EPR spectral simulation on cluster N-1b in NADH-ubiquinone oxidoreductase of bovine heart mitochondria

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24226/1/0000486.pd

Application of fast Fourier transforms to EPR spectra of free radicals in solution

A method of reducing EPR spectra of free radicals in solution is presented in detail. This method is based on the use of the fast Fourier transform algorithm and curve fitting in the Fourier space by weighted least-squares minimization. Comparison with previous work is shown for EPR spectra of methyl viologen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23183/1/0000110.pd

A novel S = 3/2 EPR signal associated with native Fe-proteins of nitrogenase

In addition to their g = 1.94 EPR signal, nitrogenase Fe-proteins from Azotobacter vinelandii, Azotobacter chroococcum and Klebsiella pneumoniae exhibit a weak EPR signal with g [congruent with]5. Temperature dependence of the signal was consistent with an S = 3/2 system with negative zero-field splitting, d = -5 +/- 0.7 cm-1. The ms, = +/- 3/2 ground state doublet gives rise to a transition with geff = 5.90 and the transition within the excited ms = +/- 1/2 doublet has a split geff = 4.8, 3.4. Quantitation gave 0.6 to 0.8 spin mol-1 which summed with the spin intensity of the S = 1/2 G = 1.94 line to roughly 1 spin/mol. MgATP and MgADP decreased the intensity of the s = 3/2 signal with no concomitant changes in intensity of the s = 1/2 signal.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25566/1/0000108.pd

EPR of a novel high-spin component in activated hydrogenase from Desulfovibrio vulgaris (Hildenborough)

The EPR of reoxidized hydrogenase from Desulfovibrio vulgaris (H.) has been reinvestigated. In contrast to other workers [(1984) Proc. Natl. Acad. Sci. USA 81, 3728-3732] we find the axial signal with g = 2.06; 2.01 to be only a minor component of concentration 0.03 spin/mol. In the spectrum of fully active reoxidized enzyme this signal is overshadowed by a rhombic signal (0.1 spin/mol) with g = 2.11; 2.05; 2.00 reminiscent of the only signal found for other oxidized bidirectional hydrogenases. In addition, a novel signal has been detected with geff = 5.0 which, under the assumptions that S = 2 and |[Delta]ms|= 2, quantitates to roughly one spin/mol. Ethylene glycol affects the relative intensity of the different signals. It is suggested that O2 sensitization parallels a spin-state transition of an iron-sulfur cluster.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26169/1/0000246.pd

On the prosthetic group(s) of component II from nitrogenase : EPR of the Fe-protein from Azotobacter vinelandii

The EPR spectrum of the reduced Fe-protein from nitrogenase has been reinvestigated. The dependences on temperature, microwave power, and microwave frequency all suggest that the observed signal represents a magnetically isolated [4Fe-4S]1+(2+;1+) cluster. Also, the signal can be simulated assuming a simple, gstrained S = system. However, the integrated intensity amounts to no more than 0.2 spins per protein molecule. It is, therefore, impossible that Fe-protein preparations contain a single type of [4Fe-4S] cluster.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25617/1/0000165.pd