Reconstitution of Azotobacter vinelandii ferredoxin I as a {2[4Fe-4S]1+/2+} protein

AbstractAs normally isolated, Azotobacter vinelandii ferredoxin I (Fd I) is a {[4Fe-4S],[3Fe-3S]} protein: (7Fe)Fd I. We report that anaerobic reconstitution of Fd I from its apoprotein yields a protein whose spectra are distinct from those of (7Fe)Fd I and typical of bacterial ferredoxins. We identify this new form of Fd I as a {2[Fe-4S]} protein: (8Fe)Fd I. (8Fe)Fd I is unstable in air and decomposes to give a ∼ 10% yield of (7Fe)Fd I. These results increase the probability that (8Fe)Fd I is the form of Fd I occurring in vivo and that (7Fe)Fd I results from oxidative degradation during purification

Selective oxidative destruction of iron-sulfur clusters Ferricyanide oxidation of Azotobacter vinelandii ferredoxin I

AbstractThe destructive oxidation of aerobically isolated 7Fe Azotobacter vinelandii ferredoxin I [(7Fe)FdI] by Fe(CN)63− is examined using low-temperature magnetic circular dichroism (MCD) and EPR. The results demonstrate that oxidation of the [3Fe-3S] cluster occurs only after essentially complete destruction of the [4Fe-4S] cluster. It is therefore feasible by controlled Fe(CN)63− oxidation to obtain a partially metallated form of FdI, (3Fe)FdI, containing only a [3Fe-3S) cluster. The MCD and EPR data demonstrate that the [3Fe-3S] cluster in (3Fe)FdI is essentially identical in structure to that in the native protein

Oxidized and reduced Azotobacter vinelandii ferredoxin I at 1.4 A resolution: conformational change of surface residues without significant change in the [3Fe-4S]+/0 cluster

The refined structure of reduced Azotobacter vinelandii 7Fe ferredoxin FdI at 100 K and 1.4 A resolution is reported, permitting comparison of [3Fe-4S]+ and [3Fe-4S]0 clusters in the same protein at near atomic resolution. The reduced state of the [3Fe-4S]0 cluster is established by single-crystal EPR following data collection. Redundant structures are refined to establish the reproducibility and accuracy of the results for both oxidation states. The structure of the [4Fe-4S]2+ cluster in four independently determined FdI structures is the same within the range of derived standard uncertainties, providing an internal control on the experimental methods and the refinement results. The structures of the [3Fe-4S]+ and [3Fe-4S]0 clusters are also the same within experimental error, indicating that the protein may be enforcing an entatic state upon this cluster, facilitating electron-transfer reactions. The structure of the FdI [3Fe-4S]0 cluster allows direct comparison with the structure of a well-characterized [Fe3S4]0 synthetic analogue compound. The [3Fe-4S]0 cluster displays significant distortions with respect to the [Fe3S4]0 analogue, further suggesting that the observed [3Fe-4S]+/0 geometry in FdI may represent an entatic state. Comparison of oxidized and reduced FdI reveals conformational changes at the protein surface in response to reduction of the [3Fe-4S]+/0 cluster. The carboxyl group of Asp15 rotates ∼90°, Lys84, a residue hydrogen bonded to Asp15, adopts a single conformation, and additional H2O molecules become ordered. These structural changes imply a mechanism for H+ transfer to the [3Fe-4S]0 cluster in agreement with electrochemical and spectroscopic results

Os cursos de ciências contábeis no Brasil e o conteúdo das disciplinas de sistemas de informação: a visão acadêmica versus a necessidade prática

O presente trabalho pesquisou um grupo de contadores profissionais (não acadêmicos) da Região de Ribeirão Preto - Estado de São Paulo /Brasil e os professores dos cursos de graduação em contabilidade do Estado de São Paulo /Brasil para identificar e quantificar a importância percebida referente a diversos tópicos da área de sistemas de Informação a se-rem ministrados nos cursos de Ciências Contábeis. Os resultados indicam que existem poucas divergências em relação à ênfase dada pelos acadêmicos e práticos em relação a 33 tópicos selecionados na área de Sistema de Informações. Uma vez que o conteúdo da área de Sistema de Informação está sendo considerado inadequado para os contadores profissionais (não acadêmicos), isto pode significar a necessidade de reestruturação dos cursos de graduação em Contabilidade para atender as necessidades práticas dos contadores, além de atender às expectativas dos acadêmicos.The purpose of this study is to identify and quantify the perceived importance given to different topics from Information System field to be taught at accounting graduate Courses. A sample of 200 accounting practitioners from the Ribeirão Preto area (State of São Paulo ) and 71 professors in Accounting from the State of São Paulo Universities (Brazil ) were investigated for this purpose. The results shows that the differences in emphasis given to the 33 selected specific topics are very small. Since the content of Information System field being taught in Accounting graduate Courses is being considered inadequate for the practitioners, this might indicate the need for restructuring the Accounting graduate course to meet the practical needs of accountants and academics expectations. Implications and results will be presented here

A randomized controlled trial of standard versus intensified tuberculosis diagnostics on treatment decisions by physicians in Northern Tanzania

10.1186/1471-2334-14-89BMC Infectious Diseases1418