Pulsed and continuous wave electron nuclear double resonance patterns of aquo protons coordinated in frozen solution to high spin MN2+

1993 ◽  
Vol 98 (7) ◽  
pp. 5147-5157 ◽  
Author(s):  
Xiaoling Tan ◽  
Marcelino Bernardo ◽  
Hans Thomann ◽  
Charles P. Scholes
Keyword(s):  
High Spin ◽  
Continuous Wave ◽  
Double Resonance ◽  
Electron Nuclear Double Resonance ◽  
Frozen Solution

Solvent effects of cobalt(II) phthalocyanine in sulfuric acid: a continuous wave and pulse EPR study

2003 ◽  
Vol 07 (02) ◽  
pp. 89-96 ◽  
Author(s):  
Cinzia Finazzo ◽  
Sabine Van Doorslaer ◽  
Arthur Schweiger
Keyword(s):  
Sulfuric Acid ◽  
Continuous Wave ◽  
Hyperfine Interactions ◽  
Double Resonance ◽  
Resonance Spectroscopy ◽  
Electron Nuclear Double Resonance ◽  
Paramagnetic Resonance ◽  
Metal Phthalocyanines ◽  
The Matrix ◽  
Detailed Assessment

Products based on metal phthalocyanines are widely used in industry. In the processing of these materials it is essential to control the conditions of the matrix the metal phthalocyanines are embedded in. Using the example of cobalt(II) phthalocyanine in sulfuric acid we show that continuous wave and pulse electron paramagnetic resonance and electron nuclear double resonance spectroscopy provide excellent tools to monitor the influence of the matrix on paramagnetic phthalocyanines. The g values, the cobalt hyperfine values, and the hyperfine and nuclear quadrupole couplings of the isoindole nitrogens, as well as the hyperfine interactions of the surrounding protons allow for a detailed assessment of the electronic structure of cobalt(II) phthalocyanine in sulfuric acid. Subtle differences between the system under study and related Co ( II ) porphyrin and corrin systems could be traced.

A continuous-wave electron–nuclear double resonance (X-band) study of the Cu2+ sites of particulate methane mono-oxygenase of Methylococcus capsulatus (strain M) in membrane and pure dopamine β-mono-oxygenase of the adrenal medulla

2002 ◽  
Vol 363 (3) ◽  
pp. 677-686
Author(s):  
Bettina KATTERLE ◽  
Rudolf I. GVOZDEV ◽  
Ntei ABUDU ◽  
Torbjørn LJONES ◽  
K. Kristoffer ANDERSSON
Keyword(s):  
Continuous Wave ◽  
Dipolar Coupling ◽  
Double Resonance ◽  
Coupling Constants ◽  
Methylococcus Capsulatus ◽  
Electron Nuclear Double Resonance ◽  
Strongly Coupled ◽  
Copper Site ◽  
Typical Type

All methanotrophic bacteria express a membrane-bound (particulate) methane mono-oxygenase (pMMO). In the present study, we have investigated pMMO in membrane fragments from Methylococcus capsulatus (strain M). pMMO contains a typical type-2 Cu2+ centre with the following EPR parameters: gz 2.24, gx,y 2.06, ACuz 19.0mT and ACux,y 1.0mT. Simulation of the Cu2+ spectrum yielded a best match by using four equivalent nitrogens (AN = 1.5mT, 42MHz). Incubation with ferricyanide neither changed nor increased the amount of EPR-active Cu2+, in contrast with other reports. The EPR visible copper seems not to be part of any cluster, as judged from the microwave power saturation behaviour. Continuous-wave electron—nuclear double resonance (CW ENDOR; 9.4GHz, 5–20K) experiments at g⊥ of the Cu(II) spectrum show a weak coupling to protons with an AH of 2.9MHz that corresponds to a distance of 3.8Å (1Å≡0.1nm), assuming that it is a purely dipolar coupling. Incubation in 2H2O leads to a significant decrease in these 1H-ENDOR intensities, showing that these protons are exchangeable. This result strongly suggests that the EPR visible copper site of pMMO is accessible to solvent, which was confirmed by the chelation of the Cu2+ by diethyldithiocarbamic acid. The 1H and 14N hyperfine coupling constants confirm a histidine ligation of the EPR visible copper site in pMMO. The hyperfine structure in the ENDOR or EPR spectra of pMMO is not influenced by the inhibitors azide, cyanide or ammonia, indicating that they do not bind to the EPR visible copper. We compared pMMO with the type-2 Cu2+ enzyme, dopamine β-mono-oxygenase (DβM). For DβM, it is assumed that the copper site is solvent-accessible. CW ENDOR shows similar weakly coupled and 2H2O-exchangeable protons (2.9MHz), as observed in pMMO, as well as the strongly coupled nitrogens (40MHz) from the co-ordinating N of the histidines in DβM. In conclusion, the resting EPR visible Cu in pMMO is not part of a trinuclear cluster, as has been suggested previously.

Photochemical processes in photosynthesis studied by advanced electron paramagnetic resonance techniques

2003 ◽  
Vol 75 (8) ◽  
pp. 1021-1030 ◽  
Author(s):  
Wolfgang Lubitz
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Continuous Wave ◽  
Double Resonance ◽  
Triplet States ◽  
Photosynthetic Reaction Centers ◽  
Electron Nuclear Double Resonance ◽  
Paramagnetic Resonance ◽  
Time Resolved ◽  
Endor Spectroscopy ◽  
Electron Paramagnetic

Various continuous-wave and pulse electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) experiments performed on the radical species occurring in photosynthetic reaction centers of plants and bacteria during light-induced charge separation are reviewed here. Emphasis is placed on time-resolved experiments performed on short-lived intermediate states such as radical pairs and triplet states for which also hyperfine information can be obtained from pulse ENDOR spectroscopy. Detailed insight into the electronic structure of these intermediates and their interaction with the protein environment is now becoming available.

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