Multiple-iron-site

Moura I, Tavares P, Ravi N. 1994. Characterization of three proteins containing multiple iron sites rubreiythrin, desulfoferrodoxin, and a protein containing a 6-iron cluster. 

Multiple iron site proposal illustrating essential features of the lowest energy path forwarded by Ahlrichs and Coucouvanis. 

Synthetic Efforts to Model N2 Reduction by Multiple Iron Sites... 

It has been suggested [21,22] that the presence of Cu and K increases the rates and extent of Fe304 carburization during reaction and the FTS rates, by providing multiple nucleation sites that lead to the ultimate formation of smaller carbide crystallites with higher active surface area. In the present investigation, Cu- and K-promoted iron catalysts performed better than the unpromoted catalysts in terms of (1) a lower CH4 selectivity, (2) higher C5+ and alkene product selectivi-ties, and (3) an enhanced isomerization rate of 1-alkene. 

Metal storage proteins also form a variety of nitrosyl complexes. Metallothi-onein has been shown to form a low-spin complex with Fe and NO (Kennedy et al., 1993). Ferritin contains multiple iron binding sites capable of forming spectroscopically distinguishable nitrosyl complexes (Lee et al., 1994 LeBrun et al., 1993). 

Finally, in proteins with multiple binding sites e.g. transferrin), or in complex protein assemblies with multiple subunits e.g. hemoglobin) there is an opportunity for allosteric interactions between redox-active iron sites. These allosteric interactions are readily probed by the spectroelectrochemical technique, as illustrated in Sections 2.3.2.2 and 2.4.2.3. 

In this chapter we describe the spectroelectrochemical technique as it applies to nonheme and heme iron proteins containing single or multiple iron-binding sites, and as single protein or multiple subunit assemblies. In this discussion, we will address the influence of the following on the spectroelectrochemical... 

Iron-Protein Interface Formation of the iron core appears to be initiated at an Fe-protein interface where Fe(ll)-0-Fe(III) dimers and small clusters of Fe(IIl) atoms have been detected attached to the protein and bridged to each other by oxo/hydroxo bridges. Evidence for multiple nucleation sites has been obtained... 

As defined in this review, complex flavoproteins catalyze more than one type of reaction used to classify enzymes. Some of these enzymes use a single active site to catalyze different chemical conversions, whereas some contain multiple active sites and other prosthetic groups, such as iron-sulfur clusters. In any case, the study of these enzymes is often more complicated than the simple examples discussed earlier. 

On this basis, ruthenium and iron complexes 151-153 with multiple polymerization sites (2,4, and 6) have been synthesized and readily electropolymerized. The electrochemical behavior of the resulting metal-containing polymers displays the typical signature of both the rr-conjugated PT backbone and the immobilized metal complex. 

Clusters with multiple metal sites Simple iron-sulfur clusters... 

Annexin V-functionalized crosslinked iron oxide (CLIO) was designed as a contrast agent for MRI, which was additionally labeled with Cy5.5 to allow colocalization with optical imaging techniques [98]. Alternatively, conjugation of multiple Gd-DTPA molecules or SPIO particles to the C2 domain of synaptotagmin I was shown to allow the detection of apoptotic cells in vitro [99]. Zhao et al. [100] were the first to apply a C2 domain-functionalized SPIO and showed very promising results for future in vivo applications of MR contrast agents for the detection of apoptotic sites. 

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