Azurins spectra

Visible MCD spectra of plastocyanin, azurin, Rhus vernicifera laccase, ascorbate oxidase and ceruloplasmin are similar on a per copper basis, but show differences from those of stellacyanin and fungal laccase. This is of interest in view of the absence of methionine from the coordination sphere of copper in stellacyanin, and the very high redox potential of fungal laccase.925 

Differences between the spectra of fluorescence and phosphorescence are immediately obvious. For all tryptophans in proteins the phosphorescence spectrum, even at room temperature, is structured, while the fluorescence emission is not. (Even at low temperatures the fluorescence emission spectrum is usually not structured. The notable exceptions include a-amylase and aldolase, 26 protease, azurin 27,28 and ribonuclease 7, staphylococcal endonuclease, elastase, tobacco mosaic virus coat protein, and Drosophila alcohol dehydrogenase 12. ) 

E. A. Burstein, V. A. Permyakov, S. A. Yashin, S. A. Burkhanov, and A. Finazzi Agro, The fine structure of luminescence spectra of azurin, Biochim. Biophys. Acta 491, 155-159 (1977). 

The indole chromophore of tryptophan is the most important tool in studies of intrinsic protein fluorescence. The position of the maximum in the tryptophan fluorescence spectra recorded for proteins varies widely, from 308 nm for azurin to 350-353 nm for peptides lacking an ordered structure and for denatured proteins. (1) This is because of an important property of the fluorescence spectra of tryptophan residues, namely, their high sensitivity to interactions with the environment. Among extrinsic fluorescence probes, aminonaphthalene sulfonates are the most similar to tryptophan in this respect, which accounts for their wide application in protein research.(5) 

In order to understand the charge transfer features of the Blue Copper site, the variable-temperature optical absorption, room-temperature circular dichroism, and magnetic circular dichroism spectra of plastocyanin, stellacyanin, and azurin were studied355. As can be seen for plastocyanin in Fig. 12, the relative intensities (and signs, in the case of CD and MCD) of these transitions vary among the different types of spectra. This is a result of the difference in selection rules for absorption, CD, and MCD spectra, as mentioned in the Introduction. A careful comparison of the three types of spectra and the absorption bandshape temperature dependence (see moment analysis in Ref. 35, pp. 176-177) 

Azoresorcinol, pyridyl-metal complexes dyes, 6, 74 Azurins, 6, 651, 652 copper(II) complexes, 2, 772 5, 721 electron transfer reactions, 6, 653 NMR, 6, 652 Raman spectra, 6, 652 spectra, 6, 652 thioether complexes, 2, 557 Azurite 

The slow electron relaxation rates of copper(II) ions were expected to broaden the NMR lines of nearby nuclei beyond detection, and high-resolution NMR studies on blue Cu(II) sites were considered unfeasible for a long time. However, when the H NMR spectra of oxidized forms from Thi. versutus and azurin from Ps. aeruginosa were recorded for the hrst time, relatively weU-resolved lines could be observed (Kalverda et al., 1996). 

For single-tryptophan proteins there is some correlation between blue-shifted fluorescence emission maximum and phosphorescence lifetime (Table 3.2). Another correlation is that three of the proteins which exhibit phosphorescence, azurin, protease (subtilisin Carlsberg), and ribonuclease Tlt are reported to show resolved fluorescence emission at 77 K. Both blue-shifted emission spectra and resolved spectra are characteristic of indole in a hydrocarbon-like matrix. 

Coherent Raman detected EPR spectroscopy is a new experimental method which combines optical and EPR transitions. It was applied for the first time to a bioinolecule, azurin. The information obtained allows to test electronic and structural models of the Cu site to be probed.23 In a subsequent report the same group of authors has applied microwave modulated circular dichroism to unravel individual resonance lines in overlapping spectra and to assign them to specific electronic transitions.24 

Blue copper proteins, 36 323, 377-378, see also Azurin Plastocyanin active site protonations, 36 396-398 charge, 36 398-401 classification, 36 378-379 comparison with rubredoxin, 36 404 coordinated amino acid spacing, 36 399 cucumber basic protein, 36 390 electron transfer routes, 36 403-404 electron transport, 36 378 EXAFS studies, 36 390-391 functional role, 36 382-383 occurrence, 36 379-382 properties, 36 380 pseudoazurin, 36 389-390 reduction potentials, 36 393-396 self-exchange rate constants, 36 401-403 UV-VIS spectra, 36 391-393 Blue species 

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