Copper hyperfine spectrum

This elongated C v effective symmetry of the blue copper site raises a significant problem with respect to the present interpretations (17-18) of the small copper hyperfine splitting observed in the EPR spectrum shown in Figure 1. The small splitting had been attributed to a mixing of Cu 4pz into the dx2 2 ground state... 

G) and different relative heights and shapes of the low field quartet of copper hyperfine lines l. A simulation of the experimental spectrum has been obtained by a superposition of spectra generated with spin Hamiltonian parameters calculated over a Gaussian distribution around an out-of-planarity angle rj of about 16° (corresponding to Ad 19°) ). 

The ESR spectrum for cupric ion bound to four equivalent imidazoles from carnosine ()8-alanyl-L-histidine dipeptide) in frozen solution shows the quality of information that can typically be obtained [233] (Fig. 15, top spectrum). The intense line on the right split by at least nine hyperfine lines is the gj feature resolved due to hyperfine splitting to copper and to nitrogen donor atoms. Three of the four copper hyperfine lines in the gy (2.25) region (left side) are observable with y4 [ = 175 G. The remaining ESR parameters can be estimated and confirmed by computer simulation. These values for carnosine aregy = 2.06, Af = 15 G and /4 = 15 G. For comparison, data for cupric ion bound to hemoglobin at the N-terminus are gy = 2.210, = 2.050,... 

Figure 2 X-band (9.107 GHz) CW spectrum of a powdered sample of Ni(dtc)2 doped 1 500 with Cu(dtc)2 obtained at 150K with 1,0 mW microwave power and LOG modulation amplitude and displayed as the traditional first derivative (a). Computer integration of the spectrum in A gives the absorption spectrum (b). The turning points in the powder pattern that correspond to the four copper hyperfine lines for molecules aligned with the magnetic field along the magnetic z-axis or in the perpendicular plane are marked...

Figure 11. ESEEM spectra of the oxidized form of the Type I copper piotein msticyanin, which has the classic His2CysMet Cu(II) binding motif. These are exact cancellation-like spectra that are obtained at spectrometer operating frequencies from 7.0 to 13 GHz. The peaks are mobile, as predicted by the nuclear Zeeman dependence. The upper spectrum is derived from an engineered form of the protein in which one of the two ligand histidines is removed the spectrum is characteristic of a single hyperfine spectrum. The lower spectrum corresponds to the modulation spectrum of two nearly equivalent N interactions and features the sum/harmonic lines in the 2-3 MHz region.

CUCI2 starting salts respectively. The difference between the spin Hamiltonian parameters for the two complexes was accounted for by the presence of the counterion in the coordination sphere of the Cu(BOX) complex, as proven by the observation of couplings in the ENDOR spectrum. The resolved copper hyperfine couplings were further split due to super-hyperfine interaction with two equivalent n nuclei. 

Copper porphyrin is one of the best-characterized of the metalloporphyrins, and its electron spin resonance (ESR) spectrum has been known for a quarter of a century.(17) More recently, electron nuclear double resonance (ENDOR) investigations have provided the complete hyperfine tensors for the metal, the nitrogens and the pyrrole protons.(18) We have used this detailed knowledge earlier(, ) to assess the quality of scattered-wave calculations. 

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