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Most rod-shaped bacteria elongate by inserting new cell wall material into the inner surface of the cell sidewall. This is primarily performed by a highly conserved protein complex, the elongasome, which moves processively around the cell circumference and inserts long glycan strands that act as barrel-hoop-like reinforcing structures, thereby giving rise to a rod-shaped cell. However, it remains unclear how elongasome synthesis dynamics and termination events are regulated to determine the length of these critical cell-reinforcing structures. To address this, we developed a method to track individual elongasome complexes around the entire circumference ofBacillus subtiliscells for minutes-long periods using single molecule fluorescence microscopy. We found that theB. subtiliselongasome is highly processive and that processive synthesis events are frequent terminated by rapid reversal or extended pauses. We found that cellular levels of RodA regulate elongasome processivity, reversal and pausing. Our single molecule data, together with stochastic simulations, show that elongasome dynamics and processivity are regulated by molecular motor tug-of-war competition between several, likely two, oppositely oriented peptidoglycan synthesis complexes bound to the MreB filament. Our data, thus, demonstrate that molecular motor tug-of-war is a key regulator of elongasome dynamics inB. subtilis, which likely also regulates the cell shape via modulation of elongasome processivity.

A non-conforming apparatus was devised to study the wear properties of hip replacement materials (stainless steel femoral head and mainly ultra-high molecular weight polyethylene, UHMWPE). The analysis was by wear depth and various types of microscope examination of the worn surfaces. The importance of proper femoral head surface conditions is emphasized. The dry worn debris matched that retrieved from revision surgery indicating the in vivo wear was without fluid lubrication. A qualitative model is presented to explain the observed wear and wear rate profiles. The long-term wear was within a narrow range that matched in vivo results. Tests on polyetherether ketone (PEEK) polymer indicated that it had superior wear properties to UHMWPE.

Controlled reaction of 1-(3-aminopropyl)imidazole with poly(γ-ethyl L-glutamate) leads to conversion of some side-chain ester groups to amides. The functionalised polymer is characterised by 1H NMR spectroscopy. Imidazole complexes have been formed between this functionalised polymer and 5,10,15,20-tetraphenylporphyrin iron(III) chloride and also deuteroporphyrin-IX dimethyl ester iron(III) chloride. Films of the polymer-porphyrin complexes formed on platinum and on tin oxide coated glass show reversible redox activity in acetonitrile and in aqueous electrolytes. Both redox states of iron are characterised as bis-imidazole ligated by their UV–VIS spectra. The influence of the degree of polymerisation of the starting poly(γ-ethyl L-glutamate), the composition of the aqueous electrolyte and the oxidation state of the iron centre on the stability of the hydrogel films towards redox cycling is examined.

The electrocatalytic hydrogenation of 4-(4-hydroxyphenyl)buten-2-one at a nickel cathode in aqueous ethanol containing sulphuric acid has been examined. HPLC was used for the analysis of reaction mixtures. The product composition is critically dependent on the method used for electrodeposition of the nickel-black surface. An electrochemically deposited nickel-black will catalyse the electrochemical hydrogenation of this substrate. Formation of 4-(4-hydroxyphenyl)butan-2-one is favoured at high concentrations of substrate and a minor amount of the corresponding secondary alcohol is also formed. The process was applied also to hydrogenation of 4-(4-methoxyphenyl)buten-2-one and 4-(4-hydroxy-3-methoxy-phenyl)buten-2-one with 63–68% current efficiency. An alternative process, the reduction of these enones at a lead cathode in presence of sodium hydrogen carbonate, gave an unsatisfactory mixture of products.

