scholarly journals Electron-nuclear-double-resonance studies of spinach plastocyanin

1983 ◽  
Vol 215 (1) ◽  
pp. 209-212 ◽  
Author(s):  
H Yokoi ◽  
Y Ohba ◽  
T Takabe
Keyword(s):  
Double Resonance ◽  
Electron Nuclear Double Resonance ◽  
Hyperfine Couplings

Electron-nuclear-double-resonance (ENDOR) studies of spinach plastocyanin revealed that 14N-hyperfine couplings from its two co-ordinated imidazole groups are characteristically small in anisotropy and relatively high in ENDOR frequencies and that the two imidazole groups are magnetically equivalent. The relatively strong copper-imidazole co-ordinate bonds of plastocyanin are interpreted to be a result of the coexistence of a strong copper-thiol co-ordinate bond.

scholarly journals Electron nuclear double-resonance (ENDOR) spectroscopy of amine oxidase from pig plasma

1986 ◽  
Vol 237 (2) ◽  
pp. 609-612 ◽  
Author(s):  
G J Baker ◽  
P F Knowles ◽  
K B Pandeya ◽  
J B Rayner
Keyword(s):  
Hyperfine Coupling ◽  
Amine Oxidase ◽  
Double Resonance ◽  
Spectroscopic Studies ◽  
Water Molecules ◽  
Electron Nuclear Double Resonance ◽  
Endor Spectroscopy ◽  
Amino Acid Histidine ◽  
Plasma Amine Oxidase ◽  
Hyperfine Couplings

Electron nuclear double-resonance (‘ENDOR’) spectroscopic studies on pig plasma amine oxidase have been carried out at 15 K. Deuterium-exchange studies show the presence of two sets of exchangeable protons, probably from two water molecules; from the magnitude of their hyperfine couplings, one is assigned to be equatorially, and the other axially, co-ordinated. Only one 14N hyperfine coupling is observed, suggesting that the bonding of all amino acid (histidine) or organic cofactor ligands is similar. Upon addition of azide, a further hyperfine coupling to nitrogen is observed which is smaller than that observed for the native enzyme; the hyperfine couplings to the remaining nitrogens are slightly altered.

scholarly journals Electron Nuclear Double Resonance of the Chlorophyll Triplet State in the Water-Soluble Chlorophyll Protein from Brassica oleracea: Investigation of the Effect of the Binding Site on the Hyperfine Couplings

2020 ◽  
Vol 51 (9-10) ◽  
pp. 925-937
Author(s):  
Alessandro Agostini ◽  
Daniel M. Palm ◽  
Harald Paulsen ◽  
Marilena Di Valentin ◽  
Donatella Carbonera
Keyword(s):  
Triplet State ◽  
Brassica Oleracea ◽  
Double Resonance ◽  
Water Soluble ◽  
Triplet States ◽  
Triplet Energy ◽  
Electron Nuclear Double Resonance ◽  
Light Harvesting Complexes ◽  
Chlorophyll Protein ◽  
Hyperfine Couplings

Abstract An investigation of the photoexcited triplet state of chlorophyll (Chl) a in the water-soluble chlorophyll protein (WSCP) of Brassica oleracea has been carried out by means of electron-nuclear double resonance (ENDOR), achieving a complete assignment of the observed hyperfine couplings corresponding to methine protons and methyl groups of Chl a triplet state. The triplet-state properties, and in particular the hyperfine couplings, were found to be similar to those previously reported for Chl a in the WSCP of Lepidium virginicum. Therefore, the porphyrin ring deformation observed in Brassica oleracea WSCP seems to only slightly affect the spin density of 3Chl a. This may be relevant when considering the robustness of triplet–triplet energy transfer mechanisms, relying on wavefunction overlap, in systems, such as the photosynthetic light-harvesting complexes, in which Chl triplet states with distorted geometries are involved.

scholarly journals Electron Nuclear Double Resonance Differentiates Complementary Roles for Active Site Histidines in (6-4) Photolyase

2006 ◽  
Vol 282 (7) ◽  
pp. 4738-4747 ◽  
Author(s):  
Erik Schleicher ◽  
Kenichi Hitomi ◽  
Christopher W. M. Kay ◽  
Elizabeth D. Getzoff ◽  
Takeshi Todo ◽  
...  
Keyword(s):  
Dna Repair ◽  
Double Resonance ◽  
Point Mutations ◽  
Proton Donor ◽  
Resonance Spectroscopy ◽  
Electron Nuclear Double Resonance ◽  
Paramagnetic Resonance ◽  
Structural Modifications ◽  
Repair Activity ◽  
Hyperfine Couplings

(6-4) photolyase catalyzes the light-dependent repair of UV-damaged DNA containing (6-4) photoproducts. Blue light excitation of the enzyme generates the neutral FAD radical, FADH·, which is believed to be transiently formed during the enzymatic DNA repair. Here (6-4) photolyase has been examined by optical spectroscopy, electron paramagnetic resonance, and pulsed electron nuclear double resonance spectroscopy. Characterization of selected proton hyperfine couplings of FADH·, namely those of H8α and H1′, yields information on the micropolarity at the site where the DNA substrate is expected to bind. Shifts in the hyperfine couplings as a function of structural modifications induced by point mutations and pH changes distinguish the protonation states of two highly conserved histidines, His354 and His358, in Xenopus laevis (6-4) photolyase. These are proposed to catalyze formation of the oxetane intermediate that precedes light-initiated DNA repair. The results show that at pH 9.5, where the enzymatic repair activity is highest, His358 is deprotonated, whereas His354 is protonated. Hence, the latter is likely the proton donor that initiates oxetane formation from the (6-4) photoproduct.

The Microscopic Structure Of Shallow Donors In Silicon Carbide

1996 ◽  
Vol 442 ◽  
Author(s):  
J.-M. Spaeth ◽  
S. Greulich-Weber ◽  
M. März ◽  
E. N. Kalabukhova ◽  
S. N. Lukin
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Double Resonance ◽  
Epr Spectra ◽  
Electron Nuclear Double Resonance ◽  
Paramagnetic Resonance ◽  
Vacancy Pair ◽  
Temperature Spectra ◽  
Electron Paramagnetic

AbstractThe electronic structure of nitrogen donors in 6H-, 4H- and 3C-SiC is investigated by measuring the nitrogen hyperfine (hf) interactions with electron nuclear double resonance (ENDOR) and the temperature dependence of the hf split electron paramagnetic resonance (EPR) spectra. Superhyperfine (shf) interactions with many shells of 13C and 29Si were measured in 6H-SiC. The hf and shf interactions are discussed in the framework of effective mass theory. The temperature dependence is explained with the thermal occupation of the lowest valley-orbit split A1 and E states. It is proposed that the EPR spectra of P donors observed previously in neutron transmuted 6H-SiC at low temperature (<10K) and high temperature (>60K) are all due to substitutional P donors on the two quasi-cubic and hexagonal Si sites, whereby at low temperature the E state is occupied and at high temperature the A1 state. The low temperature spectra are thus thought not to be due to P-vacancy pair defects as proposed previously.

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