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

A New Vision of Art Education

In this project I address two societal assumption concerning the discipline of art and their implication for art education. These assumptions are that i) art is primarily a creative endeavor with little educational value; and, ii) that the ability to make art requires some sort of rare, innate talent. In my view these are the primary reasons that art is increasingly marginalized in public school programs and our society at large

Lev Vygotsky and art education: a theoretical framework for a cultural-historical model of visual art education for primary school-age children

This study constructs a theoretical framework and argument for the development-advancing functions that art education can have during childhood as based on the theories of child development, imagination and art central to the Cultural-Historical Constructivist theory of development of the Russian psychologist Lev Vygotsky. Building on Vygotsky’s theory of development and his definition of imagination this thesis argues that during childhood imagination is in a particularly sensitive and important stage of development. At this stage its growth and ability to influence the development of other functions hinges on the ways children’s activities use and develop their imagination. Visual art education can be understood as one such activity: developing the imagination, and through it, developing the whole psychological system of the child. However, not everything called ‘art education’ for children has the characteristics needed to best develop the imagination. This study will also outline some guiding principles for art curriculum and teaching methods that can, following from Vygotsky’s theory, make art education an activity that fosters development

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

Metalloprotein electron transfer reactions: analysis of reactivity of horse heart cytochrome c with inorganic complexes.

The reactions of horse heart cytochrome c with Fe(ethylenediaminetetraacetate)2-, Co(1,10-phenanthroline)3(3+), Ru(NH3)6(2+), and Fe(CN)6(3-) have been analyzed within the formalism of the Marcus theory of outer-sphere electron transfer, including compensation for electrostatic interactions. Calculated protein self-exchange rate constants based on crossreactions are found to vary over three orders of magnitude, decreasing according to Fe(CN)6(3-) greater than Ru(NH3)6(2+) greater than Fe(EDTA)2-. The reactivity order suggests that the mechanism of electron transfer involves attack by the small molecule reagents near the most nearly exposed region of the heme; this attack is affected by electrostatic interactions with the positively charged protein, by hydrophobic interactions that permit reagent penetration of the protein surface, and by the availability of pi symmetry ligand (or extended metal) orbitals that can overlap with the pi redox orbitals of the heme group