Glycosaminoglycans are high molecular mass polymers found in living tissues. They are degraded by site specific enzymes to oligosaccharide fragments. Polymers and oligomers all carry negative charge and are found as salts soluble in water. Consequently, capillary electrophoresis has come to the fore as an analytical technique in this field. This review discusses application of the technique to the chondroitin-dermatan, heparin and hyaluronan groups of polymer and the derived oligosaccharides. Direct and indirect UV detection are discussed as well as detection methods involving precolumn derivatization. Capillary electrophoresis has found use in the characterisation of heparin and in following the changes in chondroitin and hyaluronan during the onset of arthritic disease in humans. Some glycosaminoglycans have been used as asymmetric anions in the separation of enantiomers of low molecular mass compounds by capillary electrophoresis.

One electron reduction of aryl halides is known to generate the aryl radical and halide ion. These aryl radicals will cyclize onto an adjacent benzene ring in a reaction that is potentially useful in organic synthesis and which is well documented at a mercury cathode. 5-(2-Halophenyl)-1-(4-fluorophenyl)tetrazoles are used here as representative substrates and the cyclization reaction to 7-fluorotetrazolo[1,5-f]phenanthridine is developed at cathodes of cadmium, zinc and mild-steel. A high yield of the desired cyclization product is achieved using a mild-steel cathode and a sacrificial magnesium anode in an undivided cell with acetonitrile, 0.1 M tetraethyl ammonium tetrafluoroborate as electrolyte and under an air atmosphere.

Studies by laser flash photolysis, transient Raman spectroscopy, and Raman and UV-vis spectroelectrochemistry are described in which the techniques have been used in parallel to compare the lowest energy charge-transfer excited states of Cu(I) complexes ([Cu(L) 2 ] + and [(PPh 3 ) 2 Cu(L)] + [L= 2,2'-biquinoline (BIQ) or 6,7-dihydro5,8-dimethyldibenzo[b,j] [1,10]-phenanthroline (DMCH)) with the species produced by electrochemical reduction in the same group of complexes

A two phase acidic reaction medium has been developed for the conversion of (E)-4-(2-furyl)but-3-enone into 4,7-dioxooctanoic acid in consistent yields of 50% with concomitant formation of 15% polymer. The corresponding ring opening of 1-(2-furyl)-5-methylhex-1-en-3-one proceeds in homogeneous acid solution in very high yield without polymer formation. The two furylalkenones can be reduced electrochemically to the corresponding furylalkylketones in good yields at a lead cathode in the presence of sodium hydrogen carbonate.

Electrochemical reduction of the title compounds, where the halogen substituent is Cl, Br or I, leads to cleavage of the carbon–halogen bond to leave a phenyl radical. Competition then follows between intramolecular radical substitution giving 7-fluorotetrazolo[1,5-f]phenanthridine and further reduction of the radical, then protonation, giving 1-(4-fluorophenyl)-5-phenyltetrazole. Substitution predominates but reduction and protonation becomes a more competing reaction when the halogen is Br or I. Photochemical reaction of the title compounds shows competition between carbon–halogen bond cleavage to give 7-fluorotetrazolo[1,5-f]phenanthridine and loss of nitrogen followed by cyclization to give 2-halogenophenyl-5-fluorobenzimidazole. Carbon–halogen bond cleavage predominates and becomes the only reaction when the halogen is I. The fluorine substituent allows the determination of product yields by 19F NMR spectroscopy.

A new route has been devised for intramolecular aryl radical cyclization reactions involving the electrochemical reduction of an ortho-halogenophenyl compound in acetonitrile at a mild steel cathode.

The electrocatalytic hydrogenation of 4-(4-hydroxyphenyl)buten-2-one at a nickel cathode in aqueous ethanol containing sulphuric acid has been examined. HPLC was used for the analysis of reaction mixtures. The product composition is critically dependent on the method used for electrodeposition of the nickel-black surface. An electrochemically deposited nickel-black will catalyse the electrochemical hydrogenation of this substrate. Formation of 4-(4-hydroxyphenyl)butan-2-one is favoured at high concentrations of substrate and a minor amount of the corresponding secondary alcohol is also formed. The process was applied also to hydrogenation of 4-(4-methoxyphenyl)buten-2-one and 4-(4-hydroxy-3-methoxy-phenyl)buten-2-one with 63–68% current efficiency. An alternative process, the reduction of these enones at a lead cathode in presence of sodium hydrogen carbonate, gave an unsatisfactory mixture of products.

