Copper spectroscopic term

Extensive biochemical and spectroscopic studies have been undertaken on hCP in order to investigate the nature of the copper centers and their role in structure-function relationships. However, the protein is very susceptible to aggregation, proteolysis, loss of copper, and other chemical degradations and requires careful preparation and handling in these circumstances it is difficult to review all the literature objectively and comprehensively. A three-dimensional crystal structure of hCP has been reported at a nominal resolution of 3.1A [7], but this resolution has been extended to just beyond 3.0 A. This chapter will summarize some of the more important biochemical and spectroscopic studies of the protein. It will then focus on the structural results recently obtained by X-ray crystallographic methods and attempt to explain putative functions of the protein in terms of its molecular structure. 

In addition, work by Solomon s group at Stanford University on copper binding active sites has been particularly significant in terms of establishing the power of variable temperature and field studies. The unique spectral and structural features of the copper-protein active sites and their intermediates have been studied in depth based on a wide range of different spectroscopic techniques. This has provided detailed insights into the nature of these sites that... 

The metalloproteins that have attracted most attention are those whose properties are most obviously different from those observed in the normal classical aqueous coordination chemistry of the metal ions. The challenge is to account for (initially) unique spectral or chemical properties in terms of the coordination chemistry of the metalloprotein active site, as moderated by the protein environment. With increasing frequency, as in the case of type 1 copper (Section IIIB), crystallography reveals the active site structure with sufficient clarity to provide strong clues as to the origin of the unusual spectroscopy. However, an important test of the structural and spectroscopic analyses is to reproduce the same effects in a model complex. On other occasions, as with the [4Fe-4S] proteins (Section VC), many questions remained even after the structures were known. In spite of the very impressive achievements of protein crystallography, there remain many metalloproteins for which structural data are either not available or inconclusive. 

In contrast to nucleophilic addition reactions to activated dienes, the mechanism of 1,6-cuprate additions to acceptor-substituted enynes is quite well understood, the main tools being kinetic and NMR spectroscopic investigations. C-NMR spectroscopic studies have revealed that these transformations proceed via jr-complexes with an interaction between the jr-system of the C=C double bond and the nucleophiUc copper atom (a soft-soft interaction in terms of the HSAB principle), as well as a second interaction between the hard lithium ion of the cuprate and the hard carbonyl oxygen atom (Scheme 4) q of C-labeled substrates has confirmed that the cuprate does... 

The elemental nature of the central metal (its atomic number) is its key characteristic, but several of its properties depend also on its oxidation state and on the ensuing electron configuration and spin state. Hence, we see that the two most common oxidation states for copper, Cu(l) and Cu(ll), present complexes with very different properties in terms of their coordination numbers, stereochemical preferences, as well as spectroscopic and magnetic behavior. 

Copper sites in proteins have traditionally been classified into three classes blue type 1 sites (present in the blue copper proteins), normal type 2 sites (tetragonal mononuclear copper sites), and type 3 (spin-coupled pairs of copper ions). The type 1 sites have been further classified as axial or rhombic depending on their EPR (and other spectroscopic) characteristics." Plastocyanin (axial) and nitrite reductase (rhombic) are typical examples of type 1 proteins. Proteins with properties intermediate between those of type 1 and type 2 sites have been termed type 1.5." ... 

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