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J A Fee

Publications and source records attributed to J A Fee.

120 records · Page 7Linked to original sources
PubMed1971

Tetrahedral iron in the active center of plant ferredoxins and beef adrenodoxin.

The coordination structure of the iron-sulfur complex in spinach ferredoxin and adrenodoxin is investigated by optical spectroscopy. The circular-dichroism and absorption spectra of these two-iron iron-sulfur proteins reveal weak electronic transitions in the near-infrared wavelength range, 0.8-2.5 mum (12,500-4000 cm(-1)). On the basis of the low absorption intensities and large anisotropy factors, d --> d transitions of the iron can be identified in the reduced proteins at about 4000 cm(-1) and 6000 cm(-1). The low energy of these one-center ligand-field transitions, together with the similarity to the ligand-field spectrum of the one-iron protein rubredoxin, leads to the conclusion that the reduced two-iron iron-sulfur proteins also contain a high-spin ferrous ion in a distorted tetrahedral site.

Adrenal Glands↗
PubMedDate not supplied

Potentiometric study of cytochrome c1aa3 from Thermus thermophilus.

We have examined the redox behavior of the cytochrome c1aa3 complex from Thermus thermophilus. In potentiometric titrations the cytochrome c behaves as an independent center having n = 1 and E = 205 mV (NHE). Under the assumption that the individual centers equilibrate independently in this experiment, changes in the absorption band at 603 nm have been resolved into two components: cytochrome a (n = 1, Em = 270 mV, 60% spectral contribution) and cytochrome a3 (n = 2, Em = 360 mV, 40% spectral contribution). The n = 2 process was attributed to strong chemical coupling between cytochrome a3 and CuB. The enzyme was also titrated with a mixture of NADH and PMS, and the results are shown not to conform to a model of intramolecular equilibrium according to the equilibrium constants obtained from the potentiometric titration. It is suggested that a conformational equilibrium within the complex may control electron transfer between cytochromes a and a3.

Electrochemistry↗