Poly(Nδ-4-nitrobenzoyl-L-ornithine) was obtained with average molecular weight 8.0 × 104 by reaction between the monomer N-carboxyanhydride and sodium hydride. The material was dipcoated onto platinum from dimethylacetamide solution and the behaviour of the coating examined in acetonitrile by cyclic voltammetry. Surface coverages in the range of 13.8 to 1.4 mmol cm–2 4-nitrobenzoyl residues were obtained by dipping from 0.6–0.07% solution, corresponding to from 20 to 2 layers of close-packed α-helices. The coated electrodes showed ipc proportional to scan rate. They do not show the severe ageing phenomena on repeated cyclic voltammetry that was associated with poly(NIµ-4-nitrobenzoyl-L-lysine). Expressions are developed which simulate the voltammograms by introducing activity coefficients for reduced and oxidised species within these multilayer films.

The synthesis and electropolymerization of 2-[2-(1-pyrrolyl)ethylamino]-3-chloronaphthoquinone (PNQ) and 2,5-bis[2-(1-pyrrolyl)ethylamino]-2,6-dichlorobenzoquinone (PBQ). are described. Electrochemical behaviour of poly(PNQ) and poly(PBQ) films on platinum electrodes was investigated in acetonitrile media. A stable composite film was obtained by the oxidation of PNQ on a polypyrrole coated Pt electrode.

Aqueous carbon dioxide is photochemically reduced in the presence of semiconductor suspensions and colloids. Experiments have been performed using CdS, ZnO, SiC, Ba TiO3, and SrTiO3, dispersions. Product analysis showed the formation of formic acid formaldehyde, sometimes methanol and in the presence of tetramethylammonium chloride, two-carbon products such as glyoxylic and acetic acids and sometimes acetaldehyde. Product yields and photochemical yields were studied as a function of pH, solution composition, added sacrifical electron donors and catalysts, irradiation intensity and irradiation time. A demonstration experiment with a flat-bed solar collector showed the formation of formic acid and formaldehyde using direct sunlight.

Pyrrolo[1,2-f]phenanthridine (compound 4), 3-phenylimidazo[1,2-f]phenanthridine 8, tetrazolo[1,5-f]phenanthridine 11 and benzo[c]tetrazolo[1,5-f]phenanthridine 12 have been prepared using an electrochemical cyclization procedure. Treatment of the imidazophenanthridine with singlet oxygen yields a phenanthridone by degradation of the heterocyclic system. Lithium aluminium hydride reduction of the tetrazolophenanthridines yields the phenanthridine.

Poly(thiophene-benzoquinone) films were prepared on platinum spheres by electropolymerization of the monomer 1-[3-(3-thienyl)propyl]2,4,5-trichloro-3,6-dioxo-1,4-cyclohexadiene-1-acetate (TBQ) in acetonitrile. These films were studied mainly by cyclic voltammetry and chronoamperometry in acetonitrile containing tetraalkylammonium salts as the supporting electrolyte.

Poly(pyrrole-pyromellitimide) films were prepared by the anodic oxidation of N,N'-bis[2-(1-pyrrolyl)ethyl]pyromellitimide (BEP) in acetonitrile media. These films showed a stable redox behaviour in acetonitrile as well as in water media containing 0.1 M tetraalkylammonium salt or LiClO4, as the supporting electrolyte. Poly(BEP) adsorbed a layer of poly(Nϵ-4-nitrobenzoyl-L-lysine) and this bilayer exhibited charging of both electroactive groups.

