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1. The curved plots of 1/v against 1/[S] obtained when caeruloplasmin oxidizes NN-dimethyl-p-phenylenediamine were investigated. The first free-radical oxidation product of caeruloplasmin oxidation of NN-dimethyl-p-phenylenediamine is required for curvature, as straight-line plots were obtained when activities were measured either before appreciable free-radical product had appeared or in the presence of ascorbate, which reduced it back to NN-dimethyl-p-phenylenediamine. 2. In the presence of ascorbate linear reciprocal-plots were obtained with all of the 37 substrates tested. V(max.) values varied over only an eightfold range and those for the 20 p-amino compounds over only a twofold range. K(m) values, however, varied over a 10(4)-fold range. The small range of V(max.) values indicates that the rate-limiting step in caeruloplasmin action is relatively independent of the nature of the substrate. K(m) values suggest that substrates bind primarily by ring electrons, although certain side-chain groups increased the K(m) in a manner unrelated to likely changes of ring-electron densities. A mechanism involving repulsion between negative charges on the substrate and the enzyme was supported by the variation of the K(m) of 5-hydroxyindol-3-ylacetic acid with pH.

Publication costs assisted by the Petroleum Research Fund Volume changes of mixing for an 8.4 mol % solution of m-xylene in , '-di-n-heptyloxyazoxybenzene (PHAB) are 0.1-0.3 cm3 mol"1 larger than for an 8.8 mol % solution of p-xylene in PHAB over the range of temperatures 75-130 °C. For solutions in the smectic and nematic mesophases the volume changes are positive; the volume change for the isotropic liquid changes from positive to negative with increasing temperature. The temperature ranges for the various phases of the solutions are reported; coexisting smectic and nematic phases and coexisting nematic and isotropic phases were observed.

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