Electron Transfer Reactivity of Type Zero Pseudomonas aeruginosa Azurin

Type zero copper is a hard-ligand analogue of the classical type 1 or blue site in copper proteins that function as electron transfer (ET) agents in photosynthesis and other biological processes. The EPR spectroscopic features of type zero Cu^(II) are very similar to those of blue copper, although lacking the deep blue color, due to the absence of thiolate ligation. We have measured the rates of intramolecular ET from the pulse radiolytically generated C3−C26 disulfide radical anion to the Cu^(II) in both type zero C112D/M121L and type 2 C112D Pseudomonas aeruginosa azurins in pH 7.0 aqueous solutions between 8 and 45 °C. We also have obtained rate/temperature (10−30 °C) profiles for ET reactions between these mutants and the wild-type azurin. Analysis of the rates and activation parameters for both intramolecular and intermolecular ET reactions indicates that the type zero copper reorganization energy falls in a range (0.9−1.1 eV) slightly above that for type 1 (0.7−0.8 eV), but substantially smaller than that for type 2 (>2 eV), consistent with XAS and EXAFS data that reveal minimal type zero site reorientation during redox cycling

Controlling time scales for electron transfer through proteins

Electron transfer processes within proteins constitute key elements in biological energy conversion processes as well as in a wide variety of biochemical transformations. Pursuit of the parameters that control the rates of these processes is driven by the great interest in the latter reactions. Here, we review a considerable body of results emerging from investigation of intramolecular electron transfer (ET) reactions in two types of proteins, all done by the use of the pulse-radiolysis method: first are described results of extensive studies of a model system, the bacterial electron mediating protein azurin, where an internal ET between the disulfide radical ion and the Cu(II) is induced. Impact of specific structural changes introduced into azurin on the reaction rates and the parameters controlling it are discussed. Then, the presentation is extended to results of investigations of intra-protein ET reactions that are part of catalytic cycles of multi-copper containing enzymes. Again, the rates and the parameters controlling them are presented and discussed in the context of their efficacy and possible constraints set on their evolution

Electron Transfer Reactions of Copper Proteins

Copper proteins are a widespread and diverse class, isolated from plant, animal, bacterial, and fungal sources (1, 1a). The proteins considered here are involved in oxidation-reduction reactions, either as oxidoreductases or as electron carriers; other functions of copper proteins include metal ion storage and oxygen transport

THE AMERICIUM/LANTHANIDE SEPARATION CONUNDRUM: SELECTIVE OXIDATION OR SOFT DONOR COMPLEXANTS? By

ii ACKNOWLEDGMENT During the career of a graduate student, many people help the student achieve the final goal. Of those people, the most important person to acknowledge is my advisor, Ken Nash. Ken tirelessly provided intellectual and moral support throughout my time as a student. He allowed me to make my mistakes while making sure that I did not get completely derailed. Thank you for your support and guidance over the last 5 years. I also would like to thank the many post docs that have been through the lab during my time at WSU. I would especially like to thank Dr. Leigh Martin and Dr. Peter Zalupski for both their time spent working with me at WSU and days spent at the Idaho National Lab trying to extend my separation to higher concentrations. I would also like to thank Dr. Mikael Nilsson for general support in all lab matters during his time at WSU. Thank you to all of the graduate students that helped in making my time here at WSU more enjoyable. Mark, with the many trips to Rico’s, raiding parties to Troy and great Halloween gatherings, definitely kept things lively. Maria, Kim and I became great friends during our 5 years together. I’m sure I will be harassing them for many years to come and vice versa. Cha