Non-stoichiometric manganese dioxide prepared electrochemically at room temperature and suspended in dilute sulphuric acid is used to oxidise isosafrole to piperonal in 54% isolated yield. The manganese dioxide-manganese(II) sulphate system can be recycled electrochemically at high current density. It has the further advantage that water-soluble materials derived from the chemical oxidation step can be removed by filtration at the manganese dioxide stage. Direct oxidation of isosafrole at a lead dioxide anode leads to further oxidation of the piperonal.

The chapter describes the mechanism of reduction in alkenes and conjugated alkenes. In general, an isolated alkene bond is not reducible under electrochemical conditions. Alkene conjugation lowers the energy level of the lowest π*-orbital so that polyenes and phenylethenes become reducible in an accessible potential range. Reaction involves the addition of one electron to form a delocalized radical-anion. The radical-anions of conjugated alkenes are stable on the time scale of cyclic voltammetry. Addition of a second electron occurs at more negative potentials. Compounds where the alkene function is conjugated to an electron withdrawing π-system such as carbonyl or nitrile are more easily reduced to the radical–anion. Conjugation with an electron-withdrawing group substantially lowers the energy of the lowest unoccupied molecular x-orbital, which results in less negative reduction potentials for the alkene system. Radical-anions from cis- and trans-stilbene are distinct species with individual uv- and esr-spectra. The cis-form is metastabte and slowly converts to the trans-form. The kinetic features of this interconversion have been studied by generating the cis-stilbene radical-anion in hexamethylphosphoramide by phomchemically assisted electron transfer from a second radical-anion of less negative reduction potential.

Aromatic hydrocarbons are oxidized through the loss of an electron from the highest occupied π-molecular orbital. This process generates a π-delocalized radical-cation. The electron transfer process is generally irreversible in acetonitrile under normal conditions because the radical-anion reacts rapidly with extraneous nucleophiles, including residual water. A second irreversible oxidation wave is seen at more positive potentials due to the formation of a transitory dication. Solutions of 9,10-diphenylanthracene radical-cation, however, can be prepared in acetonitrile using an electrochemical flow cell system and the reaction with water followed by uv-spectroscopy. For some substrates, in carefully purified acetonitrile containing suspended aluminium oxide to absorb residual water, both electron transfer process becomes reversible on the time scale of cyclic voltammetry. Dichloromethane and the mixtures of dichloromethane with fluorosulphonic acid or trifluoroacetic acid are better solvents to demonstrate the reversible one-electron oxidation of aromatic species. The anions present, as well as the solvents themselves, are poor nucleophiles while any water is protonated by the acid and not available for a nucleophilic attack.

The chapter describes the process of oxidation of alcohols, amines, and amides. Early electrochemical processes for the oxidation of alcohols to ketones or carboxylic acids used platinum or lead dioxide anodes, usually with dilute sulphuric acid as an electrolyte. The majority of amines show an irreversible oxidation wave on cyclic voltammetry in acetonitrite at a platinum electrode. An electron is lost from the nitrogen lone pair and the resulting radical-cation loses a proton from the α-position. Proton loss is assisted by overlap in the transition state between the p -orbital containing an unpaired electron on nitrogen and the stretching σ-orbital of the carbon-hydrogen bond. Amines are stable to electrochemical oxidation in acid solution because the nitrogen lone pair is protonated and inaccessible for reaction. However, this is not the case for N-acetylamines, which are oxidizable at a lead dioxide anode in aqueous sulphuric acid. The primary electron transfer step involves the amide function and leads to a radical-cation, which loses a proton from the carbon atom adjacent to nitrogen. Electrochemical oxidation of amides and urethanes in methanol containing an inert electrolyte has been developed into a useful procedure for the generation of α -methoxy derivatives.

