Showing papers by "James E. Penner-Hahn published in 1985"

[4Fe-4S]-cluster-depleted Azotobacter vinelandii ferredoxin I: a new 3Fe iron-sulfur protein.

Abstract: Fe(CN)6(-3) oxidation of the aerobically isolated 7Fe Azotobacter vinelandii ferredoxin I, (7Fe)FdI, is a degradative reaction. Destruction of the [4Fe-4S] cluster occurs first, followed by destruction of the [3Fe-3S] cluster. At a Fe(CN)6(-3)/(7Fe)FdI concentration ratio of 20, the product is a mixture of apoprotein and protein containing only a [3Fe-3S] cluster, (3Fe)FdI. This protein mixture, after partial purification, has been characterized by absorption, CD, magnetic CD, and EPR and Fe x-ray absorption spectroscopies. EPR and magnetic CD spectra provide strong evidence that the [3Fe-3S] cluster in (3Fe)FdI is essentially identical in structure to that in (7Fe)FdI. Analysis of the extended x-ray absorption fine structure (EXAFS) of (3Fe)FdI finds Fe scattering at an average Fe...Fe distance of approximately equal to 2.7 A. The structure of the oxidized [3Fe-3S] cluster in solutions of oxidized (3Fe)FdI, and, by extension, of oxidized (7Fe)FdI, is thus different from that obtained by x-ray crystallography on oxidized (7Fe)FdI. Possible interpretations of this result are discussed.

Exafs and Near Edge Structure III: Proceedings of an International Conference Stanford, Ca, July 16-20, 1984

Abstract: This volume contains the Proceedings of the Third International EXAFS Conference, hosted by Stanford University and the Stanford Synchrotron Radiation Laboratory on July 16-20, 1984. The meeting, co-chaired by Professors Arthur Bienenstock and Keith Hodgson, was attended by over 200 scientists representing a wide range of scientific disciplines. The format of the meeting consisted of 51 invited presenta tions and four days of poster sessions. This Proceedings is a compilation of 139 contributions from both invited speakers and authors of contributed posters. The last ten years has seen the rapid maturation of x-ray absorption spectrosco pyas a scientific discipline. The vitality of the field is reflected in the diver sity of applications found in the Proceedings. Recent work continues to probe the limits of x-ray spectroscopy, with proven techniques being extended to, for examp le, very low or high energy studies, to very dilute systems, and to studies of surface structure. In fact, the title of the conference does not at all reflect the breadth of the science discussed at this meeting. The number of fields in which x ray absorption spectroscopy is finding applications has increased dramatically even in the two years since the previous International Conference held in Frascati*. The prospects for continued growth and innovation will be even further enhanced if a new generation 6 GeV storage ring is constructed in the next five years."