EPR measurement and calculations. The reactions of these compounds with short-lived radicals generated by photolysis, as well with NO and NO2, are also reported.

Reaction of primary or secondary alcohols with BrCCl 3 and tetrahydrofuran, usually in the presence of 2,4,6-collidine, leads to the formation of 2-tetrahydrofuranyl ethers in good to excellent yield (56–92%). The reaction mechanism is believed to involve a free-radical chain reaction.

The formation of azide spin-adducts of a number of spin-traps, including PBN, DMPO, DEPMPO and TBNB, in biphasic and organic media has been studied by EPR spectroscopy. A series of hydrazyl radicals has been employed to oxidise the azide anion to the corresponding short-lived azido radical, which is subsequently trapped. The approach has typically involved the presence of the ether 18-crown-6 in order to facilitate the transport of the azide anion from water into the organic media, with further experiments in non-aqueous systems. The results can largely be rationalised in terms of a “conventional” spin-trapping mechanism, with an efficiency that depends on the relevant redox potentials, which are themselves solvent dependent; however, conditions that favour direct oxidation of the trap have also been identified. It is also established that the azide spin-adducts of some nitrones can be transformed, under certain conditions, into secondary spin-adducts by nucleophilic substitution reaction of the first-formed nitroxides.

Radical species generated on photolysis of 2-nitrobenzyl compounds, including derivatives of 1-(2-nitrophenyl)ethyl phosphate (caged ATP 1 and caged monomethyl phosphate 3) have been studied by EPR spectroscopy and their identity confirmed by independent chemical generation of the appropriate nitrogen-centred radicals. The reactions which occur include photo-isomerisation, photo-fragmentation, photo-assisted electron-transfer, intramolecular addition and spin-trapping reactions of the nitroso compounds produced via molecular rearrangement. In particular, a mechanistic scheme is advanced to explain the co-formation of a radical-anion and a cyclic aryl alkoxy aminoxyl (2 and 30, respectively, from caged ATP). Which of these species is observed in the EPR spectrum depends upon the particular experimental conditions.

EPR experiments involving the attack of oxygen-centred free radicals on polysaccharides in aqueous solution reveal two sources of regioselectivity in C–H abstraction. For SO4−˙ (derived from one-electron reduction of S2O82−), hydrogen-atom abstraction is encouraged by SOMO–σ* interactions involving β-C–O bonds which eclipse the orbital of the unpaired electron at the developing radical centre. In addition, for a series of cyclodextrins, the reactivity observed with SO4−˙ points to the selective reaction of the latter within the cyclodextrin cavity; these findings are in contrast to those obtained with ˙OH (from H2O2).

Wurtz-type radical coupling of a variety of allylic and benzylic bromides was observed on irradiation with dimanganese decacarbonyl in excellent yield (77-99%). Efficient cross-coupling of two different bromides was also readily achieved.

Radical cyclisation of various unsaturated halides using dimanganese decacarbonyl/ hv has been explored. Substituted pyrrolidinones and a pyrrolidine were isolated in good to excellent yield; the radical produced on cyclisation can undergo iodine or hydrogen atom transfer, or reaction with TEMPO.

Both free-radical and non-radical routes for peroxide oxidation of CuI can be identified for copper complexes obtained by the reduction of CuII by thiols, including glutathione. Copper(I)–thiolate complexes are obtained, except in the presence of e.g. 1,10-phenanthroline, and these undergo ready reaction with H2O2 and tBuOOH. EPR spin-trapping studies establish a free-radical reaction mechanism (to give tBuO˙) with the latter, and the formation of HO˙ from the former occurs only at low concentrations of copper. Kinetic studies (using UV-vis and EPR spectroscopies), together with NMR analysis, lead to the proposal that CuI aggregates react via non-radical pathways in contrast to monomeric CuI.

Attack by SO4–˙ (generated by photolysis and one-electron transfer) on a number of carbohydrates and some model compounds has been followed directly by EPR spectroscopy.SO4–˙ is a reactive, electrophilic species but is more selective (less reactive) than HO˙. We present evidence for the importance of polar effects and radical stabilisation, especially in determining trends in selectivity. Examples include the preference for C–H abstraction α to a ring oxygen atom in a five-membered ring (e.g. THF, sucrose, β-D-fructofuranose) and abstraction of the axial C1 hydrogen atom from β-D-glucose.The reaction of SO4–˙ with α-D-glucose is selective towards the C2, C5 and C6 positions. This reflects the activating effect of a β-oxygen substituent where the radical orbital can eclipse the β-C–O bond providing a SOMO–σ* interaction which stabilises the developing radical centre. For myo-inositol, abstraction is also observed from axial C–H bonds for which the resulting radicals are stabilised by an axial β-OH substituent but, due to the absence of a ring oxygen atom, more rapid abstraction occurs from the equatorial C–H bond.

The microenvironments of sols and gels of gelatin in water-in-oil microemulsions formed by sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in isooctane have been characterized by EPR spin-labelling and spin-probe techniques. Using spin-labelled gelatin, incorporated both in sol and gel, the changes in the microstructure(s) around the gelatin have been monitored, at different water and gelatin compositions. Specific locations of the gelatin have been found: some of the gelatin is located at the water/surfactant interface and part in pools of water. Gelatin is not found in the apolar phase. The spin-probe technique, with amphiphilic probes, provides information on changes in the structure of the aggregates as a result of gelatin incorporation. Increased microviscosity, and a tighter packing of the AOT chains is observed, confirming the location of gelatin at the water/surfactant interface. Our results favour a model for the gel structure in which all the gelatin is covered by water and surfactant, with large cavities of polar and apolar solvent.

EPR spectroscopy provides direct evidence for the intercalation of copper(II) complexes of 1,10-phenanthroline and 2,2′-bipyridine with DNA. Reduction of these complexes to copper(I) by glutathione is evidently facile, whereas ascorbate reacts more slowly. Reoxidation of copper(I) with tBuOOH (to give tBuO˙) is rapid in both systems, as judged by EPR spin-trapping results. Reaction of copper(I)–DNA with H2O2 in the presence of ascorbate leads to the generation of HO˙ and to the trapping of DNA-derived radical adducts. The role of 1,10-phenanthroline and ascorbate, especially, and the relevance to DNA scission, are discussed.