Protonation of aromatic hydrocarbon radical-anions requires a change of carbon atom hybridization from the sp 2 to the sp 3 state. This is found to be an irreversible process, which proceeds at a fast but measurable rate. Protonation of the radical-anion from nitrogen ring systems, however, involves the nitrogen lone pair and does not require a change in hybridization. The nitrogen center in the parent compound is also hydrogen bonded to any proton donors in solution. As a consequence, protonation of nitrogen ring radical-anions by available donors is often synchronous with electron transfer to the parent molecule. Most effort over the electrochemical reduction of benzene hydrocarbons has centered on finding a reaction medium, which is also a better solvent for a substrate than liquid ammonia. Aliphatic amines have proved useful solvents, and they may be used in an undivided electrochemical cell.

The chapter describes the process of reduction of carbonyl compounds, carboxylic acids, and their derivatives. The first step in the reduction of carbonyl compounds is the addition of an electron to the LUMO of the carbonyl group to form a radical-anion in which the unpaired electron is delocalized over the π-system. Conjugated aliphatic enones, aromatic aldehydes, and aromatic ketones show reversible polarographic waves at more accessible potentials in aprotic solvents due to one-electron addition with the formation of the radical-anion. The preparative scale reduction of oximes at a mercury or lead cathode in acid solution has been used in the conversion of the carbonyl function to amine. Originally, 30–50% of sulphuric acid was used as a solvent, but ethanol with dilute hydrochloric acid is usually satisfactory. Aliphatic and aromatic oximes give amines in 64–86% yields. Aromatic ketoximes are also reducible in an alkaline solution, and acetophenone oxime is converted to 1-phenylethylamine in a tri-potassium orthophosphate solution. Phenylglyoxal monoxime in acid solution is however reduced at both the carbonyl and the oxime centers by sodium amalgam to yield 2-ammo-l-phenylethanol.

Aliphatic ketones are oxidized in both acetonitrile and trifluoracetic acid at potentials less positive than required for the analogous hydrocarbons. The oxidation process is irreversible in both solvents, and cyclic voltammetry peak potentials are around 2.7 V vs. sce . Loss of an electron from the carbonyl oxygen lone pair is considered to be the first stage in the reaction. Ketones react with electrochemically generated halogens to form the α-halogenocompound. In the presence of potassium hydroxide and potassium iodide, more stable enolate is formed from the ketone and this reacts with the electrochemically generated iodine. The electrochemical oxidation of aldehydes to the carboxylic acid, catalyzed by bromide or iodide ions, is an extensively exploited process. It is the preferred route for the oxidation of reducing sugars to the aldonic acid and replaces the older technique where bromine in stoichiometric amount was used as the oxidizing agent. The reaction is carried out in aqueous solution in an undivided cell at a graphite anode using an electrolyte of sodium bromide containing suspended calcium carbonate. The oxidation of alkylcarboxylates is one of the first organic electrochemical reactions to be investigated.

Reduction of nitrocompounds involves a series of one-electron additions and chemical steps, and an important reaction intermediate is the nitrosocompound. Nitrosobenzene radical-anion is detected in a steady-state concentration during the electrolysis of a solution of the nitrosobenzene in acetonitrile within the cavity of the esr spectrometer. Both the radical-anion and the protonated radical are present, and protonation occurs at nitrogen generating nitroxide. Immediately following the generation by pulse-radiolysis, nitrosobenzene radical-anion is detected by absorption spectroscopy with λ max 450 nm. The reduction of aliphatic nitrocompounds in acid solution proceeds in two steps. The nitrosocompound is formed. A low steady state concentration of 2-methyl-2-nitrosopropane is detected during the reduction of 2-methyl-2-nitropropane. Good yields of the hydroxylamine are obtained from nitroalkanes with no α-hydrogen substituent by reduction in the acid solution. This step is used to modify the antibiotic everninomicin, a naturally occurring aliphatic nitrocompound, where the hydroxylamine is obtained by reduction at pH 8 in the presence of other functional groups.

