Subject mixed-metal clusters

The electrochemical behavior of heterometallic clusters has been reviewed clsewbcre."" The interest in examining clusters stems from their potential to act as "electron sinks " in principle, an aggregate of several metal atoms may be capable of multiple redox state changes. The incorporation of heterometals provides the opportunity to tune the electrochemical response, effects which should be maximized in very mixed"-metal clusters. Few very mixed -metal clusters have been subjected to detailed electrochemical studies the majority of reports deal with cyclic voltammetry only. Table XII contains a summary of electrochemical investigations of "very mixed"-metal clusters. 

As discussed above, luminescent protein protected clusters exist in solution with zero valent oxidation state of the metal (for example, Au° state for Au clusters). Cluster forms via the metal bound protein complex (Au" -Protein adduct for Au cluster formation) where metal is in its intermediate oxidation state.In this section we will discuss a new class of materials which were observed recently by Baksi et They have observed that when Au -Lyz adducts were subjected to laser ablation, some bare clusters were formed in the gas phase. When Au was mixed with Lyz, Au was uptaken by the protein and a corresponding change is seen in the mass spectrum in the form of appearance of multiple peaks separated by mIz 197 due to Au attachments (Lyz peak appears at mIz 14 300). Maximum 10 Au attachments were observed in the MALDI MS which was justified in terms of limited (eight cysteines forming 4 disulfide bonds) cysteine content. In the lower mass region (<10 kDa), multiple envelopes... 

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