The method of measuring k35/k31 for the alkoxide-promoted deprotiochlorination and dedeuteriochlorination reactions has been applied to C6H5C,H(CH3)CH2C1 (I-Cl), C6H5C'HC1CH2C1 (V), and C6H5C'HC1CF2C1 (III). For reactions occurring with ethanolic sodium ethoxide the following values for k3S/k31 have been measured: I-Cl-A, 1.005 90 + 0.000 13, and I-Cl-d, 1.

Kinetic constants were determined for nitrate uptake in three species, Pterocladiella capillacea (S.G. Gmelin) Santelices et Hommersand (Rhodophyceae, Gelidiales), Ulva intestinalis L. (Chlorophyceae, Ulvales) and Xiphophora chondrophylla (Turner) Montagne ex Harvey (Phaeophyceae, Fucales), of New Zealand macroalgae, with K m values ranging from 10 to 17 lM and V max values from 3 to 65 lmole g -1 dry weight h -1 . There was no effect of ammonium on nitrate uptake by Pterocladiella capillacea or Xiphophora chondrophylla. Ammonium inhibited nitrate uptake by 40% in Ulva intestinalis from a site with relatively low seawater ammonium concentrations. In contrast, U. intestinalis from an ammonium-enriched site had lower rates of nitrate uptake that were insensitive to inhibition by ammonium. It is suggested that there are (at least) two transport systems for nitrate in U. intestinalis; a constitutive transporter, which is insensitive to ammonium, and a transporter that is sensitive to ammonium inhibition and downregulation by ammonium; the implications of this for our understanding of macroalgal blooms is discussed.

Synthesis and Low-frequency Vibrational Spectra of Some Bis(a1kanethiolato)-and Bis( benzenethiolat0)-aurate( I) Complexes

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