Attempts to detect radical-anions from alkyl halides by γ-irradiation in a low temperature glass, using esr spectroscopy, have generally been unsuccessful. Irradiation of the glass generates solvated electrons that attach to the alkyl halide to generate an alkyl radical and a halide ion. There is an evidence for a weak interaction, but not bond formation, between alkyl radicals and bromide ion formed in acetonitrile at 77 K. In the more solvating methanol, there is no interaction between radicals and bromide ions. Trifluoromethyl halide molecules are the exceptions to this otherwise general behavior. These give radical-anions on irradiation in methyltetrahydrofuran at 77 K with free electron density largely in the carbon-halogen σ *-orbital. The trifluoromethyl radical is pyramidal so the tendency to complete separation from the halide ion is arrested in the glassy matrix. Alkyl radicals are planar, precluding any, strong association with the halide ion. Intramolecular dissociative electron transfer in aryl halide radical-anions involves an interaction between the π -aromatic orbital and the σ-type carbon-halogen bond. These orbitals are orthogonal, but bending of the carbon-halogen bond allows the necessary interaction. Qualitatively, the influence of several factors on the bond cleavage rate can be discerned.

The chapter describes the process of oxidation of alkanes, haloalkanes, and alkenes. Oxidation of alkanes involves the removal of an electron from either a carbon-hydrogen or a carbon-carbon σ-bond. As far as the oxidation of haloalkanes is concerned, the electrochemical oxidation of alkyl bromides and iodides leads to the loss of a nonbonding electron from the halogen substituent, followed by the cleavage of the carbon-halogen bond to form a carbonium ion and a halogen atom. The products isolated are formed by further reactions of the carbonium ion, while two of the halogen atoms combine to form the halogen molecule. Radical-cations from primary alkyl iodides are detectable as very short-lived intermediates. The electrochemical oxidization of alkenes is carried out in nucleophilic solvents, such as alcohols, acetic acid, or acetonitrile, using an undivided cell and the isolated products result from quenching of intermediate carbonium ions by nucleophiles. Most alkene hydrocarbons show a single two-electron wave at a rotating disc electrode due to the formation of a radical-cation and its subsequent reactions. The oxidation potentials of alkenes are made less positive by alkyl substitution.

Radical-anions formed by one electron attachment to aryl halides undergo cleavage of the carbon-halogen bond in a unimolecular process to give an aryl σ-radical and halide ion. Aryl σ-radicals are highly reactive intermediates and the objective of our work is to find conditions under which they can be trapped in an intramolecular reaction by an adjacent phenyl or alkene substituent. Further steps lead to a stable cyclised product and the process is of interest in synthesis. The corresponding intermolecular reactions between phenyl radicals and either benzene or an alkene have been shown to have bimolecular rate constants1 in the range 105 to 108 M−1s−1 so that the related intramolecular and unimolecular processes are expected to be very fast. Alternative reactions for the aryl σ-radical intermediates include abstraction of a hydrogen atom from the solvent and further electron transfer at the electrode surface to form a carbanion which undergoes protonation.

The glycosaminoglycan, hyaluronan, can be detected in human synovial fluid by capillary electrophoresis (CE). Variations in peak shape make this technique unsuitable for quantitative analysis of hyaluronan in raw synovial fluid. Quantitative analysis was achieved by hydrolysis of the polymeric hyaluronan to the tetrasaccharide by the action of testicular hyaluronidase and separation of the product using CE. A UV detector operating at 200 nm was used. The X-ray contrast material, omnipaque, a propriety aqueous solution of iohexol was used as internal standard. A second peak in the electropherogram of synovial fluid was quantified. The variation in concentrations of these two components correlate with the arthritic disease state of a joint.

Capillary electrophoresis was used for the separation and quantitative analysis of the glycosaminoglycan hyaluronan in human and bovine vitreous with detection by UV absorbance at 200 nm. Calibration was carried out using standards made up from known concentrations of hyaluronan of umbilical cord origin. The purity of the standard was examined by 1H NMR (nuclear magnetic resonance). Concentrations as low as 25 micrograms/mL could be detected by capillary electrophoresis. Confirmation that the signal was due to hyaluronan was obtained by depolymerization of the native mucopolysaccharide by hyaluronidase. This resulted in loss of the hyaluronan peak and appearance of several new peaks corresponding to the oligomeric fragments which had shorter migration times. Capillary electrophoresis is a reproducible and sensitive technique for the quantification and characterisation of hyaluronan in vitreous samples.

