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Coordination of deprotonated-peptide nitrogens greatly affects the binding and kinetic reactivity of Cu(II) and the ease of oxidation to Cu(III). Substitution reactions of oligopeptide and serum albumin complexes of Cu(II) are charac terized by three reaction pathways-(1) proton transfer to the peptide group, (2) nucleophilic attack on copper, and (3) a combination of proton transfer and nucleophilic attack. Depending upon the nature of the coordinated ligands, the electrode potentials of Cu(III)-Cu(II) couples vary from 0.5 to 1.0 V (vs. NHE). Copper(III)-peptide complexes are characterized in solution in terms of their electrochemical, spectral, and kinetic properties. At high pH amine groups coordinated to Cu(III) also will deprotonate. T^he binding of Cu(II) to the backbone of polypeptides by coordination J~ to deprotonated-peptide nitrogens has been known for some time (1-7), but only recently has it been discovered that this coordination facilitates the formation of Cu(III) (8, 9). This chapter concerns recent studies of Cu( II) -peptide complexes, in particular those reported since a general review of this topic by Margerum and Dukes (10), and summarizes the present knowledge of Cu(III)-peptide complexes.The presence of L-histidine as the third amino acid residue in tripeptide complexes of Cu(II) drastically decreases their susceptibility to both nucleophilic attack and acid attack (11, 12). Thus, the doubly deprotonated complex of glycylglycyl-L-histidine (Cu(H.2gly-gly-his)"shown in Structure I is relatively slow to react with the nucleophilic triethylenetetramine (trien) since this reaction is seven orders of magnitude slower than the corresponding reaction with Cu(H.2gly-gly-gly)'. The 281 Downloaded by MONASH UNIV on December 4, 2014 |

shift is the highest so far known for a neutral organic suggests a similar explanation for nitrogen resonance as compound. The general correspondence with the well. Whether this is correct or not, the I5N shifts cyclopropane carbon shift, which has been interpreted in correspond to the substantial diamagnetic shieldings terms of ring current induced diamagnetic hi el ding,^" observed for the 3C resonances of aziridine.Abstract : Triphenylsilane, tribenzylsilane, and tributylsilane are methanolyzed to hydrogen and the methoxysilanes in a specific methoxide catalyzed reaction ( p > 0.8 for triphenylsilane, > 0.5 for tribenzylsilane, > 0.7 for tributylsilane in phenol-phenoxide buffers). Deuterated silanes react more slowly by factors