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The electron paramagnetic resonance (EPR) spin labeling technique has been employed to study the properties and conformation of the thiol protease papain in solution, using (1-oxyl-2,2,5,5-tetramethyl-delta 3-pyrroline-3-methyl) methanethiosulfonate (MTS) as the spin label. The measurements of papain's amidase activity corroborate the EPR results. The major findings are: (i) the motion of the MTS spin label is very sensitive to the active site conformation of papain, which may reflect the location of the pyrroline ring of the spin label near the narrow portion of the active site cleft of papain, and thus there may be intimate interactions between the spin label and its environment; (ii) the active site cleft of papain may have a more open structure at intermediate pH (pH 4.2 to 8.0) than at higher (pH > 8.0) or lower (pH < 4.2) pH, which is consistent with the bell-shape pH curve of the enzyme's amidase activity with the optimum pH at pH 7.00; and (iii) the motion of spin label at the active site of free papain in solution becomes slower upon addition of a denaturant (urea or guanidine hydrochloride), suggesting that the denatured enzyme may have a more closed active site cleft. Urea is more effective than guanidine hydrochloride in denaturing papain at low concentration. However, both urea and guanidine hydrochloride can completely inactivate papain at high concentrations. When an appropriate spin label is selected to label the active site of papain (such as MTS spin label), the EPR spin labeling technique may offer additional insight into the conformation of papain over that obtained by optical methods. These results are discussed in terms of possible studies of biofunctional membranes, opaque assemblies in which a biological molecule is attached to a polymeric membrane.

Summary Activity of some fifty potential alkylating agents on respiration and anaerobic glycolysis and upon RNA, DNA and protein, synthesis of Walker 256 ascites tumour cells has been investigated. The sulphonylhydrazone moiety proved to be selectively toxic to hypoxic cells in some structures; use of carbohydrate residues as “carriers” led to loss of activity. One halo-deoxy sugar showed an effect upon glycolysis and RNA synthesis.

The results of experiments on the anodic oxidation of secondary amines at silver oxide electrodes are presented. The reaction differs significantly from the analogous reactions of primary amines. A reaction mechanism is proposed which involves the participation of a carbonium ion intermediate.

The reaction of 1,2:5,6-di-O-isopropylidene α- d -mannofuranosyl chloride with chloromercuri-6-benzamidopurine gives a mixture of α- and β-isomers m the ratio 39α:14β, Both isomers have been isolated as pure crystalline compounds. Some further extensions of the reaction are described, together with attempts to make nucleosides containing free aldehydo- groups.

A method is described for the conversion of hydroxy-esters to chloroesters using very mild conditions. The reaction proceeds with inversion of configuration at the reacting centre. Neighbouring optical centres are not affected.

Investigation of several routes to fluoro-carbohydrates and sugar phosphates has shown that appreciable formation of internal ethers may occur in certain cases.

The oxidation of cyclohexene with thallium III acetate has been studied under a variety of conditions and compared with oxidations by lead IV acetate and mercury II acetate under similar conditions. The products obtained vary with conditions but include cyclohexan-1,2-diols, their mono- and diacetates, cyclohex-2-enyl acetate, C-formylcyclopentane and its diacetate. Lead IV acetate produces similar mixtures, but mercury II acetate gives a simple reaction product.

A method for rapid preparation of a glycosyl halide is described. The halide may be isolated or used in situ in nucleoside synthesis. Use of di-isopinocampheyl borane for conversion of γ-lactone to furano-sugar is discussed.

An examination of the conformations adopted by acyclic sugar derivatives has been made. It is shown that 1,3-eclipsed rather than 1,2-gauche interactions are important in determining relative conformer population and that the observed conformer distribution, as determined by analysis of PMR spectra, is close to that calculated from consideration of non-bonded interactions.

A symmetrical alpha,omega-substituted sexithiophene derivative containing thermally removable branched ester solubilizing groups has been prepared. These oligomers can be solution cast into thin films and then thermolyzed to remove the solubilizing group, leaving short pendant alkene groups on the oligomer. Device testing of thin film transistors shows an increase in hole mobility from 1 x 10-5 cm2/(V s) with on/off ratios of approximately 100 before thermolysis to 5 x 10-2 cm2/(V s) with on/off ratios105 after thermolysis. This method offers an attractive route to easily processed and highly performing thiophene oligomers.

A re-examination of the oxidation of primary amines of the type R·CH 2 NH 2 by silver(II) picolinate reveals that the major product is usually the nitrile RCN, rather than the aldehyde RCHO, as had been reported previously. 4