chemia - Studia

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COMPUTATION INFORMED SELECTION OF PARAMETERS FOR PROTEIN RADICAL EPR … distances studied is ~1.7% (Figure 5, A) whereas the increase of the average A-value for β2 proton is about 8% (Figure 7, A). This fact highlights once again the conclusion [38] that McConnell relationship is approximate and that the coefficients B’ and B’’ in it are not particularly constant when the relationship is applied to different cases. The A-value dependences on shortening of the H-bond in Trp radical are not as clear monotonous curves as in the Tyr case, likely because the Ρ C3 is decreasing in Trp radical, in contrast to Ρ C1 in Tyr radical (Figure 5). CONCLUSIONS A full analysis of the EPR parameters of the 144 structures of Tyr and Trp radicals is under way and will be published elsewhere. The principal g-factor values and hyperfine interaction constants for H and N atoms will be reported for an array of ring orientations and hydrogen bond strengths (12 rotation angles x 6 H-bond distances), for each radical. This two dimensional array of data points for each EPR parameter will create a basis of analytical formulation of a continuous surface that could be used to find the parameter for any combination of rotation angle and H-bond strength. Derivation of such functions should lead to a new method of assigning of an experimental EPR spectrum of a Tyr or Trp radical to a specific Tyr or Trp site on the protein, with a high degree of confidence. EXPERIMENTAL SECTION A technical background describing relationship between empirical (simulation derived) radical parameters and those calculated by the computational chemistry methods from the crystal structure of the radicals is given elsewhere [38]. The structures as shown in Figure 1 but with variable angle of the rings rotation and with variable distance towards the water molecules were analysed. The Gaussian03 software package [41] was used for both the optimisations of the structures and the calculation of the EPR parameters, both at the B3LYP/6-31G* level of theory. During the optimization, the atom coordinates that define the rings rotation angles and the distances to the water molecule were kept frozen. Single point calculations were then performed for finding g-factor values, spin densities and hyperfine interaction constants. ACKNOWLEDGMENTS DAS acknowledges a COST Action P15 travel grant to visit the University of Siena. CB, AS and RB acknowledge the CINECA 2011 Award HP10C9HMGL, for high performance computing resources and support. 143
DIMITRI A. SVISTUNENKO, MARY ADELUSI, MARCUS DAWSON, PAUL ROBINSON, ET ALL A Figure 7. Hyperfine interaction constants for the β (methylene) protons in Tyr (A) and Trp (B) radicals. Dependences on the hydrogen bond length are presented for the case of the phenoxyl (in Tyr) and indole (in Trp) rings rotation angle of 60°. As in Figure 6, three principal components of the hyperfine interaction tensors are presented; the nomenclature of the β1 and β2 protons in each case is as given in Figure 6 caption. B REFERENCES 1. M. Sahlin; A. Gräslund; A. Ehrenberg, B.-M. Sjöberg, Journal of Biological Chemistry, 1982, 257, 366-369. 2. P. Reichard, A. Ehrenberg, Science, 1983, 221, 514-519. 3. P. Allard; A. L. Barra; K. K. Andersson; P. P. Schmidt; M. Atta, A. Gräslund, Journal of The American Chemical Society, 1996, 118, 895-896. 4. L. C. Hsi; C. W. Hoganson; G. T. Babcock, W. L. Smith, Biochemical and Biophysical Research Communications, 1994, 202, 1592-1598. 5. P. Dorlet; S. A. Seibold; G. T. Babcock; G. J. Gerfen; W. L. Smith; A. L. Tsai, S. Un, Biochemistry, 2002, 41, 6107-6114. 144
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CHEMIA 3/2011
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CORINA COSTESCU, LAURA CORPAŞ, NIC
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Studia Universitatis Babes-Bolyai C
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MONICA BAIA, MONICA SCARISOREANU, I
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STUDIA UBB CHEMIA, LVI, 3, 2011 (p.
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PREPARATION, CHARACTERIZATION AND S
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SPECTROSCOPIC EVIDENCE OF COLLAGEN
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CORNEL-VIOREL POP, TRAIAN ŞTEFAN,
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VITALY ERUKHIMOVITCH, IGOR MUKMANOV
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DUMITRU GEORGESCU, ZSOLT PAP, MONIC
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MAHDIEH AZARI, ALI IRANMANESH DEFIN
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MAHDIEH AZARI, ALI IRANMANESH V ( G
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MAHDIEH AZARI, ALI IRANMANESH Now,
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MAHDIEH AZARI, ALI IRANMANESH Let T
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MAHDIEH AZARI, ALI IRANMANESH Let G
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MAHDIEH AZARI, ALI IRANMANESH ACKNO
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CRISTINA GRUIAN, HEINZ-JÜRGEN STEI
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CYCLODEXTRINS AND SMALL UNILAMELLAR
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CYCLODEXTRINS AND SMALL UNILAMELLAR
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PROTEIN ADHESION TO BIOACTIVE MICRO
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ROZALIA VERES, CONSTANTIN CIUCE, VI
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EVALUATION OF FREE RADICAL CONCENTR
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EVALUATION OF FREE RADICAL CONCENTR
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ECCENTRIC CONNECTIVITY INDEX OF TOR
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ECCENTRIC CONNECTIVITY INDEX OF TOR
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DORINA GIRBOVAN, MARIUS AUREL BODEA
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YONG WANG, TAMARIA G. DEWDNEY, ZHIG
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ALEXANDRU LUPAN, CSONGOR MATYAS, AU
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EMILIA VANEA, SIMONA CAVALU, FLORIN
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ANDRA TĂMAŞ, MARTIN VINCZE The ma
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ANDRA TĂMAŞ, MARTIN VINCZE From t
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ANDRA TĂMAŞ, MARTIN VINCZE 2%B +
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ANDRA TĂMAŞ, MARTIN VINCZE increa
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EFFECT OF CATALYST LAYER THICKNESS
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SPECTRAL INVESTIGATIONS AND DFT STU
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TOPOLOGICAL SYMMETRY OF TWO FAMILIE
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TOPOLOGICAL SYMMETRY OF TWO FAMILIE
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NEW 1-AZABICYCLO[3.2.2]NONANE DERIV
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