Electron coupling through a beta strand has been investigated by measurement of the intramolecular electron-transfer (ET) rates in ruthenium-modified derivatives of the beta barrel blue copper protein Pseudomonas aeruginosa azurin. Surface histidines, introduced on the methionine-121 beta strand by mutagenesis, were modified with a Ru(2,2'-bipyridine)2(imidazole)2+ complex. The Cu+ to Ru3+ rate constants yielded a distance-decay constant of 1.1 per angstrom, a value close to the distance-decay constant of 1.0 per angstrom predicted for electron tunneling through an idealized beta strand. Activationless ET rate constants in combination with a tunneling-pathway analysis of the structures of azurin and cytochrome c confirm that there is a generally efficient network for coupling the internal (native) redox center to the surface of both proteins.

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Social networking sites (SNSs) have become increasingly common in recent years, and their use has become integrated into the daily lives of millions of people across the world. Attracting new users and retaining existing ones are critical to the success of SNS providers. This study applies the push‐pull‐mooring model of the migration theory to improve our understanding of factors that influence the switching behavior of SNS users. Following the migration theory, this study empirically examines the three categories of antecedents for SNS switching intention: push (i.e., dissatisfaction and regret), pull (i.e., alternative attractiveness), and mooring (i.e., switching costs) factors. The results show that the three categories of factors had varying degrees of effects on switching intention. Additionally, the strong moderation effects of both pull and mooring factors help answer the question why switching does not necessarily occur when push factors are in effect. Managerial implications are provided.

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