Resonance Raman spectroscopy centers

It will be shown that, upon interaction with water or ammonia, the T -like symmetry of the Ti(IV) centers in TS-1 is strongly distorted, as testified by UV-Vis, XANES, resonant Raman spectroscopies [45,48,52,58,64,83,84], and by ab initio calculations [52,64,74-76,88]. As in Sect. 3 for the dehydrated catalyst, the discussion follows the different techniques used to investigate the interaction. 

A variety of physical methods has been used to ascertain whether or not surface ruthenation alters the structure of a protein. UV-vis, CD, EPR, and resonance Raman spectroscopies have demonstrated that myoglobin [14, 18], cytochrome c [5, 16, 19, 21], and azurin [13] are not perturbed structurally by the attachment of a ruthenium complex to a surface histidine. The reduction potential of the metal redox center of a protein and its temperature dependence are indicators of protein structure as well. Cyclic voltammetry [5, 13], differential pulse polarography [14,21], and spectroelectrochemistry [12,14,22] are commonly used for the determination of the ruthenium and protein redox center potentials in modified proteins. 

A. Damin, F. Bonino, S. Bordiga, E. Groppo, C. Lamberti and A. Zecchina, Vibrational properties of Cr centers on reduced Phillips catalysts highlighted by resonant Raman spectroscopy, ChemPhysChem, 1, 342-344... 

The use of an Intense laser light source with biological materials Is accompanied by the concomitant problems of localized sample heating and the possibility of protein denaturetlon. A further complication Introduced by resonance Raman spectroscopy Is the Increased potential for photochemical destruction of chromo-phorlc metal centers as a result of the absorption of large amounts of Incident radiation. Both of these situations may be ameliorated by freezing samples to liquid nitrogen temperature ( 90 K), while the even lower temperatures made possible with a closed-cycle... 

Photoinduced ligation changes, nickel porphyrins, resonance Raman spectroscopy transient, 266-277 Photoinduced reversible conversion of centers, porphyrins with nonsymmetrical substitution, 83-84,85f Photooxidation,... 

The [Fe(terpy)2] cation is low-spin, as demonstrated by Mossbauer, electronic, H NMR, and resonance Raman spectroscopy and magnetic measurements (20,184,187, 228, 266). Similarly, spectroscopic studies of the iron(III) cation have indicated a low-spin ( B) ground term (382). There have been numerous electrochemical studies of the bis complexes (177, 200, 256, 298, 332, 344, 373, 378, 379, 397, 398). Ligand-centered reductions to formal oxidation states of iron(I), iron(O), and iron( — 1) and oxidations to iron(III) are observed. The complex [Fe(terpy)L][C104]2 [L = tris(2 -pyridyl)l,3,5-triazine (Fig. 15)] has been prepared (399, 442). 

Bacterial reaction centers have also been studied extensively by resonance Raman spectroscopy. Fig. 4.7-4 (for a review, see Robert, 1990 Mattioli et al., 1991a). 

Transition-metal containing zeolites such as CoY and NiY (but not the Cu, Mn and Zn forms) polymerize acetylene to give trans-polyacetylene with relatively short conjugation length, as indicated by resonance Raman spectroscopy.70 The pol3nmerization products appeared to be restricted to the zeolite crystal surfaces. The authors also point to die importance of Lewis acidic centers for the polymerization. 

H Fujiwara, H Hayashi, M Tasumi, M Kanji, YKoyamaand (Ki) Satoh (1987) Structural studies on a photosystem II reaction center complex consisting ofD-1 and D-2 polypeptides and cytochrome b-559 by resonance Raman spectroscopy and high-performance liquid chromatography. Chem Lett 10 2005-2008 GE Bialek-Bylka, T Tomo, (Ki) Satoh and Y Koyama (1995) 15-cis-carotene found in the reaction center of spinach photosystem II. FEES Lett 363 137-140... 

The first common step in AdoCbl-dependent readions is homolytic cleavage of the cobalt-carbon bond to generate a radical pair, cob(ii)alamin and the carbon-centered dAdo radical (Scheme 19.3). This reaction experiences a 10 -fold rate enhancement in B12 enzymes [14, 15] in the presence of substrate, and the mechanism for this rate acceleration has been the subject of extensive scrutiny. Thus, in methylmalonyl-CoA mutase and in glutamate mutase, little if any destabilization of the cobalt-carbon bond is observed in the reactant state, as revealed by resonance Raman spectroscopy [16, 17], and the intrinsic substrate binding is utilized to labilize the bond. In contrast, approximately half of the destabilization of the cobalt-carbon bond in diol dehydratase is expressed in the reactant state. This re-... 

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