Reaction of poly(γ-ethyl L-glutamate) with N-(3-aminopropyl)imidazole gives an imidazole doped polymer which forms 6-coordinate complexes with iron(III) porphyrins. Modified electrodes are prepared using these porphyrin containing polymers. The new materials are characterised by cyclic voltammetry, UV-visible spectroscopy and by surface enhanced resonance Raman spectroscopy. The techniques allow complete characteization of the oxidation state and ligation state of the iron centre. The modified electrodes will catalyse the reduction of dioxygen.

1. A 1H-n.m.r. method was used to measure concentrations of valine, alanine, lactate, acetate, hyaluronan and lipids in synovial fluid obtained, during the normal course of examination, from the knee joints of patients attending rheumatology and orthopaedic clinics. Fluid was available from 16 patients with osteoarthritis, 18 patients with rheumatoid arthritis, four patients with meniscal tear and one patient each with systemic lupus erythematosis, mono-arthritis, synovitis and loose bodies. Four normal specimens were obtained for comparison. 2. Valine, alanine and acetate levels all showed a normal Gaussian distribution, reflecting the distributions within the serum of the sample population. 3. Lactate concentrations divided into two distinct patterns. At concentrations below 2.5 mmol/l the lactate levels showed a Gaussian distribution, reflecting the distribution in normal serum. The normal synovial fluid specimens belong to this distribution. Above 2.5-3.0 mmol/l, lactate levels were asymmetric in distribution with a long tail at higher concentrations. These high levels of lactate can be explained by the generation of lactate through anaerobic metabolism within the synovial cavity. This metabolic process is triggered by a general inflammatory condition such as in rheumatoid arthritis. 4. The distribution of n.m.r.-observable lipid concentrations in rheumatoid arthritis and osteoarthritis each shows a normal distribution and the mean concentration is significantly higher in rheumatoid arthritis. 5. An increased n.m.r.-observable hyaluronan concentration is associated with an inflammatory situation. 6. It is concluded that raised levels of lactate and n.m.r.-observable hyaluronan and lipids are useful markers to aid the clinical distinction between rheumatoid arthritis and osteoarthritis. The results of this study confirm rheumatoid arthritis as an inflammatory disease inducing higher metabolic activity within the synovial cavity.

Substantial and characteristic changes in composition are found between normal human synovial fluid and fluid from clinically well-defined cases of osteoarthritis and rheumatoid arthritis. The peak due to uric acid is a useful marker for the region of the electropherogram where these changes occur.

A new route has been devised for intramolecular aryl radical cyclization reactions involving the electrochemical reduction of an ortho-halogenophenyl compound in acetonitrile at a mild steel cathode.

Electrochemical reduction of the title compounds, where the halogen substituent is Cl, Br or I, leads to cleavage of the carbon–halogen bond to leave a phenyl radical. Competition then follows between intramolecular radical substitution giving 7-fluorotetrazolo[1,5-f]phenanthridine and further reduction of the radical, then protonation, giving 1-(4-fluorophenyl)-5-phenyltetrazole. Substitution predominates but reduction and protonation becomes a more competing reaction when the halogen is Br or I. Photochemical reaction of the title compounds shows competition between carbon–halogen bond cleavage to give 7-fluorotetrazolo[1,5-f]phenanthridine and loss of nitrogen followed by cyclization to give 2-halogenophenyl-5-fluorobenzimidazole. Carbon–halogen bond cleavage predominates and becomes the only reaction when the halogen is I. The fluorine substituent allows the determination of product yields by 19F NMR spectroscopy.