Recent pulsed EPR studies of the Photosystem II oxygen-evolving complex: implications as to water oxidation mechanisms

AbstractThe pulsed electron paramagnetic resonance (EPR) methods of electron spin echo envelope modulation (ESEEM) and electron spin echo-electron nuclear double resonance (ESE-ENDOR) are used to investigate the structure of the Photosystem II oxygen-evolving complex (OEC), including the paramagnetic manganese cluster and its immediate surroundings. Recent unpublished results from the pulsed EPR laboratory at UC-Davis are discussed, along with aspects of recent publications, with a focus on substrate and cofactor interactions. New data on the proximity of exchangeable deuterons around the Mn cluster poised in the S0-state are presented and interpreted. These pulsed EPR results are used in an evaluation of several recently proposed mechanisms for PSII water oxidation. We strongly favor mechanistic models where the substrate waters bind within the OEC early in the S-state cycle. Models in which the OO bond is formed by a nucleophilic attack by a Ca2+-bound water on a strong S4-state electrophile provide a good match to the pulsed EPR data

Influential Factors in IT Outsourcing Relationship in a Swedish Municipality

Information Technology Outsourcing (ITO) has generated considerable interest within Information Systems (IS) research as a consequence of its benefits in terms of cost efficiency and freedom to focus on core capabilities. This study covers the area of ITO in the public sector, specifically, in Swedish Municipalities where ITO has become a mainstream strategy. The influential ITO factors of the post-contract stage of an ITO relationship are examined and debated in light of existent research literature. The research is based on a case study of a Swedish Municipality and a direct IT vendor. A thematic analysis brings light upon three new ITO influential factors which are: (1) mutual understanding and long-term engagement; (2) Multi-sourcing, and (3) Communication between Municipalities, together with other seven factors present in the research literature that have an influence on the ITO relationship. The findings of this study can support ITO decision-makers from Swedish municipalities in improving the ITO relationship between their organizations and IT vendors.</p